Georgakakos et al. (2026) Assessing streamflow depletion from agricultural groundwater use in headwater catchments using storage-discharge functions

Identification

• Journal: Journal of Hydrology
• Year: 2026
• Date: 2026-07-01
• Authors: Philip B. Georgakakos, David Dralle, Chris Dillis, W. Jesse Hahm, Dana Ariel Lapides, Theodore E. Grantham
• DOI: 10.1016/j.jhydrol.2026.135965

Research Groups

• University of California, Berkeley, Environmental Science and Policy Management
• US Forest Service, Pacific Southwest Research Station
• Simon Fraser University, Department of Geography
• USDA-ARS, Southwest Watershed Research Center

Short Summary

This study proposes a novel approach to estimate streamflow depletion from groundwater pumping in headwater catchments using storage-discharge functions. The method is applied to two well-studied watersheds in California's North Coast to quantify potential hydrologic impacts of cannabis agriculture.

Objective

• Evaluate the effects of groundwater pumping on streamflow depletion risk in upland watersheds, including potential impacts from cannabis agriculture.
• Develop a generalizable method for assessing streamflow depletion risk that can be applied to areas with limited groundwater monitoring infrastructure.

Study Configuration

• Spatial Scale: Local (two well-studied watersheds in California's North Coast)
• Temporal Scale: Daily timestep

Methodology and Data

• Models used: Storage-discharge sensitivity functions, modified formulation of Kirchner (2009) to account for dual-storage issue.
• Data sources: Streamflow timeseries data from two focal watersheds, Elder Creek and Dry Creek.

Main Results

• Lower initial flow, higher percent coverage of cannabis, higher pumping rates, and extraction from surface water all lead to lower summer discharge and more days of zero flow.
• Water extraction from wells had a muted impact on discharge relative to direct surface water diversions.
• The number of zero-flow days was most strongly influenced by water source.

Contributions

• This study provides a new approach for evaluating the potential effects of groundwater pumping on streamflow depletion in headwater catchments, including the impacts of cannabis agriculture.
• The method can be applied to areas with limited groundwater monitoring infrastructure and can help identify streams that are at risk of de-watering due to groundwater extraction.

Funding

• This research was supported by grants from the US Forest Service, Pacific Southwest Research Station, and the USDA-ARS, Southwest Watershed Research Center.

Citation

@article{Georgakakos2026Assessing,
  author = {Georgakakos, Philip B. and Dralle, David and Dillis, Chris and Hahm, W. Jesse and Lapides, Dana Ariel and Grantham, Theodore E.},
  title = {Assessing streamflow depletion from agricultural groundwater use in headwater catchments using storage-discharge functions},
  journal = {Journal of Hydrology},
  year = {2026},
  doi = {10.1016/j.jhydrol.2026.135965},
  url = {https://doi.org/10.1016/j.jhydrol.2026.135965}
}