Tulare Lake

Regional Governance of Flood Management in the Central Valley

California Department of Water Resources (DWR) | May 30th, 2014

California faces significant challenges in managing its highly variable water resources, particularly as climate change and a growing population exacerbate drought and fl

California faces significant challenges in managing its highly variable water resources, particularly as climate change and a growing population exacerbate drought and flood risks.  The California Department of Water Resources (DWR) and other state agencies have been encouraging integrated approaches to water management, taking into account the connections between water supply, water quality, flood protection, and ecosystem health. The recent California Water Action Plan calls for improved coordination between local, state and federal agencies and tribal governments in order to develop multi-­benefit water management strategies. Regional-­scale planning has become a crucial avenue for advancing these efforts. Initiated in 2002, the Integrated Regional Water Management Planning (IRWM) process has led to the formation of 48 water planning regions statewide, in which diverse local agencies have developed integrated plans for managing all aspects of a region’s water management. More recently, a Regional Flood Management Planning (RFMP) process was created in the context of the Central Valley Flood Protection Plan to advance integrated approaches to reducing flood risks. Six flood planning regions, overlapping with nine IRWM regions, were formed in 2012. This study analyzes the origins and functioning of the IRWM and RFMP processes, and the degree of coordination between them to address flood risks in the Central Valley. In particular, it examines how each is working to generate multi-­benefit strategies, and how they account for climate change. It also discusses opportunities for future coordination between the IRWM and RFMP processes, and DWR’s role in supporting this. This study is primarily based upon an analysis of publicly available documents related to the IRWM and RFMP processes. It is also informed by meeting observations and conversations with staff at DWR and the Central Valley Flood Protection Board, and participants in IRWM and RFMP processes. Since RFMPs were not yet completed at the time of this writing, this study’s findings are preliminary. Nonetheless, this report provides an indication of the overall functioning of these RFMP and IRWM regions, and some general considerations for DWR as it assesses next steps in supporting these programs.

Regional nitrate and pesticide trends in ground water in the eastern San Joaquin Valley, California

American Society of Agronomy (ASA) | September 18th, 2008

Protection of ground water for present and future use requires monitoring and understanding of the mechanisms controlling long-term quality of ground water. In this stu

Protection of ground water for present and future use requires monitoring and understanding of the mechanisms controlling long-term quality of ground water. In this study, spatial and temporal trends in concentrations of nitrate and pesticides in ground water in the eastern San Joaquin Valley, California, were evaluated to determine the long-term effects of agricultural and urban development on regional ground-water quality. Trends in concentrations of nitrate, the nematocide 1,2-dibromo-3-chloropropane, and the herbicide simazine during the last two decades are generally consistent with known nitrogen fertilizer and pesticide use and with the position of the well networks in the regional ground-water fl ow system. Concentrations of nitrate and pesticides are higher in the shallow part of the aquifer system where domestic wells are typically screened, whereas concentrations are lower in the deep part of the aquifer system where public-supply wells are typically screened. Attenuation processes do not seem to significantly affect concentrations. Historical data indicate that concentrations of nitrate have increased since the 1950s in the shallow and deep parts of the aquifer system. Concentrations of nitrate and detection of pesticides in the deep part of the aquifer system will likely increase as the proportion of highly affected water contributed to these wells increases with time. Because of the time of travel between the water table and the deep part of the aquifer system, current concentrations in public-supply wells likely reflect the effects of 40- to 50-year-old management practices.

Regional patterns in the geochemistry of oil-field water, southern San Joaquin Valley, California, USA

Applied Geochemistry (Elsevier) | September 21st, 2018

Chemical and isotopic data for water co-extracted with hydrocarbons in oil and gasfields are commonly used toexamine the source of the formation water and possible impact

