WSP10396

• File Number: 8056
• Description: Drought Preparedness
• State: CO
• Basin: Statewide
• Date: 1/1/1964
• Author: USGS
• Title: General Effects of Drought on Water Resources on the Southwest
• Water Supply Pro - Doc Type: Report/Study

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GENERAL EFFECTS OF DROUGHT ON VfATER RESOURCES

B13

Divide in the United States. Although there is no
storage upstream, the.re are diversions for about 5,000
acres of irrigated land, an acreage that has probably
changed but little during the period of record. The
measured runoff was not adjnsted, and a considerable
part of the record prior to 1928 was estimated. The
station was discontinued in 1955; runoff fo,r 1956-58
was estimated on t.he basis of records for t.he st.at.ion
below Blue Creek, near Virden, N. Mex.

5. The Rio Grande near Del Norte, Colo., drains t.he
high mountains of southern Colorado. The. runoff
was not.adjust.ed, alt.hough it is affect.ed by storage
in 6 or 7 reservoirs, by diversions for irrigation, and
by 5 t.ransmount.ain diversions t.hat. bring water int.o
t.he basin above t.he gaging st.ation. The reservoirs
are smaU and t.hel'e is usually lit.tle carryover st.orage
from season to season; yea.rly runoff, the.refore, is not
affected greatly, The diversions for irrigat.ion are
smal! and are partly offset. by t.he import.at.ions,

6. The Brazos River at. Waco, Tex" drains t.he northern
plaius of Texas, sout.h and sout.heast. of t.he Pan.
handle, although the western t.hird of t.he drainage
area is noncont.ributing. The runoff was adjusted
fot' change in contents in Possum ICingdom and
Phant.om Hil! Reservoirs since 1941, in Whit.ney
Reservoir since 1952, and in Lake St.amford since
]954, No adjustment. was made for the effect of
stora,g-e in several other small reservoirs or in a large
number of conservation, stock, and flood-control
ponds or for .relatively smal! diversions for irriga-
t.ion, municipal supply, and oil-field operat.ions. The
adjustments are considered adequat.e, except. for the
unknown effect of the several t.housa.nd ponds con-
structed as(tl, conservation measure, mostly since 1943.
Other conservation practices put. int.o effect during
the same period, such as contouring, terracing, strip
cropping, and clearing of brush may also have caused

some modification of t.he natural runoff. As no ad-
j ustment. was made for t.hese ponds and pract.ices, the
recorded runoff since t.he early 1940's may have
become progressively smaller than natural runoff.
Bar graphs of yearly runoff (fig. ]) show some of
the following similarities in t.he flow at all six stat.ions:
There are no long unbroken periods of either drought.
or high water; drought periods of several years dura-
tion almost always include some years of average or
even high flow; t.he recent drought period was preceded
on all st.reams by high runoff in 1941, and in all st.reams
except the Brazos River, t.he runoff in 1952 was a:bove
the long-t.erm mean. The years 1951 and 1956 stand
out as the years in which the recent. drought. was per-
haps greatest in severity and geographical area affected.
The g.raphs in figure 1 indicate t.hat for t.heSouthwest
as a whole the recent drought was t.he worst. within t.he
period of record, except for the drought. of 1892-1904,
Graphs of t.he rat.io of 5-year progressive average
runoff to long-term runoff (fig. 2) indicate no t.rends
or cycles common t.o all streams. There is an apparent
t.rend t.oward lower runoff since 1910, although for t.he
San Gabriel and Brazos Rivers this is t.rue only for the
period of the recent. drought. For t.he Gila and Virgin
Rivers t.his apparent downward trend may result from
the fact t.hat. records for bot.h of these streams st.a;rted
during a period when runoff was high everywhere in
the Sout.hwest..
Frequency-distribution curves (fig. 3) are plot.ted as
dimensionless ratios to permit. comparisons between
st.reams, despite the "arious lengths of record and
ranges of runoff, The most. noticeable difference be-
tween t.he curves is in t.heir slopes, which range from
relat.ively flat for the Rio Grande and the Virgin River
t.o st.eep for the San Gabriel River, These differences
in slope have import.ant implicat.ions in study of the
drought. and are one of the reasons t.hat realistic com-

