RIPARIAN ZONE VEGETATION AND IMPROVEMENT OF STREAM WATER QUALITY IN AN AGRICULTURALLY-DOMINATED WATERSHED

For decades, tributaries of the Chesapeake Bay Watershed have undergone millions of dollars of restoration aimed at improving water quality of these streams and thus of the Bay. Over time several techniques have been used, and insufficient data exists regarding the efficacy of these restoration efforts at removing excessive nutrients and improving stream quality. To address this dearth, water quality parameters were measured in six stream restoration projects in Lancaster County, Pennsylvania, an area of high agricultural activity within the Chesapeake Bay Watershed. These restoration projects were classified as utilizing one of the following approaches: broad riparian zones, narrow riparian zones, and in-stream engineering.

The Riparian, Channel, and Environmental Inventory (RCE) was used in conjunction with in situ water analyses to assess the quality of the streams. Through examination of physical structure, land use, and biota, restorations with both broad and narrow riparian-based restorations improved land use quality and stream physical structures while in-stream engineering did not. Results of water analysis indicate that broad riparian zone restorations increase dissolved oxygen (DO) levels (except under flood conditions) while narrow riparian zones and in-stream engineering do not. Additionally, broad riparian zones decrease total nitrogen more than narrow riparian zones. Restoration type appears to have little effect on turbidity, ammonia, dissolved metals, or total phosphorus (in normal flow conditions), however, these constituents were strongly influenced by nearby wastewater discharge. The presence of vegetation in the riparian zone clearly improved some aspects of downstream water quality, including reduction of nitrogen levels, but the influence from wastewater discharge suggests that watershed management also heavily influences stream water quality in this agriculturally dominated watershed.