2026-11-03 –, Compagno
Discover an open-source workflow using CVHM2 to model and quantify interconnected surface water depletion under SGMA. This session demonstrates how to isolate critical streamflow impacts to satisfy regulatory compliance, environmental stakeholders, and resource management objectives.
Summary and Problem Statement
California’s Sustainable Groundwater Management Act (SGMA) tasks Groundwater Sustainability Agencies (GSAs) with avoiding six specific undesirable results. Among these, Undesirable Result #6 (UR #6)—the chronic depletion of interconnected surface waters (ISW) that impacts beneficial uses—remains one of the most technically challenging and legally scrutinized hurdles. State regulators (DWR, CalEPA, CDFW) and conservation groups like The Nature Conservancy require highly rigorous, scientifically defensible methods to quantify these surface water-groundwater interactions.
This presentation demonstrates how to leverage regional, public-domain numerical models alongside open-source geospatial tools to isolate, quantify, and map stream depletion signals.
Methodology and FOSS Implementation
The core of this analysis utilizes the U.S. Geological Survey’s Central Valley Hydrologic Model 2 (CVHM2). While CVHM2 provides a robust, regionally calibrated framework built on MODFLOW, extracting localized, actionable insights from its massive spatial and temporal cell budget arrays presents a significant data barrier for many practitioners.
To bridge this gap, we implemented an entirely open-source geospatial data science workflow. Using Python (specifically the FloPy library to interact with MODFLOW structures, alongside Pandas and NumPy for high-throughput multi-dimensional array filtering), we systematically isolated stream leakage and budget changes across critical river corridors. By programmatically comparing model cell budgets across specific scenario boundaries, we successfully decoupled regional pumping impacts from localized stream depletion signals.
Real-World Application and Policy Impact
The output of this workflow translates complex, multi-layered grid outputs into intuitive, highly visual spatial metrics and time-series depletion curves. This allows managers to directly evaluate minimum thresholds and measurable objectives required by Groundwater Sustainability Plans (GSPs).
Attendees will leave this session with a clear understanding of how open-source geospatial data science can democratize complex USGS models, providing regulatory agencies, environmental advocates, and local water managers with a transparent, reproducible framework to protect vulnerable Groundwater Dependent Ecosystems (GDEs) and manage interconnected surface waters sustainably.
