Emerging Coastal Issues Room 202B
Jan 25, 2023 10:50 AM - 11:50 AM(America/Chicago)
20230125T1050 20230125T1150 America/Chicago Emerging Coastal Issues Room 202B 2023 Bays and Bayous Symposium mbnep@mobilebaynep.com
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Water Quality is Changing in Mobile Bay and Mississippi Sound - What Are the Mechanisms and What Are Our Options?
10:50 AM - 11:05 AM (America/Chicago) 2023/01/25 16:50:00 UTC - 2023/01/25 17:05:00 UTC
Identifying trends in estuarine water quality is important for understanding environmental change, determining natural and human causes of change, and informing management actions. In this study, data from several long-term monitoring efforts were combined and analyzed to identify water quality trends in Mobile Bay and Mississippi Sound. The datasets included: 1. Estuarine temperature, salinity, and oxygen concentration time-series data collected nearly continuously, 30-minutely, across sites in the bay and sound by the Alabama Real-time Coastal Observing System (ARCOS, 2003 to present, operated by the Dauphin Island Sea Lab), 2. Lower Alabama River and Tombigbee River daily discharge rates (USGS, 1930s to present) and monthly to seasonal concentrations of nitrogen and phosphorus (ADEM, 1970s to present), 3) Coastal daily satellite ocean color products for organic carbon, chlorophyll a, suspended particulate matter, and light attenuation (NASA VIIRS, 2012 to present), and 4) Field observations of ocean color variables from a bay-wide, monthly sampling program (2019-present, this study) used to validate the satellite products. Time-series trend analyses on the datasets revealed statistically significant trends over the last several decades of increasing bay temperature, river discharge, and river nutrient concentrations and decreasing bay salinity, bay oxygen, and ocean color variables. Potential mechanisms causing change and their interactions such as land-use change and climate both affecting river discharge and nutrients and downstream temperature, salinity, oxygen, and ocean color variables will be discussed. Implications for future water quality conditions will be presented with potential management options to consider.

John Lehrter
University Of South Alabama, Dauphin Island Sea Lab
Co-Authors Zhilong Liu
University Of South Alabama, Dauphin Island Sea Lab
Mai Fung
University Of South Alabama/Dauphin Island Sea Lab
Delineation of Groundwater Recharge Areas in Baldwin County, Alabama for Water Management and Water Policy Development
11:05 AM - 11:20 AM (America/Chicago) 2023/01/25 17:05:00 UTC - 2023/01/25 17:20:00 UTC
Implementation of Managed Aquifer Recharge (MAR) policies may provide useful tools for protecting shallow groundwater sources from natural and anthropogenic stressors that affect the amount and quality of available water. A shallow aquifer recharge model (SARM) developed for Alabama allows for the identification of potential shallow aquifer recharge areas. The model utilizes Multicriteria Decision Analysis in conjunction with the Analytical Hierarchy Process in a Geographic Information System environment to produce maps that can be modified for different climatic and land use scenarios to identify potential recharge areas. Baldwin County, one of Alabama's two coastal counties, is experiencing high growth and attendant land use conversion. Shallow aquifers are used extensively in this area to provide groundwater for domestic and irrigation purposes. Depth to the water table in Baldwin County fluctuates widely in response to changing climatic conditions, affecting water availability. The shallow aquifer contains sandy strata with high permeabilities which have the potential to promote rapid infiltration of contamination from septic tanks, agricultural runoff, and coastal flooding and storm surge during tropical storms. SARM maps indicate that extensive recharge areas have been lost over the last few decades resulting from conversion of open agricultural lands to urban landscapes, promoting surface runoff and diminishing potential aquifer recharge. Shallow aquifer contamination potential has also increased due to these changes. Implementation of MAR policies at the state and local levels can help address the loss of recharge areas by guiding management decisions that promote sustainable water resources for future growth and environmental health.
Greg Guthrie
Geological Survey Of Alabama
Mary Hastings Puckett
Geological Survey Of Alabama
Bennett Bearden
Geological Survey Of Alabama
Gary Hastert
Geological Survey Of Alabama
University of South Alabama, Dauphin Island Sea Lab
Geological Survey of Alabama
SCS Engineers
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