Estimation of groundwater residence time with deeply-derived carbon mixture considered in California

Science of the Total Environment (Elsevier) | December 16th, 2022

Groundwater has experienced long-term overdraft due to drought and human activities in California, resulting in issues of land subsidence and groundwater anthropogenic co

Groundwater has experienced long-term overdraft due to drought and human activities in California, resulting in issues of land subsidence and groundwater anthropogenic contamination. As a useful indicator of groundwater renewal rate and its residence time, groundwater age has been conventionally investigated based on 14C content and 3H concentration. However, the influence of deeply-derived (endogenic) CO2 mixture is not fully and quantitatively considered, although endogenic carbon contributes a large part of the dissolved inorganic carbon in groundwater. Combined with 3H concentration, both conventional and modified 14C-dating methods with endogenic CO2 mixture considered are employed for groundwater age determination in California. On average, the conventional groundwater 14C apparent age is overestimated by ~4.9 kyr or ~26.2 %, causing groundwater recharge rate underestimation and aquifer recovery time overestimation by ~46.0 % and ~26.2 %, respectively. High 3H concentration indicates modern water mixture in more than one fifth of groundwater samples, including those with high modified 14C apparent age (> 12 kyr, i.e., fossil groundwater) in the Central Valley and southern California, which are generally considered not to be recharged by modern water. Modern water mixture in old groundwater can potentially bring anthropogenic contamination to these groundwater resources, which should be paid attentions by the government and the managers. The results have important implications in evaluation of groundwater replenishment and its susceptibility to modern contamination in California, and in groundwater resources estimation globally.

Estuary News, June 2015

San Francisco Estuary Partnership (SFEP) | June 15th, 2015

Evaluation of a Ground-Water Flow and Transport Model of the Upper Coachella Valley, California

U.S. Geological Survey (USGS) | June 25th, 1992

A geohydrologic data base was compiled to evaluate the changes in ground-water conditions in the upper Coachella Valley, California, since 1978, when the results of a pre

A geohydrologic data base was compiled to evaluate the changes in ground-water conditions in the upper Coachella Valley, California, since 1978, when the results of a previous ground-water-model study were published. The compiled data were analyzed to improve understanding of the ground-water flow system and the effects on water quality of an existing artificial-recharge program. Analysis of well logs indicates that several zones of differing permeability can be correlated throughout the valley. Analysis of the water-quality data suggests that the artificial recharge of Colorado River water has caused increases in dissolved solids in some wells. Sparse data indicate that the recharged water moves much more rapidly through the uppermost part of the ground-water system than through deeper parts. An evaluation of the existing ground-water simulation model of the upper Coachella Valley that was developed in the 1978 study yielded several conclusions. First, the 300- to 400-foot rise in water levels in the artificialrecharge area in 1985-86 significantly affected the groundwater flow system. Transmissivities in the model had to be increased to reflect the increase in saturated thickness. Storage-coefficient values in the model had to be increased from 0.02 (used in the previous study) to 0.10-0.15 to simulate the unconfined water-level response during this period. Second, stream-recharge and underflow rates from San Gorgonio Pass during 1979-86 seem to have been higher than the values estimated for previous studies. Conditions generally were wetter in 1979-86 than during the period in which the earlier estimates were made. Third, the flow system could be simulated more accurately if the model were extended to its true southeastern boundary, the Salton Sea. Finally, there are important vertical differences in transport of the artificially recharged water that the two-dimensional areal transport model cannot simulate. The study results indicate several additional data collection and modeling needs. The drilling of several sets of monitor wells perforated at different depths could help better define the three-dimensional flow system and waterquality differences. Additional data also are needed on underflow and stream recharge, evaporation rates and infiltration rates at the artificial-recharge facilities, and net pumpage. Three-dimensional flow and transport models are needed to evaluate the effects of ground-water development on water levels and water quality.

