Project Overview

Full Title
Apparent Flow Losses in the Cape Fear River

Location
 Chatham, Wake, Lee, and Harnett Counties

Cooperating Agencies
Cape Fear Flow Study Committee of the Triangle J Council of Governments, NC Division of Water Resources

Project Chief
J. Curtis Weaver
jcweaver@usgs.gov

Period of Project
September 2008 - December 2010

Team Members
Geoff Cartano

Apparent Flow Losses in the Cape Fear River

Introduction

Background

The U.S. Army Corps of Engineers is required to release water from B. Everett Jordan Lake such that a minimum (target) flow of 600 ft³/s (± 50 ft³/s) is measured at the USGS streamgaging station located on the Cape Fear River at U.S. Highway 401 at Lillington (USGS Sta. 02102500).

The drainage area in this 24-mile reach increases from 1,689 mi² at Jordan Lake dam to 3,464 mi² at the Lillington gaging station (resulting in an intervening drainage area of 1,775 mi²). Much of the intervening drainage area in this reach includes the Deep River basin, and the downstream-most gaging station on the Deep River at Moncure (USGS Sta. 02102000) has a drainage area of 1,434 mi².

During some low-flow conditions, the sum of the estimated releases from Jordan Lake and the measured streamflow on the Deep River at Moncure is greater than the streamflow recorded downstream at the gaging station at Lillington. Consequently, either the target at Lillington is not met, or excessive water is released from Jordan Lake in an attempt to meet the target.

The difference between the inflow to this area (sum of releases from Jordan Lake dam and flow in Deep River at Moncure) and outflow from the reach (flow in the Cape Fear River at Lillington) could be because either (1) flow is measured inaccurately at one or more of the 3 measurement locations or (2) flow is being "lost" from the reach from surface-water diversions, possible alterations due to storage behind dam structures, ground-water withdrawals, evaporation, recharge (loss) to the ground water system, or a combination of these factors.