Why is Groundwater Quality Changing?
Increased Pumping in California’s Central Valley During Drought Worsens Groundwater Quality in Public Drinking Water Wells
Pumping during drought pulled shallow, contaminated groundwater down to depths commonly tapped for public drinking-water supply.
Pumping during drought pulled shallow, contaminated groundwater down to depths commonly tapped for public drinking-water supply.
Natural Fluoride Concentration Patterns Are Changing Because of Water Use
Intensive use and management of groundwater, especially in the southern part of the State, is causing changes in the natural fluoride patterns.
Intensive use and management of groundwater, especially in the southern part of the State, is causing changes in the natural fluoride patterns.
Managed Aquifer Recharge in the Coachella Valley Using Colorado River Water is the Primary Source of Increasing Salinity Concentrations in the Indio Subbasin
One third of the water supply wells are delivering saltier water than in the past.
One third of the water supply wells are delivering saltier water than in the past.
Defining Natural Background Levels of Hexavalent Chromium Cr(VI) in Hinkley, California
Scientists map the extent of human-introduced hexavalent chromium, a known carcinogen under specific circumstances, in California’s Hinkley Valley.
Scientists map the extent of human-introduced hexavalent chromium, a known carcinogen under specific circumstances, in California’s Hinkley Valley.
Artificial Recharge Can Cause Mixing with Septic Effluent Stored in the Unsaturated Zone
Artificial recharge by the Hi Desert Water District in the Warren Subbasin raised the water table to the point where septic discharge started mixing into groundwater.
Artificial recharge by the Hi Desert Water District in the Warren Subbasin raised the water table to the point where septic discharge started mixing into groundwater.
Groundwater Quality Tapped by Public Supply Wells Changes Over Time
The USGS has compiled all of the analytical data submitted by drinking water suppliers and USGS sampling from 1974–2022 into a tool that maps trends in groundwater quality.
The USGS has compiled all of the analytical data submitted by drinking water suppliers and USGS sampling from 1974–2022 into a tool that maps trends in groundwater quality.
Groundwater is a critical resource in California and water quality a key factor in water supply reliability. This web page presents a number of case studies that explain why and how groundwater quality is changing as a result of water use and management practices.
Defining Natural Background Levels of Hexavalent Chromium Cr(VI) in Hinkley, California
Media
Sources/Usage: Public Domain. View Media Details
- Natural background concentrations of Cr(VI) in groundwater are controlled by a number of factors including pH and oxygen, time since recharge, and local geology.
- The local community participated in the science by describing the meaning of “background” and by observing USGS sampling and on-site chemical analysis in the mobile lab.
Managed Aquifer Recharge in the Coachella Valley Using Colorado River Water is the Primary Source of Increasing Salinity Concentrations in the Indio Subbasin
Media
Sources/Usage: Public Domain. View Media Details
- Salinity in the Indio groundwater basin in the Coachella Valley is increasing. One third of the water supply wells are delivering saltier water than in the past.
- Imported Colorado River water is used to replenish the aquifer and is the dominant source of salinity responsible for these trends both basin-wide and in 3/4 of the water supply wells delivering highest salinity water.
- Treated wastewater and agricultural return flows also contribute salinity to some shallow areas.
- Salinity trends and concentrations are not homogenous.
Media
Sources/Usage: Public Domain. View Media Details
Artificial Recharge Can Cause Mixing with Septic Effluent Stored in the Unsaturated Zone
- Artificial recharge by the Hi Desert Water District in the Warren Subbasin raised the water table to the point where septic discharge started mixing into groundwater.
- The USGS provided a solute-transport model coupled with groundwater-flow models so water managers could simulate changes in groundwater quality at specific sites as recharge and septic sources mix.
- Cost-effective monitoring networks can be designed using modeled information.
Media
Sources/Usage: Public Domain. View Media Details
Increased Pumping in California’s Central Valley During Drought Worsens Groundwater Quality in Public Drinking Water Wells
- Increased pumping from wells in the Central Valley during drought pulled shallow, contaminated groundwater down to depths commonly tapped for public drinking-water supply.
- Water-quality problems from legacy groundwater pollution can get worse, faster, when pumping increases during drought.
- This is a regional scale pattern occurring over 30 years. Water quality delivered by individual wells can differ.
Media
Sources/Usage: Public Domain. View Media Details
Natural Fluoride Concentration Patterns Are Changing Because of Water Use
- Intensive use and management of groundwater, especially in the southern part of the State, is causing changes in the natural fluoride patterns.
- In areas like the Coachella Valley where recharge consists of imported, salty water from the Colorado River, fluoride concentrations are generally decreasing.
- In locations like Orange County, recharge with treated wastewater creates aquifer conditions that increase fluoride concentrations.
- Statewide, natural fluoride concentrations are decreasing in 9.6% of the groundwater resources used for public supply in the state and increasing in 4.6% of the resources.
Media
Sources/Usage: Public Domain. View Media Details
Groundwater Quality Tapped by Public Supply Wells Changes Over Time
- The USGS has compiled all of the analytical data submitted by drinking water suppliers and USGS sampling from 1974–2022 into a tool that maps trends in groundwater quality.
- Some noteworthy findings:
- Groundwater quality can change seasonally and over long periods of time.
- Trends can reverse.