Evaluation of Geohydrologic Framework, Recharge Estimates, and Ground-Water Flow of the Joshua Tree Area, San Bernardino County, California

U.S. Geological Survey (USGS) | July 1st, 2004

Evaluation of Surface-Water/Ground-Water Interactions in the Santa Clara River Valley, Ventura County, California

U.S. Geological Survey (USGS) | May 28th, 1999

The interactions of surface water and ground water along the Santa Clara River in Ventura County, California, were evaluated by analyzing river-discharge and water-qua

The interactions of surface water and ground water along the Santa Clara River in Ventura County, California, were evaluated by analyzing river-discharge and water-quality data and geohydrologic information collected by the U.S. Geological Survey between 1993 and 1995 for the Piru, Fillmore, and Santa Paula subbasins. Measurements of discharge and water quality were made at multiple locations along the Santa Clara River and its tributaries at eight different time periods during different releases from Lake Piru. Geologic, hydraulic, and water-quality data were collected from three new multiple-completion ground-water monitoring wells. These data, together with data collected as part of the U.S. Geological Survey Southern California Regional Aquifer-System Analysis (RASA) study, were analyzed in order to quantify rates and locations of ground-water recharge and discharge within the river, characterize the correlation of recharge and discharge rates with ground-water conditions and reservoir releases, and better characterize the three-dimensional ground-water flow system. Analysis of the data indicates that the largest amount of ground-water recharge from the river consistently occurs in the Piru subbasin. Some ground-water recharge from the river may occur in the upper part of the Fillmore subbasin. Increases in sulfate concentrations indicate that increases in flow at the lower ends of the Piru and Fillmore subbasins result from high-sulfate ground-water discharge. Increases in flow in the lower part of the Santa Paula subbasin are not accompanied by significant sulfate increases. Several sets of regressions indicate possible correlation between net flow changes in the river and depths to ground water and release rates from Lake Piru. These statistical relations may be of use for evaluating alternative Lake Piru release strategies. Data on the stable isotopes of hydrogen and oxygen from the ground-water monitoring wells that were installed as part of this investigation were used to distinguish between zones affected by recharge from the Santa Clara River and zones affected by recharge from local precipitation. Tritium data from a new multiple-completion monitoring site indicate that near the river in the upper Santa Paula subbasin, recent (post-1950) recharge water is not present at depths greater than about 350 feet below land surface. Water-level and lithologic data from the monitoring site indicate that the river and the Shallow aquifer have only limited hydraulic connection to the underlying aquifers at this location. Water-level data from the Shallow aquifer and from an in-stream drive point were used in an analytic model to estimate hydraulic properties governing stream-aquifer interactions in the upper Santa Paula subbasin. Hydraulic conductivities in all the USGS monitoring wells were estimated on the basis of slug tests.  

Evaluation of the Source and Transport of High Nitrate Concentrations in Ground Water, Warren Subbasin, California

U.S. Geological Survey (USGS) | December 13th, 2003

From early 1995 through 2001, nitrate (NO3) concentrations in ground water in the Warren subbasin, California, increased from a background concentration of 10 milligrams

From early 1995 through 2001, nitrate (NO3) concentrations in ground water in the Warren subbasin, California, increased from a background concentration of 10 milligrams per liter (mg/L) to more than the U.S. Environmental Protection Agency (USEPA) water-quality maximum contaminant level of 44 mg/L (10 mg/L as nitrogen). This increase coincided with an artificial ground-water recharge program implemented by the local water district, Hi-Desert Water District (HDWD), to reverse ground-water level declines of as much as 300 ft. Major findings on ground-water quality from this study are the following: •Septage from septic tanks was the primary source of NO3 to the ground-water system. •Rising ground-water levels, resulting from the artificial-recharge program, entrained high-NO3 septage stored in the unsaturated zone. •The potential for ground-water contamination should be evaluated before beginning an artificial- recharge program in an area that uses septic tanks.

