Guide to Compliance with California’s Sustainable Groundwater Management Act: How to avoid the “undesirable result” of “significant and unreasonable adverse impacts on beneficial uses of surface waters"

Stanford University | September 4th, 2018

In enacting the Sustainable Groundwater Management Act (SGMA) the California Legislature, for the first time ever, expressly linked the two historically distinct legal r

In enacting the Sustainable Groundwater Management Act (SGMA) the California Legislature, for the first time ever, expressly linked the two historically distinct legal regimes governing water in the state that previously had been entirely separate: one governing surface water use and the other groundwater use. SGMA requires Groundwater Sustainability Agencies (GSAs) and their Groundwater Sustainability Plans (GSPs or Plans) to consider and address the groundwater-surface water interaction, and specifically the impacts of groundwater pumping on surface water beneficial uses. SGMA defines sustainable groundwater management as the avoidance of six “undesirable results” identified in the law. The purpose of this guide is to help GSAs and other stakeholders understand and comply with the requirement of SGMA that groundwater withdrawals must not cause “significant and unreasonable adverse impacts on beneficial uses of the surface water,” known as “undesirable result no. 6.” This guide is based on the principle that existing legal frameworks (laws, regulations, court decisions, etc.) provide the clearest and most pertinent guidance on what constitutes undesirable result no. 6. This guide addresses only the explicit legal aspects of this statutory mandate. It does not address technical and scientific aspects of SGMA compliance and offers no advice on the steps GSAs must take to get an adequate technical understanding of the groundwater-surface water connections under their purview. GSAs may look to other sources for guidance on that front. In addition, “Navigating Groundwater-Surface Water Interactions under the Sustainable Groundwater Management Act,” authored by experts at the University of California Berkeley provides a helpful overview of the steps involved in implementing SGMA provisions relating to groundwater-surface water interactions.  

Guidebook for Implementation of SB 610 and SB 221 to assist water suppliers, cities, and counties in integrating water and land use planning

California Department of Water Resources (DWR) | October 10th, 2003

Senate Bills 610 (Chapter 643, Statutes of 2001) and Senate Bill 221 (Chapter 642, Statutes of 2001) amended state law, effective January 1, 2002, to improve the link bet

Senate Bills 610 (Chapter 643, Statutes of 2001) and Senate Bill 221 (Chapter 642, Statutes of 2001) amended state law, effective January 1, 2002, to improve the link between information on water supply availability and certain land use decisions made by cities and counties. SB 610 and SB 221 are companion measures which seek to promote more collaborative planning between local water suppliers and cities and counties. Both statutes require detailed information regarding water availability to be provided to the city and county decision-makers prior to approval of specified large development projects. Both statutes also require this detailed information be included in the administrative record that serves as the evidentiary basis for an approval action by the city or county on such projects. Both measures recognize local control and decision making regarding the availability of water for projects and the approval of projects.  Under SB 610, water assessments must be furnished to local governments for inclusion in any environmental documentation for certain projects (as defined in Water Code 10912 [a]) subject to the California Environmental Quality Act. Under SB 221, approval by a city or county of certain residential subdivisions requires an affirmative written verification of sufficient water supply. If coordinated and comprehensive water supply planning is underway at the time that the SB 610-water assessment is prepared, compliance with SB 221 will be greatly facilitated. SB 221 is intended as a ‘fail safe’ mechanism to ensure that collaboration on finding the needed water supplies to serve a new large subdivision occurs when it should – before construction begins. Not every project that is subject to the requirements of SB 610 would also require the mandatory water verification of SB 221 (e.g. if there is no subdivision map approval). Conversely, not every project that is subject to the requirements of SB 221 would also require the environmental document to contain an SB 610 water supply assessment. Projects approved before January 1, 2002 were not subject to the requirements of SB 610 or SB 221; however, some projects may have been subject to the requirement to prepare a water supply assessment as set forth in Senate Bill 901 of 1995 (Chapter 881, Statues of 1995). A foundational document for compliance with both SB 610 and SB 221 is the Urban Water Management Plan (UWMP). Both of these statutes repeatedly identify the UWMP as a planning document that, if properly prepared, can be used by a water supplier to meet the standards set forth in both statutes. Thorough and complete UWMPs will allow water suppliers to use UWMPs as a foundation to fulfill the specific requirements of these two statutes. Cities, counties, water districts, property owners, and developers will all be able to utilize this document when planning for and proposing new projects.

