Quantifying the role of karstic groundwater in a snowmelt‐dominated hydrologic system

Abstract

AbstractRiver discharge in mountainous regions of the world is often dominated by snowmelt, but base flows are sustained primarily by groundwater storage and discharge. Although numerous recent studies have focused on base‐flow discharge in mountain systems, almost no work has explicitly investigated the role of karst groundwater in these systems across a full range of flow conditions. We directly measured groundwater discharge from 48 karst springs in the Kaweah River and its five forks in the Sierra Nevada mountains, California, United States. Relationships between spring and river discharge showed that karst aquifers and springs provide significant storage and delayed discharge to the river. Regression models showed that, of all potential seasonal groundwater storage compartments in the river basin, the area of karst (0.1–4.4%) present provides the best explanation of base‐flow recession in each fork of the Kaweah River (directly measured contributions from karst springs ranged from 3.5 to 16% during high‐flow to 20 to 65% during base‐flow conditions). These results show that, even in settings where karst represents a small portion of basin area, it may play an over‐sized role in seasonal storage and water resources in mountain systems. Karst aquifers are the single most important non‐snow storage component in the Kaweah River basin, and likely provide similar water storage capacities and higher base flows in other mountain river systems with karst when compared with systems without karst.