Depletion Requiremements in California’s Sustainable Groundwater Management Act

Environmental Defense Fund (EDF) | May 17th, 2018

Successful implementation of the Sustainable Groundwater Management Act (SGMA), including its provision to avoid signicant and unreasonable depletion of interconn

Successful implementation of the Sustainable Groundwater Management Act (SGMA), including its provision to avoid signicant and unreasonable depletion of interconnected surface water, is a high priority for the Environmental Defense Fund (EDF). The lack of established mechanisms for addressing depletions of interconnected surface water makes the implementation of this aspect of SGMA especially challenging. Accordingly, EDF offers recommendations to address the requirements of the law related to depletion of interconnected surface water, commonly referred to as “Undesirable Result No. 6” (UR #6). We believe that our proposed approach provides a reasonable balance among the con icting factors of rigor, cost, uncertainty, and enforceability that weigh on the implementation of this requirement. Our goal is to offer a pathway to achieve the fundamental and critical objective of UR#6 – preventing signi cant impacts to water users and ecosystems—in a way that is not unreasonably costly or unproductively burdensome on the Groundwater Sustainability Agencies (GSAs), water users, and state agencies who will bear most of the burden of complying with—or ensuring compliance with—SGMA.

Effectiveness and Impacts of Dust Control Measures for Owens Lake

National Academy of Sciences (NAS) | March 3rd, 2020

During the 20th century, the city of Los Angeles diverted surface water flowing into Owens Lake for water supply, transforming the large, closed-basin, saline lake into

During the 20th century, the city of Los Angeles diverted surface water flowing into Owens Lake for water supply, transforming the large, closed-basin, saline lake into a small brine pool surrounded by dry playa. Under high winds, the exposed lakebed produced large amounts of airborne dust, resulting in the highest concentrations of airborne particulate matter with an aerodynamic diameter of 10 micrometers or less (PM10) in the United States. Since 2000, the Los Angeles Department of Water and Power (LADWP), at the direction of the Great Basin Unified Air Pollution Control District (District), has been constructing and implementing dust control measures (DCMs) on the dry lakebed, with the objective of meeting the U.S. Environmental Protection Agency (EPA) National Ambient Air Quality Standards (NAAQS) for PM10 and the PM10 standards set by the state of California. LADWP reported that it has spent $2.1 billion on dust control efforts as of May 2019 and that many of the DCMs require large amounts of water, energy, and maintenance to sustain their performance.1 Shallow flooding is, by far, the most widespread DCM, by surface area, that is applied at Owens Lake. Other DCMs, such as managed vegetation and gravel, are also applied over several areas on the lakebed, and a few small areas ordered for PM10 management are currently uncontrolled. On average since 2007, water use for dust control required 31 percent of LADWP’s fresh water supplies available at Owens Lake, 2 with a range of 17 to 51 percent. In 2014, a Stipulated Judgment agreed to by LADWP and the District3 ended litigation concerning dust control requirements and acknowledged the need “for additional effective DCMs that do not rely on water that can be substituted in areas currently under control or applied in areas ordered to be controlled.” The Judgment also acknowledged “the need to balance the requirements to control dust emissions and conserve water with the requirements to minimize impacts to cultural and biological resources.” As part of the Judgment, LADWP and the District agreed to contract with the National Academies of Sciences, Engineering, and Medicine to establish the Owens Lake Scientific Advisory Panel (OLSAP, or the panel) to provide ongoing advice on the reduction of PM10 in the Owens Valley. In addition, the Judgment intends the panel to foster communication and collaboration between the LADWP and the District within this context. The panel’s first task is to evaluate the effectiveness of alternative DCMs for their dust control and water use. The task includes consideration of the associated energy, environmental, and economic impacts and assessing the durability and reliability of such DCMs. In interpreting its task, the panel was informed by the definition of environment provided in the California Environmental Quality Act (CEQA), which encompasses impacts on land, air, water, minerals, flora, fauna, ambient noise, and objects of historical or aesthetic significance. The panel discussed key factors within the broad context of that definition with implications for dust management. The panel assessed 15 DCMs (see Box S-2) that represent a range of mitigation approaches that are either being applied at Owens Lake or at various stages of development. The panel’s evaluation criteria included reported PM10 control efficiency, water use, capital and operating costs, habitat value, protection of cultural resources, durability, reliability, and other factors. OVERALL CONCLUSIONS DCMs applied at Owens Lake during the past 20 years have significantly reduced PM10 concentrations in the Owens Valley, although further progress in controlling dust is needed to meet air quality standards. The panel evaluated 15 DCMs based on their potential effectiveness in reducing PM10 emissions, water use, and environmental impacts. Based on available data, none of the control measures has been documented to achieve mandated levels of dust control while substantially reducing water use (compared to shallow flooding) and consistently providing quality habitat, although some measures show promise with the need for additional research and testing. Progress toward these multiple goals, including protection of environmentally sensitive areas by reducing land disturbance from DCMs, can be more effectively achieved through a systems approach that considers outcomes over a large spatial scale and interactions among control measures. To inform these decisions, additional research is needed on individual and hybrid DCMs and on the landscape-scale effects of dust control configurations. Evaluation of operational performance of DCMs should be based on airborne PM10 measurements rather than surrogate measures, such as the percentage of a control area that must be covered by vegetation or surface water. Using a systems approach and evaluating DCM performance with PM10 measurements would promote innovative and hybrid strategies for dust control.