Guidebook to Assist Urban Water Suppliers to Prepare a 2010 Urban Water Management Plan

California Department of Water Resources (DWR) | March 17th, 2011

Guidebook to Assist Urban Water Suppliers to Prepare a 2010 Urban Water Management Plan (Guidebook) has been developed by the California Department of Water Resources (

Guidebook to Assist Urban Water Suppliers to Prepare a 2010 Urban Water Management Plan (Guidebook) has been developed by the California Department of Water Resources (DWR) to assist urban water suppliers in complying with requirements of the Urban Water Management Planning Act (the UWMP Act) and the Water Conservation Bill of 2009. It is meant to help suppliers better understand UWMP Act requirements, but water suppliers are solely responsible for ensuring they’ve complied with the requirements of the UWMP Act or applicable laws. For the purposes of this Guidebook and the UWMP Act, urban water suppliers with 3,000 or more service connections or supplying 3,000 or more acre-feet of water per year are to prepare a UWMP every five years.

Guidelines for Preparing Economic Analyses

U.S. Environmental Protection Agency (EPA) | May 30th, 2014

The Guidelines for Preparing Economic Analyses are part of a continuing effort by U.S. Environmental Protection Agency (EPA) to develop improved guidance on the preparati

The Guidelines for Preparing Economic Analyses are part of a continuing effort by U.S. Environmental Protection Agency (EPA) to develop improved guidance on the preparation and use of sound science in support of the decision-making process. This document builds on previous work first issued in December of 1983 as the Guidelines for Performing Regulatory Impact Analysis (U.S. EPA 1983) and later revised in the late 1990s. In September of 2000, the EPA issued its Guidelines for Preparing Economic Analyses (Guidelines) (U.S. EPA 2000b), revised to reflect the evolution of environmental policy making and economic analysis that had accrued over the decade and a half since the original guidelines were released. At the time of release, EPA committed to periodically revise the Guidelines to account for further growth and development of economic tools and practices. In an effort to fulfill that commitment, this document incorporates new literature published since the last revision of the Guidelines. It describes new Executive Orders (EOs) and recent guidance documents that impose new requirements on analysts, and fills information gaps by providing more expansive information on selected topics. Furthermore, a loose-leaf format has been adopted to facilitate the incorporation of new information in the future. This new, more flexible format, in addition to the electronic release of the document, will allow future updates and additions without requiring a wholesale revision of the document.

Guidelines for the Small Community Drought Relief Program

California Department of Water Resources (DWR) | September 20th, 2022

Handbook for Assessing Value of State Flood Management Investments

California Department of Water Resources (DWR) | June 8th, 2014

Millions of people and over half a trillion dollars in assets are exposed to flood risk in California (DWR 2013a). This remains the case even as State, federal, and local

Millions of people and over half a trillion dollars in assets are exposed to flood risk in California (DWR 2013a). This remains the case even as State, federal, and local flood management agencies have worked for decades to reduce the risk and consequences of flooding in the State. The people of California have shown that they understand the increasing flood risk due to population growth, environmental concerns, climate change, and land use practices, and they are willing to invest in flood risk management projects. This requires the public agencies responsible for California’s flood risk management to demonstrate the value of those investments both before and after they are implemented. This Handbook for Assessing Value of State Flood Management Investments (HAV) supports that effort. The California Department of Water Resources (DWR) has identified foundational goals that shape the State’s water management investment strategy. Those goals are: Improving public safety Fostering environmental stewardship Supporting economic stability

Handbook for Developing Watershed Plans to Restore and Protect Our Waters

U.S. Environmental Protection Agency (EPA) | March 20th, 2008

This handbook provides information on developing and implementing watershed management plans that help to restore and protect water quality. A watershed is the area of la

