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652.0106 State supplement
(a) General
These South Carolina supplements to NEH Part 652
Irrigation Guide were written to include state-specific
data for designs and information contained in earlier
sections of the Guide – NRCS National Engineering
Handbook (NEH), Part 652. They are meant to be
used in conjunction with calculations and tabular data
contained in NRCS NEH, Part 623 (Section 15) and
other state information contained in NRCS Field Office Technical Guides and state soil surveys. To the
extent possible, material that would duplicate discussion or data already in these chapters was eliminated.
The layout of these supplements follows the layout of
Part 652. Supplement sections of chapters, are meant
to be placed at the end of the corresponding chapter.
Figure 1–1
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Chapter headings, footers, pagination, table and figure numbers, and section numbers follow those of the
corresponding Part 652 chapter. For several chapters,
content in the existing chapter was adequate for use
in South Carolina, and no supplement section was
created for the State.
(b) Meteorological Conditions in
South Carolina
(1) Precipitation
The average precipitation in the South Carolina river
basins is about 50 inches. The United States average
is about 30 inches. Precipitation is typically well distributed throughout the state (Fig. 1-1). On average
there is slightly more precipitation along the Lower
Coastal Plains where diurnal and seasonal on-shore
winds bring in moist Atlantic air. Precipitation is
greatest in the northeast where orographic cooling
drains clouds as they cross the mountains.
South Carolina precipitation norms, based on 1970-2000. (Wachob et al., 2009)
(210-vi-NEH, January 2014 – SC)
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The year-to-year variability of total annual precipitation creates one of the greatest incentives for range
irrigation. Based on more than 100 years of record,
the statewide mean is about 48 inches, but extremes
from 33 inches in 1954 to 72 inches in 1964. The past
50 years illustrates that annual variability (Fig. 1-2).
Extremes of 50% more and 50% less than average
can be seen locally as well as statewide.
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Significantly, the annual precipitation is rarely as low
as the mean precipitation in the United States – 30
inches. Nonetheless, recent rainfall deficits, especially those since the late 1990’s, have occurred during a
time when irrigation became an option in crop production. At that same time, growers and banks that
fund them have grown more risk averse. The drive
toward irrigation remains strong.
60
55
50
45
40
35
1960
Figure 1–2
1970
1980
1990
2000
2010
Statewide average of annual precipitation (inches) 1960 to 2011. (Data: Southeast Regional Climate Center, State average data. http://www.sercc.com/)
The Seasonal Distribution of average precipitation
shows slightly higher amounts during the summer
months of June, July and August, when evapotranspiration of natural and crop vegetation is greatest (Fig.
1-3). It declines slightly in the spring and more so
during fall. In general, South Carolina is blessed with
well-distributed precipitation that maintains streamflow throughout the year and recharges the state’s
aquifers, particularly in winter and spring months.
While monthly precipitation is moderate throughout
the year, it still falls below evaporative demand of
growing crops (Fig. 1-3). During May the deficit is
as much as 3.5 inches, while in April and June
through August the deficits vary from 2.5 to 3.0 inches. It is those expected, growing-season deficits that
justify grower investments in irrigation infrastructure.
9.00
8.00
7.00
Evap
Precip
6.00
5.00
4.00
3.00
2.00
1.00
0.00
J F M A M J J A S O N D
Mean monthly pan evaporation and
precipitation (inches) in SC, 19611992. Pan evaporation approximates the evaporative
demand over a full canopied crop, forage or forest.
(Data: South Carolina State Climatology Office.
http://www.dnr.sc.gov/climate/sco)
Figure 1–3
(210-vi-NEH, January 2014 – SC)
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Another way to examine the precipitation deficits that
irrigators may need to make up is to look at chart of
monthly precipitation over the 4-year period 1997 to
2000 (Fig. 1-4). The period includes both high precipitation months as well as very dry months even
though part of this period included the severe 1998 to
2002 drought. In some growing season months as
little as 1-inch was received, while in others precipi-
Figure 1–4
tation nearly matched the 6.0- to 7.5-inch evaporative
demand. During severe dry months, growers may
need to supply all of a crop’s water needs. One challenge in designing irrigation systems is balancing
costs for larger capacity systems that could meet all
crop needs in the worse years with less expensive
designs that might fall short in some very dry
months.
Statewide average of annual precipitation (inches) 1960 to 2011. (Data: Southeast Regional Climate Center, State average data. http://www.sercc.com/)
(2) Temperature
Average daily temperatures for South Carolina remain well above freezing across the State (Fig. 1-5).
In general, the average temperature at the height of
the summer is about 80 degrees Fahrenheit; slightly
higher than the summer average of 75 degrees Fahrenheit seen through much of the continental US.
The average daily temperature range is about 20 degrees Fahrenheit, with the minimum usually at sunrise and the maximum usually in early afternoon.
Variations in this pattern occur, of course, with
frontal passage and a change of air mass, strong wind
and mixing, and with dense clouds. Through much of
the summer growing season, afternoon cloudiness,
with or without thundershowers, moderates the late
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afternoon rise in temperature. With unusually long
duration of cloudiness or with dense clouds daily
temperature range may be less than 10 degrees Fahrenheit; with clear skies, dry air, and light wind, the
range frequently exceeds 30 degrees Fahrenheit.
These last conditions are common during periods of
drought. While they create ideal crop growing conditions, they also increase crop evaporative demand
and, often, the need for supplemental water.
On an average January day, the temperature rises to
more than 50 degrees Fahrenheit in the mountains,
the low 60’s in the central part of the state, and
reaches 70 degrees Fahrenheit in the extreme southeast part. The minimum temperature during an average January day is 30 degrees Fahrenheit in the
(210-vi-NEH, January 2014 – SC)
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Figure 1–5
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South Carolina mean annual temperature, based on 1970 to 2000. (Wachob et al., 2009)
mountains, 40 degrees Fahrenheit in the central part,
and nearly 50 degrees Fahrenheit in the extreme
southern portion.
In July the average daily maximum temperature is
about 90 degrees Fahrenheit over most of South Carolina. When extremes occur, approaching or slightly
exceeding 100 degrees Fahrenheit, they tend to develop along the fall line from Augusta through Columbus. Those extremes are moderated by sea breezes and cloudiness along coastal areas and by elevation in the mountains. During a typical night in July,
the temperature falls to about 70 degrees Fahrenheit
over most of the central and coastal areas of the state
and to about 60 degrees Fahrenheit in the mountain.
(3) Growing Season
The growing season is defined as the period between
the last occurrence in spring and the first occurrence
in fall of temperatures below a given temperature
base. This base is different for different plants, some
being hardier than others. Tomatoes are damaged at
temperatures below 32 degrees Fahrenheit, whereas
peas and cabbage can withstand temperatures as low
as 24 degrees Fahrenheit for brief periods.
The average frost-free period or length of growing
season ranges from about 200 days in the mountain
valleys to 290 days in the extreme southeast, with
most of the state having about 230 days (Fig. 1-6).
These values vary from year to year. In the north, the
(210-vi-NEH, January 2014 – SC)
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Figure 1–6
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Introduction
Average frost-free period (days) in South Carolina (Date: 1931-1960.)
growing season is within about 20 days of the average two-thirds of the years. In the south it is within
30 days of the average two thirds of the year.
The average date of the last freeze in spring (Fig. 1-7)
and first freeze in the fall (Fig. 1-8) are shown for
temperature sensitive plants. For hardy plants, the
average growing season would be about 25 days earlier in spring and about 20 days later in fall.
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The very long growing season in South Carolina
opens agricultural fields to numerous crop options.
Long-season crops like peanut and cotton can be reliably grown without fear of frost. Many multiple
cropping options, including those with a variety of
vegetables, winter grains, and traditional row crops
are feasible. Agronomic reasons for crop rotations,
especially for weed, nematode and disease suppression, create challenges for the design of irrigation
systems with sufficient flexibility to supply supplemental water to the diversity of crops made available
by that growing season.
(210-vi-NEH, January 2014 – SC)
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Figure 1–7
Average dates of last freeze in Spring. (Data: Temp. below 32 F, 1931-1960)
Figure 1–8
Average dates of first freeze in Fall. (Data: Temp. below 32 F, 1931-1960)
(210-vi-NEH, January 2014 – SC)
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(4) Wind
In South Carolina winds move from southwest to
northeast when off shore systems, mostly the Bermuda high that dominates during summer. When on land
highs dominate winds moves mostly from northeast
to southwest.
For certain orchard applications, the direction might
be a consideration in tree and irrigation system layout
but normally predominant wind direction will not
impact irrigation design. Average daily wind speeds
are only 5 to 10 miles per hour for the state.
Physiographic influences are evident in the state.
Wind speeds in open coastal areas are affected by a
diurnal on/off shore winds and average speeds are
typically 7 to 10 miles per hour. On exposed ridges
and open plateaus, average wind speeds of 8 to 10
miles per hour are observed. In relatively sheltered
valleys areas, such as around Columbia, winds average 5 to 7 miles per hour. Local variation is affected
by the dominant tall pine and hardwood trees found
in forests and fencerows surrounding many irrigated
fields.
For most of the growing regions where irrigation is
installed and for most of the growing season when
irrigation is used, daily patterns for wind speed follow a pattern. From about two hours before to about
two hours after sunrise, wind speed is negligible.
