Investigating the Link Between Surface Water and Groundwater in the Tule Lake Subbasin, Oregon and California

Portland State University | August 13th, 2014

Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surf

Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surface water shortages because of shifts in allocation toward in-stream flows for Endangered Species Act-listed fishes. The largest increase in groundwater pumping has been in and around the Bureau of Reclamation’s Klamath Irrigation Project, which includes the Tule Lake subbasin in the southern part of the upper Klamath Basin. Previous groundwater flow model simulations indicate that water level declines from pumping may result in decreased flow to agricultural drains in the Tule Lake subbasin. Agricultural drains on the Klamath Project are an important source of water for downstream irrigators and for the Tule Lake and Lower Klamath Lake National Wildlife Refuges. To better assess the impact of increased pumping on drain flow and on the water balance of the groundwater system, flow data from agricultural drains were evaluated to investigate the changes that have taken place in groundwater discharge to drains since pumping volumes increased. Additionally, a fine-grid groundwater model of the Tule Lake subbasin was developed based on the existing regional flow model. The fine-grid model has sufficient vertical and horizontal resolution to simulate vertical head gradients, takes advantage of time-series data from 38 observation wells for model calibration, and allows agricultural drains to be more explicitly represented. Results of the drain flow analysis show that the groundwater discharge to agricultural drains has decreased by approximately 4000 hectare-meters from the 1997-2000 average discharge. Most of this decrease takes place in the northern and southeastern portions of the subbasin.  Results of the groundwater model show that the initial source of water to wells is groundwater storage. By 2006, approximately 56% of the water from wells is sourced from agricultural drains.

Inyo County: Monitoring Groundwater Dependent Vegetation to Inform Groundwater Management

Nature Conservancy | August 1st, 1989

Inyo County and the City of Los Angeles have shown innovative and progressive leadership in the protection of groundwater dependent ecosystems in Owens Valley,

Inyo County and the City of Los Angeles have shown innovative and progressive leadership in the protection of groundwater dependent ecosystems in Owens Valley, and thanks to a landmark agreement between Inyo County and the Los Angeles Department of Water and Power (LADWP), the outlook for groundwater dependent ecosystems (GDEs) in this area is promising. In 1991, the Inyo/Los Angeles Long-Term Water Agreement (Agreement) established an elaborate system to manage groundwater pumping by LADWP to avoid substantial declines in groundwater dependent vegetation in the Owens Valley. Implemented to settle the County’s 1971 CEQA challenge of LADWP’s proposed method to fill its second aqueduct, the Agreement resolved years of litigation between the County and LADWP.

Irrigation in the Earth system

Nature Portfolio (Springer Nature) | June 20th, 2023

Isolating the Poroelastic Response of the Groundwater System in InSAR Data From the Central Valley of California

American Geophysical Union (AGU) | April 28th, 2023

It is the Discharge

National Groundwater Association (NGWA) | September 1st, 2007

We all know the mantra Keep It Simple—the principle KISS. I have been thinking of another mantra for ground water—It Is the Discharge. Let me explain: In a re

We all know the mantra Keep It Simple—the principle KISS. I have been thinking of another mantra for ground water—It Is the Discharge. Let me explain: In a recent conversation with one of my distinguished colleagues, he bemoaned our lack of understanding of ground water recharge. I keep thinking about that conversation. In a broad sense as hydrogeologists, we are hoping to understand how aquifer systems function, more particularly how much water is flowing through a particular system—the focus on recharge is simply one facet of the larger task. In studying the system, there are at least three aspects that we can focus on—(1) the recharge; (2) the aquifer itself as a transmission mechanism; and (3) the discharge from the aquifer.

James Groundwater Sustainability Agency Groundwater Sustainability Plan

James Groundwater Sustainability Agency (JGSA) | December 12th, 2019

James Groundwater Sustainability Agency Groundwater Sustainability Plan (Revised)

James Groundwater Sustainability Agency (JGSA) | July 22nd, 2022

*Submitted to the Department of Water Resources on July 22, 2022. No date or signature accompany the seal from the preparer at Provost and Pritchard.

*Submitted to the Department of Water Resources on July 22, 2022. No date or signature accompany the seal from the preparer at Provost and Pritchard.

