Distribution of Lakes in the United States

Scientific American | June 12th, 1880

There are numerous lacustrine basins to be found in the States bordering the Pacific Ocean. As in other regions of the globe, their distribution is determined by the co

There are numerous lacustrine basins to be found in the States bordering the Pacific Ocean. As in other regions of the globe, their distribution is determined by the configuration of land, or, more specifically, by the forms of the great hydrographic basins in the interior of the continent; hence some general idea of the topography of the western portions of the United States is an essential preliminary.

Divergent effects of climate change on future groundwater availability in key mid-latitude aquifers

Nature Portfolio (Springer Nature) | July 24th, 2020

Groundwater provides critical freshwater supply, particularly in dry regions where surface water availability is limited. Climate change impacts on GWS (groundwater stora

Groundwater provides critical freshwater supply, particularly in dry regions where surface water availability is limited. Climate change impacts on GWS (groundwater storage) could affect the sustainability of freshwater resources. Here, we used a fully-coupled climate model to investigate GWS changes over seven critical aquifers identified as significantly distressed by satellite observations. We assessed the potential climate-driven impacts on GWS changes throughout the 21st century under the business-as-usual scenario (RCP8.5). Results show that the climate-driven impacts on GWS changes do not necessarily reflect the long-term trend in precipitation; instead, the trend may result from enhancement of evapotranspiration, and reduction in snowmelt, which collectively lead to divergent responses of GWS changes across different aquifers. Finally, we compare the climate-driven and anthropogenic pumping impacts. The reduction in GWS is mainly due to the combined impacts of over-pumping and climate effects; however, the contribution of pumping could easily far exceed the natural replenishment.

Documentation of a Groundwater Flow Model (SJRRPGW) for the San Joaquin River Restoration Program Study Area, California

U.S. Geological Survey (USGS) | September 23rd, 2014

To better understand the potential effects of restoration flows on existing drainage problems, anticipated as a result of the San Joaquin River Restoration Program (SJRRP

To better understand the potential effects of restoration flows on existing drainage problems, anticipated as a result of the San Joaquin River Restoration Program (SJRRP), the U.S. Geological Survey (USGS), in cooperation with the U.S. Bureau of Reclamation (Reclamation), developed a groundwater flow model (SJRRPGW) of the SJRRP study area that is within 5 miles of the San Joaquin River and adjacent bypass system from Friant Dam to the Merced River. The primary goal of the SJRRP is to reestablish the natural ecology of the river to a degree that restores salmon and other fish populations. Increased flows in the river, particularly during the spring salmon run, are a key component of the restoration effort. A potential consequence of these increased river flows is the exacerbation of existing irrigation drainage problems along a section of the river between Mendota and the confluence with the Merced River. Historically, this reach typically was underlain by a water table within 10 feet of the land surface, thus requiring careful irrigation management and (or) artificial drainage to maintain crop health. The SJRRPGW is designed to meet the short-term needs of the SJRRP; future versions of the model may incorporate potential enhancements, several of which are identified in this report. The SJRRPGW was constructed using the USGS groundwater flow model MODFLOW and was built on the framework of the USGS Central Valley Hydrologic Model (CVHM) within which the SJRRPGW model domain is embedded. The Farm Process (FMP2) was used to simulate the supply and demand components of irrigated agriculture. The Streamflow-Routing Package (SFR2) was used to simulate the streams and bypasses and their interaction with the aquifer system. The 1,300-square mile study area was subdivided into 0.25-mile by 0.25-mile cells. The sediment texture of the aquifer system, which was used to distribute hydraulic properties by model cell, was refined from that used in the CVHM to better represent the natural heterogeneity of aquifer-system materials within the model domain. In addition, the stream properties were updated from the CVHM to better simulate stream-aquifer interactions, and water-budget subregions were refined to better simulate agricultural water supply and demand. External boundary conditions were derived from the CVHM. The SJRRPGW was calibrated for April 1961 to September 2003 by using groundwater-level observations from 133 wells and streamflow observations from 19 streamgages. The model was calibrated using public-domain parameter estimation software (PEST) in a semi-automated manner. The simulated groundwater-level elevations and trends (including seasonal fluctuations) and surface-water flow magnitudes and trends reasonably matched observed data. The calibrated model is planned to be used to assess the potential effects of restoration flows on agricultural lands and the relative capabilities of proposed SJRRP actions to reduce these effects.

Domestic well vulnerability to drought duration and unsustainable groundwater management in California's Central Valley

Environmental Research Letters (IOP) | March 18th, 2020

Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and th

Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and the possibility of longer drought duration under climate change threatens domestic well reliability, yet we lack tools to assess the impact of such events. Here, we leverage 943,469 well completion reports and 20 years of groundwater elevation data to develop a spatially-explicit domestic well failure model covering California’s Central Valley. Our model successfully reproduces the spatial distribution of observed domestic well failures during the severe 2012–2016 drought (n=2027). Next, the impact of longer drought duration (5–8years) on domestic well failure is evaluated, indicating that if the 2012–2016 drought would have continued into a 6 to 8 year long drought, a total of 4037–5460 to 6538–8056 wells would fail. The same drought duration scenarios with an intervening wet winter in 2017 lead to an average of 498 and 738 fewer well failures. Additionally, we map vulnerable wells at high failure risk and find that they align with clusters of predicted well failures. Lastly, we evaluate how the timing and implementation of different projected groundwater management regimes impact groundwater levels and thus domestic well failure. When historic overdraft persists until 2040, domestic well failures range from 5966 to 10 466 (depending on the historic period considered). When sustainability is achieved progressively between 2020 and 2040, well failures range from 3677 to 6943, and from 1516 to 2513 when groundwater is not allowed to decline after 2020.