Chemical and isotopic data for water co-extracted with hydrocarbons in oil and gasfields are commonly used toexamine the source of the formation water and possible impacts on groundwater in areas of oil and gas de-velopment. Understanding the geochemical variability of oil-field water could help to evaluate its origin anddelineate possible contamination of shallow aquifers in cases where oil-field water is released to the environ-ment. Here we report geochemical and multiple isotope (H, C, O, Sr, Ra) data from 22 oil wells, three sources ofproduced water that are disposed of in injection wells, and two surface disposal ponds in four oilfields in thesouthern San Joaquin Valley, California (Fruitvale, Lost Hills, North and South Belridge). Correlations betweenCl andδ18O, as well as other ions, and gradual increases in salinity with depth, indicate dilution of one or moresaline end-members by meteoric water. The saline end-members, represented by deep samples (610 m–2621 m)in three oil-bearing zones, are characterized by NaeCl composition, near-seawater Cl concentrations (median20,000 mg/L), enrichedδ18OeH2O (median 3.4‰), high ammonium (up to 460 mg-N/L), and relatively highradium activity (226Ra+228Ra = 12.3 Bq/L). The deepest sample has low Na/Cl (0.74), high Ca/Mg (5.0), andlow87Sr/86Sr (0.7063), whereas the shallower samples have higher Na/Cl (0.86–1.2), Ca/Mg near 1, and higher87Sr/86Sr (∼0.7083). The data are consistent with an original seawater source being modified by various depthand lithology dependent diagenetic processes. Dilution by meteoric water occurs naturally on the east side of thevalley, and in association with water-injection activities on the west side. Meteoric-waterflushing, particularlyon the east side, results in lower solute concentrations (minimum total dissolved solids 2730 mg/L) and totalradium (minimum 0.27 Bq/L) in oil-field water, and promotes biodegradation of dissolved organic carbon andhydrocarbon gases like propane. Acetate concentrations andδ13C of dissolved inorganic carbon indicate biogenicmethane production occurs in some shallow oil zones. Natural and human processes produce substantialvariability in the geochemistry of oil-field water that should be considered when evaluating mixing between oil-field waters and groundwater. The variability could result in uncertainty as to detecting the potential source andimpact of oil-field water on groundwater.

Relative risk of groundwater-quality degradation near California (USA) oil fields estimated from 3H, 14C, and 4He

Applied Geochemistry (Elsevier) | June 5th, 2021

 Relative risks of groundwater-quality degradation near selected California oil fields are estimated by examining spatial and temporal patterns in chemical and isotopic

 Relative risks of groundwater-quality degradation near selected California oil fields are estimated by examining spatial and temporal patterns in chemical and isotopic data in the context of groundwater-age categories defined by tritium and carbon-14. In the Coastal basins, western San Joaquin Valley (SJV), and eastern SJV; 82, 76, and 0% of samples are premodern (pre-1953 recharge), respectively; and 3, 0, and 31% are modern (recharged during or after 1953), respectively. Carbon-14 and helium-4 data indicate most premodern samples are 1000 to 10,000 (33%) or >10,000 (50%) years old. Organic chemicals that could be associated with deeper hydrocarbon reservoirs (e.g. thermogenic gases and benzene) occur most frequently in premodern groundwater, suggesting premodern groundwater has a higher risk of degradation from upward migration of hydrocarbons than modern and mixed-age groundwater. Low sulfate concentrations in some premodern groundwater containing high thermogenic-methane concentrations (>28 mg/L) indicate methane attenuation associated with sulfate reduction can be limited in premodern groundwater. The more common occurrence of manufactured compounds, like tetrachloroethene, in modern and mixed-age groundwater than in premodern groundwater indicates modern and mixed-age groundwater has a higher risk of degradation from land-surface sources than premodern groundwater. Time-series data for chloride in groundwater affected by disposal of oil-field water in unlined ponds indicate some modern and mixed-age groundwater are susceptible to chemical migration within 2–3 km of surface sources. Timescales for diluting chloride concentrations in groundwater with fresh recharge once disposal ponds are decommissioned are shorter in mixed-age groundwater with large fractions of modern water (9–14 years in one example) than in mixed-age groundwater with large fractions of premodern water (no evidence of dilution after 12 years of monitoring in one example). The presence of predominantly premodern groundwater in the Coastal basins and western SJV indicates these areas have relatively high risk from upward migration of hydrocarbons, reduced methane attenuation capacity, and long dilution times, whereas predominantly modern-and mixed-age groundwater in the eastern SJV indicates this area has relatively high risk from chemical migration from land-surface sources and subsequent extensive spreading. Age-based characterizations of relative risk could inform the design of groundwater-monitoring programs near oil fields in terms of the spatial distribution of monitoring points relative to source areas and monitoring frequency and duration. 