Effects of Groundwater Pumping on Agricultural Drains in the Tule Lake Subbasin, Oregon and California

U.S. Geological Survey (USGS) | July 24th, 2015

Since 2001, irrigators in the upper Klamath Basin have increasingly turned to groundwater to compensate for reductions in surface-water allocation caused by shifts from

Since 2001, irrigators in the upper Klamath Basin have increasingly turned to groundwater to compensate for reductions in surface-water allocation caused by shifts from irrigation use to instream 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. 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. U.S. Geological Survey regional groundwater-flow model simulations and records of irrigation-return flow pumped from the Tule Lake subbasin into the adjacent Lower Klamath Lake subbasin have indicated that water-level declines from pumping may be causing decreased flow of shallow groundwater to agricultural drains. To better define the effect of increased pumping on drain flow and on the water balance of the groundwater system, the annual water volume pumped from drains in three subareas of the Tule Lake subbasin was estimated and a fine-grid, local groundwater model of the Tule Lake subbasin was constructed. Results of the agricultural-drain flow analysis indicate that groundwater discharge to drains has decreased such that flows in 2012 were approximately 32,400 acre-ft less than the 1997–2000 average flow. This decrease was concentrated in the northern and southeastern parts of the subbasin, which corresponds with the areas of greatest groundwater pumping. Model simulation results of the Tule Lake subbasin groundwater model indicate that increased supplemental pumping is the dominant stress to the groundwater system in the subbasin. Simulated supplemental pumping and decreased recharge from irrigation between 2000 and 2010 totaled 323,573 acre-ft, 234,800 acre-ft (73 percent) of which was from supplemental pumping. The response of the groundwater system to this change in stress included about 180,500 acre-ft (56 percent) of decreased groundwater discharge to drains and a 126,000 acre-ft (39 percent) reduction in aquifer storage. The remaining 5 percent came from reduced groundwater flow to other model boundaries, including the Lost River, the Tule Lake sumps, and interbasin flow.

