Comprehensive Assessment of the Atlantic Coastal Plain

Objectives

A 2004 report by the Advisory Committee on the Management and Protection of the State's Water Resources highlighted the need for further study of the Atlantic Coastal Plain aquifer system. In response to this recommendation, a draft science plan is being prepared by the Maryland Geological Survey and U.S. Geological Survey to address the need for a comprehensive assessment of the Atlantic Coastal Plain Aquifer System in Maryland. The five major science goals identified in the draft science plan are:

1. Characterization of the regional hydrogeologic framework for the entire Maryland Atlantic Coastal Plain aquifer system and hydrologically appropriate areas of neighboring states.

2. Detailed study of the regional flow system and water budget for the Maryland Atlantic Coastal Plain aquifer system.

3. Improved documentation of spatial patterns of water quality in all aquifers of the Maryland Coastal Plain.

4. Enhancement of ground-water-level, stream flow, and water-quality monitoring networks in the Maryland Coastal Plain.

5. Development of management tools to facilitate scientifically sound allocation of ground water in the Maryland Coastal Plain.

Statement of Problem

Unconsolidated sediments that underlie the Atlantic Coastal Plain (ACP) form a complex aquifer system that is an important and sometimes sole source of water supply in over half of the land area of the State of Maryland. The coastal plain deposits are comprised of layers of sand, sand and gravel, silts, and clays that form a wedge that begins at the boundary of the Piedmont Physiographic Province (the Fall Line) and gently dips and thickens to the southeast toward the Atlantic Coast. The buried sands and gravels form a sequence of confined aquifers that is overlain by generally sandy surficial deposits that form a water-table aquifer. Except for suburban areas around Washington, D.C., this aquifer system is the sole source of water supply for most of southern Maryland and nearly all of the Eastern Shore. It is also an important water supply source for the counties northeast of Baltimore along the western shore of Chesapeake Bay.

However, ground-water levels in confined aquifers in the ACP have been declining for several decades by an average of about 2 feet per year in some of these aquifers. The declines are especially large in southern Maryland and parts of the Eastern Shore where the population is projected to grow significantly in the next 20 to 30 years. Continued declines at this rate could affect the long-term sustainability of ground-water resources in Maryland's heavily populated Coastal Plain communities and the agricultural industry of the Eastern Shore. Water budgets and ecological resources in wetlands and coastal areas could also be affected.

In Maryland, officials from ground-water management and regulatory agencies and State and local planners need to know how much ground water is available in the different areas of the ACP for public and domestic water supply, as well as for agricultural, industrial, and electric power generation use. These officials also need to understand where and when continued extraction of ground water may induce undesirable changes in water quality that would require additional treatment or limit the potential uses and/or the aesthetic appeal (taste and odor) of the water resource.

The management of ground-water resources in Maryland is accomplished through a Water Appropriations Permit Program (WAPP) in the Maryland Department of Environment. WAPP needs a comprehensive regional assessment of the flow system and available ground-water resources throughout the entire aquifer system. The information also needs to be available to a broad audience of government officials and integrated into land-use, sewer, and water distribution planning and zoning activities at both state and local levels of government. These officials also need information tools and computer modeling tools for assessing the potential environmental and economic impacts of different patterns of growth in population and water use.

Strategy and Approach

Accomplishing these science goals is seen as a long-term, multi-year effort divided into three phases. Phase I is considered to be a three-year effort in which the investigation team will build the partnerships, develop the data-base architecture, and compile what is known about the aquifer system from previous studies and other data sources. Important gaps in data and other information will be identified in Phase 1 and acquisition of appropriate new data will begin. The regional flow model will be designed and initial flow simulations will be done to prepare for the development of a more detailed model with finer grids in pumping centers. In addition, research will be done to prepare for the development of the ground-water management model and related decision support tools.

Phase II may overlap the final year of Phase I and will consist of a series of specific studies to investigate recharge, leakage, gaps in understanding of the hydrogeologic framework, flow in the surficial aquifer, and water-quality patterns. The bulk of the work on calibrating the ground-water flow model will be done in Phase II. Phase III will involve the development and use of a ground-water management model with a user interface that can be used for optimizing usage patterns for ground water in the aquifer system and decision support. Phases II and III will probably overlap each other in time, depending on the availability of funding and the priority given to some of the specific studies mentioned in Phase II. Most of the planning for Phases II and III will be done in Phase I.