MENANAM POHON
UNTUK
MEMANEN AIR HUJAN
GROUNDWATER
Soemarno - psdl ppsub 2013
GROUNDWATER USE AND RECHARGE
There is a substantial amount of ground water recharge
from surface water and ground water used to irrigate
agricultural crops. Some of the irrigation water flowing in
unlined ditches and some of the water that is applied to
irrigate crops infiltrates into the soil, percolates through
the root zone and recharges the ground water basins
Ground water
Ground water occupies the zone of saturation. Ground water
moves downward through the soil by percolation and then
toward a stream channel or large body of water as seepage. The
water table separates the zone of saturation from the zone of
aeration.
The water table fluctuates with moisture conditions, during wet
times the water table will rise as more pore spaces are occupied
with water. Ground water is found in aquifers, bodies of earth
material that have the ability to hold and transmit water. Aquifers
can be either unconfined or confined. Unconfined (open) aquifers
are "connected" to the surface above.
AQUIFERS
The rate of ground water flow depends on the
permeability of the aquifer and the hydraulic
gradient. Permeability is affected by the size and
connectivity of pore spaces. Larger, better
connected pore spaces creates highly permeable
earth material. The hydraulic gradient is the
difference in elevation between two points on the
water table divided by the horizontal distance
between them.
The rate of ground water flow is expressed by
the equation:
Ground water flow rate = permeability X
hydraulic gradient
Groundwater flow rates are usually quite slow.
Average ground water flow rate of 15 m per day
is common. Highly permeable materials like
gravels can have flow velocities of 125 m per
day.
GROUNDWATER
Ground water in an aquifer is under pressure called hydrostatic
pressure. Hydrostatic pressure in a confined aquifer pushes
water upward when a well is drilled into the aquifer.
The height to which the water rises is called the peizometeric
surface. If the hydrostatic pressure is great enough to push the
peizometeric surface above the elevation of the surface, water
readily flows out as an artesian well.
www.uwsp.edu/geo/faculty/ritter/geog101/textb...
PROFIL LENGAS TANAH
Following an infiltration event, in which the entire soil profile becomes
saturated with water (indicated by a solid vertical line corresponding to a
water saturation of 1.0), water will drain from the soil profile primarily
under the influence of gravity (i.e., the pressure gradient is negligible).
Assuming that no additional water enters the system, the soil water
saturation profile at static equilibrium (dashed line) will decrease from a
value of 1.0 in the saturated zone (groundwater and capillary fringe) to a
value corresponding to field capacity below the root zone. In effect, the
soil water profile is analogous to a soil water retention (pressuresaturation) curve. Hence, the solid and dashed lines represent the limits
in water content (saturation) between which soil water percolation occurs
in soils overlying an unconfined aquifer.
www.informaworld.com/smpp/95829679-70617050/c...
Sumber: ga.water.usgs.gov/edu/earthgwdecline.html
Water is recharged to the ground-water system by percolation of
water from precipitation and then flows to the stream through the
ground-water system.
.
Water pumped from the ground-water system causes the water
table to lower and alters the direction of ground-water movement.
Some water that flowed to the stream no longer does so and
some water may be drawn in from the stream into the groundwater system, thereby reducing the amount of streamflow.
Contaminants introduced at the land surface may infiltrate
to the water table and flow towards a point of discharge,
either the well or the stream.
(Not shown, but also important, is the potential movement
of contaminants from the stream into the ground-water
system.)
Water-level declines may affect the environment for plants and
animals.
For example, plants in the riparian zone that grew because of the
close proximity of the water table to the land surface may not
survive as the depth to water increases.
The environment for fish and other aquatic species also may be
altered as the stream level drops.
11
SIKLUS HIDROLOGI DI ALAM
The fate of applied water can be better understood if the total hydrologic
cycle is understood first. The hydrologic cycle describes the movement
of water through its different forms and locations. Important processes
in the hydrologic cycle are:
1. Evaporation -the transformation of liquid water into water vapor from
free water surfaces.
2. Precipitation (rain or snow).
3. Runoff -water moving overland or in a river or stream.
4. Infiltration -the movement of water into the soil.
5. Percolation -the movement of water through the soil.
6. Freezing - liquid water turning into ice
7. Thawing - melting of ice
8. Transpiration - the movement of water vapor out through plant/animal
tissue surfaces into the atmosphere.
