One-page technical summaries on the core concepts and analysis methods behind one of SGMA's six sustainability indicators. Each page is designed to stand alone as a printable reference and to read together as a curriculum.
Gaining vs. losing streams, connected vs. disconnected systems, the hyporheic zone, and why streams and aquifers must be analyzed together.
Theis, Glover–Balmer, Jenkins SDF, Hantush leaky, and Hunt streambed‑conductance solutions — with an interactive parameter explorer.
Leake capture maps, Barlow capture vs. capture-zone, time scales of effect, and why "the well that turned on yesterday" isn't the one taking water today.
Zipper et al.'s rapid framework for estimating depletion from many wells across many streams — a practical middle ground between analytical and numerical methods.
The sustainability indicator framework: beneficial uses and users, undesirable results, minimum thresholds, measurable objectives, and the path from data to determination.
Analytical, semi‑analytical, ADF, numerical, and field methods — what each is good for, what each assumes, and an interactive decision guide.
Seepage meters, temperature methods (heat as a tracer), Darcy fluxes from piezometers, differential gaging, and direct ET measurement.
Depletion of interconnected surface water (ISW) is one of six sustainability indicators under California's Sustainable Groundwater Management Act. It is also the indicator most often cited by reviewers as inadequately addressed in GSPs — partly because the underlying science is unfamiliar to many practitioners and partly because the language of the statute ("significant and unreasonable") leaves room for interpretation.
These summaries aim to demystify the technical concepts so that GSAs, stakeholders, and consultants can have substantive conversations about what is being analyzed, why a given method was chosen, and how to interpret the results.