Project Overview

Full Title
Coastal Plain Ground-Water Recharge

Location
Coastal Plain surficial aquifer

Cooperating Agencies
· USGS Ground Water Resources Program
· NCDENR Ground Water Section

Project Chief
Alissa Coes

Period of Project
2003-2005

Team Members

Tim Spruill

Melinda Chapman

Jeanne Robbins

Mary Giorgino

Coastal Plain Ground-Water Recharge

Introduction

In 1992, a project was initiated by the North Carolina Department of Environment and Natural Resources (DENR) to characterize ground-water recharge rates in the surficial aquifers of North Carolina. A 1:500,000-scale map was produced to delineate discharge areas along major stream networks in the State (Heath, 1993). Recharge maps (1:24,000-scale) for the Neuse and Tar-Pamlico River basins were compiled by characterizing drainage-basin landforms as upland flats, valley slopes, or riverine bottomland and with further refinements from county soils maps. Recharge rates for the full mapped area were estimated with Monte Carlo model simulations using calculated recharge for 11 U.S. Geological Survey (USGS) gaged drainage basins in the North Carolina Coastal Plain. The Rorabaugh-Daniel hydrograph separation model (Rutledge, 1993) was used to estimate ground-water recharge in each gaged basin (Mew and others, 2002). Recharge maps were developed from most of the state by weighting initial recharge estimates by mean rainfall rates (Mew and Spruill, 2000).

Although the DENR method provides a useful framework for estimating ground-water recharge rates for different geomorphic settings over large areas of the North Atlantic Coastal Plain, the estimated recharge rates have not been verified with direct field measurements. Therefore, in 2003, the USGS began a project to evaluate recharge estimates for different geomorphic settings in the North Carolina Coastal Plain. Recharge estimates derived from the DENR method will be compared with field measurements of recharge for each geomorphic setting.

The DENR calculated recharge estimates are based on long-term averages for the period of record at each USGS gaging station and represent average annual recharge. To better define seasonal variability, seasonal recharge rates will be estimated for different geomorphic settings by using direct field measurements and hydrograph separation techniques. Seasonal recharge estimates are needed to more accurately evaluate seasonal ground-water availability and the potential for contaminant infiltration, transport, and movement.