2022 Annual Review of the Construction and Operation of the State Water Project

California Water Commission (CWC) | January 18th, 2023

A Synthesis of Aquatic Science for Management of Lakes Mead and Mohave

U.S. Geological Survey (USGS) | January 29th, 2013

Lakes Mead and Mohave, which are the centerpieces of Lake Mead National Recreation Area, provide many significant benefits that have made the modern development of the So

Lakes Mead and Mohave, which are the centerpieces of Lake Mead National Recreation Area, provide many significant benefits that have made the modern development of the Southwestern United States possible. Lake Mead is the largest reservoir by volume in the nation and it supplies critical storage of water supplies for more than 25 million people in three Western States (California, Arizona, and Nevada). Storage within Lake Mead supplies drinking water and the hydropower to provide electricity for major cities including Las Vegas, Phoenix, Los Angeles, Tucson, and San Diego, and irrigation of more than 2.5 million acres of croplands. Lake Mead is arguably the most important reservoir in the nation because of its size and the services it delivers to the Western United States. This Circular includes seven chapters. Chapter 1 provides a short summary of the overall findings and management implications for Lakes Mead and Mohave that can be used to guide the reader through the rest of the Circular. Chapter 2 introduces the environmental setting and characteristics of Lakes Mead and Mohave and provides a brief management context of the lakes within the Colorado River system as well as overviews of the geological bedrock and sediment accumulations of the lakes. Chapter 3 contains summaries of the operational and hydrologic characteristics of Lakes Mead and Mohave. Chapter 4 provides information on water quality, including discussion on the monitoring of contaminants and sediments within the reservoirs. Chapter 5 describes aquatic biota and wildlife, including food-web dynamics, plankton, invertebrates, fish, aquatic birds, and aquatic vegetation. Chapter 6 outlines threats and stressors to the health of Lake Mead aquatic ecosystems that include a range of environmental contaminants, invasive species, and climate change. Chapter 7 provides a more detailed summary of overall findings that are presented in Chapter 1; and it contains a more detailed discussion on associated management implications, additional research, and monitoring needs.

Adapting to Climate Change and Drought in Selected California Groundwater Basins: Local Achievements and Challenges

California Natural Resources Agency | August 27th, 2018

Climate change projections are for higher temperatures and extreme droughts by the end of the 21st century. This will alter the natural recharge of groundwater, including

Climate change projections are for higher temperatures and extreme droughts by the end of the 21st century. This will alter the natural recharge of groundwater, including decreased inflow from runoff, increased evaporative losses, and warmer and shorter winter seasons, impacts that are likely to exacerbate already existing groundwater overdraft in many basins. Additionally, the imported surface water that can be delivered from the Central Valley Project (CVP) and State Water Project (SWP) to areas reliant on this water for groundwater recharge and consumptive use is projected to be less reliable and more expensive. Yet groundwater is a critical water supply source during drought when it compensates for reduced surface water supplies. The need for proactive adaptation strategies to address the extreme droughts projected under climate change are frequently discussed, yet there are limited examples of such groundwater management strategies. This paper therefore explores:  1) How groundwater management agencies are planning for drought  2) What new approaches are currently being used that show promise for addressing the more extreme droughts projected under climate change? 

Analysis and simulation of regional subsidence accompanying groundwater abstraction and compaction of susceptible aquifer systems in the USA

Boletín de la Sociedad Geológica Mexicana | January 17th, 2013

Regional aquifer-system compaction and land subsidence accompanying groundwater abstraction in susceptible aquifer systems in the USA is a challenge for managing groundwa

Regional aquifer-system compaction and land subsidence accompanying groundwater abstraction in susceptible aquifer systems in the USA is a challenge for managing groundwater resources and mitigating associated hazards. Developments in the assessment of regional subsidence provide more information to constrain analyses and simulation of aquifer-system compaction. Current popular approaches to simulating vertical aquifer-system deformation (compaction), such as those embodied in the aquitard drainage model and the MODFLOW subsidence packages, have proven useful from the perspective of regional groundwater resources assessment. However, these approaches inadequately address related local-scale hazards—ground ruptures and damages to engineered structures on the land surface arising from tensional stresses and strains accompanying groundwater abstraction. This paper presents a brief overview of the general approaches taken by the U.S. Geological Survey toward understanding aquifer-system compaction and subsidence with regard to a) identifying the affected aquifer systems; b) making regional assessments; c) analyzing the governing processes; and d) simulating historical and future groundwater flow and subsidence conditions. Limitations and shortcomings of these approaches, as well as future challenges also are discussed 