TABLE 1.- Yearly runoff, in thousands of acre-feet, adjusted for storage and diversion to show approximate natural flow at selected gagings
stations in the Southwest-Continued

1 Adjusted for diversion by Kern River No.3 Canal.
~ Most of the estimated figures prior to 1921 from report ,. Utilization of water
resources in southern portion of Banta Barhara County" by Quinton, Code and Hill-
Leeds and Barnard, Feb. 27, 1939; since 1921, records computed on basis of changes in
contents of Gibraltar Reservoir and other hydrologic items necessary to compute
inflow.
3 Adjusted for diversions by Doheny ditch and Piru Water 00. for 1928-34. Regu-
lated by Lake Plru after October 1955; figures for 1956-1957bnsed on Piru Oreekabove
Lake Piru.
1 Adjust(ld for diversion by Santa Paula Water Works since 1928.
5 Adjusted for diversion, storage, evaporation from reservoirs, and imported water.
6 Adjusted for diversion by Southern Oalifornia Edison Co.'s canal.
7 Adjuc:tcd for diversions by Southern Oalifornia Edison Co.'s conduit and Fontana
Union Water Oo.'s infiltration line.
S Runoff for 1951 was recorded as zero; adjusted runoff estimated as 500 acre-feet
because of diversions in dry year.
9 Publlshed as Strawberry Creek prior to 1953. Adjusted for diversion by Del
Rosa Water Co. for 1932--43.
10 Adjusted for diversion by Southern Calilornla Edison Co.'s canal and for storage
in Big Bear Lake.
II Published as "near Mesa Grande" prior to 1954. Adjusted for 1954, 1955 for
storage in Sutherland Reservoir and for other hydrologic !toms necessary to compute
inflow. Estimated reeord for 1929-36 based Oil discharge measurements made by
city of San Diego.
U Adjusted for diversion by Sprillgdale Canal.
I~ Adjusted for change in contents in Bartlett Reservoir since 1939 and in Horseshoe
Reservoir since 1946.
690-212 0-00-3

It Including flow on Tonto Creek.
15 Adjusted for diversion by Brown Canal.
16 Runoff from 5,140 square miles downstream from Coolidge Dam computed as
runoff of Gila River at Kelvin less runoff of Gila River below Coolidge Dam.
11 Adjusted for change in contents in Vallecito Reservoir since 1941.
18 Runoff for water years 1891-1903 from report of Rio Grande Joint Investigation.
19 Missing winter periods for years prior to 1948 estimated to complete yearly run-
off figures.
~o Records for water years 1891-95, 1905-12, 1915, 1917-19 from reports of Rio Grande
Joint Investigation. Adjusted for change in contents in El Vado Reservoir since 1935,
21 Preliminary revision.
~~ Based on Rio Charna near La Puente reduced by 4 percent.
2:l Records for water years 1905-13, 1918, 1926 from reports of Pecos River Joint
Investigation as given in Sena.te Document No. 109.
21 Adjusted for change in contents in, and diversions from, Lake Colorado City
since 1949, Oak Creek Reservoir since 1953\ and Lake Thomas since 1964.
2~ Adjusted for diversion by Noyes Cana since 1925.
~6 Records since 1932 furnished by International Boundary and Water Oommission.
Station discontinued August 19~7.
21 Adjusted for change in contents in Possum Kingdom and Fort Phantom Hill
Reservoirs since 1941, in Whitney Reservoir since 1951, and in Lake Stamford since
1964.
28 Adjusted for change in contents in Belton Reservoir since 19M.
2~ Adjusted for change in contents in Belton Reservoir since 1954 and for diversion
by Aluminum Co. of America since 1956.