Warming of the ground and vegetation results in a
steady increase in wind speed throughout the morning into early afternoon. Depending upon development of clouds and thunderstorms, wind speed may
peak between 3 and 5 pm. When thunderstorms are
not present, wind speed again drops in the evening,
often precipitously in early evening and it remains so
until the night-time mixing with light wind from 3 to
4 am.
The pattern of wind allows growers some control of
wind sensitive operations including agricultural
spraying and irrigation. For irrigation systems most
affected by wind – high pressure impact sprinklers
and big guns – application should be avoided whenever possible during the afternoon when moderate to
gusty winds can disrupt intended application patterns.
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The winds may also lead to offsite or off target overspray. Additionally the afternoon wind speed peaks
when air temperatures are near daily maximums and
air relative humidity are at their daily lowest - conditions favoring maximal evaporative irrigation water
loss during application for any spray irrigation method. Conversely, nighttime and early morning application will make most effective use of water pumped to
the field and will apply it with the uniformity designed for the system.
To permit irrigation to be used primarily at nighttime, the system and its water source must be sized to
apply the average daily water replacement (typically
at least 0.25 inch and preferably 0.30 inch) in 18
hours or less a day. Likewise, the system must be
designed to require minimal attention during these
night-time application periods. Systems designed this
way provide the flexibility to keep up with water demands of the crop during longer rainless periods, and
still take advantage of off-peak utility rates, further
increasing irrigation efficiency.
(5) Data Sources
There are several sources of climate data available to
planners and irrigation designers. NRCS provides
basic parameters – mean annual precipitation, mean
annual temperatures, and frost free period. Each is
tied to the soil map units. Once a site is known, and
soils identified in the field, the data can be retrieved
using the full “Map Unit Description” report at the
Soil Data Mart (http://soildatamart.nrcs.usda.gov/).
The Field Office Technical Guide also provides these
data and summaries for South Carolina locations. For
most counties, both TAPS station summaries, and
more extensive WETS stations data sets and summaries in the online eFOTG Section II, Climate Data.
More detailed data can be obtained through South
Carolina’s Department of Natural Resources at their
climate site (http://www.dnr.sc.gov/climate/sco/).
Data there are generally arranged by stations, and
there are stations in most agricultural counties. Data
include temperature and precipitation, and those
analyses break down probabilities of rainfall during
individual months. Growing season, dates of first and
last frost are well documented there.
(210-vi-NEH, January 2014 – SC)
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(c) Surface Water Resources
Available for Irrigation
(1) General
In South Carolina, surface water flows predominantly
from northwest to southeast as elevation decreases
from the Appalachian mountains to the Flatwoods
and coastal waters of the Atlantic (Fig. 1-9). Of the
four major river basins, only the Ashley-CombaheeEdisto (ACE) river basin lies entirely within the state.
The Savannah River basin is about evenly split between Georgia and South Carolina, but the river itself
forms the boundary between the states. Withdrawals
from surface waters of the Savannah River basin may
be the subject of interstate compacts, especially withdrawals taken directly from the Savannah River and
its in-stream reservoirs. Those operate under rules
established by the U.S. Congress and implemented by
the U.S. Army Corps of Engineers.
Figure 1–9
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The Santee and Pee-Dee major river basins have their
headwaters in North Carolina. Unlike the Savannah,
North Carolina users withdraw water upstream from
South Carolina. Flow remaining in the rivers and
streams that enter South Carolina are affected by to
those NC withdrawals. As a result the two states have
been in negotiations over equitable use of the waters
in these basins. Surface water users in South Carolina’s portions of these basins may be subject to actions of any interstate compact between the states.
Most South Carolina irrigators will not suffer direct
affects from withdrawals or impoundments made by
North Carolina users. Typically South Carolina withdrawals for irrigation are made directly from small
streams or from farm ponds that collect runoff or impound flow in small streams. The catchment area for
these streams and drainage ways lie within the state,
often within the farm or those of neighbors.
Major stream basins and sub-basins of South Carolina. (Wachob et al., 2009)
(210-vi-NEH, January 2014 – SC)
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Irrigation withdrawals can be made directly from
continuously flowing streams and rivers, subject to
the laws of South Carolina (see Section f, below).
This eliminates the necessity for costly impoundments. Stream-side pumps can be installed as portable pumps mounted on trailers or sleds. Typically
these are powered by diesel- or propane-fueled engines – or they can be permanent installations powered by an electric motor. A stream-side or streambed dugout may be needed to assure sufficient flow at
all stream levels into the siphon tube. In many cases
there is sufficient base flow in these streams, but it is
important to remember that irrigation needs are
greatest when river flows are at their lowest levels.
Direct stream and river withdrawals have inherent
risks. In addition to risks of insufficient flows during
droughts, there may be restriction on irrigation pumping when the stream flow has reach a predetermined
limit needed for permitted waste water discharges
and their associated waste assimilation or a limit set
to protect flow for fish and other animal and plant
habitats. There may also be permitted withdrawers
downstream with prior claims on the flow.
Figure 1–10
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There are risks during flood flows as well. Unless
built onto sturdy platforms and mounted at an elevation above expected flood stages, stream-side pumps
may be submerged or dislodged and damaged. Even
normal flood flows in winter can carry enough silt
and sand to fill in dugouts made for siphon tubes,
creating an annual maintenance chore.
Physiography works against direct stream withdrawals. In the Coastal Plain regions of the State (Fig. 110), in particular, streams and rivers meander in
broad flood plains. Soils in these floodplains are subject to periodic flooding. Also, they are usually poorly or somewhat poorly drained. Areas immediately
adjacent to the stream, locations that would be most
amenable for direct pumping, thus do not make productive row-crop or vegetable fields. To use direct
stream withdrawals, water would have to be pumped
further, increasing capital and operating costs for
pumping.
This is less often a problem in Piedmont or Mountain
Valleys. Streams may flow adjacent to adequately
drained terraces or upland locations that have produc-
Principal physiographic regions in South Carolina. (Wachob et al., 2009.)
(210-vi-NEH, January 2014 – SC)
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tive crop fields and orchards. However, even in these
regions, the distance from major streams to fields
needing irrigation is often too great to justify the expense of mile-long and greater pressurized pipe lines.
Unless the irrigator owns the land all the way to the
river there may also be costs associated with rightsof-way for the pipeline.
For all these reasons, farm operators most commonly
rely upon small, on-farm streams and impoundments
to secure their access to surface water. With these
catchments and watersheds lying within the State,
even complete cessation of river flow from North
Carolina would not directly affect the South Carolina
irrigators. Interstate Compacts or South Carolina laws
designed to protect downstream users in the State are
another matter. Courts or state regulators could pass
mandates that affect on-farm sources of water, as has
happened in the West.
(1) Average Streamflow
The average annual streamflow in South Carolina
represents about 22 inches average depth over the
Figure 1–11
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State (U.S. Geological Survey, 1985), compared to
the United States average of about 8 inches. The remainder of the 48 inches of average annual precipitation is lost to evapotranspiration or enters and recharges the various aquifers in the state. The range of
annual streamflow is from about 10 inches in the
lower Coastal Plain and lower Piedmont to about 35
inches in the Blue Ridge (Fig. 1-11).
With an average of 15 inches of runoff from farm
fields and forests in the row-crop areas of the state, it
would seem, at first glance, that there would be little
need for irrigation, let alone farm ponds. However, as
was pointed out in meteorology, the precipitation and
subsequent runoff is not distributed uniformly
through the growing season. Average rainfall is at a
deficit compared to average evaporative demand in
spring and summer months. Summer precipitation
produces little net runoff, except locally under severe
thunderstorms. Impoundments are needed near irrigated fields to retain spring runoff and to capture
runoff during those periodic storm events.
Distribution of average annual runoff and base flow in South Carolina 1948-1990. (Wachob et al.,
2009; Badr et al., 2004)
(210-vi-NEH, January 2014 – SC)
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(2) Seasonal Distribution of Streamflow
Although related, the seasonal distribution of streamflow does not match the seasonal distribution of precipitation. Regardless of variations in the seasonal
precipitation pattern, the average streamflow, except
in certain coastal areas, is high in early spring and
recedes to a low in late autumn. This average seasonal regime is typical even of most small streams in the
rural areas. The summer precipitation peak does not
ordinarily produce a summer runoff peak because
summer showers usually fall on relatively dry soil.
Much of the rainfall is quickly transpired by vegetation. Some even evaporates directly from leaf surfaces and soil to the air; thus, summer rain contributes
relatively little to runoff during this time of year.
(3) Low Flows
Streams in the Lower Coastal Plain and Lower Piedmont normally have poorly-sustained base flows, and
some streams periodically go dry during late summer
and fall. This is in contrast to the Blue Ridge province and upper Coastal Plain (Fig. 1-10) where base
flows are well-sustained. In the mountains, precipitation is greater, infiltration is enhanced by highly porous floor of hardwood forests. Fractured shale and
sandstone aquifers there store, transmit, and discharge that water over an extended period. In the Upper Coastal Plain, precipitation infiltrates the sandy
surface soils where much of the spring rains are
transmitted through thick well-drained soils into shallow aquifers of the Sand Hills and Upper Coastal
Plain. Streams in the region are well connected with
and drain surficial aquifers they flow through.
