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TIle Divel·sity in Streanlfl()w RespOIlse froID
Upland Basins in A)~izo)la
Malchus B. Baker, Jr.1
A.bstract--Althou~lh water yield from a basin is a function of a number
of factors, soil depth is considered foremost in t~xplaining hydrograph
differences from study areas in Arizona. The most attenuated hydrograph
found was in the chaparral vegetation type, which has the greatest soil
dt~pth, whilethe most n~sponslveorpt~al<ed hydrographswerefound inthe
pinyon Juniper and ponderosa pine types, which have soil depths of 3 feet
or less.
Streamflow Response
In Arizona, most of the 97 million acre feet of precipitation
that reaches the soil is returned to the atmosphere and about
3%. runs off as streamflow (Hibbert 1979). Nearly all of the
water yield in Arizona is derived from 33(10 of the land area.
Water yields range from 0.4 to 5 inches, with the ponderosa
pine type contributing 59(10, pinyon juniper 27%., c,haparral
10%, and mbced conifer 4% of the streamflow.
Water yield is a functi.on of geology, soil, elevation, orie,n~
tati.on, vegetation, and climate. All of these factors modify to
various degrees the disposition of energy and precipitation
falling on an area and, therefore, the quantity of runoff or
hydrologic response. The keys to the type of hydrologic
response are (1) how far water must travel to influence
channel flow, and (2) the mechanism by which it is delivered.
Basins in Arizona have a large diversity of controlling factors,
and consequently produce a significant amount of variation in
streamflow response.
The shape of the hydrograph is an indkation of the
responsiveness of a basin, and is determined by the delivery
rate of water and length of the flow path to the source area. The
following spring streamflow hydrographs were produced
during the unusually wet water year of 1973. Bec.ause of the
large range. in strea.mflow response derived from these basins,
a wet water year wa.s selected to avoi.d the potentia.! problems
caused by local soil moisture deficits that affect watershed
response to precipitation and to snowmelt, and to insure that
an adequate amount of streamflow was ava.ilable. for visual
comparison of the hydrographs.
Streamflow in figure 1a is from the 3 Bar D chaparral
watershed. Parent material is coarse granite. Soil in the basin
includes all porous material in which weathering and roots are
active, and reaches depths up to 30 feet (Hibbert et al.1974).
Streamflow normally occurs about one third of the time..
October precipitation, which normally averages 2.7 inches
totaled 14.6 inches in 1972. This unusually wet month resulted
in the initiation of continuous flow from the normally ephemeral stream channel that continued throughout the remainder
of the water year and on until June of 1974. Spring snowme~t
bel~an on February 11 (fig. 1a) at a baseflow level of 0.5 ft 3
s-1 mi- 2 gradualJ-y rising to a baseflow rate of 3 ft 3 s-l mt2 on
April 5, which then gradualJ.y receded back to 0.5 ft3 s-l mt 2
on May 19. Peak discharges during this period were associated
with rain on snow events; the first, on February 12, reached 5
ft 3 5- 1 mi.. 2 . Discharge reached a maximum of 9ft3 s-l nU,-2 on
1\1arch 29. After each precipitation event, the general recession flow level was increased. Normal runoff to precipitation
ratio on this basi.n is 0.13 ..vhile the same rati.o for water year
1973 was 0.22 (table 1). Of the 11.4 inches of streamflow for
the year, 6.4 inches or 56% was produced during the period of
February through April.
Objecti\:es and Study Area
The objectives of this study were to select hydrographs
from basins that demonstrate the diversity in streamflow
response found in Arizona, and to identify the major factors
responsible for the diversity. These basins include 3 Bar D in
the chaparral vegetation type; three basins on the Beaver
Creek drainage in the pinyon juniper woodland and ponder~
osa pine types; and Castle ('reek, Thomas Creek, and ,\\Tork~
man Creek in the mjxed conjfer type. Characteristics of these
watersheds are presented in table 1. Addi.tional information
about these watersheds can be found in Baker 1986, 1984;
Hibbert et al. 1974; and Rich and Thompson 1974.
1Hydrologist, F~ocky Mountain Forest and Hange Experiment Station, Forestry Sciences Laboratory, Arizona State University, Tempe, Az.
85287.
211
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a. CHAP'ARRAL
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PRECIPIT A TION (mm)
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MARCH
FEBRUARY
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PRECIPrfATION (mm)
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PRECIPITATION (mm)
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c. ALLIGATOR JUNIPER
d. PONDEROSA PINE
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Figure 1.--Selected hydrographs demonstra.tlng diversity, In
streamfloVi response (metric SCille can be conver1ed tC) (13 s-1
ml-2 by dividing by 0.0109.
