Analysis of Colorado River Basin Storage Suggests Need For Immediate Action

John Fleck | September 11th, 2025

Analysis of Groundwater Basin Yield, Upper Santa Clara River Groundwater Basin, East Subbasin, Los Angeles County, California

Castaic Lake Water Agency | August 15th, 2005

This report presents an evaluation of the long-term sustainability of existing groundwater management practices in the Santa Clarita Valley, located in northwestern Los

This report presents an evaluation of the long-term sustainability of existing groundwater management practices in the Santa Clarita Valley, located in northwestern Los Angeles County, California. The groundwater system in the Santa Clarita Valley is identified by the California Department of Water Resources (DWR) as the Santa Clara River Valley Groundwater Basin, East Subbasin (Basin No. 4-4.07) and lies within the DWR-designated Upper Santa Clara River Hydrologic Area. Groundwater in the basin is pumped from a shallow Alluvial Aquifer and deeper groundwater resources that are present in an older, underlying unit called the Saugus Formation. Most groundwater pumping is by the local water purveyors (the Upper Basin Water Purveyors [herein referred to as the Purveyors1]) for municipal uses (in the range of approximately 23,000 to 28,000 acre-feet per year [AF/yr] in recent years), with some continuing pumping by private landowners, primarily for irrigation uses (approximately 15,000 to 16,000 AF/yr in recent years). The Purveyors also have access to other sources of water, including imported State Water Project (SWP) water, groundwater banking outside the basin, recycled water, short-term water exchanges, and dry-year water purchase programs (Luhdorff & Scalmanini Consulting Engineers [LSCE], 2005a). The water management practices of the Purveyors call for maximizing the use of Alluvial Aquifer and imported water during years of normal or above-normal availability of these supplies, and limiting the use of the Saugus Formation during these periods, then temporarily increasing Saugus Formation pumping during years when supplemental imported water supplies are significantly reduced because of drought conditions. The evaluation of the Purveyors’ current groundwater management practices has been performed using a detailed numerical groundwater flow model of the basin. The model, called the Santa Clarita Valley Groundwater Model (Regional Model), simulates the occurrence and flow of groundwater, including its interaction with streams in the area. The Regional Model has been developed for the Purveyors as a tool for the analysis of groundwater management options in the context of future water demands and water supply conditions in the valley. Among the objectives in developing the model were (1) to be able to evaluate the long-term sustainability (yield) of the Alluvial and Saugus aquifer systems under a range of existing and potential future water resource management conditions, and (2) to facilitate general management of water quantity and water quality issues. Figure 1-1 is a map showing the area simulated by the model (tables and figures are located at the end of each section).  

Analysis of Potential Water-Supply Management Options, 2010-60, and Documentation of Revisions to the Model of the Irwin Basin Aquifer System, Fort Irwin National Training Center, California

U.S. Geological Survey (USGS) | October 31st, 2014

The Fort Irwin National Training Center is considering several alternatives to manage their limited water-supply sources in the Irwin Basin. An existing three-dimensional

The Fort Irwin National Training Center is considering several alternatives to manage their limited water-supply sources in the Irwin Basin. An existing three-dimensional, finite-difference groundwater-flow model—the U.S. Geological Survey’s MOD-FLOW—of the aquifer system in the basin was updated and the initial input dataset was supplemented with groundwater withdrawal data for the period 2000–10. The updated model was then used to simulate four combinations, or scenarios, of groundwater withdrawal and recharge over the next 50 years (January 2011 through December 2060). The scenarios included combinations of continuing withdrawals from currently active production wells, supplementing any increases in demand with withdrawals from an inactive production well, reducing withdrawal amounts and rates, and reducing the discharge of treated wastewater to infiltration ponds that provide a recharge source to the underlying aquifer. Results of the simulations indicated that, depending on the scenario implemented, groundwater levels would rise (over the next 50 years) from 40 feet to as much as 65 feet in the northwestern part of the Irwin Basin, and from 5 feet to 10 feet in the southeastern part.

