CONSTRAINING MODERN AND PALEOHYDROLOGY OF THE LAKE CLOVER AND LAKE FRANKLIN PLUVIAL SYSTEMS, NORTHEASTERN NEVADA, GREAT BASIN, U.S.A

Pluvial lakes were abundant in the Great Basin of the western United States during the last Pleistocene glaciation. The small pluvial lakes in northeastern Nevada, which were located in basins between the larger Lakes Bonneville and Lahontan, constructed well-preserved shoreline features representing multiple Late Pleistocene highstands. Two of these small pluvial lakes, Lakes Clover and Franklin, occupied valleys that still host small lakes today. These locations, therefore, present an opportunity to characterize modern and paleolake hydrology, which can provide useful limits on temperature and precipitation that accompanied pluvial lake highstands. A calibrated evaporation scheme, modern monthly meteorological data, and the historical dimensions of modern lakes were combined into a numerical water balance model to constrain a subsurface water storage parameter and modern surface runoff. The subsurface water storage parameter was used to solve for the range of temperature and precipitation combinations that could have accompanied pluvial lake highstands. Model results constrain the subsurface water storage parameter to a range of values (604 to 5027 mm) strongly dependent on the dimensions of the extant lake. Lower values reflect the dimensions of extant lake prior to agricultural diversions and are used to solve for temperature and precipitation accompanying pluvial lake highstands. At 17 ka, when Lakes Clover and Franklin attained their maximum extent, model results indicate that precipitation in these two valleys was likely 80 to 100 percent greater than modern. Spatial analysis of precipitation patterns in the valleys occupied by Lakes Clover and Franklin indicates that the volume of direct precipitation delivered to the lake surfaces greatly exceeded that delivered by runoff. This result is consistent with the high pluvial indices of the two lakes.