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.
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.
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.
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.
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.
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.
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.