Geologic controls on baseflow generation across watershed scales
Abstract
Runoff generation processes have been linked to spatial characteristics in a number of catchments. Studies on spatial predictors of runoff generation typically focus on event dynamics, while many questions still exist regarding controls on baseflow. Geochemical evidence suggests that baseflow is often derived from more than one water source, although source water is commonly conceptually presented as a single homogeneous regional groundwater input. Understanding what water sources comprise baseflow and how they relate to spatial watershed characteristics may help us better understand how these systems respond to future scenarios of change. Here, we examined dominant baseflow water sources in six catchments in a structurally complex, mountainous landscape in central coastal California through repeat surface water sampling campaigns during the summer dry down period. Spatiotemporal variability in surface water contributions were determined using endmember mixing model analysis (EMMA), and source fractions were assimilated as either shallow subsurface water (SSW) or deep, regional groundwater (GW). Source fractions generated from EMMA were then related to catchment scale characteristics (e.g., geology, topography, land use, and soil indices). We found that bedrock permeability was the best standalone predictor of dominant water source fractions to individual catchments through the recession period (R2=0.83, p<0.01). Catchments that were more impermeable had the lowest GW proportions. Results from this work highlight the importance of (1) considering baseflow as a dynamic process with the potential to receive water from multiple sources, (2) using structurally complex systems to better understand the hierarchy of spatial drivers, and (3) the dominant role of geology in controlling baseflow generation in geologically heterogeneous systems.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H31O1958R
- Keywords:
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- 1804 Catchment;
- HYDROLOGY;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1839 Hydrologic scaling;
- HYDROLOGY;
- 1847 Modeling;
- HYDROLOGY