Impacts of Stream Restoration on Nitrogen Processing in a Coupled Stream-Aquifer System

WRD PROJECT #: MD169
PROJECT CHIEF: Doheny, Edward
BEGIN DATE: 01-August-2001
END DATE: 31-July-2004

Customers currently supporting the project:

U.S. Environmental Protection Agency

Problem

Nitrate (N03) is a common pollutant in watersheds throughout the world. Riparian zones of streams, the vegetated region parallel to stream ecosystems, attenuate anthropogenic nitrate through microbial denitrification, a process that occurs only under anaerobic conditions (e.g. saturated soils) and is limited by the supply of dissolved organic carbon (DOC) to microbes. The hyporheic zone of streams, the region in which stream and ground waters mix, also is thought to be a zone of high denitrification activity. Restoring and manipulating these zones to enhance denitrification processes may provide important tools for reducing nitrate pollution in watersheds.

Stream reaches in several locations in Baltimore County have been restored using Rosgen approaches, to reconstruct highly incised streambeds. Restoration has involved replacing lost sediments to elevate streambeds, planting vegetation in riparian zones, and reconstructing point bars and stream meander features. Although these efforts restore stream geomorphic stability, the benefits for improving stream water quality have not been quantified. This research will investigate the effects of restoration on stream hydrology, denitrification, and overall water quality.

Objectives

The stated goal of restoration at Mine Bank Run is to restore geomorphic stability of the stream. However, these restoration efforts also may have significant positive effects on groundwater and surface water quality by reconnecting stream channel and flood plain hydrology. This project wi11 examine Mine Bank Run before and after restoration, therefore we will be able to directly assess restoration effects on water quality. We will collect data to enable researchers to answer whether or not stream restoration alters groundwater and stream hydrology and associated hyporheic processes. Complementary studies designed to measure denitrification will be conducted by other researchers. The combined data set will allow us to determine if stream restoration enhances the nutrient removal capacity of the riparian zone.

Approach

• Watershed Reconnaissance
• Sediment History
• Surface/Subsurface Water Interaction
• Surface Water Evaluation/Monitoring
• Stream-tracer Tests
• Other USGS Project Activities