Executive Order N-4-23

State of California | March 10th, 2023

Executive Order N-7-23

State of California | May 17th, 2023

Five-century record of climate and groundwater recharge variability in southern California

Nature Portfolio (Springer Nature) | December 3rd, 2019

Modifications to the rates of water flowing from the surface to groundwater (groundwater recharge) due to climate variability are the most difficult to assess because of

Modifications to the rates of water flowing from the surface to groundwater (groundwater recharge) due to climate variability are the most difficult to assess because of the lack of direct long-term observations. Here, we analyze the chloride salt distribution below the surface soil on a plateau near Los Angeles to reconstruct the amount of recharge that occurred in the last five centuries. Over this time interval, periods of major high and low recharge with different duration follow each other and this cyclicity is consistent with long-term atmospheric forcing patterns, such as the Pacific Decadal Oscillation. This study determines the range and the natural variability of recharge to groundwater, which sustains local freshwater flow system, and helps forecast future availability of groundwater resource in southern California, where water scarcity is critical to both local and global populations.

FLOOD- MAR Using Flood Water for Managed Aquifer Recharge to Support Sustainable Water Resources

California Department of Water Resources (DWR) | June 26th, 2018

The effects of climate change are necessitating wholesale changes in how water is managed in California.  With less water storage from snowpack, California needs to leve

The effects of climate change are necessitating wholesale changes in how water is managed in California.  With less water storage from snowpack, California needs to leverage both the current water system and new opportunities to provide sustainable alternatives that can simultaneously accommodate longer and deeper droughts, and more severe, and frequent, episodic and seasonal flooding. This recent cycle of drought and flood, and the passage of the Sustainable Groundwater Management Act (SGMA), provide an enhanced opportunity to modernize State policies related to the nexus between flood management, land use, groundwater management, and ecosystem enhancement. Partnerships, among DWR; other State, federal, tribal, regional, and local entities; and university and private researchers, are actively exploring opportunities to determine how flood and groundwater management can be integrated for multiple benefits. Although integrating flood and groundwater management is not a new concept, the time is ripe to implement an expanded, large-scale integrated program. With the passage and early implementation of SGMA, in combination with climate-induced extreme events, the logic for communities to partner and integrate is evident and imperative. This partnership will help reduce the impacts of future swings between high- and low-flow periods while meeting their communities’ objectives, with the added benefits of improving floodplain ecosystems, preserving working landscapes, and engaging California’s agricultural community in needed solutions, among others. This white paper explores “Flood-MAR”, an integrated and voluntary resource management strategy that uses flood water resulting from, or in anticipation of, rainfall or snowmelt for groundwater recharge on agricultural lands and working landscapes, including but not limited to refuges, floodplains, and flood bypasses. Large-scale implementation of Flood-MAR will fundamentally change how flood and groundwater management are managed. Flood-MAR can be implemented at multiple scales, from individual landowners diverting flood water with existing infrastructure, to using extensive detention/recharge areas and modernizing flood protection infrastructure/operations. Flood-MAR’s potential and value for California is achieved by integrating Flood-MAR with other regional recharge efforts, changing management of California’s water system to better integrate surface water and groundwater, upgrading conveyance, storage, and operations, and considering Flood-MAR’s opportunities as related to water transport and transfers are some of the system integration considerations. This white paper demonstrates the need for Flood-MAR to become an important part of California’s portfolio of water resource management strategies, now and in the future, to help significantly improve water resources sustainability and climate resiliency throughout the state.  Using Flood Water for Managed Aquifer Recharge Can Provide Broad Benefits. There is a clear State interest in encouraging, and participating in, Flood-MAR projects because they can provide broad and multiple public and private benefits for Californians and the ecosystems of the state. Potential public benefits include: - Flood Risk Reduction. - Drought Preparedness. - Aquifer Replenishment. - Ecosystem Enhancement. - Subsidence Mitigation. - Water Quality Improvement. - Working Landscape Preservation and Stewardship.