More information on low flows of streams in South
Carolina may be obtained from the following publications of the South Carolina Water Resources
Commission by Bloxham (1976, 1979, 1981.) Additionally, the South Carolina State Water Assessment
provides a good overview of stream flow in many
areas of the state (Wauchob et al., 2009). Full citations may be found in the reference list.
(4) Surface Water Withdrawals
The average surface water discharge from South Carolina is about 33 billion gallons per day (U.S. Geological Survey, 1985). Between 1970 and 1980, total
offstream water use in South Carolina nearly doubled
to 5,780 million gallons per day. The South
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Carolina Water Resources Commission projected this
amount to increase to about 8,550 million gallons per
day by the year 2020 (Snyder et al., 1983). However,
the 2010 Annual Use Report showed that offstream
water use had already reached 9,770 million gallons
per day a decade earlier (SC-DHEC, 2010). Of that
nearly 10 billion gallons per day, reported surface
withdrawals for irrigation made up only 28 million
gallons per day as reported by 268 users.
(5) Surface Water Quality
South Carolina manages its withdrawal permitting,
discharge permitting and reporting for eight designated water quality management basins (Fig 1-12). State
code and regulations that affect agricultural operations are described more fully below (Section f: Regulatory Environment for Irrigation)
The natural temperature in large streams is near the
average monthly air temperature. In smaller streams,
day-to-day fluctuations in water temperature are
greater than for the larger streams and in the smallest
streams, hour-to-hour variations are evident with the
daily range of temperature being nearly as great as
for the nearby air.
Neither dissolved solids nor acidity presents problems in most South Carolina surface water supplies.
The range of dissolved solids for surface water in
South Carolina is from less than 15 to more than 100
mg/L with values generally ranging from 20 to 80
mg/L. The pH of surface water generally will be in
the range from about 5.0 to 7.5 with alkalinity ranging from about 1 to 40 mg/L.
The quality of South Carolina's surface water is generally suitable for irrigation use. The water is soft and
has a low buffering capacity. There are no known
significant quality problems concerning the use of
surface water for irrigation of row crops and orchards.
South Carolina has listed streams with impaired water quality, and even unlisted streams and impoundments may contain bacteria or other contaminants
from runoff or discharge. These create risks for food
borne diseases. Generally, untreated surface waters
should not be used for irrigation of fresh-market
fruits and vegetables.
(210-vi-NEH, January 2014 – SC)
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Figure 1–12
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South Carolina DHEC water-quality management basins. (Wachob et al. 2009)
(210-vi-NEH, January 2014 – SC)
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(d) Groundwater Resources
Available for Irrigation
(1) General
Groundwater is often the preferred choice for irrigation in South Carolina. In most cases wells will be
drilled on the property of the farm where it will be
used, adding value to the farm and providing some
measure of water security during drought years. In
many productive farming regions in South Carolina,
well yields are sufficient to directly supply high capacity systems including large drip irrigation fields
and center pivots. In others, wells may refill reservoirs or ponds from which the irrigation is operated.
Water from most water-bearing formations – aquifers
– in South Carolina is free of the potential contaminate especially bacterial that may get into surface
waters of the State. It can be used without treatment,
in most cases, on vegetables and fruits for fresh market consumption. It is also free of surface water sediments and algae that clog microirrigation systems.
The major disadvantage of groundwater for irrigation
has been the high capital costs for well drilling and
construction and the added annual costs for energy to
lift water from the water table to the surface. As effective earth grounds, wells and especially their
pumps are subject to damage from lightening. In recent years, regulations on well drilling, permitting for
water withdrawals from selected aquifers, and monitoring and reporting have added to those disadvantages. Even so, the advantages of a certain and
high quality water source have led many considering
irrigation the make the additional investment in
wells.
Farmers in the South often believe, in their soul and
in their gut, that water taken from below their own
property belongs to them. It can be used by them in
any quantity, for any use, and at any time for only the
cost of drilling a well and pumping that water. This
traditional view clashes with a more scientificallybased understanding of geology and hydrology. In
most cases, the water under a land-owners property is
part of larger and interconnected water bearing formations. Water withdrawn by one farmer may affect
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the availability of water under their neighbor’s property. Collectively, withdrawals can lower water tables, or hydraulic head in confined aquifers, in a large
region. This can impact others with shallow wells,
dewater surficial aquifers, reduce discharge from aquifers to streams, eliminate natural surface water
storage features, or even enable salt water intrusion.
The State has attempted to use education, scientific
monitoring and modeling, and regulation to protect
long term sustainability of groundwater resources for
all water users and ecosystems. Their rules and regulations (see section f below) are not always accepted
with open arms. It is important to be sensitive to the
clash of traditional, scientific, and regulatory views
of groundwater use when discussing plans that involve expansion of groundwater for irrigation.
(2) Water-Bearing Formations (Aquifers)
South Carolina ground water resources differ substantially from one Physiographic Regions (Fig. 110) to the next.
Piedmont and Blue Ridge aquifers occur in alluvial
deposits of sand and gravel, in weathered saprolite,
and in joints, fractures and fault zones of crystalline
bedrock. These are surficial aquifers, i.e. their water
surface is open to (at) atmospheric pressure. Water
surfaces that are free from pumping tend to follow
the contours of the land surface, and most discharge
to drainage ways, streams, and rivers that dissect the
landscape. That discharge forms the base flow in
Blue Ridge and Piedmont streams, and pumping from
these aquifers will affect that stream flow.
Coastal Plain groundwater flows in large water bearing formations that were formed as layers of sediment laid down in shallow coastal oceans. Its aquifers
occur in wedge-shaped layers consisting of gravel,
sand, and limestone sediments overlaying metamorphic and sedimentary rocks. These are interlayered
with less permeable clay layers that separate formations into principal and secondary aquifers Although many of the aquifers lie under greater areas
than shown on the surface map (Fig. 1-13), the ease
of access and quality of water lead to regional preferences as to which is tapped by wells for irrigation,
drinking water, and other uses.
(210-vi-NEH, January 2014 – SC)
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Figure 1–13
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Distribution of primary withdrawal areas for SC's principal aquifers. The aquifers themselves may
extend beyond the primary withdrawal zones. (Lichtler and Aucott, 1985)
A cross-section of the South Carolina illustrates the
general aquifer formations and their relationship to
their recharge areas (Fig. 1-14). The major source of
recharge to the Coastal Plain aquifers is precipitation
in the outcrop areas of these formations. These major
recharge areas occur where the formation is exposed
at the ground surface or only buried shallowly under
permeable soil that formed over those outcrops.
From the recharge areas, fresh water moves downward and ocean-ward within the aquifer. The principle aquifers extend under the Atlantic for some distance. A wedge, thickening from the Fall Line toward
the coastline, can be divided into aquifers and intervening confining units based on relative permeabilities, and other factors (Fig. 1-15) Water generally
moves laterally within each aquifer with confining
units inhibiting but not preventing vertical movement
of water between aquifers. (Ancott and Speiran,
1984d)
Fresh water is lighter than sea water. Even so fresh
water moving downward below mean sea level
(MSL) has flushed out or partially salt water left behind during deposition and formation of the Coastal
Plain aquifers. Hydraulic head, in the form of water
tables elevated above sea level, drives fresh water
ocean-ward along flow lines in these confined aquifer
layers. As long as fresh water from precipitation sustains the elevated water table in the recharge areas,
and as long as pumping from the aquifer does create
areas with hydraulic head lowered below mean sea
level, denser saline water will remain in the deeper
and seaward areas of these important aquifers.
While there are local exceptions, groundwater in
South Carolina’s Coastal Plain will have higher levels of dissolved solids, sodium, and chloride in the
deepest and seaward areas of the aquifers. Well drillers thus attempt to balance depths that will provide
sustained yield, use casing and grout to prevent water
from poorer quality layers from entering the well.
(210-vi-NEH, January 2014 – SC)
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Figure 1–14
Generalized cross section of South Carolina showing the principal groundwater aquifers.
Figure 1–15
Hydrogeologic sections across the SC Coastal Plain. At left, from Columbia to Charlestown; at
right along the coast. The combined aquifers are deepest (almost 4000 feet) near Hilton Head.
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(210-vi-NEH, January 2014 – SC)
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(3) Well Depths and Yields
Most water is stored in the top several hundred feet in
the Piedmont and Blue Ridge Provinces, thus well
depths usually stay within this range. Productive
wells yield 10 to 30 gallons per minute with water
levels generally less than 100 feet but sometimes exceeding 200 feet below the ground surface. Almost
half of the wells in the Piedmont yield less than 10
gallons per minute. Use of these wells for irrigation
would be limited to very small areas – a few acres at
most – unless pumped water can be stored in reservoirs or tanks.