Anthropogenic warming impacts on California snowpack during drought

American Geophysical Union (AGU) | March 15th, 2017

Sierra Nevada climate and snowpack is simulated during the period of extreme drought from 2011 to 2015 and compared to an identical simulation except for the removal of t

Sierra Nevada climate and snowpack is simulated during the period of extreme drought from 2011 to 2015 and compared to an identical simulation except for the removal of the twentieth century anthropogenic warming. Anthropogenic warming reduced average snowpack levels by 25%, with middle‐to‐low elevations experiencing reductions between 26 and 43%. In terms of event frequency, return periods associated with anomalies in 4 year 1 April snow water equivalent are estimated to have doubled, and possibly quadrupled, due to past warming. We also estimate effects of future anthropogenic warmth on snowpack during a drought similar to that of 2011–2015. Further snowpack declines of 60–85% are expected, depending on emissions scenario. The return periods associated with future snowpack levels are estimated to range from millennia to much longer. Therefore, past human emissions of greenhouse gases are already negatively impacting statewide water resources during drought, and much more severe impacts are likely to be inevitable.

Assessing the Effects of Climate Change on Middle Rio Grande Surface Water Supplies Using a Simple Water Balance Reservoir Model

American Meteorological Society (AMS) | August 12th, 2022

The middle Rio Grande is a vital source of water for irrigation in the region. Climate change is impacting regional hydrology and is likely to put additional stress on a

The middle Rio Grande is a vital source of water for irrigation in the region. Climate change is impacting regional hydrology and is likely to put additional stress on a water supply that is already stretched thin. To gain insight on the hydrologic effects of climate change on reservoir storage, a simple water balance model was used to simulate the Elephant Butte–Caballo Reservoir system (southern New Mexico). The water balance model was forced by hydrologic inputs generated by 97 climate simulations derived from CMIP5 global climate models, coupled to a surface hydrologic model. Results suggest that the percentage of years that reservoir releases satisfy agricultural water rights allocations over the next 50 years (2021–70) will decrease relative to the past 50 years (1971–2020). The modeling also projects an increase in multiyear drought events that hinder reservoir management strategies to maintain high storage levels. In most cases, changes in reservoir inflows from distant upstream snowmelt is projected to have a greater influence on reservoir storage and water availability downstream of the reservoirs than will changes in local evaporation and precipitation from the reservoir surfaces.

Balancing Flood Risk and Water Supply in California: Policy Search Integrating Short-Term Forecast Ensembles With Conjunctive Use

American Geophysical Union (AGU) | September 24th, 2018

Short-term weather forecasts have the potential to improve reservoir operations for both flood control and water supply objectives, especially in regions currently relyin

Short-term weather forecasts have the potential to improve reservoir operations for both flood control and water supply objectives, especially in regions currently relying on fixed seasonal flood pools to mitigate risk. The successful development of forecast-based policies should integrate uncertainty from modern forecast products to create unambiguous rules that can be tested on out-of-sample periods. This study investigates the potential for such operating policies to improve water supply efficiency while maintaining flood protection, combining state-of-the-art weather hindcasts with downstream conjunctive use to transfer surplus flood releases to groundwater storage. Because available weather hindcasts are relatively short (10–20 years), we propose a novel statistical framework to develop synthetic forecasts over longer periods of the historical record. Operating rules are trained with a recently developed policy search framework in which decision rules are structured as binary trees. Policies are developed for a range of scenarios with varying forecast skill and conjunctive use capacity, using Folsom Reservoir, California, as a case study. Results suggest that the combination of conjunctive use and short-term weather forecasts can substantially improve both water supply and flood control objectives by allowing storage to remain high until forecasts trigger a release. Further, increased conjunctive use capacity reduces the importance of forecast skill, since surface storage can be moved to groundwater during the flood season without losing water supply. This analysis serves the development of forecast-based operating policies for large, multipurpose reservoirs in California and other regions with similar flood hydroclimatology.

Bulletin 17-65, Dams within Jurisdiction of the State of California

California Department of Water Resources (DWR) | August 31st, 1965

Bulletin 17-71, Dams within Jurisdiction of the State of California

California Department of Water Resources (DWR) | October 29th, 1971

Bulletin 17-74, Dams within Jurisdiction of the State of California

California Department of Water Resources (DWR) | May 31st, 1974