Effects of montane watershed development on vulnerability of domestic groundwater supply during drought

Journal of Hydrology (Elsevier) | April 1st, 2020

Climate change is expected to reduce recharge to montane aquifers in the western United States, but it is unclear how this will impact groundwater resources in waters

Climate change is expected to reduce recharge to montane aquifers in the western United States, but it is unclear how this will impact groundwater resources in watersheds where intensive surface-water development has disrupted the natural hydrologic regime. To better understand sources of recharge and associated vulnerabilities of groundwater supply in this setting, we made a detailed geochemical survey of domestic wells finished in fractured bedrock throughout the Yuba and Bear River watersheds (Sierra Nevada foothills, northern California) during historic drought (2015–2016). Stable isotopes of water and noble gas recharge temperatures closely tracked atmospheric lapse rates across a broad elevation gradient (100–2000 m), indicating groundwater inputs are dominated by local precipitation that rapidly recharges fractured bedrock during the winter wet-season. However, nearly one-quarter of wells had water isotopes that were fractionated by evaporation and warm recharge temperatures, indicative of mixing with dry-season recharge by surface water. Monte Carlo mixing models suggest evaporation-impacted groundwater samples are mixtures of local rain with an average of 28% ± 13% from diverted surface water that can recharge bedrock aquifers during the dry-season by either irrigation return flow or seepage from extensive distribution infrastructure. Wells that received recharge subsidies from diverted surface water had elevated levels of nitrate and coliform bacteria compared to those replenished exclusively by local precipitation, which are more vulnerable to supply shortage during drought. It is important to consider the impacts of increased surface-water development on the quantity and quality of groundwater recharge in rapidly developing montane watersheds.

Effects of structure and volcanic stratigraphy on groundwater and surface water flow: Hat Creek basin, California, USA

Hydrogeology Journal (Springer) | January 16th, 2022

Hydrogeologic systems in the southern Cascade Range in California (USA) develop in volcanic rocks where morphology, stratigraphy, extensional structures, and attendant ba

Hydrogeologic systems in the southern Cascade Range in California (USA) develop in volcanic rocks where morphology, stratigraphy, extensional structures, and attendant basin geometry play a central role in groundwater flow paths, groundwater/surface-water interactions, and spring discharge locations. High-volume springs (greater than 3 m3/s) flow from basin-filling (

Effects of Surface-Water Use on Domestic Groundwater Availability and Quality During Drought in the Sierra Nevada Foothills, California

U.S. Geological Survey (USGS) | January 13th, 2020

Approximately 2 million California residents rely on privately owned domestic wells for drinking water. During the California drought of 2012−16 groundwater lev

Approximately 2 million California residents rely on privately owned domestic wells for drinking water. During the California drought of 2012−16 groundwater levels declined in many parts of the state and wells were deepened in response. Most of the wells deepened during this time were domestic wells that were drilled into fractured bedrock throughout the Sierra Nevada foothills region of northern California (California Department of Water Resources, 2014). To understand the impacts of extreme drought on groundwater supply availability and quality in this setting, the United States Geological Survey (USGS) completed a geochemical survey of domestic wells throughout the Yuba and Bear River watersheds during 2015–16 (fig. 1) as part of the State Water Board’s Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP). This fact sheet highlights key findings from the GAMA-PBP assessment (Levy and others, 2020).

Electrical Resistivity Investigation of Fluvial Geomorphology to Evaluate Potential Seepage Conduits to Agricultural Lands along the San Joaquin River, Merced County, California, 2012–13

U.S. Geological Survey (USGS) | ?

Increased flows in the San Joaquin River, part of the San Joaquin River Restoration Program, are designed to help restore fish populations. However, increased seepage los