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MAY
212
during a warming period, along with a similar increase in the
slower subsurface flow component. Streamflow ended on
May 29, indicating the reduced water storage capacity of this
basin. Although daily peaks were generally greater than on the
c.haparral basin (fig.la), they were usually lower than from the
less densely covered alligator juniper basin (fig. lc). About
32% of the runoff produced during water year 1973 came
during the April through 1\fay melt pe.riod.
The streamflow hydrograph from the mixe.d comfe.r type
on the South Fork of ~Torkman Creek (fig. Ie) reflects the
higher water storage capacity of the basin (perennial
streamflow) and owerall lower responsiveness (generally
lower daily peaks) (fig.ld). Surface soils are loam to clay loam
in texture; subsoil varies in texture from clay loam to clay (Rich
and Thompson 1974). Soil de.pth varies from 2 inches to more
than 15 feet. Snowmelt initiation is identical to that on the
ponderosa pine basin at Beaver Creek (fig. 1d) but the daily
peaks and delayed flow rates are generally not as high. A
selection ha.n:est on South Fork removed 46% of the merchantable timber; a second treatment converted the entire
South Fork basin to ponderosa pine. with 40 ft 2 ac- 1 of basal
area. This heavy re.duction in overstory basal area has allowed
more energy to reach the snowpack, re.sulting in the higher
daily peaks from A pril5 to 20 than observed on the ponderosa
pine basin (fig.ld). However, daily peaks during the latter part
of April were smaller and snowmelt was essentially finished by
May 5 on ~Torkman Creek (fig. Ie) while continuing until after
May 15 on the pine basin (fig. 1d).1\fa.:rimum daily discharge
peak (derived entirely from snowmelt) reached 35 ft3 s-1
mt 2. Snowmelt lasted only } month ending with a major
rainfall derived peak of 72 ft.3 s-1 mt 2 produce.d by a storm
event of 2.7 inches.
Streamflow patterns from the mixe.d conifer on East Fork
of Castle Creek were similar to that on Workman Creek (fig.
1e) but more attenuated (fig. H). The Castle Creek area, at a
Figures Ib, c, and d are streamflow hydrographs produced
in three different vegetation types on the Beaver Creek
drainage. Soils on Beaver Creek are developed from volcanic
materials, primarily basalt, and depth is generally less than 3
feet. The soil typically has an A horizon that is 0.4 to 6 inches
deep. Snow melts in the Utah juniper (fig.lb) during the same
time pe.riod as in the chaparral type on 3 Bar D (February
through April). Streamflow from this basin is much more
responsive than from the c.havarral basin. Daily discharge
peaks are often over 10 ft 3 s~l mt 2 and usually return to zero
within hours, jndicating much faster travel time and shorter
flow paths. Saturate·d overland flow has been observed regularly during spring snowmelt on the Beaver Creek drainage. In
water year 1973, measured run()ff was 19% of the measured
annual precipitation, with 61% of the streamflow occurring
during the spring snowmelt period.
At a higher elevation, streamflow fluctuation in the alligator juniper type (~Tatershed 4) is also very high (fig.1c). The
daily peaks from snowmelt are~ more numerous and greater
than peaks on the Utah juniper or chaparral basins (figs. Ib
and a, respectively) reflecting the greater amount of snowpack
at the highe.r ele:vation and smaller amount of overstory basal
area on the alligator juniper basin. The highest peaks during
this snowmelt period resulted entirely from snowmelt, reac.hing 51 ft 3 s-1 00- 2 on 1\larch 19 and 73 ft3 s-1 mt 2 on Apri16.
Although streamflow did not go to zero until April 14, daily
lows often approached 1 or 2 ft3 s-1 mt2 . Periods of precipitation caused significant declines in flow by reducing incoming
energy needed to melt snow.
The snowmelt hydrograph from the basin in the ponderosa
pine type (Watershe.d 8) is almost fre.e of any precipitation
eve.nts, and was initiated about two months later than on the
preceding basins (fig.1d). Even for this wet year (46.0 inches
of pre.cipitation compared to the normal of 26.8 inches) spring
snowmelt lasted only 6 weeks. Daily peaks would increase
Table 1.--Physlcal characteristics of study watersheds.
