Groundwater

Tracking the Contamination of California’s Aquifers

Californians began building pumps to extract groundwater from the state’s aquifers over 100 years ago; due to the seasonal availability and general scarcity of surface water, the state’s farms, industries, cities, and rural populations have relied on this precious resource since statehood. Today, more than half of Californians rely on groundwater as a source of drinking water, and in some areas it is the only water source. There are more than 10,000 public supply groundwater wells throughout the state.  In an average year, groundwater accounts for 25 to 40% of California’s water supply, and can reach 65% in a drought year.  California uses more groundwater than any other state, pumping nearly 15 billion gallons of groundwater every day.  Use of groundwater for domestic supplies (private wells) occurs most often in the central part of California, where land use is dominated by agriculture.

Water stored in our underground aquifers is fragile, and inextricably linked the quality of surface waters above.  California’s groundwater is threatened by the same sources of pollution that imperil our surface waters, sources such as agricultural operations, landfills, septic systems, leaky underground storage tanks, and over-pumping.  Contamination can render the water in groundwater aquifers unusable as a resource, or require costly treatment to restore beneficial uses.  Groundwater contamination, when present, will persist and often worsen, sometimes exposing Californians to dangerous levels of toxic contaminants like nitrates and arsenic.

California’s 305(b) Report, the most comprehensive state report on California’s groundwater resources, estimates that one third of the areal extent of the state’s groundwater resources is contaminated to such a severe degree that they cannot be used for the purposes that the state designated as appropriate.  Continuing contamination of groundwater aquifers is a widespread and severe threat to the viability of groundwater as a current and future resource for Californians.  The 2005 State Water Plan estimated that it would cost approximately $20 billion to clean up the State’s groundwater aquifers. Despite this costly estimate, information on groundwater quality and supplies is extremely limited in most areas of the state. Where there is relatively reliable data, it tends to be concentrated in the central area of the state. Examples are the National Water Quality Assessment Program (NAWQA) and National Water Information System (NWIS), which are U.S. Geological Survey (USGS) water quality datasets.  Updated information, however, is being compiled, with the interactive "GeoTracker GAMA" website providing the most comprehensive compilation of California groundwater information to date.

CCKA Is Taking Action

Using the same approach as the USGS, CCKA combined groundwater data from the NAWQA and NWIS to show contaminant concentrations across land uses and geographic areas. CCKA chose to map these same datasets because they were chosen by USGS in their most recent (2007) state-by-state analysis of domestic well water quality for the Center for Disease Control's National Environmental Public Health Tracking Program.  CCKA chose to examine nitrate and arsenic due to their potential human health concerns.  Learn how nitrate and arsenic are contaminating California’s groundwater aquifers, the human health impacts of that contamination, and its sources, with CCKA’s Groundwater Maps.

CCKA works to improve the scope and quality of available data and information on California’s groundwater aquifers as the Public Representative on the California Water Quality Monitoring Council.  The Council is working across agencies to release a comprehensive, interactive, user-friendly portal of groundwater data by Fall 2010.  To protect the state's groundwater as a continued public resources, responsible agencies such as the State Water Board, the Department of Public Health, and the Department of Water Resources must develop, through a coordinated approach, a thorough understanding of the contaminants affecting the state’s groundwater basins, as well as the sources of such contaminants, and provide that information to the public.

Beyond calling for better groundwater data, CCKA advocates for strong enforcement of water quality laws designed to protect groundwater quality.  In conjunction with member Waterkeepers, and conservation groups such as the Pacific Coast Federation of Fishermen’s Associations, Clean Water Now!, and the Environmental Justice Coalition for Water, CCKA submitted written comments to the State Water Board calling for increased regulation of pollutant discharges to groundwater, and application of anti-degradation policy to groundwater.