The Mono Basin Ecosystem Effects of Changing Lake Level (1987) / Chapter Skim
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1. Introduction
1. Introduction
Pages 8-21
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From page 8... ...
With the passage of the California Wilderness Act in 1984, Congress established the Mono Basin National Forest Scenic Area and placed management of the basin under the jurisdiction of the U.S. Forest Service acre-ft/yr (Los Angeles Department of ft since 1941 The Bureau of Land Management previously had had responsibility for managing the area.
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From page 9... ...
Changes in lake level, which in recent times have resulted primarily from diversions of most of the streams carrying freshwater runoff from the eastern escarpment of the Sierra Nevada to Mono Lake, affect the lake system itself, the shoreline and upland portions of the basin, and wildlife in the basin. No streams drain the lake, so the amount of water in it is determined by inputs from rainfall, snowmelt, and springs and loss from evaporation.
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From page 10... ...
an inventory of all terrestrial and aquatic species, including current and probable future population levels; (2) the critical lake level needed to support current wildlife populations; (3)
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SCALE IN MILES FIGURE 1.2 Hydrologic drainage of Mono Basin (from Vorster, 1985~.
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From page 12... ...
In the remainder of this introduction, the climatology, physiography, and geology of the Mono Basin and the prehistoric and historic fluctuations in lake level are briefly described, and Mono Lake is compared with other saline lakes. CLIMATOLOGY, PHYSIOGRAPHY, AND GEOLOGY OF THE MONO BASIN Mono Basin., which lies in eastern California approximately 190 mi east of San Francisco and 300 mi north of Los Angeles, is a closed hydrologic basin walled in by the steep-faced eastern escarpment of the Sierra Nevada on its western side and by Great Basin ranges on the north, south, and eastern sides (Figure 1.2~.
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From page 13... ...
Analyses of these data can be used to define mean values of monthly air temperature and precipitation and the relative frequency of occurrence of extreme events. Of particular importance to the Mono Basin ecosystem are the occurrence of periods of prolonged drought and of episodes of heavy precipitation and climatic trends resulting from natural events or anthropogenic effects.
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From page 14... ...
A distinctive feature of the Mono Basin is the tufa towers, formed underwater as calcium in freshwater springs combines with carbonates in the lake water. The deposits accumulate and form picturesque towers.
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From page 15... ...
has reconstructed the fluctuations in lake level over the past 3500 years using geomorphic, biotic, historic, and radiocarbon evidence along with information from sedimentary sequences and tephra exposed in the stratigraphy (Figure 1.3~. The figure indicates that the lake was at its lowest about 1850 radiocarbon years before the present.
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From page 16... ...
Lake levels have been estimated back to 1857 using cartographic, historical, and climatic evidence. Figure 1.4 shows these estimated and measured historic lake levels.
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From page 17... ...
Hence, although large, deep, saline lakes are rare, salinity on record (474 g/l) Is that ot Lion arctica, a calcium chloride water (Meyer et al.,
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From page 18... ...
, has particular relevance to Mono Lake in a few areas. Most pertinent are biogeographic studies of the tolerance of aquatic organisms to salinity, geochemical analyses of saline waters as a function of dilution and concentration, paleoecological examination of the extent and rates of changes of salinity, and investigations of vertical mixing, especially the occurrence of incomplete mixing, or meromixis.
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From page 19... ...
Of further relevance to Precambrian paleoecology is the recent speculation that the ancient sea had high alkalinity, high pH, and low calcium and magnesium concentrations, much as Mono Lake does today (Kempe and Degens, 1985~. REFERENCES Anderson, R
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From page 20... ...
1968. Late Quaternary Stratigraphy and Geologic History of Mono Basin, Eastern California.
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From page 21... ...
1983. Establishing the Mono Basin National Forest Scenic Area in the State of California.
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