Wate~shed
Beaver Creek
Watershed
Watershed
Workman
Creek
Castle
Creek
Characteristics
3 Bar 0
2
4
8
South Fork
East Fork
Vegetation type
Chaparral
Utah
juniper
Alligator
juniper
Ponderosa
pine
Mixed
conifer
Mixed
conifer
Size (ac)
Mid area elevation (ft)
Thomas
Creek
South Fork
Mixed
conifer
82
126
257
1804
319
1164
563
4200
5200
6250
7300
7150
8200
8700
30
3
3
3
13
<6
<6
Basal area (ft2 aC-1)
751
60
22
130
40
120
180
Annual precipitation (in)
29.5
18.1
20.1
26.8
31.9
25.6
29.1
3.9
1.2
4.3
6.9
3.5
:3.5
3.2
AR/AP
0.13
0.07
0.21
0.26
0.11
0.14
0.11
1973 Precipitation (in)
5:3.0
26.8
:34.4
4E5.0
6204
:37.0
42.9
1973 Runoff (in)
11.4
5.1
:~1.1
2:3.1
22.0
1:3.8
14.3
RIP
0.22
0.19
0.151
0.50
0.:35
0.37
0.33
Soil depth (ft)
Annual runoff (in)
1Percent crown cover.
213
mean elevation of 8,200 feet, is predominantly covered by
ponderosa pine, but is immediately adjacent to the extensive
mixed conifer stands in the White l\lountains of eastern
Arizona. Because of its climatologic and hydrologic similarity
to mixed conifer and di.ssimilarity to much of the ponderosa
pine in Arizona, it is considered mhed conifer in this study
(Rich and Thompson 1974). Soils are developed from basalt
and depths are generally less than 6 feet with a heavy day layer
at 2 feet.
Peak flow and delayed flow increased daily during the
warming period that began on April 6 (fig. If). Although the
daily flow spikes are obvious, they are much less responsive
than those on Workman Creek, indicating a higher relative
resistance resulting from an integration of a slower water
delivery rate and a)onyer f~ow path. Daily peaks were usually
between 3 and 5 ft.3 s- mi- 2 with the highest snowmelt peaks
of 14 and 15 ft3 s-1 mt 2 on Apri.l13 and 14, respectively.l\lost
snow was lost by the end of April. The streamflow events on
l\1ay 5 and 14 are dominated by 'rainfall.
Streamflow from the mhed c()l1ifer type on the South Fork
of Thomas Creek is often perennial, but occasionally ceases
for a 1 or 2 month period. The basalt derived soils are generally
less than 6 feet in depth. Streamflow in water year 1973 (fig.
19) began to rise gradually on April 11, leveling off from April
15 through April 25, and then started to rise again. Daily
fluctuation generally consists of a small increase, and then a
leveling off until the next daily increase. Streamflow produced
by rain on snow is obvious, such as on May 5 and May 13. The
storm event on l\fay 13 apparently depleted the snowpack
because, after l\lay 14, the hydrograph consisted of a gradual
recessional flow which lasted through the end of the month.
Although the annual precipitation of 42.9 inches (about 1.5
times normal) produced 14.3 inches of streamflow (4.6 times
norma~, maximum daily peak discharge only reached 12 ft3
s-1 mt ,excluding any influence of rain events which caused
disc.harge to reach 15 ft3 s-l mt2 ,4
Discussion
Although this is a limited set of hydrographs from one wet
year (1973), some observations can be made, and one can get
a feel for how much the various factors affect streamflow
response, and how much these factors can interact in Arizona.
Runoff efficiency rates (ratio of runoff to precipitation)
nearly doubled or tripled on all study basins in 1973, showing
the influence precipitation can have on streamflow (table 1).
The chaparral basin is at the lowest elevation, but receives the
second highest average annual precipitation (29.5 inches).
This basin had the most attenuated or least responsive hydrograph (fig. la), even though it received the second highe.st
amount of precipitation (53.0 inches) in 1973. It also has the
deepest soil (30 feet). Similar chaparral basins have been
shown capable. of producing perennial flo\\' once the chaparral
overstory is converted to grass, suggesting the influence of soil
depth on the storage of precipitation and its eventual release
(Hibbert et a1. 1974).
