STREAM RESTORATION EFFECTIVENESS IN REDUCING EXCESSIVE NUTRIENTS

The Chesapeake Bay, the world’s largest estuary, is facing several significant environmental issues. In particular, excessive nutrients from fertilizer runoff causes eutrophication events in the bay. More than 25% of the Chesapeake Bay Watershed is used for agricultural purposes, and Lancaster County, PA has contributed to the poor Bay water quality with its agricultural practices, specifically fertilizer application. Various types of stream restoration, including riparian expansion and in-stream engineering, have been constructed in tributaries to improve local water quality, with the ultimate goal of improving water quality in the Chesapeake Bay. This research investigates the effectiveness of riparian expansion and in-stream engineering as viable long-term methods of stream restoration in the agricultural-dominated watersheds in central Pennsylvania and the greater Chesapeake Bay Watershed.

Total nitrogen, total phosphorus, and ammonia were analyzed in six streams located in Lancaster County, PA, representing three different types of stream restoration techniques: broad riparian expansion, narrow riparian expansion with in-stream engineering, and in-stream engineering.Water samples were collected up-, in-, and downstream of the selected stream restorations, in addition to collecting water samples at inlets, water treatment outlets, and tributaries introducing water into the restorations. The initial data show all stream restoration types do exhibit some levels of improvement in downstream water quality. However, both broad and narrow riparian zones out-performed in-stream engineering zones. Rehabilitating riparian zones as part of the restoration should be considered in future stream restoration practices for central Pennsylvania and the Chesapeake Bay Watershed. Also, restoration age seems significant in effectiveness with newer restorations out-performing older, however, additional research is planned to include more sites to discern if the difference identified between older and newer restorations can be replicated.