Nonpoint-Source Nutrient Loads for Birch Branch, Worcester County, Maryland

WRD PROJECT #: MD147
PROJECT CHIEF: Majedi, Brenda F.
BEGIN DATE: 01-October-1999
END DATE: 30-September-2000

Customers currently supporting the project:

U.S. Environmental Protection Agency

Problem

Eutrophication has been identified as one of the most important problems facing Maryland's Coastal Bays. Excessive amounts of nutrients are currently being introduced into the Coastal Bays system. The nutrients contribute to an acceleration of the eutrophication process, and a corresponding degradation of the aquatic environment of the Coastal Bays. An accurate estimate of the portion of the total nutrient load contributed by surface-water discharge into the Coastal Bays is important to resource managers responsible for maintaining the quality of the coastal bays' aquatic environment.

The St. Martin River Basin is one of the most degraded parts of the Maryland Coastal Bays estuary. The effective management of the factors affecting water quality in this basin is a critical to the continued viability of many economically and aesthetically important aquatic species in the estuary, and to maintaining acceptable water quality for human recreation.

Objectives

This project is intended to assist the Maryland Coastal Bays National Estuary Program (MChesapeake Bay Program) in developing a Comprehensive Conservation Management Plan for the Maryland Coastal Bays estuary. Pursuant to the MChesapeake Bay Program Request for Proposals to estimate nutrient loads from nonpoint surface-water runoff, the Maryland-Delaware-D.C. District of the USGS proposes to install and operate a continuous-record streamflow gage and collect water-quality data at a point on Birch Branch, a major tributary to the St. Martin River. The data collected will be used to estimate a load for the project year, which can be used by MChesapeake Bay Program to develop informed resource-management guidelines for Birch Branch.

Approach

In order to support the estimation of nonpoint source nutrient loads for Birch Branch, the USGS will install and operate a continuous-record streamflow gage in conjunction with collection of water samples for water-quality analysis. The resulting information about streamflow rate and constituent concentrations will be used to estimate nutrient loads for Birch Branch.

In order to estimate nutrient loads within a defined range, of accuracy it is necessary to collect data that can be used to verify the estimate. Data collected during this project will include streamflows and nutrient concentrations. The streamflow will be monitored on a continuous basis, while the nutrient concentrations will be determined at discrete points in time during the year. The nutrient sampling will cover base flow as well as storm events.

The construction and operation of streamflow gages is one of the major tasks) conducted on a regular basis by the USGS. Guidance in proper siting, construction, and operation of gages is available from the Surface-Water Analysis Section of the Maryland-Delaware-D.C. District The stage-discharge relation that is developed through data collection at the gage allows accurate flow estimates to be made for the stream even after continuous data collection is discontinued, provided that there is no subsequent, major change in the streambed geometry.

The collection of water-quality data for the determination of nutrient concentration will be carried out during times of base flow during flows that result from storm events. Analysis of samples collected under a range of conditions allows the accurate assessment of the annual nutrient load to the stream during the sampling effort.

Surface-water discharge will be measured and both base-flow and storm samples will be taken and analyzed to determine nutrient concentrations. These measurements (discharge and nutrient concentration over a range of flow conditions) will be used to estimate annual loads of nutrients.