Analysis of the Carmel Valley Alluvial Ground-Water Basin, Monterey County, California

U.S. Geological Survey (USGS) | June 14th, 1984

A two-dimensional, finite-element, digital model was developed for the Carmel Valley alluvial ground-water basin using measured, computed, and estimated discharge

A two-dimensional, finite-element, digital model was developed for the Carmel Valley alluvial ground-water basin using measured, computed, and estimated discharge and recharge data for the basin. Discharge data included evapotranspiration by phreatophytes and agricultural, municipal, and domestic pumpage. Recharge data included river leakage, tributary runoff, and pumping return flow. Recharge from subsurface boundary flow and rainfall infiltration was assumed to be insignificant. From 1974 through 1978, the annual pumping rate ranged from 5,900 to 9,100 acre-feet per year with 55 percent allotted to municipal use principally exported out of the valley, 44 percent to agricultural use, and 1 percent to domestic use. The pumpage return flow within the valley ranged from 900 to 1,500 acre-feet per year. The aquifer properties of transmissivity (about 5,900 feet squared per day) and of the storage coefficient (0.19) were estimated from an average alluvial thickness of 75 feet and from less well-defined data on specific capacity and grain-size distribution. During calibration the values estimated for hydraulic conductivity and storage coefficient for the lower valley were reduced because of the smaller grain size there. The river characteristics were based on field and laboratory analyses of hydraulic conductivity and on altitude survey data. The model is intended principally for simulation of flow conditions using monthly time steps. Time variations in transmissivity and short-term, high- recharge potential are included in the model. The years 1974 through 1978 (including "pre-" and "post-" drought) were selected because of the extreme fluctuation in water levels between the low levels measured during dry years and the above-normal water levels measured during the preceding and following wet years. Also, during this time more hydrologic information was available. Significantly, computed water levels were generally within a few feet of the measured levels, and computed flows were close to gaged river flows for this simulation. However, the nonuniqueness of solutions with respect to different sets of data indicates the model does not necessarily validate the correctness of the individual variables. The model might be improved with additional knowledge of the distribution of confining sediments in the lower end of the valley and the aquifer properties above and below them. The solution algorithm could account for confinement or partial confinement in the lower end of the valley plus contributions from the Tularcitos aquifer.

Analysis of the costs and benefits of using marsh restoration as a sea level rise adaptation strategy in San Francisco Bay

Bay Institute | February 22nd, 2013

The purpose of this study is to examine opportunities to protect San Francisco Bay’s recovering tidal marsh ecosystems while helping bayshore communities to manage the

The purpose of this study is to examine opportunities to protect San Francisco Bay’s recovering tidal marsh ecosystems while helping bayshore communities to manage the impacts of sea level rise. Specifically, it considers the flood risk management functions that tidal marshes perform naturally and evaluates the possibility of integrating those functions into a co-beneficial shoreline management strategy. The study’s intended audience is planners, politicians, regulators, and other stakeholders with the authority to make or affect decisions that influence the configuration and use of the San Francisco Bay shoreline. The study examines the current functions of San Francisco Bay tidal marshes as well as existing flood risk management strategies. It considers how environmental conditions are likely to change in the era of climate change, and how we can adapt our marshes and our flood risk management practices to accommodate these changes.

Anatomy of a range contraction: Flow–phenology mismatches threaten salmonid fishes near their trailing edge

National Academy of Sciences (NAS) | March 31st, 2025

Climate change is redistributing life on Earth, with profound impacts for ecosystems and human well-being. While repeat surveys separated by multidecadal intervals can de