Wells in the Coastal Plains often produce adequate
yields at depths less than 500 feet, but it is not rare
for depths to exceed 1000 feet or greater. The 2009
State Water Assessment (Wauchob et al., 2009) provides maps showing depths to the top of each of the
principal aquifers and typical hydraulic head (static
water levels) to be found in wells drilled into those
aquifers. In upland areas of the upper Coastal Plain,
water levels prior to development may be deeper than
200 feet, (personal communication, Gary Speiran,
1986)
Most large capacity wells in the Coastal Plain are
screened in the Black Creek or the Middendorf Aquifer (Fig. 1-13). Potential yields range from several
hundred to greater than 2000 gallons per minute. After development, water levels in wells screened in the
Black Creek and Middendorf aquifer are commonly
in the range from 50 to more than 250 feet from the
soil surface at the pumping well, (personal communication, Gary Speiran, 1986) The actual water level at
any particular well during pumping is dependent on
many factors including static water level prior to
pumping, permeability of in-place materials and the
gravel pack or filter at the screened sections, the well
screen itself, transmissibility of the aquifer, and the
discharge of the well.
Screens or perforated casings are utilized in unconsolidated sand and gravel aquifers to allow water to
enter the well and to stabilize the aquifer material.
Consolidated rock aquifers often may be completed
without perforated casing or screen. Due to the cost
of screens, usually only the higher yielding zones are
screened, resulting in some wells being multiscreened. Zones of poor quality water should not be
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screened if ample quantity of good quality water is
available at different depths to dilute dissolved solids
to levels that will not cause short or long-term problems with crops, soils, and application equipment.
(4) Groundwater Withdrawals
The 1980 withdrawal of ground water in South Carolina was slightly less than 210 mgd (Lonon & Others,
1983). This was equivalent to about two-sevenths
inch average depth per year over the southeastern
half of the state. By 2010 that withdrawal had reportedly increased to only 215 mgd, as based upon a reporting from 575 agricultural and 1300 other wells in
the state (Butler, 2011). It is unlikely that these reported withdrawals provide the full report for the tens
of thousands of known wells in the State.
Ground-water withdrawals for irrigation are seasonal,
usually are spaced widely, and are located mostly in
the upper part of the Coastal Plain where aquifer
yields are large. Because of these conditions, declines
in water levels due to irrigation are very localized and
seasonal thus no deep permanent cones of depression
have developed due to irrigation alone. (Lichtler &
Aucott, Water Supply Paper 2275)
Municipal, industrial and other groundwater users
have worried about what rate of withdrawal could be
sustained. As indicated by water level declines in
areas where ground water pumpage is greatest (Myrtle Beach, Florence, Sumter, and Savannah/Hilton
head, withdrawals may be approaching maximum
sustainable yields locally. In other areas of the
Coastal Plain, ground water is relatively undeveloped
thus significant increases in withdrawals over present
rates should be sustainable in most situations.
In certain coastal areas, gradual increases in salinity
and chloride in drinking water wells raised those
concerns. Beginning in the 1980’s the US Geological
Survey and Georgia, and South Carolina agencies
began studying this salt water intrusion problem in
earnest. Georgia enacted a ban on municipal, industrial, and agricultural well drilling in its 24 coastal
counties. That ban was partially lifted only after
changes were made to reduce groundwater consumption in the most populous areas.
(210-vi-NEH, January 2014 – SC)
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South Carolina has enacted legislation to protect
against further degradation of the aquifers The South
Carolina Department of Health and Environmental
Control identifies “Capacity Use Areas” that require
a plan to be drawn up and followed. Groundwater
users must be permitted in these areas, and permits
are subject to review every 5 years. As part of these
plans governments in these areas are taking significant steps to reduce their dependence upon failing
groundwater supplies. In Horry County, most of the
municipal water systems have shifted from groundwater to surface water supplies, using the increasingly saline wells as only backup systems.
Figure 1–16
1-23
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Currently, there are four capacity use areas established. The Waccamaw Capacity Use Area comprises
Horry and Georgetown Counties. The Low Country
Capacity Use Area comprises Beaufort, Colleton,
Hampton, and Jasper Counties. The Trident Capacity
Use Area comprises Charleston, Berkeley, and Dorchester Counties, and the Pee Dee Capacity Use Area
comprises Darlington, Dillon, Florence, Marlboro,
Marion, and Williamsburg Counties. For each of
these there is an action and permitting plan to protect
long range use and quality of the water supply. These
areas can be seen in Figure 1-16.
Capacity Use Areas within South Carolina delineate groundwater use areas with identified water
and or water use issues.
(210-vi-NEH, January 2014 – SC)
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(5) Groundwater Quality
General – Ground water quality for irrigation is
generally good to excellent in South Carolina. At
points along the coast, salt-water intrusion is becoming a problem; and inland there are scattered places
where salinity or sulfur limit use. Probably the most
widespread problem concerns acidity (alkalinity) and
dissolved solids and their effect upon metal parts of
irrigation systems.
Temperature – In general, temperature of ground
water is about the same as mean annual air temperature at the water table and increases to more than
100° F at depths greater than 2500 feet. Temperature
of water from very shallow wells or from very small
springs varies seasonably but temperature of water
from deeper aquifers changes very little. Temperature
of shallow ground water ranges from about 64 to 69°
F in the Coastal Plain and slightly cooler north of the
Fall Line to below 60° F in the mountains (Personal
Communication, G. Patterson, USGS, Columbia, SC)
Dissolved Solids and Acidity – The pH and alkalinity increases going from the west toward the coast
within the range from about 4.0 to 9.0 (pH) with alkalinity less than 1 to greater than 1,000 mg/L. Values of pH are generally between 6.0 and 8.6. (personal communication-Glenn Patterson, USGS, Columbia, SC) At the lower end of the pH range, (acid)
damage may occur to well casings, screens, pumps,
and the metal parts of the irrigation system. Both
acidity and low total dissolved solids, which are
known causes of corrosion, are recognized problems
in several center pivot systems in Lee and Sumter
Counties. Some steel pipes have been severely corroded and have failed after only two to five years use.
Results of chemical testing, provided by the Water
Resources Commission to irrigators, indicate the
probable cause of deterioration of pipes in this area to
be a combination of these two problems (acidity and
low total dissolved solids). However, there may be
some other contributing source not yet investigated.
At the opposite end of the pH spectrum alkalinity can
also create problems. In certain areas boron dissolved
in alkaline water may exceed recommendations for
this micronutrient in certain crops.
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within aquifers. Technical personnel are encourages
to discuss the acidity and dissolved solid problems
with irrigators to make them aware of the known potential problem areas and the need to have their water
analyzed. In most cases, alternate sources or aquifer
levels are available.
The water source for the known problem sites is primarily the Tuscaloosa (Middendorf) aquifer. The
suspect area is a strip along the fall line including the
upper Coastal Plains from Augusta, Georgia, through
Chesterfield, South Carolina. Future ground-water
investigations to be conducted by the Water Resources Commission will provide additional data to
better define the area and refine treatment procedures.
It is recommended that irrigators have their water
supply analyzed to determine the water quality,
whether surface or subsurface source is being used.
This can be accomplished at the Clemson University
Agricultural Services Laboratory
(http://www.clemson.edu/public/regulatory/ag_svc_l
ab/ ) There are also many commercial companies that
provide comparable analyses of water sample.
For specific information about water quality in a particular location, landowners should address inquiries
to their local Department of Health and Environmental Control Office. The Departments operates its own
well water testing program, although its principal
clients are residential well owners.
More information about water quality defects and its
impact on irrigation can be found in Chapter 13 of
this Irrigation Guide (NEH 652).
Variation by source – Water quality varies significantly between aquifers and even between layers
(210-vi-NEH, January 2014 – SC)
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(e) Irrigation Development in
South Carolina
(1) General
Irrigation in South Carolina proceeded, as in other
areas of the Southeast, through private investments of
individual farm businesses and operators. Water
could be withdrawn directly from the plentiful
streams and rivers cutting through or bordering those
farms. Farmers dug out ponds and trenches in areas
with high water table or constructed impoundments
to retain runoff and seepage for ponds that could be
used for irrigation as well as for livestock and other
uses.
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deliver enough water to spread across a practicalsized field. Often, extensive land-leveling work is
needed to plane or terrace fields for this use. Heavy
showers and tropical storms may add unwanted, excess water that must be removed from fields. A system of tail-water drainage also becomes a necessity.
Water delivery and drainage require coordinated efforts among land holders.
By 2000, about 2200 acres of surface irrigation remained (Smith, 2000), only 1.5 percent of the states
total irrigation. Of that 75 percent was supplied by
flooding from ditches and the rest from use of layflat
pipe.
SubIrrigation: Though not a widely applied irrigaCrops are irrigated by South Carolina farmers for
several reasons: increasing overall profitability, stabilizing income over dry as well as wet years, and insuring they can meet contractual obligations including marketing agreements, operating loan and other
farm indebtedness. Irrigation allows farmers to enter
new enterprises such as vegetables or other produce
for fresh and processing markets. Turfgrass sod can
be grown for sale, and ornamental plants may be
grown in-ground or in containers for wholesale markets. Irrigation increases the overall efficiency of
crop land and investments that must be made annually for crop production. Expensive land preparation,
seed and seed technology fees, fertilizers, fuel, and
agrichemicals can be wasted when drought lowers
crop yield or crop quality. Beginning in the late
1980s, South Carolina farmers began a conversion of
their farming practices from dryland to irrigated.
tion practice in the U.S. subirrigation does find uses
in certain South Carolina fields where drainage is
necessary to make a field productive. By decreasing
the spacing of subsurface drains or seepage ditches in
a field, the drainage system can be used in reverse to
maintain a water table shallow enough to meet crop
water needs. The practice developed and studied in
nearby North Carolina flatwoods in the 1980’s was
installed in about 3600 acres that had the select conditions to make it feasible and economic.
