Yucca Flat and from about 4.060 ft to 2,503 ft above sea level in the western and northern parts of Yucca Flat.T h C mmt notahlc fcciturc in the central part of Yucca Flat is the presence of four ground-water Water-level altitudes ranged from about 2,377 ft to 2,770 ft above sea level in the central part of3mf Test Hole 9 Water Well A' U-3kv Test Well D' U4ak U-4au U4av U-4r UE-4aa',3 UE-4ab' U E -~~C ' .~ UE-4ah' UE-4t U-6e3 Test Well B Ex.' UE-6d ' UE-6e'. Water Well 4 Water Well 4A Water Well 3 '.

Average‐annual volumes of runoff, evapotranspiration, channel loss, upland (interchannel) recharge, and total recharge were estimated for watersheds of 53 channel sites in the Amargosa River basin above Shoshone, California. Estimates were based on a water‐balance approach combining field techniques for determining streamflow with distributed‐parameter simulation models to calculate transmission losses of ephemeral streamflow and upland recharge resulting from high‐magnitude, low‐frequency precipitation events. Application of the water‐balance models to the Amargosa River basin, Nevada and California, including part of the Nevada Test Site, suggests that about 20.5 million cubic meters of water recharges the ground‐water reservoir above Shoshone annually. About 1.6 percent of precipitation becomes recharge basinwide. About 90 percent of the recharge is by transmission loss in channels, and the remainder occurs when infrequent storms yield sufficient precipitation that soil water percolates beyond the rooting zone and reaches the zone of saturation from interchannel areas. Highest rates of recharge are in headwaters of the Amargosa River and Fortymile Wash; the least recharge occurs in areas of relatively low precipitation in the lowermost Amargosa River watershed.

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