The Mono Basin Ecosystem Effects of Changing Lake Level (1987) / Chapter Skim
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2. Hydrology of the Mono Basin
2. Hydrology of the Mono Basin
Pages 22-49
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From page 22... ...
Similarly, salinity and its consequences for wildlife are determined by the amount of water that flows into the lake. This chapter gives an overview of the hydrologic processes in the Mono Basin and the models used to predict future lake levels and salinity.
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From page 23... ...
The Sierra Nevada acts as a barrier to the moisture. Most of the precipitation from these storms falls in the high elevations, with very little reaching the east side of Mono Lake.
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From page 24... ...
, Nevada, and Colorado, is mainly dependent on air mass Owens Valley and Often these storms west and south of The cyclone may then move slowly .
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From page 25... ...
, two related hydrometeorological phenomena have attracted attention: the increased incidence of extreme weather events, including extremely wet and extremely dry periods (Policansky, 1977; Goodridge, 1981; Karl et al., 1984) and the rise in level of Great Salt Lake, Pyramid Lake, Walker Lake, and Mono Lake.
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From page 26... ...
The rise in Great Basin lakes during the 1 980s is well documented. In June 1986 Pyramid Lake had risen to an elevation of 3817 ft above sea level, higher than it had been since 1944, and Mono Lake had risen ~ ft since 1982.
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From page 27... ...
. A -- ~_~AHO ~1 \l RNO ~0 at\ at'''\ BIH - Bishop EKO - Elko ELY- Ely lAS - Las Vegas \ 27 l A_ _' |` WYOMING SLC _ _ o WMC O EKO o GREAT BASIN I IELY o MLF o \ LAS /~ ~ \` /~ hi\ ~ UTAH ARIZONA MLF- Milford RNO - Reno SLC - Salt Lake City WMC - Winnemucca / FIGURE 2.2 Great Basin region and eight weather stations selected for precipitation study.
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From page 28... ...
Water derived from melting snow and rainstorms reaches ~tr~.nm~ hv ov~rl~nr1 flow and groundwater seepage. Thus, the dominant processes controlling the distribution of water within the basin are precipitation, surface runoff in streams, groundwater discharge to the lake, lake evaporation, and terrestrial evapotranspiration.
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From page 29... ...
Nevertheless, both studies estimate the mean annual precipitation over the lake to be approximately ~ in. Surface Runoff Much of the surface runoff in the basin originates in the Sierra Nevada, where most precipitation occurs.
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From page 30... ...
Period of Elevation Period of Period of Station Record (ft) Record 1941-1985 Bodie 1965-1968 8370 19.2 - Cain Ranch 1931-1932 to 1984-1985 6850 11.44 11.34 East Side Mono Lake 1975-1976 to 1984-1985 6840 5.70 - Ellery Lake 1925-1926 to 1984-1985 9645 25.68 20.42 Gem Lake 1925-1926 to 1984-1985 8970 21.81 20.91 Mark Twain Camp 1950-1955 7230 6.80 - Mono Lake 1951-1968 6450 12.50 - Rush Creek Power House 1957-1979 7235 25.20 -Estimates of ungaged runoff will clearly introduce inaccuracies into computation of the moisture budget for the basin.
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From page 31... ...
Mono Lake acts as a regional groundwater sink; groundwater moves toward the lake, discharging at discrete springs and zones of diffuse seepage along the lakeshore and beneath the lake. Nearshore Groundwater Flow From the perspective of the Mono Basin ecosystem, the most important aspect of groundwater flow is the seepage
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From page 32... ...
Nearshore shallow groundwater in this area has high total dissolved solids and is either residual lake water, remaining after the lake elevation declined, or lake water drawn into the sediments by evaporation in the salt flats. In areas of extenS;~; iala ci~v~iopment, such as fine Ala Marina, Simon's Spring, and Warm Springs, gradients are erratic and the locations of springs are controlled by fractures and tufa ridges.
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From page 34... ...