Kaweah Subbasin Probationary Hearing Draft Staff Report

California State Water Resources Control Board (SWRCB) | May 2nd, 2024

The State Water Board recognizes that local public agencies in the Kaweah Subbasin have made significant efforts since the passage of SGMA to form three groundwater susta

The State Water Board recognizes that local public agencies in the Kaweah Subbasin have made significant efforts since the passage of SGMA to form three groundwater sustainability agencies (GSAs) and then develop detailed technical and other information supporting the adoption and implementation of three groundwater sustainability plans (GSPs) for the subbasin. Despite those efforts, in January of 2020, DWR reviewed the three GSPs to determine if the GSPs met SGMA’s requirements and found the GSPs to be incomplete. Following revisions made by the GSAs in the subbasin, DWR reevaluated the GSPs in March of 2023, determined the GSPs to be inadequate, and referred the subbasin to the State Water Board, as required by SGMA. Consistent with SGMA, the State Water Board may now consider whether to designate the Kaweah Subbasin as a “probationary basin,” a term that is used in SGMA to describe a basin in the first stage of state intervention.  Click here for Water Board updates on hearings. A January 5, 2025 has been cancelled to allow more time to review updated groundwater sustainability plans.

Kaweah Subbasin Staff Assessment

California State Water Resources Control Board (SWRCB) | October 14th, 2025

The Kaweah Subbasin is managed by three GSAs: East Kaweah GSA, Greater Kaweah GSA, and Mid-Kaweah GSA (collectively, the Kaweah GSAs or GSAs). Each GSA wrote their own GS

The Kaweah Subbasin is managed by three GSAs: East Kaweah GSA, Greater Kaweah GSA, and Mid-Kaweah GSA (collectively, the Kaweah GSAs or GSAs). Each GSA wrote their own GSP, East Kaweah GSP (EKGSP), Greater Kaweah GSP (GKGSP), and Mid-Kaweah GSP (MKGSP). The three GSPs are tied together by a coordination agreement. The primary use of groundwater within the subbasin is irrigated agriculture; in 2020, irrigated agriculture used more than 94 percent of the groundwater in the subbasin (2024 Coordination Agreement, Appendix 1, p. 27). The subbasin is critically overdrafted, which means that groundwater is pumped out of the subbasin faster than it is recharged by precipitation and other sources. On average, the amount pumped from the subbasin in a year is 104,000 acre-feet greater than the amount recharged (2024 GKGSP p. 1-1). Overdraft can cause the land surface to sink, potentially damaging infrastructure and reducing aquifer storage. In addition, overdraft threatens groundwater levels and drinking water quality and could have disparate impacts on communities that rely on shallower groundwater levels. Due to historic and political factors, many of these are economically disadvantaged and communities of color. As of 2022, the subbasin has an estimated population of 296,632 people with most of the population being Hispanic or Latino (60.6%) followed by white (31%) (American Community Survey, 2022). The average annual household income within the subbasin in 2022 is $71,000, which is significantly less than the state average of $91,551 (ibid.).

Kern County Subbasin Groundwater Sustainability Plan 2025

Kern County Subbasin Groundwater Sustainability Agency (KCSGSA) | August 29th, 2025

The Kern Subbasin (Kern Subbasin) Amended Groundwater Sustainability Plan (2025 Plan)  presents the overview of each of the seven GSPs that together constitute the 2025

The Kern Subbasin (Kern Subbasin) Amended Groundwater Sustainability Plan (2025 Plan)  presents the overview of each of the seven GSPs that together constitute the 2025 Plan, including which GSAs are covered by each GSP and whether the GSP includes supplemental “blue pages” specific to the portion of the Kern Subbasin that the GSA manages consists of seven closely coordinated (and nearly identical) Groundwater Sustainability Plans (GSPs) and the Kern Subbasin Coordination Agreement. The 2025 Plan represents a critical milestone in the Kern Subbasin and all 20 Kern Subbasin Groundwater Sustainability Agencies’ (GSAs) ongoing commitment to achieving long-term groundwater sustainability under California’s Sustainable Groundwater Management Act (SGMA). Developed collaboratively by all 20 GSAs, the 2025 Plan responds directly to regulatory feedback from the California Department of Water Resources (DWR) and the State Water Resources Control Board (SWRCB), incorporating the latest data, technical refinements, and input from interested parties.