Sumber: www.forestry.ubc.ca/.../forwady/forwady.htm
HUTAN DAN SIKLUS HIDROLOGI
The surface water in a stream, lake, or wetland is most
commonly precipitation that has run off the land or flowed
through topsoils to subsequently enter the waterbody. If a
surficial aquifer is present and hydraulically connected to
a surface-water body, the aquifer can sustain surface flow
by releasing water to it.
In general, a heavy rainfall causes a temporary and
relatively rapid increase in streamflow due to surface
runoff. This increased flow is followed by a relatively slow
decline back to baseflow, which is the amount of
streamflow derived largely or entirely from groundwater.
During long dry spells, streams with a baseflow
component will keep flowing, whereas streams relying
totally on precipitation will cease flowing.
Generally speaking, a natural, expansive forest
environment can enhance and sustain relationships in the
water cycle because there are less human modifications to
interfere with its components.
A forested watershed helps moderate storm flows by
increasing infiltration and reducing overland runoff.
Further, a forest helps sustain streamflow by reducing
evaporation (e.g., owing to slightly lower temperatures in
shaded areas). Forests can help increase recharge to
aquifers by allowing more precipitation to infiltrate the soil,
as opposed to rapidly running off the land to a downslope
area.
Penebangan pohon berdampak meningkatnya
ancaman banjir
Forested areas provide storm water
protection and protect the quantity and
quality of groundwater
Forests and prairies rarely yield runoff
regardless of steepness, even when frozen
Groundwater –Surface Water Flows
16
Black Earth Creek Study
Wooded hill slopes
generate no
significant runoff
• Black Earth Creek receives 80% of its water from
groundwater
• Main recharge occurs in spring and fall
• Recharge from the agricultural uplands is highly variable
• Forested slopes are significant recharge areas
Pohon memperbaiki Kapasitas infiltrasi lapisan
tanah permukaan
Effects are greatest during the growing season
Effects are greatest on sites whose soils are
relatively impermeable
The impact of urban trees on hydrology is extremely variable and
complex, in general increases in tree cover and tree size over a site
will result in reduced total runoff amounts and peak runoff rates.
Pohon dan Storm Water
•
•
•
Trees have a relatively greater effect on smaller storm runoff
amounts than on large storm events
Surface and below-ground effects on runoff are much more
significant than the above-ground effects
All of the effects on runoff are greatest when urban trees are
large and well-established on undisturbed sites
Pohon memperbaiki kenyamanan thermal lingkungan
sekitarnya
Contact Information:
Mindy Habecker
Dane County UW-Extension 224-3718
Habecker@co.dane.wi.us
www.cropscience.org.au/.../1399_shahbazkhan.htm
22
Sumber: www.ene.gov.on.ca/envision/gp/4329e_1.htm
23
Sumber:
www.aucklandcity.govt.nz/.../hgiapp15.asp
Typical root systems are made up of a combination of four types
of roots:
major lateral roots
sinker roots
woody feeder roots
non-woody feeder roots.
25
Sumber: www.dof.virginia.gov/urban/landscape-manual.shtml
Tajuk pohon mengamankan lingkungan di
sekitarnya, di atas tanah dan di bawah tanah.
Tree and Root System on Bank of Darling River,
Kinchega National Park, Outback, New South
Wales, Australia
Sumber: en.allexperts.com/q/Trees-739/DouglasFir-Roo...
www.forestry.ubc.ca/.../forwady/f
orwady.htm
29
GROUNDWATER RECHARGE
Groundwater recharge or deep drainage or deep
percolation is a hydrologic process where water
moves downward from surface water to
groundwater.
This process usually occurs in the vadose zone
below plant roots and is often expressed as a
flux to the water table surface.
Recharge occurs both naturally (through the
water cycle) and through anthropogenic
processes (i.e., "artificial groundwater
recharge"), where rainwater and or reclaimed
water is routed to the subsurface.
http://en.wikipedia.org/wiki/Groundwater_recharge
GROUNDWATER RECHARGE
Processes
Groundwater is recharged naturally by rain and snow
melt and to a smaller extent by surface water (rivers
and lakes). Recharge may be impeded somewhat by
human activities including paving, development, or
logging. These activities can result in loss of topsoil
resulting in reduced water infiltration, enhanced
surface runoff and reduction in recharge. Use of
groundwaters, especially for irrigation, may also
lower the water tables.
