Ground Water Brochure

PROTECTING  LOUISIANA'S GROUND WATER

Louisiana Department of Environmental Quality
Office of Environmental Assessment
Water Quality Assessment Division 

This page last updated: 5/2/06


BACKGROUND

Louisiana currently has an abundance of high quality ground water. Drinkable water is a resource of increasing value in a nation where good water quality is becoming increasingly scarce.

Ground water is the primary source of drinking water for 61 percent of Louisiana's residents. Of this 61 percent, 12 percent use domestic wells and 49 percent rely on public water supplies. (DOTD/USGS, 1995)

Ground water is stored in aquifers. These are permeable, saturated zones of rock, sand or gravel that contain sufficient water to yield usable amounts to wells.

The potential for aquifer contamination is impacted by the depth to ground water below the surface, the depth and types of soils above the aquifer and other factors. Fortunately, many parts of Louisiana have surface clays of relatively low permeability which impede downward migration of contaminants into underlying aquifers.

PURPOSE

The purpose of Louisiana's ground water protection strategy is to protect the health and well-being of Louisiana citizens by safeguarding the ground water we drink and use. The goal of the state's program is to prevent contamination, identify, address and mitigate areas of concern and encourage state and local governments to work together to protect our ground water resources.

A TEAM APPROACH

The development of a long term, well coordinated strategy for the state is a group effort. The Ground Water Advisory Group is comprised of environmental professionals representing private, federal, state and local agencies dealing with water resources in Louisiana.

The Louisiana Departments of Natural Resources (DNR), Transportation and Development (DOTD), Health and Hospitals (DHH), Agriculture and Forestry (DAF), Wildlife and Fisheries (DWF) and the United States Geological Survey (USGS) are working together with the Louisiana Department of Environmental Quality (DEQ) to develop a long term strategy to protect Louisiana's ground water and prevent contamination.


WELLHEAD PROTECTION

The Louisiana Wellhead Protection Program is an integral part of the state's ground water protection strategy. The fundamental goal of the Wellhead Protection Program is to protect public water supplies from contamination, which may have adverse effects on human health.

The term "wellhead protection area" refers to the surface and subsurface area around a public water supply well through which contaminants are likely to move, possibly reaching the well.

The Wellhead Protection Program defines these protection areas to ensure that aquifers feeding community water wells are protected from contamination. Each community's water system is then able to inventory, inspect and control potential sources of contamination.

The Wellhead Protection Program was designed to allow every community the opportunity to take an active role in maintaining ground water quality.

With the assistance of state regulatory programs, local governments can manage these areas by using ordinances, site plan reviews, design and operating standards, source prohibitions, property purchases and development rights. In addition, local governments can create support for ground water protection through public education.

Through cooperative agreements over a 30-year period, the Louisiana Department of Transportation and Development and the United States Geological Survey have characterized and mapped the state's aquifers. The Louisiana Geological Survey characterized and mapped the state's aquifer "recharge zones" for DEQ in 1989.

Recharge zones are land areas where aquifers are replenished by infiltration of rain water or surface water. Recharge zones are sensitive areas where contaminants can be directly introduced into aquifers.

WHAT IS NEEDED?

Information is needed on less detectable widespread "nonpoint" sources of aquifer contamination. Such sources include septic tanks, animal waste, urban runoff, fertilizer runoff and pesticide misuse.

Proper management of Louisiana aquifers is necessary to avoid contamination of drinking water via salt water encroachment due to overpumping of wells.

PRINCIPLES OF A WELLHEAD PROTECTION AREA AT WORK

Wellhead protection area boundaries are delineated so that any contaminants from sources outside the wellhead protection area require a substantial amount of time to reach wells.

Contaminants that reach the ground water outside of the wellhead protection area are diluted, degraded or absorbed to some extent before reaching the boundaries of the wellhead protection area. Monitoring wells may be used to discover any undiluted contaminants passing within the boundaries, allowing sufficient response time to prevent contamination of the water supply.

Potential sources of contamination within the wellhead protection area can be closely controlled by using ordinances and best management practices to prevent releases of contaminants.

 Click here to view a graphic representation of potential sources of contamination (click on figure and expand to regular size to view)

MONITORING PROGRAMS

The following state programs are designed to evaluate specific water quality concerns. DEQ uses information gained from these programs to determine problem areas and additional monitoring needs.