Climate change is redistributing life on Earth, with profound impacts for ecosystems and human well-being. While repeat surveys separated by multidecadal intervals can determine whether observed shifts are in the expected direction (e.g., poleward or upslope due to climate change), they do not reveal their mechanisms or time scales: whether they were gradual responses to environmental trends or punctuated responses to disturbance events. Here, we document population reductions and temporary range contractions at multiple sites resulting from drought for three Pacific salmonids at their ranges’ trailing edge. During California’s 2012 to 2016 historic multiyear drought, the 2013 to 2014 winter stood apart because rainfall was both reduced and delayed. Extremely low river flows during the breeding season (“flow–phenology mismatch”) reduced or precluded access to breeding habitat. While Chinook (Oncorhynchus tshawytscha) experienced a down-river range shift, entire cohorts failed in individual tributaries (steelhead trout, O. mykiss) and in entire watersheds (coho salmon, O. kisutch). Salmonids returned to impacted sites in subsequent years, rescued by reserves in the ocean, life history diversity, and, in one case, a conservation broodstock program. Large population losses can, however, leave trailing-edge populations vulnerable to extinction due to demographic stochasticity, making permanent range contraction more likely. When only a few large storms occur during high flow season, the timing of particular storms plays an outsized role in determining which migratory fish species are able to access their riverine breeding grounds and persist.

Anderson Subbasin Groundwater Sustainability Plan

Enterprise Anderson Groundwater Sustainability Agency | January 20th, 2022

This GSP covers all of the 98,700 acres of the Anderson Subbasin. The GSP describes the current groundwater conditions and hydrogeologic conceptual model, establishes a

This GSP covers all of the 98,700 acres of the Anderson Subbasin. The GSP describes the current groundwater conditions and hydrogeologic conceptual model, establishes a water budget, outlines local sustainable management criteria (SMC or SMCs), and describes projects and management actions for maintaining sustainability through the GSP planning and implementation period. Due to size, this file has been divided into 9 parts. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9

Anderson-Cottonwood Irrigation District Integrated Regional Water Management Program – Groundwater Production Element Project

U.S. Bureau of Reclamation (USBR) | August 15th, 2011

This project would improve the flexibility and reliability of the District’s water supply, particularly during dry and critically dry water years. In 2004, ACID’s sur

This project would improve the flexibility and reliability of the District’s water supply, particularly during dry and critically dry water years. In 2004, ACID’s surface water rights were reduced from 165,000 to 121,000 ac-ft per year as part of the renegotiation of the 40-year Settlement Contract. Furthermore, the west side of the District’s system has little to no downstream control. Control of the system is achieved at the head of the 35-mile main canal, causing some delivery difficulties at the downstream end of the service area. By pushing water from upstream to downstream without an ability to manage intermediate water surface elevations, downstream response time to water delivery needs can be greatly hindered. This project would help with the flexibility and reliability required to meet agricultural water needs.

Annotated Bibliography for Sycamore Alluvial Woodland Habitat Mapping and Regeneration Studies Project

San Francisco Estuary Institute (SFEI) | February 27th, 2017

The California sycamore (Platanus racemosa) is a riparian tree native to California and northern Baja California. California sycamore is the dominant species in sycamore

The California sycamore (Platanus racemosa) is a riparian tree native to California and northern Baja California. California sycamore is the dominant species in sycamore alluvial woodland (SAW), a habitat type defined as open to moderately closed, winter-deciduous broad-leafed riparian woodland dominated by well-spaced Platanus racemosa (Holland 1986), and California sycamore also occurs in the “Platanus racemosa woodland alliance” with various associated species (Sawyer, Keeler-Wolf, and Evens 2009). The central California sycamore alluvial woodland (SAW) habitat type is cited in the Santa Clara Valley Habitat Plan (VHP) as a “very rare and threatened land cover type,” and the VHP contains various goals to conserve and restore SAW habitat. The San Francisco Estuary Institute (SFEI) and H. T. Harvey & Associates (HTH), in conjunction with the Santa Clara Habitat Agency, have undertaken the Sycamore Alluvial Woodland Habitat Mapping and Regeneration Studies Project to assess biotic and abiotic factors that influence California sycamore stand health and regeneration. The study is intended to gather and generate data that will be used by the Santa Clara Habitat Agency to guide acquisition and management of California sycamore habitat to meet its conservation goals. 

Annual Ground-Water Discharge by Evapotranspiration from Areas of Spring-Fed Riparian Vegetation Along the Eastern Margin of Death Valley, 2000–02

U.S. Geological Survey (USGS) | July 1st, 2006