Groundwater recharge is an important process for
sustainable groundwater management, since the
volume-rate abstracted from an aquifer in the long
term should be less than or equal to the volume-rate
that is recharged.
Recharge can help move excess salts that
accumulate in the root zone to deeper soil layers, or
into the groundwater system. Tree roots increase
water saturation into groundwater reducing water
runoff. Flooding temporarily increases river bed
permeability by moving clay soils downstream, and
this increases aquifer recharge.
http://en.wikipedia.org/wiki/Groundwater_recharge
GROUNDWATER RECHARGE
http://en.wikipedia.org/wiki/Groundwater_recharge
Trees and groundwater
This question of water sources for trees is not
easy to answer. During the wet season, rainfall
becomes surface run-off or enters the soil. Given
the high rainfall of the Top End, the soil’s
capacity to soak up water is soon exceeded and
water drains from the soil recharging shallow
groundwater aquifers or flowing through into
streams. During the dry season therefore, trees
could be using soil water exclusively, or
groundwater, or a mixture of both.
Excavations of root systems have revealed a
concentration of roots in the top 1-1.5 m of soil.
Further, large and small trees are able to flush
their canopies with new leaves during
September and October, periods when upper soil
moisture levels (top 2 m) are at a minimum and
the water table is around 10 m below the surface.
This leaf growth requires a considerable amount
of water and small trees do not have deep root
systems. This suggests they have adequate
access to water from the soil alone.
http://savanna.org.au/savanna_web/publications/savanna_links_issue
Trees and groundwater
Hypothetical root distribution for a mature Eucalypt tree
growing in the Darwin region. Figure modified from that of
Kimber (1974) The root systems of Jarrah. Forests
Department of Western Australia, Research Report No. 10,
5 pp .
http://savanna.org.au/savanna_web/publications/savanna_links_issue
Trees and groundwater
Surplus groundwater?
As part of the TS-CRC project, CSIRO scientists
Drs Tom Hatton and Peter Cook constructed a
water balance for the research catchment.
Using changes to aquifer CFC concentrations
with depth below ground, the rate of recharge
was estimated to be 200 mm year-1. This
includes a 20 mm ‘groundwater surplus’.
An error analysis suggests that this surplus may
be as small as zero, or as large as 140mm.
If we assume it is about 20 mm for a catchment
such as the Howard River, this represents a
sustainable yield of at least 2500 Ml of water per
year.
While we currently think groundwater extraction
is unlikely to threaten the eucalypt savanna,
other ecosystems may be vulnerable, such as
spring-fed monsoon vine forests.
http://savanna.org.au/savanna_web/publications/savanna_links_issue
Trees and groundwater
Hydrological cycle and water balance of Top End
tropical eucalypt savanna
http://savanna.org.au/savanna_web/publications/savanna_links_issue
deep drainage from tree belts
The clearing of natural vegetation for agriculture in southern
Australia has increased deep drainage, led to increased
groundwater recharge and, hence, the salinisation of land and
streams.
Alley farming systems, comprising alternate belts of trees and
crops, have been proposed for reducing deep drainage but their
effectiveness is unknown. This paper describes an application of
ecological optimality theory to estimate the equivalent no
drainage (ENOD) width B (m) for a tree belt.
The relative drainage RD from an alley farm, compared to
conventional agriculture is, therefore, 1 − B/W, where W is the
centre spacing of the belts. We present a method for estimating
BLA from the leaf area per unit length of belt LLA (m2 m−1), divided
by the leaf area index LAI (m2 m−2) of nearby natural vegetation.
Preliminary evaluation of BLA showed good agreement with BWB
measured from water balance and BDD measured from deep
drainage. The estimation of BLA for calculation of RD allows rapid
estimates of the relative drainage reduction expected from alley
farms in water-limited environments.
. An ecological optimality approach for predicting deep drainage from tree belts of
alley farms in water-limited environments
Tim Ellis, Tom Hatton, Ian Nuberg. Agricultural Water Management.
Volume 75, Issue 2, 15 July 2005, Pages 92–116.
