February 14, 2020:
Are we running out of Southern Hills Aquifer water in the Baton Rouge Area?
Dr. Doug Carlson
For the past seventy-five years water levels in the Southern Hills Aquifer System (SHAS) have declined tens to hundreds of feet depending on which unit was examined. In addition, there has been saltwater intrusion in most of the ten major sands: 400 foot, 600 foot, 800 foot, 1000 foot, 1200 foot, 1500 foot, 1700 foot, 2000 foot, 2400 foot, and 2800 foot sands; that comprise the SHAS. Two in particular, 1500 foot and 2000 foot sands have experienced the most rapid saltwater intrusion. These two results could be the bases of some officials stating the aquifer will run out of water within the next 75 to 100 years. However, is this really the case?
Recent observations indicate this is not the case. The volume of water within storage can meet current demands for at least 50 years and likely longer. However, the SHAS is receiving inflow from three sources: 1) surface recharge; 2) lateral flow into the parish and 3) induced recharge drawing water from clays between the sands. As a result of these fluxes regression analysis of dozens of USGS monitoring wells indicate that for the past 10 years the Evangeline Equivalent and Jasper Equivalent sands, 800 foot sand and below, have reached a steady state, while steady state conditions haven been present for the past 40 years for Chicot Equivalent sands, 400 foot and 600 foot sands. This should not be surprising since the rate of pumping within the SHAS has been approximately constant since 1970 which is approximately 130 + 10 million gallons/day (mgd), yielding a new steady state.
The concern of saltwater intrusion is a local problem impacting the aquifer for a few square miles in the southwest portion of East Baton Rouge Parish south of the Industrial Area north of downtown Baton Rouge and the Lula Street cluster of municipal wells and north of the Baton Rouge Fault. Saltwater intrusion has been occurring for over fifty years in the 1500 foot and 2000 foot sands. A number of modeling studies indicate that with a few scavenger wells, one to four, and rates of pumping of 1 mgd within the 1500 foot sands and 2.5 mgd within the 2000 foot sands could stop the advancing saltwater front and within a few decades draw it southward protecting both municipal and industrial water consumers from future saltwater intrusion which could impact these wells within a few decades if nothing is done.
In summary the SHAS could supply current East Baton Rouge Parish water needs for decades to hundreds of years. Saltwater intrusion can be managed with a modest investment of a few scavenger wells so as to avoid greater financial impacts that could occur if the Baton Rouge Water Company needed to shut off the Lula Street cluster of wells and replace them with wells further northeast in the parish and/or industry switching to meeting its needs by building a treatment plant to use Mississippi River water.
Dr. Doug Carlson is currently an Associate Professor of Research with the Louisiana Geological Survey. He has worked for Survey for the past 17 years. His research has focused on aquifer characterization, stream monitoring, groundwater-surface water interactions and use of geophysical techniques in understanding aquifer systems. He has taught introductory geology, environmental geoscience and environmental science at the University of Wisconsin-Milwaukee, introductory astronomy and introductory physics at Ball State University, and introductory physics, earth physics, and statics at the University of Wisconsin-Stout over the years 1984 through 2002. Doug has both a B.S.in Geology (1981) and a B.S. in Geophysics (1981) from the University of Minnesota Institute of Technology, a M.S in Geophysics (1983) from the New Mexico Institute of Mining and Technology, and Ph.D. in Geosciences/Hydrology (2001) from the University of Wisconsin-Milwaukee. Doug has served the BRGS as Vice President, President, and Director in previous years and is a licensed Professional Geoscientist in Louisiana.
THE BATON ROUGE GEOLOGICAL SOCIETY
BRGS generally meets the second Friday of the month
Meals begins at 11:30 a.m. Talk begins at 12:00 p.m.
Mike Anderson Seafood Restaurant, located at 1031 West Lee Drive
Cost is $20 for members and $25 non-members, and $5 for students.