Increased flows in the San Joaquin River, part of the San Joaquin River Restoration Program, are designed to help restore fish populations. However, increased seepage losses could result from these higher restoration flows, which could exacerbate existing drainage problems in neighboring agricultural lands and potentially damage crops. Channel deposits of abandoned river meanders that are hydraulically connected to the river could act as seepage conduits, allowing rapid and widespread water-table rise during restoration flows. There is a need to identify the geometry and properties of these channel deposits to assess their role in potential increased seepage effects and to evaluate management alternatives for reducing seepage. Electrical and electromagnetic surface geophysical methods have provided a reliable proxy for lithology in studies of fluvial and hyporheic systems where a sufficient electrical contrast exists between deposits of differing grain size. In this study, direct-current (DC) resistivity was used to measure subsurface resistivity to identify channel deposits and to map their subsurface geometry. The efficacy of this method was assessed by using DC resistivity surveys collected along a short reach of the San Joaquin River in Merced County, California, during the summers of 2012 and 2013, in conjunction with borings and associated measurements from a hydraulic profiling tool. Modeled DC resistivity data corresponded with data from analyses of core samples, hand-auger samples, a hydraulic profiling tool, and aerial photographs, confirming that DC resistivity was effective for differentiating between silty and sandy deposits in this setting. Modeled DC resistivity data provided detailed two-dimensional cross-sectional resistivity profiles to a depth of about 20 meters. The distribution of high-resistivity units in these profiles was used as a proxy for identifying areas of high hydraulic conductivity. Estimates of the cross-sectional area of channel deposits from DC resistivity pseudosections can provide critical input for groundwater-flow models designed to simulate river seepage and evaluate seepage-management alternatives.

Environmental flow limits to global groundwater pumping

Nature Portfolio (Springer Nature) | October 2nd, 2019

Groundwater is the world’s largest freshwater resource and is critically important for irrigation, and hence for global food security. Already, unsustainable groundwa

Groundwater is the world’s largest freshwater resource and is critically important for irrigation, and hence for global food security. Already, unsustainable groundwater pumping exceeds recharge from precipitation and rivers, leading to substantial drops in the levels of groundwater and losses of groundwater from its storage, especially in intensively irrigated regions. When groundwater levels drop, discharges from groundwater to streams decline, reverse in direction or even stop completely, thereby decreasing streamflow, with potentially devastating effects on aquatic ecosystems. Here we link declines in the levels of groundwater that result from groundwater pumping to decreases in streamflow globally, and estimate where and when environmentally critical streamflows—which are required to maintain healthy ecosystems—will no longer be sustained. We estimate that, by 2050, environmental flow limits will be reached for approximately 42 to 79 per cent of the watersheds in which there is groundwater pumping worldwide, and that this will generally occur before substantial losses in groundwater storage are experienced. Only a small decline in groundwater level is needed to affect streamflow, making our  estimates uncertain for streams near a transition to reversed groundwater discharge. However, for many areas, groundwater pumping rates are high and environmental flow limits are known to be severely exceeded. Compared to surface-water use, the effects of groundwater pumping are markedly delayed. Our results thus reveal the current and future environmental legacy of groundwater use.

Environmental Law Foundation, et al. Petitioners, v. State Water Resources Control Board, et al. Respondents

State of California | July 15th, 2014

Evaluating the hydrologic effects of the 2021–2022 Scott and Shasta irrigation curtailments using remote sensing and streamflow gages

Klamath Tribal Water Quality Consortium | September 11th, 2023

Key Points • Satellite remote sensing data indicated that curtailment orders in 2022 reduced consumptive water use (evapotranspiration, ETa) on agricultural lands i

Key Points • Satellite remote sensing data indicated that curtailment orders in 2022 reduced consumptive water use (evapotranspiration, ETa) on agricultural lands in Shasta Valley, but not Scott Valley. • Streamflow gage data indicate that flows in the Shasta River and some Scott River tributaries (Shackleford and French creeks) were substantially higher in summer 2022 than 2020 or 2021, but similar increases did not occur in the mainstem Scott River. • A likely major reason for the lack of Scott River flow increases was that groundwater use was allowed to continue under Local Cooperative Solutions (LCS) agreements in which water users agreed to reduce pumping by 30% from a prior year baseline. Despite abundant worldwide evidence that reducing consumptive use (i.e., evapotranspiration) is key to increasing environmental water, all LCS cropping and irrigation practices were given equal weight toward the 30% reduction, regardless of the effects on consumptive use. Pumping was not measured and compliance was primarily self-reported, with limited independent verification.