Schematic diagram of a typical tree belt vegetation community of
an alley farm in a water-limited environment where Dc is the deep
drainage under the crop/pasture. The ENOD concept is a ‘step’
approximation (bold dashed line) to the likely actual deep
drainage (curvilinear line) such that areas a + b = c.
. An ecological optimality approach for predicting deep drainage from tree belts of
alley farms in water-limited environments
Tim Ellis, Tom Hatton, Ian Nuberg. Agricultural Water Management.
Volume 75, Issue 2, 15 July 2005, Pages 92–116.
Where ground water occurs
Rock materials may be classified as consolidated rock
(often called bedrock) and may consist of sandstone,
limestone, granite, and other rock, and as unconsolidated
rock that consists of granular material such as sand,
gravel, and clay.
Two characteristics of all rocks that affect the presence
and movement of ground water are porosity (size and
amount of void spaces) and permeability (the relative ease
with which water can move through spaces in the rock).
http://pubs.usgs.gov/gip/gw_ruralhomeowner/
Where ground water occurs
Consolidated rock may contain fractures, small cracks, pore
spaces, spaces between layers, and solution openings, all of
which are usually connected and can hold water.
Bedded sedimentary rock contains spaces between layers that
can transmit water great distances. Most bedrock contains
vertical fractures that may intersect other fractures, enabling
water to move from one layer to another.
Water can dissolve carbonate rocks, such as limestone and
dolomite, forming solution channels through which water can
move both vertically and horizontally. Limestone caves are a
good example of solution channels.
Consolidated rock may be buried below many hundred feet of
unconsolidated rock or may crop out at the land surface.
Depending upon the size and number of connected openings,
this bedrock may yield plentiful water to individual wells or be a
poor water-bearing system.
http://pubs.usgs.gov/gip/gw_ruralhomeowner/
Where ground water occurs
Unconsolidated material overlies bedrock and may consist
of rock debris transported by glaciers or deposited by
streams or deposited in lakes.
It also may consist of weathered bedrock particles that
form a loose granular or clay soil.
Well-sorted unconsolidated material can store large
quantites of ground water; the coarser materials—sand
and gravel—readily yield water to wells.
http://pubs.usgs.gov/gip/gw_ruralhomeowner/
Where ground water occurs
http://pubs.usgs.gov/gip/gw_ruralhomeowner/
Using Trees to Control Groundwater Recharge: How Many
are Enough?
Trees are important in preventing groundwater recharge
and are complementary to other methods, such as
establishing perennial pasture, improving crop
productivity and natural regeneration.
Trees are recommended for land where either perennial
pastures cannot b reliably established, will not persist or
will be unable to provide adequate protection from
groundwater recharge.
http://www.dpi.vic.gov.au/agriculture/farming-management/soil-water/salinity/usingtrees-to-control-groundwater-recharge-how-many-are-enough
Using Trees to Control Groundwater Recharge: How Many
are Enough?
How much water could trees use?
The reduction of groundwater recharge by vegetation depends
on its ability to use or evaporate water from the soil. the deep
root systems and large, evergreen crowns of many native trees
means they can use more water than other types of vegetation (e.
g pastures, crops, shrubs).Nevertheless, trees do not have an
unlimited capacity to use water.
Evaporation of water from trees or any vegetation, depends upon
three things:
1. Water - a tree can only use as much water as it has access to
in the soil (soil moisture). Soil moisture varies throughout the
year and is lowest during late summer and early autumn. The
maximum water use by a stand of trees growing in recharge
areas will be the annual rainfall. Surface run-off and recharge
that occurs between root systems, however, reduces the
potential water use.
2. Sunlight - the energy for evaporation comes mainly from the
sun. In most parts of Victoria it has the potential to evaporate
up to 1500 millimetres of water a year.
3. Leaf area - most evaporation takes place through the leaves.
As a tree grows its leaf area increases and so does its water
use.
http://www.dpi.vic.gov.au/agriculture/farming-management/soil-water/salinity/usingtrees-to-control-groundwater-recharge-how-many-are-enough
Using Trees to Control Groundwater Recharge: How Many
are Enough?
How much water do trees use?
The following information has come from recent research.
Table 1 Results of some Victorian investigations into water use
by eucalypts growing on recharge.