This handbook provides information on developing and implementing watershed management plans that help to restore and protect water quality. A watershed is the area of land that contributes runoff to a lake, river, stream, wetland, estuary, or bay. A watershed management plan defines and addresses existing or future water quality problems from both point sources and nonpoint sources of pollutants. Experience over the past decade has shown that effective watershed management includes active participation from stakeholders, analysis and quantification of the specific causes and sources of water quality problems, identification of measurable water quality goals, and implementation of specific actions needed to  solve those problems. This handbook is intended to serve as the basis for developing and implementing watershed plans to meet water quality standards and protect water resources. Although watershed plans are useful for all watersheds to protect and restore water resources, as well as to meet other community resource goals, they are critical for impaired or threatened waterbodies. The most recent national water quality assessment reported that 40 to 50 percent of the nation’s assessed waterbodies are impaired or threatened. 3/20This handbook is designed to provide a framework to help you develop a scientifically defensible plan that will lead to measurable results and an overall improvement in the water quality and watershed conditions that are important to your community.

Hazard: The Future of the Salton Sea With No Restoration Project

Pacific Institute | May 1st, 2006

The Salton Sea lies on the brink of catastrophic change. The amount of water flowing into the Sea in the next twenty years will decrease by more than 40%, causing

The Salton Sea lies on the brink of catastrophic change. The amount of water flowing into the Sea in the next twenty years will decrease by more than 40%, causing its surface elevation to drop by more than 20 feet, rapidly shrinking its volume by more than 60%, tripling its salinity, and exposing more than 100 square miles of dusty lakebed to the desert’s blowing winds. These changes will cause four major impacts: Human health in the Imperial and Coachella valleys – currently home to more than 400,000 people and growing quickly – will be harmed by the estimated 33% increase in the amount of fine windblown dust in the basin. The Imperial Valley already suffers from the highest childhood asthma hospitalization rate in the state; the growing number of retirees living in both valleys are especially susceptible to poor air quality. Air quality in these two valleys – which already fails to meet state and federal air quality standards – would get much worse, increasing the cost of bringing these areas into compliance. Air quality-related litigation and state liability will increase. California has assumed ultimate responsibility for managing only those lands exposed due to a recent set of water transfers, constituting about half of the estimated 134 square miles exposed in 30 years. Responsibility for managing any dust blowing off the other 60 or so square miles will rest with the individual property owner. However, there is no clear way to determine which lands will be exposed due to the water transfers and which will be exposed due to other actions. Total air quality management costs at Owens Lake have exceeded $400 million. Costs at the Salton Sea could be higher. Many – if not most – of the hundreds of thousands of birds that currently use the Sea will lose their roosting and breeding habitats and their sources of food. The Sea’s fish will be almost entirely gone within a dozen years. Those birds that remain will suffer from disease and the reproductive deformities and failures that plagued the Kesterson National Wildlife Refuge twenty years ago. Some of the endangered and threatened species that use the Sea may be able to find other habitats, but others could suffer significant population losses. The tremendous scale of the Sea adds to its complexity, and the difficulty of finding a viable solution. The Sea currently runs almost 35 miles long, and 15 miles at its widest point, covering about 365 square miles. It has the largest surface area of any lake in California, yet is barely 50 feet at its deepest point. The Sea is 1/3 saltier than the ocean, and, fed by the fertilizers running off of neighboring fields, sustains incredible levels of biological productivity. Until recently, the amount of water entering the Sea was roughly balanced by the amount of water evaporating from its broad surface. Stabilizing the Sea at its current salinity would require the removal of more than four million tons of salt each year, assuming flows to the Sea do not change. But they will change. Under a set of agreements signed in 2003, the Imperial Valley has begun to transfer water to San Diego County, ultimately reducing flows to the Salton Sea. Other actions, including actions in Mexico, will also reduce the amount of water flowing to the Sea, by 45% or more in the next 30-40 years. These changes will dramatically decrease the size of the Salton Sea and the quality of its water. In September, 2003, the California legislature passed a set of laws that implement the 2003 water agreements and provide a 15-year reprieve for the Sea. The legislation offers the prospect of more than $300 million of restoration funds, but it does not guarantee a long-term restoration project for the Salton Sea. California’s Resources Agency will submit a Salton Sea Ecosystem Restoration Plan and related documents to the state legislature by December 31, 2006. The cost of any long-term restoration plan will almost certainly exceed a billion dollars. Although various private-public partnerships have been suggested, funding and implementation of any restoration plan is far from certain, especially given the lack of consensus on a preferred alternative.

