WSP02732

• File Number: 8276.852
• Description: Moapa Valley Unit - Colorado River Salinity Control Program
• State: NV
• Basin: Colorado Mainstem
• Date: 2/1/1981
• Title: Salinity Control and Environmental Assessment
• Water Supply Pro - Doc Type: EIS

Water Budget - The average annual outflow of Muddy River to Lake
Mead is estimated to be 16,400 acre-feet. Surface outflow is 5,250 acre-
feet and sub-surface outflow is 11,150 acre-feet. A summary of water
supply and depletions for Muddy River is given in Table 4, Water and
. Salt Budgets.

Water Quality - The water of Muddy River at Muddy Springs has an
average dissolved mineral or salt concentration of 683 milligrams per
liter (mg/1). The average concentration increases to 941 mg/1 at the
stream gage near Glendale. At Wells Siding Diversion and Bowman Reservoir
in the Lower Valley, the average surface water quality is 1,111 mg/l.
Drain water concentrations in Lower Moapa Valley range. from 4,494 to
5,825 mg/1. The average salt concentration of ground water in wells
is 1,971 mg/1. The surface water flowing into Lake Mead has an average
annual salt concentration of 2,397 mg/1. The ground water entering Lake
Mead has an estimated salt concentration of 3,722 mg/1 (weighted value
of drains and wells). A map illustrating the change in salinity concen-
tration of the surface water of Muddy River is shown in Figure 6-A.

Muddy River has moderately mineralized water which has a high proportion
of calcium, magnesium, and sulfate in relation to sodium and chloride.
The concentration of dissolved solids and the relative abundance of sulfate
in Muddy River increase downstream. Increases result from the addition of
more saline ground water, irrigation return flows during the growing
season, and other factors such as evaporation. Table 5 shows typical con-
centrations of constituents in the surface waters of Muddy River. Tables
6 and 7 give typical compositions of drain and ground water in Moapa'Va11ey.

Salt Budget - Approximately 38,900 tons of salt flow annually from
Muddy River Springs in Upper Moapa Valley. Downstream, additional salts
are contributed from ground and surface waters of Meadow Valley Wash,
California Wash, and from irrigation return flows. The salt loading at
Glendale gage, near the mouth of Upper Moapa Valley increases to about
41,900 tons.

The average annual salt load at Wells Siding Diversion Dam near the
head of Lower Moapa Valley is 49,500 tons. The increase in salt load in
the Narrows between Glendale gage and Wells Siding Diversion Dam is from
subsurface flow (through saline aquifers) and erosion. Agricultural irrigation
is estimated to add 21,300 tons of salt to.the outflow of Lower Moapa Valley.
Erosion processes in Lower Valley are estimated to add 2,700 tons of salt
to the total outflow. Total salt contribution each year from Muddy River
Drainage is estimated to be 73,400 tons.

The salt budget is given in Table 4.
of component salt loads. Figure 6-C shows
loads.

Figure 6-B illustrates the magnitude
the cumulative addition of component

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