Dorina Murgulet The University of Alabama Assessing the Extent of Saltwater Intrusion in the Aquifer System of Southern Baldwin County, Alabama

OUTLINE 1) Introduction Objectives Site description and background information 2) Methodology 3) Results 4) Discussions and conclusions

Introduction

determine the extent and severity of saltwater intrusion in the aquifers underlying southern Baldwin County, Alabama using the most recently collected geochemical, geological and hydrogeological information. determine the extent and severity of saltwater intrusion in the aquifers underlying southern Baldwin County, Alabama using the most recently collected geochemical, geological and hydrogeological information. Provide the current state of regional and local groundwater flow for the study area. Provide the current state of regional and local groundwater flow for the study area. Collect and compile information to develop a detailed groundwater model of Southern Baldwin County. Objectives:

Location of the study area and surveyed groundwater wells per aquifer system

Hydrogeologic Cross Section of Southern Baldwin County, Alabama Source: B. Gillett et al.,2000 Gillett et al., 2000

The Hydrologic System Is a complex interaction between water and the physical environment. Is a complex interaction between water and the physical environment. The area is bordered for the most part by brackish to saline bay and coastal waters. The area is bordered for the most part by brackish to saline bay and coastal waters. Losses from the freshwater zones are by diffusion into the surrounding subsurface saline waters, by spring discharge, by ET, and by water-well production. Losses from the freshwater zones are by diffusion into the surrounding subsurface saline waters, by spring discharge, by ET, and by water-well production.

Study Area Southern Baldwin County with the Fastest Growth Rates, Baldwin County has one of the highest population increases in Alabama, second only to Shelby County.

L ULC and Agriculture Area, 2001 Major types of land use: agriculture, recreation and tourism, seafood industries, and urbanization. The economy of the county is based primarily on: agriculture, tourism, fishery, and seafood processing industries. Agriculture=41.94% of total area

Increase in Agriculture and Urban LULC from 1987 to 2001 Agriculture increase = 14.5% Urban increase = 1.1% Agriculture Urban

With increasing development and tourism in these regions both ground water resources and environmentally sensitive areas such as coastal wetlands and ecological coastal habitats will be at risk. With increasing development and tourism in these regions both ground water resources and environmentally sensitive areas such as coastal wetlands and ecological coastal habitats will be at risk. Unsustainable ground water extraction or aquifer overdevelopment may lead to the incursion of salt water into freshwater aquifer zones, shifting the natural freshwater/salt water interface further inland. Unsustainable ground water extraction or aquifer overdevelopment may lead to the incursion of salt water into freshwater aquifer zones, shifting the natural freshwater/salt water interface further inland. Background Information

Methodology

The existence of the saltwater/freshwater interface is distinguished by the presence of water with high Salinity, Chloride and TDS concentrations into the freshwater aquifers. The existence of the saltwater/freshwater interface is distinguished by the presence of water with high Salinity, Chloride and TDS concentrations into the freshwater aquifers. The presence of the principal seawater ions such as: chloride and sodium, increase water conductivity. The presence of the principal seawater ions such as: chloride and sodium, increase water conductivity. Thus, water quality in coastal environments can be determined by measures of fluid conductivity. Thus, water quality in coastal environments can be determined by measures of fluid conductivity. Methodology

The ArcGIS was used to compile the geospatial data, to record and map well locations, well depths, hydrogeological information, and concentration data collected from fieldwork and to generate the final contamination and groundwater potential surface and general flow direction maps. The ArcGIS was used to compile the geospatial data, to record and map well locations, well depths, hydrogeological information, and concentration data collected from fieldwork and to generate the final contamination and groundwater potential surface and general flow direction maps. For more confidence, the output maps were compared with output maps developed from interpolation of same data using Surfer and compared with the actual concentrations and water levels For more confidence, the output maps were compared with output maps developed from interpolation of same data using Surfer and compared with the actual concentrations and water levels

Results

Aquifer zone A1: a) Chloride concentration map. b) Salinity concentration map c) TDS concentration map. d) Groundwater potential surface

Aquifer zone A2 a) Chloride concentration map. b) Salinity concentration map. c) TDS concentration map. d) Groundwater potential surface.

Aquifer zone A3 a) Chloride concentration map. b) Salinity concentration map. c) TDS concentration map. d) Groundwater potential surface.

Binary Masking Method The output concentration grid layers for each of the three parameters (Cl-, salinity and TDS) were reclassified using the binary masking method. The output concentration grid layers for each of the three parameters (Cl-, salinity and TDS) were reclassified using the binary masking method. Through this process critical areas such as those that exceed Cl- concentrations of 250 mg/l, salinity concentrations of 500 mg/l and TDS concentrations of 500 mg/l. were reclassified as 1 and all other areas that include concentrations within the limits were reclassified as 0. Through this process critical areas such as those that exceed Cl- concentrations of 250 mg/l, salinity concentrations of 500 mg/l and TDS concentrations of 500 mg/l. were reclassified as 1 and all other areas that include concentrations within the limits were reclassified as 0.