Sprinkler Methods: In South Carolina, the agricul-
When farmers convert fields from non-irrigated to
irrigated production, they have several options for
irrigation equipment, but also several limitations.
tural rolling topography and sandy topsoils, as well as
small land holdings, made extensive use of surface
irrigation and subirrigation impractical. As a result of
these difficulties, flood and furrow irrigation, so
common in the Western US and elsewhere around the
world, never became widely established in this state.
That was fortunate since these methods typically
have a low water use efficiency. As Farahani et al.
(2008) point out irrigation system efficiency and uniformity can be improved to 85% for many sprinkler
systems and to even 95% with drip irrigation.
Surface Irrigation: In many areas of the world, in
Portable Pipe Systems: Early sprinkler irrigation
the western US, and even in the Mississippi Delta as
well as Florida flatwoods, the first choice of irrigation was often surface irrigation. That held true for
limited number of locations in South Carolina’s flatwoods. For surface irrigation, water is distributed by
flooding the field or channeling water down long furrows. These distribution techniques typically require
an infrastructure of canals or very large pumps to
in South Carolina was accomplished with portable
pipe and impact sprinklers. Portable pipe usually involved 20 foot sections of aluminum pipe latched
together. Sprinklers were often attached on vertical
riser pipes on every 2nd to 4th section. Parallel rows
of pipes left risers in square or diamond patterns with
overlapping patterns to effectively cover the crop.
(2) Early Irrigation
1-25
(210-vi-NEH, January 2014 – SC)
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Introduction
Figure 1–17 Portable pipe removed from fields
after final irrigation.
When pipe was limited, it had to be moved after each
irrigation set - each part of the field. It was very labor
intensive to set up irrigation in the field after the crop
was established. For tractor operations like spraying
pipe had to be moved, and then pipe had to be completely dismantled and removed before harvest could
begin. Large fields were impractical to irrigate, so
most crops that were irrigated were high value crops
like tobacco. Despite the labor requirements, almost
any field shape, soil, or crop could be irrigated this
way. Portable pipe still finds some use in plant and
tree nurseries.
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Figure 1–18 Peach orchard equipped with solidset sprinklers on tall risers for frost
protection. In-season irrigation is accomplished by
micro-sprinklers (blue and red sprinklers fed from
plastic tubes.)
Solid Set Sprinkler Systems: While portable pipe
is seldom found on South Carolina farms today, their
successor - solid-set sprinklers - remain in use in certain orchard, vegetable, and ornamental applications,
especially where frost protection may be needed
(blueberries, strawberries, etc.) In modern solid set
systems, water is distributed by buried plastic pipe
and a manifold of distribution pipes carries water
from pumps to different zones within a field or orchard. Like their counterparts in home lawns, the system lends itself well to automation. Timers or other
automation will assure that irrigation is regularly applied. Any size or shape field can be irrigated with
these systems. These systems are expensive; materials cost $1500/ acre and installation is labor intensive. Their use is limited today to high cash value
crops. Solid set systems accounts for fewer than 4%
of all systems in South Carolina (Smith, 2000).
Figure 1–19 Solid-set sprinklers on a turf farm
(210-vi-NEH, January 2014 – SC)
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Traveler Systems: As farm labor shortages grew,
farmers looked for other tools for irrigation. Portable
systems, generally classified as "travelers", were a
common entry-level irrigation system. Travelers included several designs that dragged a cart with a
large water cannon, as well as a large hose, through
the field. Large sprinklers delivered water over 100
feet, but they required pumps capable of delivering
200 to 500 gallons per minute at high pressure. The
high pressure spray to spread water over large areas
used considerable energy, and the resulting high trajectory spray was subject to water losses by evaporation and drift. Typically, application efficiency over
the course of a day was 50% or less. The high pressure sprays precluded their use on large tree crops,
except for initial establishment, and soil splash, compaction and potential runoff limits their use in vegetable crops. Most tied up a tractor for power and anchor, and they required an alley of cropland be cut
out for the hose and cart. Once a run was started, the
irrigation could proceed several hours unattended, but
shutdown for pumps and travelers was not reliably
automated.
Figure 1–21 Hose-reel traveler parked at edge of
field ready for its next use.
Farmers who used travelers regularly and repeatedly
during the growing season set up rows of risers connected by underground pipe to the pump. They preferred rectangular fields where a riser could be used
for irrigation runs in two directions perpendicular to
the row of risers.
Figure 1–20 Big gun (traveler) irrigation a tobacco crop.
Any shaped field could be irrigated by travelers, but
the pattern of cart movement was always in a straight
line or gentle curve. With a sprinkler spraying an
even pattern on both sides of the travel path, the wetted path of a single run looked like a hot-dog
stretched throughout a field. To cover all areas of an
unevenly edged field meant that some water had to be
directed out of the field into surrounding vegetation,
buildings, or highways. Alternatively, only part of a
full crop field would receive water.
1-27
Figure 1–22 Traveler systems operating in an odd
shaped field.
Travelers are sometimes used for drought rescue irrigation, including pastures. With drought rescue, a
farmer doesn't plan a full-season control of the crop's
water needs. Instead, irrigation will be set up to save
a crop that is severely threatened by long rainless
periods.
(210-vi-NEH, January 2014 – SC)
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Center Pivot Systems: The real growth in irrigated area in South Carolina began in the early 1990's as
center pivots began to move here. This was 10 to 20
years later than a similar boom in Georgia, and it is
likely that competition among cotton, corn, and soybean producers there prompted some of that growth.
South Carolina has smaller groundwater resources
than Georgia, and its Coastal Plain has a greater percentage of flatwood soils, so it is unlikely that the
state can develop a proportional area of the state in
center pivot irrigation. Early growth in Georgia occurred as poorer pine forests on sandy soils were
cleared. It appears that most pivot construction in
South Carolina took place on existing cropland, although those fields may be expanded to allow the pivot to operate effectively.
Figure 1–23 Heavy spray from the sprinkler temporarily knocked down leaves of this
crop, showing the pattern of spray and movement of
this traveler.
Travelers are sometimes used for drought rescue irrigation, including pastures. With drought rescue, a
farmer doesn't plan a full-season control of the crop's
water needs. Instead, irrigation will be set up to save
a crop that is severely threatened by long rainless
periods. With their portability, they can be dragged
into fields that have a nearby water source like a
pond. Portable pumps, often on wheeled trailers, and
portable pipe can be brought in quickly to supply the
traveler. This temporary setup requires considerable
labor for each travel run.
In general, fields described and labeled as irrigated
by travelers are not irrigated every year. In a fiveyear field monitoring study, fields described as traveler-irrigated typically received water only 50 to 75%
of the time even in drought years. In a wetter than
normal year, as many as 85% of monitored traveler
sites were not irrigated at all. (AWP, 2005). Traveler
systems reached their peak use in 1982 when 4,900
systems were in use in Georgia. By 2008, their use
had dropped to 2,100 as farmers found more permanent and reliable solutions for field crop irrigation.
(CES, 2009)
Figure 1–24 A pipe span is supported by a truss
rod structure and nozzles are attached to openings on the top.
Center pivots are well engineered structures that effectively deliver water to large fields. A main water
delivery pipe is suspended over the field out of the
way of the crops. Sprinklers or spray nozzles can be
spaced along that pipe to apply water wherever the
pipe is traveling. At each tower pipe sections are
connected with a flexible joint. The joint allows the
pipe to move through a limited range without twisting or breaking. This flexibility also allows vertical
bending that allows pivots to climb moderate
hillslopes.
(210-vi-NEH, January 2014 – SC)
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End guns are a common feature on most pivots in
South Carolina. The guns themselves are large impact sprinklers. They may throw water as far as 130
feet beyond the pivot hardware, although the effective watering radius would only be about 100 feet of
that. Adding 100 feet to the radius of the circle substantially increases the field area that can watered by
the pivot. For small pivot circle, say 25 acres, this
would increase area 36%, providing another 9 acres
of irrigated cropland. On a large pivot of 200 acres
the increase is only 12%, but 24 acres of irrigated
land are added using this single end gun.
Figure 1–25 Center pivots most efficiently cover
field areas when they are square-or
rounded, but when necessary other field shapes can
be operated in a partial circle.
Each pivot is designed specifically for the field in
which it is constructed. This is a process of matching
design criteria to available natural resources. Farmers
usually try to build out the pivot hardware as far as
possible in a field. Fences, property lines, highways
and barns, wooded areas, power poles, and ponds are
common obstructions that limit the length of the pivot pipe. These rarely surround the field in a circular
pattern. End guns allow water to be thrown beyond
the pipe length into outlying parts of the field where
crops can be grown. In these cases, "end gun shutoff
devices" may be used to turn off water to the end gun
when it would spray out into uncropped areas.
1-29
Figure 1–26 Large impact sprinklers - end guns extend the reach of the pivot. Together with overhang pipes, they can add irrigation to
areas where the pivot towers cannot travel.
