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Research about Walker Lake

Source-linked reports with geographic coverage including Walker Lake.

4 recordsLinked to original sources
USGS2014

Collaborative modelling and integrated decision support system analysis of a developed terminal lake basin

A terminal lake basin in west-central Nevada, Walker Lake, has undergone drastic change over the past 90 yrs due to upstream water use for agriculture. Decreased inflows to the lake have resulted in 100 km 2 decrease in lake surface area and a total loss of fisheries due to salinization. The ecologic health of Walker Lake is of great concern as the lake is a stopover point on the Pacific route for migratory birds from within and outside the United States. Stakeholders, water institutions, and scientists have engaged in collaborative modeling and the development of a decision support system that is being used to develop and analyze management change options to restore the lake. Here we use an integrated management and hydrologic model that relies on state-of-the-art simulation capabilities to evaluate the benefits of using integrated hydrologic models as components of a decision support system. Nonlinear feedbacks among climate, surface-water and groundwater exchanges, and water use present challenges for simulating realistic outcomes associated with management change. Integrated management and hydrologic modeling provides a means of simulating benefits associated with management change in the Walker River basin where drastic changes in the hydrologic landscape have taken place over the last century. Through the collaborative modeling process, stakeholder support is increasing and possibly leading to management change options that result in reductions in Walker Lake salt concentrations, as simulated by the decision support system.

Nevada↗
USGS1987

Bouguer gravity anomaly and isostatic residual gravity maps of the Walker Lake 1 degree by 2 degrees Quadrangle, California and Nevada

The accompanying gravity anomaly maps are part of a folio of maps of the Walker Lake 1° by 2° quadrangle, California and Nevada, prepared under the Conterminous United States Mineral Assessment Program. The quadrangle encompasses an area of about 19,500 km 2 along and to the east of the east flank of the Sierra Nevada (fig. 1). The Bouguer gravity anomaly map of the Walker Lake quadrangle was prepared by interpolating gravity values among 3,447 gravity stations established in the quadrangle and additional stations from adjacent quadrangles. An isostatic residual gravity map was prepared in order to reduce the effect; of interfering gravity gradients associated with the isostatic root of the Sierra Nevada. Methods of data reduction and factors that limit the accuracy of the gravity values are discussed in the following sections of this report. The geologic interpretation of the gravity maps is based on previous studies, sample measurements, and correlation with other maps of the folio including a geologic map (Stewart and others, 1982) and a map showing Mesozoic plutonic rocks (John, 1983). The purpose of the interpretative part of this report is to demonstrate the correlation between gravity anomalies and the mapped geology, to assess the continuation of exposed geologic units beneath the surface, and to suggest the location of concealed subsurface bodies with mineral resource potential. A three-dimensional model of the Little Walker caldera (fig. 6) is used to illustrate a possible quantitative interpretation of a gravity anomaly. A concealed 25 by 75-km Cenozoic batholith along the east flank of the Sierra Nevada with possible lateral extensions is suggested in this report. A possible magmatic mechanism is discussed to augment contemporary explanations for the extensional origin of valleys. The possibility of lower gravity anomalies indicating thinner roof rocks in the basement beneath mountain ranges also is discussed. Furthermore, interpretation of gravity anomalies was applied in discussions with W.D. Menzie (oral commun. , 1982) as one of the criteria used to identify and to delineate areas of mineral resource potential.

California, Nevada↗
USGS1982

A relation between landsat digital numbers, surface reflectance, and the cosine of the solar zenith angle

A method for estimating the reflectance of ground sites from satellite radiance data is proposed and tested. The method uses the known ground reflectance from several sites and satellite data gathered over a wide range of solar zenith angles. The method was tested on each of 10 different Landsat images using 10 small sites in the Walker Lake, Nevada area. Plots of raw Landsat digital numbers (DNs) versus the cosine of the solar zenith angle (cos Z) for the the test areas are linear, and the average correlation coefficients of the data for Landsat bands 4, 5, 6, and 7 are 0.94, 0.93, 0.94, and 0.94, respectively. Ground reflectance values for the 10 sites are proportional to the slope of the DN versus cos Z relation at each site. The slope of the DN versus cos Z relation for seven additional sites in Nevada and California were used to estimate the ground reflectances of those sites. The estimates for nearby sites are in error by an average of 1.2% and more distant sites are in error by 5.1%. The method can successfully estimate the reflectance of sites outside the original scene, but extrapolation of the reflectance estimation equations to other areas may violate assumptions of atmospheric homogeneity.

Nevada↗