Location (rainfall)
Age (years)
Tree water uselitres per day and
range (average)
Burkes Flat
(450mm)
6
10-100 (30)
Warrenbayne (800
mm)
20
0-160 (50)
Warrenbayne
(800mm)
>100
10-450 (140)
Table 1 shows the variation in water use over a year by
eucalypts on recharge zones. The lower figures areduring
rainy days in winter and the higher figures are in early
summer before the soil moisture is depleted. Daily water
use by a tree therefore can vary considerably throughout
the year. The averages over the year are given in brackets.
Table 1 also shows that age (due to growing leaf area and
root system) also has a significant effect on the ability of
trees to use water.
http://www.dpi.vic.gov.au/agriculture/farming-management/soil-water/salinity/usingtrees-to-control-groundwater-recharge-how-many-are-enough
Using Trees to Control Groundwater Recharge: How Many
are Enough?
Table 2 shows the importance of stand density and water use. In
a paddock the amount of water any one tree uses has little
significance in recharge control. What is mostimportant is the
water use by the whole stand.
Table 2. Stand density and water use
Average tree
Stand
Stand
water use -from
density(trees
water
Table 1(litres per
per hectare) use(mm)
day)
Location
Tree age
(years)
Burkes Flat
6
30
200
200
Warrenbayne
20
10
20
35
Warrenbayne
over 100
140
20
105
http://www.dpi.vic.gov.au/agriculture/farming-management/soil-water/salinity/usingtrees-to-control-groundwater-recharge-how-many-are-enough
Using Trees to Control Groundwater Recharge: How Many
are Enough?
Opportunities for trees to control groundwater recharge
Since a tree's capacity to use water is limited, careful
planning is required to ensure that trees are effective in
controlling recharge. Planning must achieve a balance
between:
1. the amount of water to be evaporated;
2. the density of trees in the plantation;
3. what is an acceptable delay before the control of
recharge is achieved.
To calculate the approximate number of litres per day each
tree would have to average over the year, use this
equation:
No. of
Litres
per day
= water use required (mm a year) x 25
number of trees a hectare
This equation enables you to calculate whether or not you are
'asking too much' of your trees to achieve your required level of
recharge control.
If the most water we can expect a mature tree to evaporate
averages 140 litres per day (Table 1), it follows that to use a given
amount of water a minimum number of trees per hectare are
required. For example at least 100 trees per hectare are needed
to use 500 nun of rain per year.
To reduce the amount of time to achieve a certain level of water
use, more trees per hectare should be planted.
http://www.dpi.vic.gov.au/agriculture/farming-management/soil-water/salinity/usingtrees-to-control-groundwater-recharge-how-many-are-enough
Using Trees to Control Groundwater Recharge: How Many
are Enough?
How many trees are enough?
Dense plantations (at least 500 trees a hectare) are clearly
the best means of achieving rapid and effective control of
groundwater recharge.
However, recharge control will not always be compatible
with other land management objectives, such as
maintaining grazing or growing trees commercially.
Therefore the answer to the question of 'how many trees
are enough to control recharge?' must begiven for each
general type of rural tree growing.
http://www.dpi.vic.gov.au/agriculture/farming-management/soil-water/salinity/usingtrees-to-control-groundwater-recharge-how-many-are-enough
Using Trees to Control Groundwater Recharge: How Many
are Enough?
Protection and landscape plantings
Most tree growing in rural areas is for either protection (control
of land degradation, stock shelter) or landscape (visual beauty,
wildlife habitat) purposes.
Dense plantations will generally be needed to meet
theseobjectives. However establishment costs of these
plantations can be expensive, since no direct commercial returns
are expected.
Assuming a stand density of at least 400 trees a hectare (5 x 5
metre spacing) is necessary for protection and landscape
plantings, it may take around 10 years for the trees to control
groundwater recharge (depending upon rainfall and rate of
recharge).
Higher densities, can be relatively easily and cheaply achieved
through direct seeding or fencing areas off to allow natural
regeneration.These techniques can significantly reduce the delay
before achieving recharge protection.
http://www.dpi.vic.gov.au/agriculture/farming-management/soil-water/salinity/usingtrees-to-control-groundwater-recharge-how-many-are-enough
Using Trees to Control Groundwater Recharge: How Many
are Enough?
