Quantifying concentrated and diffuse recharge in two marble karst aquifers: Big Spring and Tufa Spring, Sequoia and Kings Canyon National Parks, California, USA

Abstract

To improve water management in mountain systems, it is essential that we understand how water moves through them. Researchers have documented the importance of porous-media aquifers in mountain river systems, but no previous research has explicitly included mountain karst as part of conceptual models. To do so, we used discharge and geochemical parameters measured along upstream- to-downstream transects under high- and low-flow conditions in 2010 to assess storage characteristics and geochemical properties of two mountain marble-karst systems, the Big Spring and Tufa Spring systems in Sequoia and Kings Canyon National Parks, California. During both high- and low-flow conditions, we quantified the relative contributions of concentrated and diffuse recharge in both karst systems, and we used a simple linear mixing model to calculate specific conductance in unsampled diffuse sources that ranged from 34 m Sc m 21 to 257 m Sc m 21 . Data show that the Big Spring system has a much higher seasonal storage capacity than the Tufa Spring system, and that diffuse sources dominate discharge and geochemistry under baseflow conditions in both aquifer systems. Baseflow in Big Spring was 0.114 m 3 s 21 and in Tufa Spring it was 0.022 m 3 s 21 . Snowmelt-derived allogenic recharge dominates both systems during high discharge periods, measured at Big Spring as 0.182 m 3 s 21 and Tufa Spring as 0.220 m 3 s 21 . A conceptual model is proposed that explicitly includes the effects of karst aquifers on mountain hydrology when karst is present in the basin.