Contamination maps by aquifer zones: a) Aquifer zone A1; b) Aquifer zone A2; c) Aquifer zone A3

Increasing development associated with overdevelopment of the aquifer system. Increasing development associated with overdevelopment of the aquifer system. Aquifer hydrogeologic properties. Aquifer hydrogeologic properties. Salt water infiltration from the surface from different sources. Salt water infiltration from the surface from different sources. Periods of low recharge from the surface due to low precipitation rates. Periods of low recharge from the surface due to low precipitation rates. Potential causes of the groundwater seawater contamination in southern Baldwin County:

Hydrogeologic Properties The transmissivity of the Miocene-Pliocene aquifer system of Baldwin County, was estimated to range from 700 to 5,400 ft²/day ( Robinson et al., 1996) The storage coefficients were estimated as ranging from to (Walter and Kidd 1979).

PRECIPITATION and RECHARGE Rain is the primary source of recharge to groundwater, Rain is the primary source of recharge to groundwater, Precipitation, throughout southern Baldwin County averages about cm/ year (USGS, 1936 to 2005). Precipitation, throughout southern Baldwin County averages about cm/ year (USGS, 1936 to 2005). Data collected from three stations for the year of 2006, indicated that the annual-mean precipitation reported is appreciatively uniform throughout Baldwin County with a range from cm/year in Robertsdale to cm/year in Bay Minette (data from USGS, 2006). Data collected from three stations for the year of 2006, indicated that the annual-mean precipitation reported is appreciatively uniform throughout Baldwin County with a range from cm/year in Robertsdale to cm/year in Bay Minette (data from USGS, 2006).

2006 annual precipitation rate = 45 cm Annual-Average Precipitation from Three Different Sites Located in Baldwin County, Alabama

The compilation of data into a user-friendly GIS database allowed for useful graphical visualizations, data interpretation, data analyses, and current assessments of groundwater quality and availability for the region. Examination of the Cl -, salinity and TDS parameters revealed the Gulf of Mexico as the source of saltwater intrusion. Discussions and conclusions:

For aquifer A1, the elevated salinity, chloride, and TDS concentrations may be the result of a combination of both saltwater intrusion and surface contamination. Aquifer zone A2 is vulnerable to saltwater intrusion, particularly in areas where wells are in close proximity to the Gulf of Mexico. Saltwater contamination of aquifer zone A2 might be the result of aquifer overdevelopment and infiltration from aquifer A1. It appears that aquifer zone A3 is less vulnerable to saltwater intrusion however this does not mean that saltwater intrusion has not occurred in the aquifer zone. Discussions and conclusions:

S N Not at scale Discussions and conclusions:

REFFERENCES Dowling, C.B.; Poreda, R.J.; and Carey, A.E. 2004, Ground Water Discharge and Nitrate Flux to the Gulf of Mexico, Ground Water, v.3, no.3, p Dowling, C.B.; Poreda, R.J.; and Carey, A.E. 2004, Ground Water Discharge and Nitrate Flux to the Gulf of Mexico, Ground Water, v.3, no.3, p Chandler, R.V.; Moore, J.D.; and Gillett, B. 1985, Ground-Water Chemistry and Salt-Water Encroachment, Baldwin County, Alabama: Geological Survey of Alabama Bulletin 126. pp. 16, 17, 53, 54, 78-80, Chandler, R.V.; Moore, J.D.; and Gillett, B. 1985, Ground-Water Chemistry and Salt-Water Encroachment, Baldwin County, Alabama: Geological Survey of Alabama Bulletin 126. pp. 16, 17, 53, 54, 78-80, Gillett, B.; Raymond, D.E.; Moore, J.D.; and Tew, B.H. 2000, Hydrogeology and Vulnerability to Contamination of Major Aquifers in Alabama: Area 13: Geological Survey of Alabama Circular 199A. Gillett, B.; Raymond, D.E.; Moore, J.D.; and Tew, B.H. 2000, Hydrogeology and Vulnerability to Contamination of Major Aquifers in Alabama: Area 13: Geological Survey of Alabama Circular 199A. Kidd, R.E. 1988, Hydrogeology and Water-Supply Potential of the Water-Table Aquifer on Dauphin Island: United States Geological Survey Water-Resources Investigation Report Kidd, R.E. 1988, Hydrogeology and Water-Supply Potential of the Water-Table Aquifer on Dauphin Island: United States Geological Survey Water-Resources Investigation Report Kopaska-Merkel, D. and Moore, J.D. 2000, Water in Alabama: Geological Survey of Alabama Circular 122O. Kopaska-Merkel, D. and Moore, J.D. 2000, Water in Alabama: Geological Survey of Alabama Circular 122O. Speiran, G.K., Hamilton, P.A., and Woodside, M.D. 1997, Natural Processes for Managing Nitrate in Ground Water Discharge to Chesapeake Bay and Other Surface Waters: More than Forest Buffers, United States Geological Survey, Report FS Speiran, G.K., Hamilton, P.A., and Woodside, M.D. 1997, Natural Processes for Managing Nitrate in Ground Water Discharge to Chesapeake Bay and Other Surface Waters: More than Forest Buffers, United States Geological Survey, Report FS

Funding: Alabama Department of Conservation and Natural Resources ADCNR Thanks: My Committee members: Dr. Geoffrey R. Tick, Dr. Chunmiao Zheng, Dr. Rona Donahoe, Dr. Andrew Goodliffe, and Dr. Christian Langevin. To people of Baldwin County Enid Probst (ADEM) Blakney Gillett, Marlon Cook, and others (GSA) Weeks Bay Reserve Joe Kington Valeriu Murgulet Acknowledgments