Project Overview

Full Title
Investigation of effects of land-use and land-use change on water-quality of small streams in the Treyburn Development of the Falls Lake Watershed

Location
 Treyburn Development in Durham County

Cooperating Agencies
City of Durham

Project Chief
Jason M. Fine
jmfine@usgs.gov

Period of Project
1988-present

Science Topic:
Increased Population and Water Resources

Effects of land-use change on water-quality in the Treyburn Development of the Falls Lake Watershed

Project Summary

Background

Since 1988, the U.S. Geological Survey (USGS) has been collecting data at 18 sites in and around Treyburn, North Carolina, which is an 8-square-mile (mi²) residential, commercial, and industrial development located in the Falls Lake watershed. Water-quality data, assessments of biological conditions, and streamflow information have been collected at the sites over different time intervals. No single stream drains the entire Treyburn development.

In cooperation with the Triangle Area Water Supply Monitoring Steering Committee, the USGS is conducting a water-quality investigation of major inflow streams to Falls Lake. Some of these inflow streams receive drainage from Treyburn and, consequently, are sampled as part of the Treyburn project and the Triangle Area Water Supply Project.

Objectives

During the course of this project, the Treyburn water-quality monitoring network has been modified to meet the following primary objectives:

1. Identify, through water quality monitoring, the extent to which development affects water quality and aquatic biology in streams draining Treyburn;
2. Determine sediment, nutrients, and metals loading in streams draining the Treyburn development and in tributaries to Falls Lake through streamgaging and water-quality monitoring;
3. Identify trends in water quality through long-term monitoring and provide a warning mechanism to alert the City of Durham about potential water-quality problems.

Approach

A network of five sampling sites in and around Treyburn is monitoring water quality and stream discharge. The network is designed to collect information on loadings from Treyburn sites, including the effects of Mountain Creek on loadings to Little River Reservoir and the effects of Flat River on loadings to Lake Michie.

Summary of results

The U.S. Geological Survey (USGS) has been collecting streamflow and water-quality data in and around the Treyburn development since 1988. Water-quality data, assessments of biological conditions, and streamflow information have been collected at as many as 17 different sites during the study. Since 1995, however, data collection has occurred more or less continuously at the same 5 sites: Flat River Tributary near Willardville, Flat River at Bahama, Mountain Creek at SR1617 near Bahama, Little River Tributary near Fairntosh, and Little River below Little River Tributary near Fairntosh.

During the project approximately 1000 water-quality samples have been collected by the USGS in the Treyburn Development area. The types of data collected at the Treyburn sites have varied during the project. Nutrients, suspended sediment, metals, and pesticides have been collected consistently for the life of the project, while major ions were collected between 1988 and 1998, and biological samples were collected in 1995.

The original Treyburn study plan called for analysis of data and publication of interpretive reports at 5-year intervals. Two reports have been produced since the project began. Garrett and Bales (1995) provided a compilation of data collected during the first 5 years of the project, with some statistical characterization of the results. Oblinger and others (2002) produced the only significant interpretive report during the life of the project. The report included results from special studies of benthic macroinvertebrates in Treyburn streams, channel habitat, and water-trends. Some findings from this report included:

• Benthic macroinvertebrate variation in Treyburn streams was more a function of drainage basin size than land use.
• Pesticides were most often found at the golf course / residential site.
• Metals were seldom found in detectable concentrations, and then typically only in the Flat River at Bahama.
• Phosphorus concentrations were highest at the golf course / residential site.
• Loadings of sediment and nutrients were calculated, but there were not enough data to make any statistical distinctions among the sites.
• The only trend in water-quality conditions was at the undisturbed site, where total nitrogen concentrations declined, most likely because of a decline in organic nitrogen.