Mattawoman Water Quality Monitoring

Objectives

1. Continue the collection of stage data at Mattawoman Creek near Pomonkey, MD according to standard USGS protocols; refine the rating curve for continuous discharge determination; determine and report discharge data in the annual data report, as well as on-line through the real-time web page.

2. Continue to collect and analyze monthly base-flow as well as stormflow samples at Mattawoman Creek near Pomonkey, MD, for nutrients (N and P) and suspended-sediment concentration; want 35 to 45 samples per year, including qc, per proposal.

3. Expand data collection at Mattawoman Creek near Pomonkey, MD to include real-time reporting of additional waterquality parameters (pH, dissolved oxygen, turbidity, specific conductance, temperature).

4. Plan, coordinate, and oversee sample collection at all sites, including the quality-assurance data collection effort.

5. Manage all data collected for the project and publish annually in the MD-DE-DC Water Science Center annual data report

Statement of Problem

The Mattawoman Creek Watershed is located within the Coastal Plain physiographic province in Prince George's and Charles Counties, Maryland. Mattawoman Creek and its tidal and non-tidal wetlands were identified in a 1981 Maryland Department of State Planning report on areas of Critical State Concern. In 1998, the Maryland Clean Water Action Plan assessed watersheds in Maryland for water quality, aquatic living resources, landscape parameters, and clean water requirements. In the water-quality category, Mattawoman Creek Watershed was in the top 25% of all watersheds in Maryland for having the highest modeled nitrogen and phosphorus loadings per acre. These two nutrients are known to cause algae blooms which block sunlight to submerged aquatic vegetation (SAV). Nitrogen and phosphorus also consume large amounts of dissolved oxygen from the water that fish and plants need to survive.

Mattawoman Creek exceeds two federal clean water quality requirements - nutrients and sediments - and is listed on the State's 303(d) list, which indicates water bodies that are impaired and require the development of a Total Maximum Daily Load (TMDL). Out of 138 watersheds in Maryland, the 1998 Maryland Clean Water Action Plan identified Mattawoman Creek Watershed as one of thirteen highest priority watersheds in need of restoration and protection.

USGS maintained a stream gage (station ID 01658000) and water-quality monitoring station on Mattawoman Creek near Pomonkey, MD, in cooperation with Maryland Department of the Environment (MDE), from 2001 through September of 2002. The broad goal of the project described below is to continue and expand water-quality data collection in support of Maryland's and Charles County's needs with regard to the Clean Water Action Plan, TMDLs, and the Charles County Comprehensive Plan.

Strategy and Approach

This project will collect samples for nutrients and suspended sediment at Mattawoman Creek near Pomonkey, Maryland, on a monthly basis, and during storm events using automatic sampling equipment. Additionally, continuous water-quality data will be collected, including water temperature, specific conductance, dissolved oxygen, turbidity, and pH.

In subsequent project years, once adequate samples have been collected, the measured nutrient concentration values will be related to concurrent values of continuously measured parameters (water temperature, specific conductance, turbidity, pH, and dissolved-oxygen content) to estimate nitrate, total nitrogen, total phosphorus, and suspendedsediment concentrations in the stream water at 15-minute intervals. The load for each time interval will be calculated by multiplying the estimated concentration by the discharge for the interval computed from the stage-discharge relation established for the site. Total loads for any given period of time can be calculated by summing the loads computed for each measurement interval during the specified period.