The most responsive or peaked hydrographs occurred on
the Beaver Creek drainage area with a mean soil depth of
about 3 feet. The Utah juniper basi.n receives the lowest: mean
annual precipi.tation amount (18.1 inches). However, the
influence of the. soil depth and the re.l.atively impermeable. B
horizon seems apparent in the highly responsi.ve daily
streamflow peaks (fig. Ib). Daily peak discharge rates, even
from snowmelt, are relatively large and recede rapidly (in
hours), which suggests a relatively small soil water storage
capacity and short flow paths (overland flow and shallow
subsurface flow).
Streamflow from the alligator juniper basin was similar to
the tJ tah juniper basin, but the higher elevation, higher annual
precipitation, and lower overstory basal area produced more
numerous and higher daily peaks (fig. lc).
The ponderosa pine basin on Beaver Cree.k has similar soil
characteristics and similar responsive daily peaks (ng. Id).
However, its higher ele.vation apparently resulted in a delay of
the snowmelt of about 2 months (from February to April). This
basin has the highest long term runoff efficiency of the 7 study
basins (0.26) and the second highest for the 1973 water year
(0.50). Daily peaks were usually lower than on the alligator
juniper basin, probably due to the influence of the less dense
overstory basal area on snowmelt rates. Flow ·on the three
Beaver Creek watersheds generally terminates within a few
days of the disappearance of the snowpack, while streamflow
often lasts longer on the other study sites. Even watersheds in
the chaparral type, generally considered a dry vegetation type,
can produce perennial flow after conversion of shrubs to more
shallow rooting species, such as grass (Hibbert et al.1974). The
streamflow hydrographs from Be.aver Cree.k also exhibit the
greatest range in daily peaks and the largest range in mean
annual streamflow (1.2 inches with 18.1 inches of mean annual
precipitation to 6.9 inches with 26.8 inches of precipitation)
(table 1).
Annual precipitation at the nuxed conifer basin on Workman Creek is highest of the 7 study basins (31.9 inches), and
streamflow is normally perennial. H ydrograph responsiveness
is similar to that on the ponderosa pine basin, but daily peaks
are higher in the beginning of the melt period and lower
towards the end suggesting the influence of the heavy reduction in overstory basal area on snowmelt rates (fig. Ie).
Streamflow in the mixed conifer on Castle Creek is similar
to that on vVorkman Creek, but is less responsive or more
attenuated, probably as the result of the influence of the higher
elevation (8,200 feet) 011 snowmelt rates (fig. If). Daily snowmelt peaks are still recogniz.able on Castle Creek but greatly
reduced. Annual precipitation and overstory basal area are
similar to that on the ponderosa pine basin, but the long term
runoff effici.ency ratio is only about one half as muc.h (0.14
versus 0.26).
The mixed conifer type on Thomas C:reek is located at the
highest elevation (8,700 feet) and receives the second highest
annual precipitation amount (29.1 inches). Daily snowmelt
peaks are barely apparent, indicating much more resistance or
longer flow distance to the channel. Overland flow or evidence
214
of overland flow has seldom been observed on the mixed
conifer basins.l\fean annual streamflows on these 3 basins are
relatively uniform (3.2 to 3.5 inches) even though mean annual
precipitation ranges from 25.6 to 31.9 inches. Although some
attenuation of the hydrographs on the two higher mixed
conifer basins is the result of lower snowmelt rates, the high
annual precipitation amounts, longer streamflow period, and
lower runoff efficiencies suggest that the major factor is the
influence of soil depth and texture.
Literature Cited
Baker, l\fa.Ic.hus B., Jr. 1986. Effects of ponderosa pine treatments on water yield in Ar.izona. Water Resources Researe.h. 22: 67-73.
Bake.r, Malchus B., Jr. 1984. Changes in streamflow in an
herbidde treated pinyon juniper wate.rshed in Arizona.
Water Resources Research. 20: 1639-1642.
Hibbert, Alden R. 1979. Managing vegetation to increase flow
in the Colorado River Basin. Gen. Tech. I'ap. RM-66. Fort
Collins, CO: U. S. Department of Agriculture, Forest
Service, Rocky l\fountain Forest and Range Experime.nt
Station. 27 p.
Hibbert, Alden R.; Davis, Edwin A.; Scholl, David G. 1974.
Chaparral conversion potential in Arizona. Part I: Water
yield response and effects on other resources. Res. Pap.
Rl\f-126. Fort Collins, CO: U. S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range
Experiment Sta~ion. 36 p.
Rich, Lowell R.; Thompson, J. R. 1974. Watershed management in Arizona's mixed conifer forest: The status of our
knowledge. Res. Pap. Rl\f-130. Fort Collins, CO: U. S.
Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 15 p.
215