34 ~20 ~40 6300 "20 6380 6340 63001 ~ 2~0 Me ~~o B~" ^~~ a Glut ~ / _ V, / ,~ / ~ ~ Her Ala u~ surface / ~ / Plazem~m / b ~- surface ~ Nat BEACH 1 1 1 1 1 1 1 2= ~ ~ 8~ 1~0 HOWL DISTANCE OR PURIM 12000 Go_ ~ / ~ P_m_ I I I 1 I I 1 1 1 1 4~ 60" 8000 10000 FIGURE 2.S Location of test holes at transects.
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From page 35... ...
V At/ ~ March Lake surface Plezomotors Water table / 6300 ~ 1 1 1 1 1 I 1 4000 6000 8000 10000 12000 14000 ~7 4000 6000 8000 10000 HORIZONTAL DISTANCE (no) Ground surface If/ f ~Water~biblo L Plezometers 12000 14000 _.
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From page 37... ...
This lack of control on aquifer geometries and hydraulic properties is the fundamental reason why no attempt has been made to construct a numerical groundwater model to estimate rates of groundwater flow into the lake.
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From page 38... ...
Given the importance of lake evaporation in the basin water balance, additional efforts should be made to obtain better estimates of evaporation from the lake. Terrestrial Evapotranspiration Terrestrial evapotranspiration in the Mono Basin occurs as evaporation from the bare ground, evaporation of subsurface soil moisture, and evapotranspiration from vegetation.
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From page 39... ...
surveyed and evaluated previously developed water balance models for the Mono Lake and Basin. In addition, Todd (1984)
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From page 40... ...
Assuming groundwater inflows into the valley sediments are small, inflow is defined by precipitation on the lake and basin fill and streamflows across the boundary of the problem domain where approximately 75 to 85 percent of the surface runoff is gaged. Vorster did not treat groundwater inflow as a distinct term, out Instead combined unknown groundwater inflows and unmeasured surface runoff inflows into a single term.
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From page 41... ...
t ~ 1e EXPORTS Grant ~ Stream Channel _ lake Runoff l - 1 IPr~ipl~tlonh e _' ~ . Mono ~ Springs Lake L e- evaporation ET = evapo~nspiraUon 41 ~ IMPORTS ~ Ate Inflltratlon and _ Soll Moisture Storage _ ' 1 L Groundwater Storage | 1 1 ~ 1 FIGURE 2.6 Components of hydrologic mass balance model for Mono Lake.
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From page 42... ...
. The governing equation is: PB + ISWF + IGWF - EBX - EML - EBT = ~SML + ~SBGW + ~SBSM + /`SBSR where previously undefined components are: PB= precipitation on the basin fill and Mono Lake ISWF= surface water inflows to the basin fill IGWF = groundwater inflows to the basin fill EBX = exports from study region EBT = evapotranspiration from basin fill including losses from lakeshore vegetation SBGW = change in groundwater storage in the basin fill SBSM = change in soil moisture storage in the basin fill ASBSR = change in storage of surface runoff within the basin fill Case III: A boundary at the lakeshore.
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From page 43... ...
As expected, uncertainty in lake evaporation estimates had the greatest influence on model results. Depending on the volume of surface water exports, a change of +S percent in estimates of lake evaporation rates resulted in a variation of 2 to 14 ft in projected long-term lake levels.
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From page 44... ...
Vorster's model was also adjusted to include the most recent bathymetric data from Pelagos Corporation (1987~. Both models were then used to simulate the elevation of Mono Lake as a function of flow at the diversion points (Figure 2.7~.
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From page 45... ...
Small fluctuations in lake level still occur due to oscillation in the climatic data. A comparison of the results of Figures 2.7, 2.S, and 2.9 indicates that the Vorster model predicts lower lake elevations for the same values of releases to Mono Lake.
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From page 46... ...
~ 25,000 FIGURE 2.8 Lake level versus year predicted from LADWP model (1987) using an evaporation rate of 42 in./yr.
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From page 47... ...
To improve the modeling capability for the Mono Basin, a new set of models with a monthly time increment, based on a comprehensive surface water and groundwater hydrologic data collection network, is needed. This data collection network would need to focus on the components with limited or missing data, such as nearshore and deep groundwater, the ungageo surface runoff areas, lake evaporation, and terrestrial evapotranspiration.
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From page 48... ...
Pp. 6-38 in An Ecological Study of Mono Lake, California, D
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From page 49... ...
1985. A Water Balance Forecast Model for Mono Lake, California.
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