Center pivots owe their popularity to their convenience and durability. During the growing season, a
single worker can go to the field, throw a few switches or set automated control panels to power and operate the unit and its attached pumps. A pivot is usually
left in unattended mode after that, while the systems
safeties will keep the unit operating within design
limits or shut it down it something fails. Center pivots are easily automated, tracked by remote monitors,
or even controlled remotely. Changes in sprinkler
packages can improve overall operating and especially water-use efficiencies.
(210-vi-NEH, January 2014 – SC)
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Drip and MicroSprinkler Systems: These efficient water application systems developed in parallel
with center pivots in South Carolina. Their special
applications in vegetables, orchards, vineyards, and
other crops important to the State led to adopting
these precision irrigation systems as they expanded
these high value operations. While center pivots now
apply most of the irrigation to farm lands in South
Carolina, drip and other micro-irrigation systems
have many advantages in vegetable, fruit, and other
specialty crops. Their use in small fields is increasing
as more specialty crops are produced. Features common to these systems are partial root zone wetting
and minimal evaporative loss during irrigation.
Figure 1–28 Canteloupe (above), watermelon,
squash, and cucumbers may be produced on large fields with overhead irrigation or may
be produced on plastic mulch and irrigated by drip.
Figure 1–27 Drip tubing is exposed where the
plastic mulch is cut and pulled back
on these beds of staked tomatoes.
In some applications a micro-sprinkler is placed under a tree and a portion of the soil in the orchard
where the tree roots are located is sprayed. Water
may spray out a few feet or a dozen or more feet, depending on the size of the tree and its canopy. In other micro-irrigation applications, emitters are very thin
tubes. During the irrigation cycle, water drips out of
the ends of the tube like a leaky faucet. The small
tubes allow the water to be placed a few feet from
water delivery lines. Interior diameter and length
control the flow rate. Weights may be added at the
ends to keep them in the right place. Both microsprinkler and tubing emitters are found where plants
like trees and shrubs will be in place for several
years.
Figure 1–29 Eggplant (above), tomato and pepper
are among several staked vegetables
Grown under plastic and irrigated by drip systems.
Drip and other micro-irrigation systems often require
complex distribution and control systems. Although
the slow drip of emitters and weak streams from micro-sprinklers give the appearance that little water is
being applied, a quick calculation shows the combined application of emitters to a field or orchard is
quite large. For example to apply as much as 0.35
inch of water a day during peak use times would require 6.5 gallons per minute for each acre, and the
(210-vi-NEH, January 2014 – SC)
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Introduction
pump would have to run all day and night. For a 50
acre orchard, this would mean pumping continuously
at 325 gallons per minute. Water pressure would have
to be carefully managed as pressure is stepped down
from pump operating pressures to the 10 pounds per
square inch that drip and distribution tubes require.
Because water pressure decreases as it travels along
the drip/distribution tubes, the length of these drip
tubing sections must be considered. The result of
these hydraulic considerations is that each drip
system must be carefully engineered and installed to
operate effectively. Usually zones - smaller field or
orchard areas - are irrigated separately. This allows
for down time of pumps and infiltration and drying
cycles for soils. Electronic controls allow swithching
between zones and they control the length of time
each zone is irrigated.
Subsurface Systems: Subsurface drip irrigation
(SDI) is one form of micro-irrigation that can be used
in row crops.With SDI, a drip tube with in-line
emitters is buried to depths of 8 to 16 inches. It has
only recently come into use in the state. Difficulties
with establishing a crop (the water may not reach up
into the seed germination zone in many applications),
and challenges with tillage (avoiding damaging the
relatively long-term buried tape) are reducing the
adoption of a potentially efficient irrigation system
for row crops.
Figure 1–30 Buried tubing of subsurface drip irrigation (SDI) makes the installation
Expensive, but all of the water is placed into the root
zone for potentially very high water use efficiency.
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(3) Current Irrigation Practices
Recent mapping using 2011 orthoimagery from the
from National Agricultural Imagery Program’s county mosaics provided an updated view of what irrigation practices were prominent and where they were
located in South Carolina (James E. Hook, personal
communication). Fields with visible irrigation features or typically irrigated crops were drawn for 24 of
the State’s 46 counties. These were the counties with
the greatest irrigated area in the most recent South
Carolina Irrigation Survey – the 2000 survey
(http://www.clemson.edu/irrig/acreage.htm).
Of the more than 1600 center pivots that were
mapped, irrigated area averaged 66 acres and ranged
from part-circle systems that covered only 3 acres to
large pivots covering almost 400 acres. About 36% of
the center pivots could only operate in a part-circle
pattern that ranged from 20% to 95% of a full circle.
These latter operate in a back and forth irrigation pattern that somewhat lowers their flexibility and increases per acre costs of ownership and operation.
Obviously, farmers have found that the advantages of
using center pivots in corners and rectangular fields,
or places where buildings, power lines, and other obstructions exist simplicity outweigh any additional
inconvenience or unit cost.
Relatively few towable pivots remain in South Carolina. Only about 3.5% of center pivot-irrigated fields
relied upon these units. Towable pivots represent an
entry-level into pivot ownership, and they work in
selected rotations, but most farmers find that once
they have irrigation, they would prefer that it be
available for every field as needed. The extra labor
needed to move these unwieldy devices leads most
farmers to buy a second pivot as soon as they can
afford it.
A few large Linear Move systems have found their
way into South Carolina. These require either a towable hose for water supply or a water-filled ditch parallel to the direction of linear movement. In a few
Carolina Bay sites, level fields, existing drains, and
possibly experience with surface irrigation have enabled farmers to install large field systems that cover
as much as 800 acres each. The limited number of
suitable sites will prevent Linear Move systems from
making inroads in South Carolina.
(210-vi-NEH, January 2014 – SC)
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Introduction
(f) Regulatory Environment for
Irrigation
(1) General
Irrigation in South Carolina proceeded, as in other
areas of the Southeast, through private investments of
individual farm businesses and operators. Water
could be withdrawn directly from the plentiful
streams and rivers cutting through or bordering those
farms. Farmers dug out ponds and trenches in areas
with high water table or constructed impoundments
to retain runoff and seepage for ponds that could be
used for irrigation as well as for livestock and other
uses.
Many areas of the state are underlain by highyielding aquifers that can sustain pumping for irrigation. Land owners tapped these water sources with
wells located on their property, often in the immediate vicinity of the fields needing irrigation.
With water directly available to most farms, there
was no need for major reservoirs, canals, or pipelines
to support irrigation. Likewise there was no need for
water management districts or agencies to manage
and regulate water distribution for agriculture irrigation.
Water withdrawals for agriculture were unregulated
through the 1980’s and 1990’s while irrigated land
area began to grow in South Carolina. Irrigation water supply did not require state or federal investments
and the accompanying government control. Infrastructure was developed and withdrawals controlled
by many individuals in an economic sector that traditionally shunned regulation. Agricultural irrigation
created a diffuse system of water withdrawals whose
impact was difficult to ascertain. With no restrictions
in place, farmers invested in equipment and operated
them strictly based upon their business needs.
The first regulations on agricultural withdrawals did
not come because of irrigation, but irrigation became
wrapped up with state and regional efforts to protect
shared water supplies. Water users along the lower
coastal areas of Charleston and Hilton Head found
evidence of increasing salinization in wells that supplied drinking water, irrigation for homes and golf
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courses, and water for commercial and industrial
needs. Salinization occurs in coastal areas primarily
when hydraulic head in those aquifers drops below
mean sea levels. While the impact is felt most immediately in areas adjacent to the ocean, withdrawals
throughout the aquifer contribute to those declining
heads.
In 2001, the South Carolina legislature passed laws
requiring the state’s Department of Health and Environmental Control (DHEC) regulate withdrawals in a
way that would provide long term protection of these
aquifers. Competition for water withdrawals to support the State’s growing industrial base and expansion of residential areas and improved agricultural
production have led to limited expansions of controls
and reporting in other areas of the state.
Also in 2001, South Carolina, in the midst of a 5-year
drought that taxed all water resources in the state,
implemented a drought mitigation act. The act was to
include significant user input in deciding what, where
and how water restrictions would be put in place.
In 2010, surface waters of the state came under similar scrutiny and control. The State and its cities became concerned with their ability to supply water for
drinking and commercial interests during periods of
extended drought experienced during the 1990’s and
2000’s. Surface withdrawals impact water destined
for reservoirs that were developed to provide hydropower, recreation, and other uses. Stream flows may
drop below levels needed to meet waste assimilation
requirements for discharges that the state has already
permitted. Withdrawals for irrigation, in particular,
lower summer flows when needs for waste assimilation and aquatic habitats protection are most critical.
South Carolina’s legislature creates laws in accordance with federal laws and regulation regarding land
and water and provides state-specific laws in accordance with the needs and wishes of its citizens. Those
laws affecting soil and water use, management, and
protection are encoded and made public through the
States website:
http://www.scstatehouse.gov/code/statmast.php. Most
of the laws regarding water fall under Title 49 of S.C.
Code of Laws.
