The Southern Hills Aquifer System in Southeast Louisiana
One of the great sources of groundwater in the nation, the Southern Hills Aquifer System is a formation of aquifers layered one atop the other that stretches across 14,000 square miles in southwest Mississippi and southeast Louisiana. Inside Louisiana’s borders, the system reaches west to the Atchafalaya Basin, south to Lake Pontchartrain, and east to the Pearl River, covering virtually all of the Florida Parishes. It is a large, prolific resource that in 2013 supplied more than 170 million gallons a day to the five-parish region that comprises the Capital Area Ground Water Conservation District.
The U.S. Census estimates that more than 527,000 people call the District home, with some 440,000 of them living in East Baton Rouge Parish alone. Almost all of these Louisiana residents get their daily drinking water from the Southern Hills Aquifer System. The needs of such a large population and a diverse economic base require the careful management of this resource to provide for long-term sustainability.
Groundwater Use in Baton Rouge and Saltwater Encroachment
At Baton Rouge, the Southern Hills Aquifer System comprises ten sands named after their depths (in feet) at a spot near the State Capitol, close to the Mississippi River. These are the “400-ft,” “600-ft,” “800-ft,” “1,000-ft,” “1,200-ft,” “1,500-ft,” “1,700-ft,” “2,000-ft,” “2,400-ft,” and “2,800-ft” sands. Altogether, these sands provide a prolific amount of groundwater that has been utilized extensively since the early 1900s both for public supply, or “drinking water,” as well as for industrial needs because of its high quality.
As the city’s population and heavy industrial base expanded in the middle decades of the 20th century, groundwater use increased. Since the 1960s, East Baton Rouge Parish (EBR) consistently has ranked as one of the top four largest consumers of groundwater in the State of Louisiana, and has been among the top three since the 1990s. Today, only Jefferson Davis and Acadia Parishes, in the heart of Louisiana’s water-intensive rice and crawfish industries, pump groundwater nearly as much as or more than EBR.
Although the groundwater use footprint has declined since the 1970s, about 150 million gallons still are pumped daily from the Southern Hills Aquifer System in EBR. Public supply draws about 72 million gallons a day, while industrial facilities use about 75 million gallons a day. Another seven million gallons a day are used for power generation.
These large volume groundwater withdrawals have caused saltwater from the south to encroach into the freshwater sands at Baton Rouge. Groundwater investigations in the 1960s first delineated this freshwater/saltwater interface near the Baton Rouge fault. The fault, which runs parallel to the Interstate 10 corridor before continuing on to the east-southeast, has served in the past to keep saltwater at bay. Heavy pumping has been pulling saltwater across this barrier, though, for several decades.
The Capital Area Groundwater Conservation Commission has wide authority to manage local groundwater resources and combat this saltwater encroachment. It has embraced a management philosophy based on utilizing the best available science to halt saltwater encroachment while ensuring the continued, sustainable use of the Southern Hills Aquifer System into the future.
The District has entered into a contract with the Water Institute of the Gulf and LSU to develop a 3D model of the aquifer and to provide engineered solutions to halt the salt water intrusion. The District is also implementing an independent metering program to be able to monitor all the wells which pump water from the aquifer. Currently all the wells are "self-reported" and only about 1/3 of them are metered. this new metering program will allow for accurate flow and chloride data to be recorded and used in the completion of the 3D model.