  • DEQ's Environmental Technology Division currently requires ground water monitoring for a variety of contaminants at 300 solid and hazardous waste sites.
  • The Water Quality Assessment Division's Baseline Monitoring Program is an ambient monitoring program established to determine and monitor the quality of ground water in Louisiana. Currently, approximately 140 of a projected 180 water wells are included in a statewide well grid.
  • These water wells are located in 14 aquifers and aquifer systems and are sampled on a three year rotation. For each well, samples are collected and analyzed for parameters which include metals, nutrients, volatile organic compounds (VOCs), semi-volatile organic compounds, pesticides, PCBs, and other basic water quality parameters.
  • Field parameters collected at the time of sampling include temperature, pH, specific conductance and salinity. In addition to these, the geographic location (latitude and longitude) of each well is determined using differentially corrected GPS.
  • Analytical data derived from the sampling and field data is provided to the well owners and included in a year-end report of the Baseline Monitoring Project's activities.
  • Beginning in 1995, the physical and chemical data are being incorporated into DEQ's Geographic Information System to improve data management and to better serve the private and corporate citizens of Louisiana.
  • DEQ's Remediation Services Division maintains records on the location and ownership of underground storage tanks (USTs). Contamination releases are investigated, documented and the appropriate corrective action is recommended. All unregistered and abandoned USTs within 1000 feet of municipal public supply wells are reported to the Remediation Services Division by wellhead protection program staff.
  • DEQ's Office of Environmental Assessment fixed station, long term monitoring network provides data from 189 monitoring sites. Samples are collected on a monthly or bi-monthly basis. The basic network includes 44 fixed benchmark water quality monitoring stations which have provided data over a 30 year period of record.
  • The remaining 145 stations were established to address data needs in high priority areas, or were added to obtain baseline information on conditions not covered by the benchmark stations.
  • DAF regulates pesticide usage in the state. DAF currently monitors for pesticides at 45 selected surface water locations and 50 ground water locations, a total of 95 sites. Other sites are selected and sampled as necessary during the year.
  • DOTD's Water Resources Section ensures that proper construction and plugging and abandonment procedures are followed. DOTD is the primary cooperator with the U.S. Geological Survey. USGS collects chemical, physical and biological water quality data at 544 ground water monitoring stations in the state.
  • DHH, through the Safe Drinking Water Program administered by the Office of Public Health (OPH), monitors public water supplies for all contaminants regulated by EPA under the Safe Drinking Water Act.
Regulated contaminants include bacteriological agents as well as organic and inorganic chemicals and radionuclides. Approximately 1900 public water systems in the state are presently monitored for some 120 contaminants, with about 90,000 samples analyzed annually.

WHY IS PROTECTION VITAL?

Louisiana is fortunate to have abundant sources of high quality ground water. Cleaning up and treating contamination--or securing and transporting alternative water supplies, even on a temporary basis--is expensive. Protection of existing ground water will provide affordable clean drinking water now and for the future.

LOUISIANA AQUIFERS

The principal aquifers and aquifer systems of Louisiana are shown below. These divisions are mapped based on their surface extent. From youngest to oldest, the aquifer groups are:

  • Recent alluvial deposits, including Red River Alluvial and Mississippi River Alluvial Aquifers;
  • Pleistocene Age, including the Chicot Aquifer, Chicot Equivalent Aquifer (Southern Hills Aquifer) and the Upland Terrace Aquifer;
  • Pliocene-Miocene Age, including the Evangeline, Jasper, and Catahoula Aquifers of central Louisiana and the "800 foot" and deeper sands near Baton Rouge;
  • Eocene Age: Cockfield-Sparta aquifer group of north Louisiana;
  • Paleocene Age: Carrizo-Wilcox aquifer group of northwest Louisiana; and
  • Areas where no fresh water occurs at any depth.
Click here to view a map of the principal aquifers and aquifer systems of Louisiana
(click on figure and expand to regular size to view)

Detailed information on the ground water quality of each major aquifer group is available in the Louisiana Ground Water Protection Strategy document.

HYDROGEOLOGIC COLUMN OF AQUIFERS (click on figure and expand to regular size to view)

For more information about Louisiana's Ground Water contact:
Louisiana Department of Environmental Quality
Office of Environmental Assessment
Water Quality Assessment Division
Aquifer Evaluation and Protection Section
phone: (225) 219-3510 or
e-mail address: SECTAQEVA@LA.GOV

 

 

Louisiana Department of Environmental Quality 602 N. Fifth Street Baton Rouge, LA 70802
Call or e-mail a hotline · Office Address/Phone listing · Locate a DEQ employee
Call 1-866-896-LDEQ or e-mail our Customer Service Center with questions or comments