(210-vi-NEH, January 2014 – SC)
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Introduction
South Carolina’s Department of Health and Environmental Control (DHEC) and its oversight boards
bear responsibility for creating and implementing
regulations in accordance to South Carolina code affecting water users, including agriculture. Information on their official website will contain the most
current regulations regarding surface and groundwater withdrawals and should be consulted for up-todate regulations, forms, and procedures:
http://www.scdhec.gov/.
As noted below, there are two exceptions to the
DHEC agency authority. Rules regarding drought
are, for the most part, handled by the Department of
Natural Resources.(http://www.dnr.sc.gov/) Regulations regarding chemigation and fertilizer use in irrigation are managed by The Division of Regulatory
and Public Service Programs at Clemson University
under authority given in the Pesticide Control Act.
(http://www.clemson.edu/public/regulatory)
(2) Surface water withdrawals
SC DHEC regulations regarding surface water use
are based upon S.C. Code of Laws, Title 49, Chapter
4, currently entitled “Surface Water Withdrawal,
Permitting Use, and Reporting Act.” The code is implemented through regulations R.61-119, “Surface
Water Withdrawal, Permitting and Reporting,” effective June 22, 2012. Accordingly, “it establishes a system of rules for permitting and registering the withdrawal and use of surface water from the state of
South Carolina and those surface waters shared with
adjacent states.”
The Regulations – For withdrawal quantities exceeding 3,000,000 gallons during any one month,
DHEC specifies permitting, registration, use, and
reporting requirements. Agricultural irrigators are
included in these requirements, but there are specific
exemptions that affects them.
First, persons withdrawing water for agricultural purposes are required to register that use, as opposed to
obtaining a permitting.
Second, withdrawals from farm ponds (defined as
ponds completely situated on private property) that
are used for providing water for agriculture purposes,
including irrigation, are exempt from the requir
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ments of R.61-119.
More generally, the act makes an exemption for a
person withdrawing surface water from any pond
completely situated on private property and which is
supplied only by diffuse surface water (i.e. nonconcentrated surface runoff), or supplied by springs
completely situated on the private property, or supplied by groundwater. The groundwater use, however, would still be subject to provisions of the R.61113, “Groundwater Use and Reporting,” effective
June 23, 2006.
Despite the exemption for withdrawals from farm
ponds, irrigators are specifically allowed to obtain a
permit for this use or to register for this use. For the
farmer with varied sources of water, some of which
do require permitting or registration and reporting,
obtaining a permit for all wells may be preferred. It
would allow a systematic management of permitting
and pumping records. Perhaps, more importantly,
courts historically protect the rights of established
users who can document reasonable and beneficial
use of the resource. Should laws change or interstate
compacts dictate future use restrictions, a water user
with a permitted or registered and documented use
pattern may stand on stronger ground than a user
without records. Irrigators may want to consult legal
counsel before choosing the exemption rather than
permitting or registering farm pond withdrawals.
Irrigators with non-exempted surface water withdrawals that existed prior to January 1, 2011 were
required to register that use or obtain a permit prior to
December 20, 2012 (180 days after the effective date
of R.61-119.)
Irrigators needing to increase non-exempt withdrawals and irrigators who plan to create new withdrawals
after 2010 must register that intention or apply for
permits and follow other provisions of the Surface
Water Withdrawal Permitting and Reporting Act.
Registration procedures – Registration of agricultural surface water withdrawals provides DHEC with
the opportunity to determine if the proposed (or expanded) withdrawal quantity is within the safe yield
for that water source as of the time of the request.
DHEC will notify the applicant by registered mail
(210-vi-NEH, January 2014 – SC)
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Introduction
whether the registered surface water withdrawal is
within safe yield or whether some adjustments are
needed. The applicant is not authorized to install and
use the new source without the determination of safe
yield.
Application forms are provided and required information specified in the official web pages of DHEC:
http://www.scdhec.gov/environment/water/sfw.htm .
NRCS personnel may receive requests for assistance
from their cooperators for filling out those registrations. Specifically, quantity of surface water requested for withdrawal, in million gallons per month, at
each relevant withdrawal point is required. This
would be based upon the design capacity of the existing or pending intake structure (pump capacity, presumably). The type of intake, permanent or mobile, is
also needed.
Registration for each withdrawal point creates challenges for agriculture irrigation users. While some
long-term irrigation installations – fixed center pivots, buried drip tubing, solid set irrigation – the water
supply is often fixed, as well. A well is located at the
pivot point, a pump delivers water at a fixed location
on a pond, etc. Registering and reporting use for
these installations is a simple matter. These systems
are typically put to use each year.
Commonly, though, South Carolina irrigators rotate
their crops and with them they move their irrigation.
Vegetables may be planted for a few years in one
location and drip irrigated from one source. At some
point, the field’s productivity declines or market demand for the crop changes. The farmer will remove
the plastic mulch, tubing, and even parts of the water
distribution system. The existing drip field will be
idled or rotated into forage or row crop to rest the
soil, extract accumulated fertilizer, and suppress pests
and weeds. New or rested fields are then used for the
vegetables, and a new water withdrawal point put
into use.
Similarly, tobacco and other row crop farmers may
use traveler irrigation systems in droughty fields. The
application systems themselves and commonly the
pumps and pipe that supply them are portable. They
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are moved from one field and withdrawal location to
another, even within a growing season. Because of
the additional labor to use these, they are not put to
use every year.
Questions regarding the transferability of registered
or permitted withdrawal points, idling and annual
reporting for idled locations, and registration for
temporary locations will need to be addressed by
DHEC personnel.
Annual Reporting – Water withdrawals must be
measured by one of the methods stipulated in the
regulation. The user is responsible for installing and
managing the water or other meter. Surface water
withdrawals must be reported annually before February 1st on forms furnished by DHEC.
Previous Regulations and Reporting – Prior to
2011, reporting of agricultural water withdrawals was
under the authority of the SC Department of Natural
Resources (DNR) and implemented by their Regulations Chapter 121, Section 10. In this regulation, in
place between 2001 and 2010, farmers reported to
County Agents of the Clemson University Cooperative Extension Service, who in turn reported to DNR.
With the passage of Act 247 of the 2010 legislative
session, reporting functions were moved to DHEC.
Act 247 substantially amended S.C. Code of Laws,
Title 49, Chapter 4. The current (September, 2012)
on-line Regulations of DNR Chapter 121-10 do not
yet reflect this change.
(3) Groundwater withdrawals
SC DHEC regulations regarding groundwater use are
based upon S.C. Code of Laws, Title 49, Chapter 5
currently entitled “Groundwater Use and Reporting
Act.” The code is implemented through regulations
R.61-113, “Groundwater Use and Reporting,” effective June 23, 2006. Accordingly, “The Department
finds the standards and procedures prescribed are
necessary to maintain, conserve, and protect the
groundwater resources of the state.”
The Regulations – Unlike the surface water withdrawals, the requirement for groundwater withdrawal
permitting vary by location within the state. Based
upon study of drawdown, salt-water intrusion, com
(210-vi-NEH, January 2014 – SC)
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petition for water, and other aquifer and use information, DHEC has designated most of the lower
Coastal Plain as a “Capacity Use Area” (Fig. 1-31).
Permits are required for all groundwater withdrawals
in capacity use areas if withdrawal quantities will
exceed 3 million gallons per month in any month.
Outside of the Capacity Use area, groundwater users
will follow Registration procedures similar to agricultural uses of surface water. An exception is that
areas of the Upper Coastal Plain, and a few areas
north of the Fall Line, DHEC has designated a “Notice of Intent” (Fig. 1-31) area.
While permits for surface water withdrawal (for those
that are required) are issued for 30 years before renewal, permits for groundwater withdrawal in capacity use areas are issued for a 5 year period before requiring renewal.
The difference between this area and the remainder
designated Piedmont or “Registration” area (Fig. 131) areas is that the person who intends to construct a
new well or increase the rated capacity of an existing
well must notify the DEHC at least 30 days prior to
initiating the activity
Capacity Use Areas and Notice of Intent Areas within South Carolina delineate groundwater use
areas with specific regulations regarding drilling, withdrawal permitting, and reporting. (Source:
Wauchop et al. 2009)
Figure 1–31
1-35
(210-vi-NEH, January 2014 – SC)
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Introduction
Well Drilling – Separate legislation and regulation,
R.61-44, governs the permit required, notice of intent, and fees for drilling a new or replacement well
or for abandoning an unused well. Drilling, which
must be done be a South Carolina licensed well driller, is covered under provisions of R.61-71 “Well
Standards.” These standards stipulate slurries materials used in drilling and sealing of well casings, define
materials and procedures used for screens and well
casing, and describe final surface preparation and
well-head protection. Also, creation and reporting of
well logs during drilling are stipulated.
Normally NRCS personnel will not be involved with
the design and installation of wells or participating in
the record keeping and reporting of well logs. However, the desired pumping rate for the irrigation under
design may be specified by the agency. After the well
is completed, the actual sustained pumping rate and
depth to the static and pumping water levels will often be needed for the system design and economics.
The water quality may affect design elements, especially for drip and micro-irrigation systems.
Permit/Registration procedures – NRCS personnel may receive requests for assistance from their
cooperators for filling out permit applications, notice
of intent, or registration. Specifically, quantity of
groundwater requested for withdrawal, in million
gallons per month, from each well. This would be
based upon the design of the irrigation system.