Drift of Earth's Pole Confirms Groundwater Depletion as a Significant Contributor to Global Sea Level Rise 1993–2010

American Geophysical Union (AGU) | June 15th, 2023

Drinking Water and Exclusion: A Case Study from California's Central Valley

California Law Review | February 1st, 2012

The American West is notorious for its water wars, and California's complex water allocation and governance challenges serve as a bellwether for contemporary water gove

The American West is notorious for its water wars, and California's complex water allocation and governance challenges serve as a bellwether for contemporary water governance across western states, Policy makers and environmental advocates typically represent California's water woes as a regulatory problem - a failure to balance the needs of growing urban populations with ecological preservation and agricultural irrigation. These debates, however, often elide the issue of water deprivation, and they do not adequately address the concerns of an important constituency: low-income, rural communities. This Comment argues that a focus on regulation misses a fundamental feature of water inequality: the structure and design of local water districts. Utilizing a case study of California's Central Valley to illustrate how these structural barriers operate, I argue that Calfornia's complex system of local water districts fractures governance, limits electoral participation, and undermines the State's stated environmental, equity, and utilitarian water goals. I offer suggestions for alternative local water district organization in order to address the constraints of Calfornia's current water governance regime.

Drought and Groundwater Sustainability in California’s Farming Regions

Public Policy Institute of California (PPIC) | June 25th, 2024

Drought impact on cropland use monitored with AVIRIS imagery in Central Valley, California

Science of the Total Environment (Elsevier) | November 19th, 2022

During 2012–2016 California experienced the longest and most severe drought in the last centuries. This water scarcity led to an increase in non-cultivated croplands du

During 2012–2016 California experienced the longest and most severe drought in the last centuries. This water scarcity led to an increase in non-cultivated croplands during this period. The objective of this study was to quantify agricultural trends in the Central Valley (California) at peak growth from 2013 to 2016 during the drought and in 2017–2018 post-drought. For this purpose, we analysed yearly official harvested area reported at county level for the main crops and compared them to visible-shortwave infrared (VSWIR) spectra acquired by the Airborne Visible/Infrared Imaging-Spectrometer (AVIRIS-classic) over 2334 km2 of the Central Valley each year. Multiple Endmember Spectral Mixture Analysis (MESMA) was applied to AVIRIS data to estimate green vegetation (GV), non-photosynthetic vegetation (NPV) and soil fractions in crop fields each year. MESMA and crop reports (R2 = 0.9) showed that soil (i.e.; non-cultivated areas) increased during the summers of the drought; with the smallest GV area in 2015, the second year classified with exceptional drought in this period. According to MESMA, 34 % of the cropland was covered by GV in 2015, and 69.5·104 ha according to the crop reports. MESMA also registered the highest value of soil area in 2015 (48 %). The year with most cultivated area was 2017, the wettest year in the studied period, with 54 % of the croplands covered by GV and 75.2·104 ha. This study verified that the non-cultivated areas increased in the Central Valley during the exceptional drought period and validated the use of AVIRIS imagery to monitor broad-scale cropland use changes in future climatic extreme events.

Dry groundwater wells in the western United States

Environmental Research Letters (IOP) | July 28th, 2017

Declining groundwater levels are common in parts of the western US, but their impact on the ability of wells to pump groundwater is not known. Here we collate groundwater

Declining groundwater levels are common in parts of the western US, but their impact on the ability of wells to pump groundwater is not known. Here we collate groundwater well records for the western United States and present the recorded locations, depths, and purposes of more than two million groundwater wells constructed between 1950 and 2015. We then use the well records to estimate the percentage of wells that were dry during the years 2013–2015. During the two-year period, dry wells were concentrated in rural areas with high agricultural productivity, such as parts of the California Central Valley and the High Plains. Our results support anecdotal evidence that wells used for domestic purposes are more susceptible to drying than wells used for agricultural purposes throughout California’s Central Valley because the former tend to be shallower. However, this is not the case in all regions. Our findings suggest that declining groundwater levels are threatening drinking water reliability and agricultural productivity, and consequently, have key implications for both domestic and agricultural water security. Ongoing reductions to groundwater storage are drying groundwater wells in the western US, and this manifestation of water scarcity warrants innovative groundwater management transcending status quos.

East Kaweah GSA Groundwater Sustainability Plan

East Kaweah Groundwater Sustainability Agency (EKGSA) | February 17th, 2019

Final GSP delivered to the Department of Water Resources 1/31/20 per DWR; final online draft awaiting uploading per inquiry to EKGSA 2/13/20

Final GSP delivered to the Department of Water Resources 1/31/20 per DWR; final online draft awaiting uploading per inquiry to EKGSA 2/13/20