CONTRIBUTIONS OF KARST GROUNDWATER TO WATER QUALITY AND QUANTITY IN A MOUNTAIN RIVER BASIN: THE KAWEAH RIVER, SEQUOIA AND KINGS CANYON NATIONAL PARKS, CALIFORNIA
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Under current climate conditions, hydrology of Sierra Nevadan rivers is primarily controlled by three mechanisms: rainfall-runoff, snow accumulation and seasonal melting, and groundwater recharge, storage, and subsequent discharge. Snowmelt and groundwater storage provide temporal distribution of the seasonal precipitation and support stream flows during the annual dry season. The role of snowmelt hydrology in biogeochemical processes and maintaining river discharge has been the focus of numerous studies. However, the extent to which groundwater contributes to discharge and the temporal distribution of water in these systems has not previously been quantified. To address this need, field documentation of karst springs in the Kaweah River basin was conducted from 2010 - 2012. These data show that karst springs fall into two distinct categories: one with high seasonality and another with minimal seasonal variation in flow and chemistry. A more in depth look at Big Spring (low seasonal variability) and Tufa Spring (high seasonal variability) show that most low flow discharge from these aquifers is water that was stored within the aquifer, rather than quick flow through the system via large conduits. This pattern of water storage also plays a role in controlling nutrient movement through these karst groundwater systems. Finally, when karst of the Kaweah basin is taken as a whole, it represents a large component of baseflow river discharge, likely controlling the baseflow characteristics of the river.