Old groundwater influence on stream hydrochemistry and catchment response times in a small Sierra Nevada catchment: Sagehen Creek, California

Abstract

[1] The relationship between the chemical and isotopic composition of groundwater and residence times was used to understand the temporal variability in stream hydrochemistry in Sagehen basin, California. On the basis of the relationship between groundwater age and [Ca 2+ ], the mean residence time of groundwater feeding Sagehen Creek during base flow is approximately 28 years. [Cl À ]: [Ca 2+ ] ratios in Sagehen Creek can be used to distinguish between two important processes: changes in the apparent age of groundwater discharging into the creek and dilution with snowmelt. The mean residence time of groundwater discharging into the creek is approximately 15 years during snowmelt periods. The results from this study have implications for hydrograph separation studies as groundwater is not a single, well-mixed chemical component but rather is a variable parameter that predictably depends on groundwater residence time. Most current models of catchment hydrochemistry do not account for chemical and isotopic variability found within the groundwater reservoir. In addition, this study provides valuable insight into the long-term hydrochemical response of a catchment to perturbations as catchmentflushing times are related to the mean residence time of water in a basin.

Temporal variation in end‐member chemistry and its influence on runoff mixing patterns in a forested, Piedmont catchment

“…[33] While the temporal variation of end-member chemistry and its potential implications for runoff mixing have been recognized [Rice and Hornberger, 1998;Rademacher et al, 2005] specific information on how and when these changes occur for individual end-members has been lacking. Our results clearly show that temporal variation in endmember chemistry can be substantial, especially for surficial watershed sources such as litter leachate (LT) and soil water (WSW).…”

Are we missing the tail (and the tale) of residence time distributions in watersheds?

“…Residence times have been used to understand streamflow generation processes [Kendall and McDonnell, 1998;McGuire and McDonnell, 2006], weathering rates in watersheds [Pacheco and Van der Weijden, 2012;Frisbee et al, 2013], time scales of ecological processes [Brunke and Gonser, 1997;Hancock et al, 2005], and recently, the watershed response to climate change [Rademacher et al, 2005;Singleton and Moran, 2010;Manning et al, 2012]. Given the broad interest in applications of residence times in watershed science, it is critically important that methodologies provide accurate and physically justifiable estimates of mean residence times and residence time distributions (RTDs).…”

Exploring Streamwater Mixing Dynamics via Handheld Thermal Infrared Imagery

“…Likewise, it is a prerequisite for hydrometric measurements such as salt dilution gauging [8]. Streamwater samples can be strongly influenced by lateral inflows from soil or groundwater [9][10][11].…”