Remote sensing is a viable tool for mapping soil salinity in agricultural lands

University of California, Davis (UC Davis) | April 7th, 2017

Replenishing Groundwater in the San Joaquin Valley

Public Policy Institute of California (PPIC) | April 1st, 2018

The San Joaquin Valley—which has the biggest imbalance between groundwater pumping and replenishment in the state—is ground zero for implementing the 2014 Sustainable

The San Joaquin Valley—which has the biggest imbalance between groundwater pumping and replenishment in the state—is ground zero for implementing the 2014 Sustainable Groundwater Management Act (SGMA). Expanding groundwater recharge could help local water users bring their basins into balance and make a dent in the long-term deficit of nearly 2 million acre-feet per year. The experience with recharge in 2017?the first wet year since the enactment of SGMA?offers valuable insights in how to expand recharge. A survey of valley water districts’ current recharge efforts revealed strong interest in the practice, and a number of constraints. The following actions are needed to better capitalize on future opportunities: Clarify rules on water available for recharge. The State Water Board needs to develop an expeditious process for enabling water users to capture surface water when it is available. Beyond the legal aspects of establishing rights for diversion and storage, an essential part of this process is technical: developing a simple, rapid way to determine when river flows exceed water required for environmental purposes and downstream users. Evaluate infrastructure capacity. One of the key challenges for expanding recharge is that most available flows are in the northern part of the valley, while most of the overdraft?and best recharge lands?are in the south. In addition, these flows are mainly available for just a few months. A top priority is to evaluate opportunities for improving the use of existing infrastructure (conveyance facilities, surface reservoirs, and recharge basins) and determine where additional investments are warranted. A big bottleneck is likely to be regional conveyance, which is inadequate for capturing and moving high flows to suitable recharge locations. Improve recharge on farmland. Active recharge on farmland may be one of the most promising ways to capture water cost-effectively in wetter years, but it is low relative to its potential. Significantly ramping up this practice will require addressing a suite of technical issues and establishing incentives. Address regulatory barriers. State and federal agencies need to improve processes for approving construction of new recharge projects, moving recharge water through their conveyance facilities, and enabling more flexibility in where water is stored. Water managers and growers also need guidelines from the state for implementing on-farm recharge in ways that are consistent with water quality rules. Strengthen groundwater accounting. Better accounting of water going into and out of groundwater basins is key to sustainable management. It is also needed for developing incentives for growers to recharge, encouraging recharge partnerships, and informing decisions on new investments. Making the most of recharge opportunities will require high levels of cooperation among a wide variety of stakeholders. Local and regional partnerships?for capturing and moving water efficiently, making new investments, and devising projects that bring multiple benefits?are key to helping the region manage this critical resource over the long-term.

Replenishing Groundwater in the San Joaquin Valley: 2024 Update

Public Policy Institute of California (PPIC) | June 6th, 2024

Strategies to replenish groundwater basins—long used in some areas of the San Joaquin Valley—have increasingly come into focus as the region seeks to bring its overd

Strategies to replenish groundwater basins—long used in some areas of the San Joaquin Valley—have increasingly come into focus as the region seeks to bring its overdrafted groundwater basins into balance under the Sustainable Groundwater Management Act (SGMA). In late 2023, following a very wet winter and spring, we conducted a repeat survey of local water agencies about their recharge activities and perspectives, building on a similar survey at the end of 2017, a year with similar levels of precipitation. We found signs of progress on recharge since 2017, as well as areas where more work is needed to take full advantage of this important water management tool.

Report Card for California's Infrastructure 2019

American Society of Civil Engineers (ASCE) | May 9th, 2019

Report of Financial Consultants to State of California Department of Water Resources On Financial Aspects of Program for State Water Resources Development System

California Department of Water Resources (DWR) | October 26th, 1960

Report of the Governor's Task Force on the Acreage Limitation Problem

State of California | January 4th, 1968