The Mississippi Embayment Regional Aquifer Study (MERAS)—Model Construction, Simulation of Groundwater Flow, and Potential Uses of a Regional Flow Model

Author(s): Clark, B. ;  Hart, R.

The U.S. Geological Survey (USGS) Groundwater Resources Program supports projects to determine groundwater availability in multiple areas across the United States. One project is the Mississippi Embayment Regional Aquifer Study (MERAS). The primary tool used to evaluate groundwater availability in the embayment is the MERAS groundwater flow model. The construction of the MERAS model, using the USGS MODFLOW-2005 modeling software, included 2,700 geophysical logs for hydrogeologic framework development; 137 years of groundwater withdrawal information; 70,000 groundwater withdrawal locations; 39 rivers comprising 6,900 river miles; and precipitation, land use, surficial geology, and aquifer properties covering 78,000 square miles. Model calibration data include 55,000 ground-water level observations and streamflows at 14 stream-gage locations.

The MERAS model simulates groundwater flow from 1870 to 2007 and has been used to project impacts of climate variability on groundwater flow to the year 2037. Values of root mean square error between simulated and observed hydraulic heads of all observations up to 2007 ranged from 12.23 ft in 1919 to 48.19 ft in 1951. The MERAS model has been used to simulate climatic effects on the groundwater flow system by changing precipitation and streamflow input values based on projections of historic climate data analysis. Preliminary results of the groundwater flow model indicate deepening cones of depression over the next 30 years in the Mississippi River Valley alluvial aquifer in the northern part of the embayment.

Local stakeholders may also benefit from the use of additional MODFLOW-2005 methods and processes in conjunction with the MERAS model; the Local Grid Refinement (LGR) method and the Groundwater Management (GWM) process can provide excellent information for the local water manager. Potential use of the LGR method allows for more finely discretized local-scale areas to be simulated within the embayment while using the MERAS model as a boundary which contributes or receives flow. The GWM process allows for the optimization of groundwater pumpage given constraints such as drawdown, water level, and streamflow. These types of analyses with LGR and GWM can be particularly useful in areas where intense pumping stresses the groundwater- surface water system by lowering groundwater levels, reducing base flow, and ultimately inducing leakage from surface water bodies to the groundwater system. In a broader sense, the GWM process might be used in a regional application to evaluate issues related to resource sustainability on an intrastate or interstate scale.


Technical Presentations

  • Delta Water Quality
  • Delta Water and Agriculture
  • Wetlands
  • Water Quality
  • Sediments
  • Non-Point
  • Management and Sustainability
  • Wood Treatment
  • Modeling
  • Soil and Water Treatment


Responsible Site Design: Implementing Innovative Stormwater Management Strategies

The primary goal of the workshop is to create a dynamic learning experience that examines the role of stormwater management in the built environment. The workshop will focus on integrating ecologically sound water management approaches into site design. After the workshop, attendees will be familiar with the following concepts and technical issues:

  • Knowledge of the stormwater treatment chain
  • Knowledge of the impact of land use codes on stormwater management
  • Application of a design process that mitigates the effects of stormwater on-site
  • Knowledge of the relationship between land use codes and design for innovative stormwater management


For information contact:
Jessie Schmidt
Box 9680
Mississippi State, MS 39762