Hazy Futures: Projecting the local impacts of global warming is a stubborn challenge. But cities need answers fast

American Association for the Advancement of Science (AAAS) | June 5th, 2025

A wastewater treatment plant isn’t top on everyone’s sightseeing itinerary. But on a cloudless, breezy day in April, Agmed Weber, operations manager for the Walnut Cr

A wastewater treatment plant isn’t top on everyone’s sightseeing itinerary. But on a cloudless, breezy day in April, Agmed Weber, operations manager for the Walnut Creek plant—which handles more than half of the sewage here in Texas’s booming capital city—is an enthusiastic tour guide. He marvels at the foresight of those who built the jumbo plant a half-century ago, when Austin was a third of its current size. “They were really thinking about the future,” he says. Weber feels a similar pressure—to prepare for not only continued population growth, but also a hotter future. Austin is “in a tight space where we need to think ahead,” he says.

HEC-HMS Models for the Sacramento and San Joaquin River Basins Comprehensive Study

U.S. Army Corps of Engineers (USACE) | August 1st, 2001

Due to several large and damaging flood events on the Sacramento and San Joaquin Rivers (California) during the 1980s and 1990s, the U.S. House of Representatives

Due to several large and damaging flood events on the Sacramento and San Joaquin Rivers (California) during the 1980s and 1990s, the U.S. House of Representatives directed the Sacramento District to develop comprehensive plans for flood control for the two rivers and to develop hydrologic and hydraulic models of the river systems. The models will be used to provide better forecasts and evaluations of flood damage reduction alternatives. Additionally, the model results will be used as input for reservoir simulation models. The Sacramento River Basin and the San Joaquin River/Tulare Lake Bed Basins comprise nearly 60,000 square miles, drain California’s Central Valley floor and receive much of their runoff from the Sierra Nevada mountain range. Developing hydrologic models for the tributary basins (which included extremely variable terrain) within a ten month time period was a formidable task. The District contacted the Hydrologic Engineering Center (HEC) to assist with the development of these models. HEC used the Hydrologic Modeling System program, HEC-HMS, and introduced the HEC-GeoHMS grid-based technology to perform the hydrologic study. GeoHMS is an ArcView® extension that provides automated subbasin delineation methods and calculates many physical characteristics used for estimation of hydrologic parameters. HEC developed and calibrated 33 individual HEC-HMS models for the major tributaries and portions of the valley floors of the Sacramento River Basin and the San Joaquin River / Tulare Lake Bed Basins. GeoHMS was used to delineate the individual river basins, perform initial subbasin delineation and develop the physical characteristics for the subbasins. Tools within GeoHMS allowed the modelers to iteratively redelineate their subbasins, as appropriate, to meet project needs. Keeping the modeling effort consistent was critical to the success of the study. To ensure this consistency of procedures and results, HEC developed modeling guidelines that each of the 11 modeling teams followed. Once the grid-based HEC-HMS models were developed, HEC contracted with the Corps’ Cold Regions Research and Engineering Laboratory (CRREL) to perform a snowmelt study for the watersheds. HEC provided a gridded precipitation file (4 km2) to CRREL. Through the use of their Distributed Snow Process Model (DSPM), CRREL then provided a gridded snowmelt/ precipitation file to HEC. DSPM computes snowmelt and rainfall depths at the soil surface on a grid-cell basis. This data is used directly by HEC-HMS as precipitation on the watershed. The ModClark rainfall to runoff transformation was used to compute the subbasin hydrographs. HEC-HMS parameter optimization models were developed at hourly flow gages for the unregulated headwater streams. The runoff parameter optimization models allowed the modelers to develop the runoff parameters necessary for the regression analysis. A number of physical characteristics were evaluated for correlation with variations in Clark’s time of concentration, TC, for the optimization models. The results of the regression analysis allowed the modelers to populate the ungaged subbasins with appropriate unit hydrograph parameters. Approximately 200 hourly flow gages and 83 reservoirs were considered in calibrating the models. The 33 individual basin models were then given to the Sacramento District.