A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 7a – Water Quantity: rain, snow, and temperature

Rice, Robert; Bales, Roger

Precipitation, snowpack and air temperature, the primary physical determinants of climate, are the foundation for multiple focal resources in the Parks. Over thousands to millions of years they interact with the geologic template to determine soil formation and weathering. Over seasonal to decadal time scales they determine ecosystem health and the distribution of species. Temperature determines the elevation of rainfall versus snowfall, and thus the timing, partitioning, and seasonal magnitude of fluxes making up the hydrologic cycle in the Parks.The current analysis included retrieving, assembling, documenting, and doing quality assurance/and quality control of measured temperature, snow, rainfall, and related paleoclimatic data for the four main river basins that SEKI lies within, the San Joaquin, Kings, Kern, and Kaweah River basins (Table 1, Figure 1). Part of the Tule River basin is also within SEKI, but it was not included in the analysis due to the small area that is within the boundary of the park (20 km2) and the similarities in topography to the Kaweah basin. The San Joaquin drains into the San Joaquin River of the in the Central Valley, while the Kings, Kaweah, and Kern are normally endorheic basins, though they do empty into the San Joaquin in exceptionally wet years with intense spring runoff. The Kings and Kaweah formerly emptied into Tulare Lake and the Kern formerly emptied into Buena Vista Lake at the southern end of the Central Valley. The total area of SEKI is 3502 km2. Since 91% of the elevations are above 1800 m, with a snow/rain transition zone of 1500-1799 m, seasonal snow is the fundamental driver of the hydrologic processes in SEKI.This chapter focuses on one subset of the water cycle within SEKI: snowpack, snowmelt, and precipitation, with the latter being the sum of rainfall and snowfall (Figure 2). These fluxes, plus snowpack and soil-water storage, determine the amount of water available for evapotranspiration (sum of evaporation and transpiration), and streamflow. Snowpack is a critical SEKI resource that provides seasonal storage of water for soil moisture, lakes and streams. It is particularly important given the seasonal cycle of precipitation and long summer-fall dry period in the southern Sierra Nevada. Soil moisture is also a critical SEKI resource, which also provides seasonal storage for sustaining lakes, streams and vegetation year round. The results presented here are based largely on data plus simple models, and set the stage for a further analysis of other water-cycle fluxes and reservoirs, e.g. evapotranspiration, streamflow, and soil moisture. Data to accurately estimate soil moisture and evapotranspiration (ET) across the landscape are generally not available, and streamflow is available at only a few locations in SEKI. Extending all of these quantities across the landscape will require a more-detailed hydrologic model, combined with characterization of vegetation and physiographic features of the landscape. Thus a more-extensive analysis of the water cycle, while clearly needed to assess critical Park resources, is beyond the scope of the current analysis.

A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 7a – Water Quantity: rain, snow, and temperature

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