Annual Reporting – Whether in a Capacity Use
area or not groundwater withdrawal quantities must
be reported to DHEC annually by January 30.
(4) Drought Regulations
SC DHEC regulations regarding drought mitigation
and water use restrictions are based upon S.C. Code
of Laws, Title 49, Chapter 23 currently entitled
“South Carolina Drought Response Act.” Unlike the
permitting and reporting of water withdrawals
drought mitigation and response planning is assigned
to the South Carolina Department of Natural Resources (DNR.) The code is implemented through
DNR Chapter 121 section 11, “Drought Planning
Response,” effective February 23, 2001. Under the
authorizing legislation, “The department shall formu-
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late, coordinate, and execute a drought mitigation
plan. The plan must be developed consistent with the
South Carolina Water Resources Planning and Coordination Act, as provided in Chapter 3 of Title 49.”
In effect DNR is required to monitor water flows and
levels in lakes and groundwater to determine if
drought conditions are developing in areas of the
state. The act specifically asks DNR not to be overly
broad in defining the areas of incipient drought conditions.
Through State and appropriate Local Drought Response Committees, the department must work to
develop a plan of action that identifies what levels of
drought will require action. The committees, made up
of all sectors of water users, must work with DNR to
identify which non-essential water withdrawals may
be curtailed for the different action levels.
DNR then has responsibility of providing information
to users and informing them if and how their use may
be curtailed. In the event of severe or widespread
droughts the Governor would be notified and he/she
may initiate emergency actions to protect life, health,
and property.
For agricultural irrigators, it should be noted that Title 49, Chapter 23 was substantially altered in the
2005 legislative session by Act 99. The current (September, 2012) on-line Regulations of DNR Chapter
121-11 do not yet reflect this change.
In effect, 2005 Act 99 added “agricultural irrigation
used for food production” to the list of “essential”
water uses, and hence exempting that use from potential disruption by drought mitigation actions of DNR
or any of its local drought response committees.
Also under 2005 Act 99, before water use for agricultural irrigation of non-food products can be curtailed,
farmers must be given the opportunity to request exemption on the basis of “critical economic loss” that
might occur under mandatory curtailment of water
use. Presumably, non-food crops include cotton, tobacco, sod farms, and ornamental plant nurseries.
These crops constitute a substantial portion of the
agriculture irrigation and economy in South Carolina.
(210-vi-NEH, January 2014 – SC)
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(5) Irrigating with Animal Waste
Irrigation using wastewater, slurries, or solids from
agricultural animal operations is covered by provisions of DHEC R.61-43, “Standards for the Permitting of Agricultural Animal Facilities.” Similar but
separate regulations cover swine, Part 100, and all
other animal wastes, Part 200. See below for Pollutant Discharge Permitting regarding large Confined
Animal Feeding Operations (CAFO).
The Regulations – Rules for both swine (Part 100)
and other animals (Part 200) allow spray application
of liquid animal manure using irrigation equipment.
This includes all methods of surface spray application, including but not limited to, fixed gun application, traveling or mobile gun application, or center
pivot application.
Section 110 of Parts 100 and 200 stipulate that on
manure utilization area, slopes cannot exceed 10 percent unless approved by DHEC. Animal manure irrigation systems must be designed so that the distribution pattern optimizes uniform application.
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Also, a system for monitoring the quality of groundwater may also be required for the proposed manure
utilization areas. The location of all the monitoring
wells would be approved by DHEC. The number of
wells, constituents to be monitored, and the frequency of monitoring would be determined on a case-bycase basis based upon the site conditions such as type
of soils, depth of water table, etc.
Spray application systems should be designed and
operated in such a manner to prevent drift of liquid
manure onto adjacent property.
(6) Irrigating with Municipal Waste
Irrigation with treated wastewater is covered by
DHEC Regulations R.61-9 “Water Pollution Control
Permits.” Specifically, R.61-9.505.42 sets the conditions applicable to special categories of Land Application Permits – irrigation with treated wastewater
using solid set, big gun, traveler, and center pivot
systems.
The Regulations – Land Application Permits stipu-
Hydraulic application rates will normally be based on
the agronomic rate for the crop to be grown in the
manure utilization area. However, the maximum rate
may be reduced below the agronomic rate to ensure
no surface ponding, runoff, or excessive nutrient migration to the groundwater occurs. Further the hydraulic application rate may be limited based on nutrient or other constituent loading including any constituent required for monitoring under this regulation.
late maximum rates of application, since most of
these systems are more concerned with safely applying as much of the treated wastewater as possible
rather than supplying minimum water needs of a forage or crop. The permits have stringent monitoring
and reporting procedures for groundwater and surface
water quality in and around the irrigation area, as
well as set-backs distances from drinking water wells
and water supply inlets. Setbacks also limit potential
for spray drift onto nearby properties.
Because runoff and redistribution of applied wastes
can be affected by water already in the soil profile,
the waste cannot be applied when the vertical separation between the ground surface and the seasonal
high water table is less than 1.5 feet at the time of
application (unless approved by the DHEC on a caseby-case basis, usually for something deemed and
emergency.)
Generally speaking, NRCS Cooperators would not be
involved with these treated wastewater land application systems for farm commodities, except for their
production of green-chop and hay that may be included in animal feed. However any such irrigation
or use of commodities and produce from treated
wastewater irrigation would be subject to conditions
of the DHEC Pollution Control Permit.
Conservation measures, such as terracing, strip cropping, etc., may be required in specific areas determined by the Department as necessary to prevent potential surface runoff from entering or leaving the
manure utilization areas.
DHEC also has Pollution Control Permitting provisions (R.61-9.505) for similar irrigation using municipal sewage sludge.
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(210-vi-NEH, January 2014 – SC)
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Introduction
Animal wastes generated at existing large CAFOs
also fall into the provisions of DHEC regulations
R.61-9 requiring Pollution Control permits. Irrigation
involving treated wastewater (lagoon effluent) or
slurries and solids from these large operations will be
handled much the same as treated wastewater and
sewage sludge. These provisions kick in when animal
production equals 1,000,000 pounds or more normal
production live weight for swine. Per provisions of
R.61-43.100.110, regarding the Permitting of Agricultural Animal Facilities, new large swine facilities
with 1,000,000 pounds or more normal production
live weight are prohibited from utilizing spray application systems for manure application. Manure must
be incorporated into the manure utilization fields utilizing subsurface injection at a depth of not less than
six inches.
(7) Applying chemicals using irrigation
Regulations regarding irrigation to apply fertilizers
and chemicals are encoded under South Carolina Department of Agriculture Title 46, Section 46-1-140.
They include the requirement that irrigation systems
designed or used for application of fertilizer, pesticide, or chemicals be equipped with anti-syphon device. Clemson University’s Division of Regulatory
and Public Service Program enacts the law using regulations R.27-1090 that defines the Chemigation Act
and its general provisions; R.27-1091 that provides
provisions for the Act’s enforcement; and R.27-1092
that gives the actual (plumbing) specifications for
backflow prevention in agricultural irrigation systems.
The Regulations – Any irrigation system which is
designed or used for the applications of fertilizer,
pesticide, or chemicals must be equipped with an anti-syphon device adequate to protect against contamination of the water supply. The minimum acceptable
anti-syphon device shall include a check valve, vacuum breaker, and low pressure drain on the irrigation
supply line between the irrigation pump and the point
of injection of fertilizer, pesticide, or chemicals. The
vacuum breaker must be upstream from the check
valve. The low pressure drain must be upstream from
the vacuum breaker. The injection pump must be tied
to the irrigation pump either mechanically or electrically so that the injection pump shall stop operating if
the irrigation pump fails to function.
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Any person who uses an irrigation system for the
application of fertilizer, pesticide, or chemicals which
is not equipped with an anti-syphon device as required by this section is subject to a civil penalty of
not more than five hundred dollars. Each day's violation is subject to an additional fine.
The Division of Regulatory and Public Service Programs at Clemson University shall formally announce regulations with the advice of the Department
of Health and Environmental Control as it considers
necessary to implement this section and is also
charged with enforcing this section.
According to the regulations, all new and prior-use
chemigation activities were to be brought to code by
June 1988. The regulations stipulate that individual
applications of fertilizers and agrichemicals injected
into the irrigation system must be recorded, and those
records must be available for inspection for a period
of 2 years. Farmers must immediately self-report any
spills or suspected backflow events to the Division at
Clemson University.
The Division at Clemson University was chosen because they implement the South Carolina’s Pesticide
Control Act. This includes training programs regarding pesticides, licensing and renewal of applicators,
and record keeping. It should be noted any
agrichemical application using irrigation must be
made in accordance with the pesticide label.
For those pesticides which specifically are permitted
for irrigation application care should be taken to follow special formulation, mixing, and potential water
quality concerns that may cause undesirable reactions
with the chemical. Some pesticides, such as fungicides or insecticides that must adhere to the leaves
will require oil or similar based formulations to get
the material to “stick” to the leaves as the large volume of irrigation water is being applied. Other chemicals that become active in the soil should be in soluble or emulsified formulations that wash off and enter
the soil with the water. Complete flushing of the irrigation application equipment is required at the end of
the any chemical injection application cycle.
(210-vi-NEH, January 2014 – SC)
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