Trees in pasture
There are two forms of tree growing in pasture that may
play a role in the management of groundwater recharge
areas:
1. agroforestry - where both the trees and pasture are
managed to provide a commercial return, and;
2. low density protection plantings - where trees are
planted at a wide spacing to allow grazing to continue
but close enough so that some, and perhaps eventually,
complete recharge control is achieved.
Appropriate densities for tree growing over pasture are 20200 trees a hectare. At the lower range, recharge control
will only be very slowly achieved (50+ years) and will rely
on the trees not significantly affecting the evaporation
from the pastures below.
At densities lower than 20 a hectare (23 x 23 metre
spacing) the average daily water use to achieve a given
level of annual evaporation issimply asking too much of
the trees.
http://www.dpi.vic.gov.au/agriculture/farming-management/soil-water/salinity/usingtrees-to-control-groundwater-recharge-how-many-are-enough
How to Recharge Ground Water and Prevent
Contamination?
Rainfallis the main source of ground water recharge. Other
sources include rechargefrom rivers, streams, irrigation water
etc.
Rainfall is limited for a fixedduration, natural recharge of ground
water is restricted to a particular periodonly. Large volume of
rainfall flows into the sea and is evaporated. Since wecannot
depend on rains to recharge ground water we have to adapt
artifcialmethods that are low in cost, and easy to use.
http://kayjayr-akshay.blogspot.com/2012/05/how-to-recharge-ground-waterand.html
How to Recharge Ground Water and Prevent
Contamination?
Recharge by Dugwell Method:
There are thousands of dug wells, which have either gone dry, or
the water levels have declined considerably. These dug wells can
be used as structures to recharge the ground water reservoir.
Storm water, tank water, canal water etc. can be diverted into
these structures to directly recharge the dried aquifer.
http://kayjayr-akshay.blogspot.com/2012/05/how-to-recharge-ground-waterand.html
How to Recharge Ground Water and Prevent
Contamination?
Rain garden to recharge ground water:
Rain garden is designed to hold rain water runoff from roof
tops, drive ways, patios, or lawns. It contains native
shrubs, perennials, plants etc. Every time it rains, water
runs off impermeable surfaces, such as roofs or
driveways,collecting pollutants like particles of dirt,
fertilizer, chemicals, oil, garbage, and bacteria along the
way. The pollutant-laden water enters storm drains
untreated and flows directly to nearby streams and ponds.
Rain gardens collect rainwater runoff, allowing the water to
be filtered by the vegetation and percolate into the soil
recharging groundwater aquifers. This process filter out
pollutants.
The advantages of rain Garden are:
1.
2.
3.
4.
5.
6.
7.
Improve the water quality by filtering pollutants.
Pleasing appearance to the building.
Preserves native vegetation.
Provides strom water and flood control.
Attracts bees, birds, insects.
Maintenance is easy.
Helps in ground water recharge.
http://kayjayr-akshay.blogspot.com/2012/05/how-to-recharge-ground-waterand.html
How to Recharge Ground Water and Prevent
Contamination?
Rain-gardens
http://kayjayr-akshay.blogspot.com/2012/05/how-to-recharge-ground-waterand.html
How to Recharge Ground Water and Prevent
Contamination?
Phytoremediation to recharge Ground water:
In addition to all other above methods planting and
cultivation of woody trees help in replenishing ground
water conservation because the roots help in percolation
of rain water deep into the soil and keep the water table
steady. Cultivation of trees not only enriches the quality of
water but also raises the ground water table.
They also remove, transfer, stabilize, and/or destroy
contaminants present in the soil and in the ground water.
They clean up contaminated soil, sludge and ground
water.
This method of cleaning up ground water pollution and
maintaining the water table and soil contaminants using
different species of plants and trees is a low cost,
environmentally friendly and effective for a wide range of
chemicals such as pesticides, solvents,crude oil, poly
aromatic hydrocarbons and metals etc.
http://kayjayr-akshay.blogspot.com/2012/05/how-to-recharge-ground-waterand.html
How to Recharge Ground Water and Prevent
Contamination?
Phytoremediation to recharge Ground water:
http://kayjayr-akshay.blogspot.com/2012/05/how-to-recharge-ground-waterand.html