SAMPLING THE LAMPREY RIVER WATERSHED ACROSS SPACE AND TIME – NEW DATA COLLECTION EFFORTS TOWARD UNDERSTANDING NITROGEN SOURCES

Recent concerns about water quality in the Great Bay Estuary of New Hampshire have heightened the need to understand and manage the sources of nutrients to the bay. The Lamprey River watershed, at 550 km², is the second largest tributary to the Great Bay-Piscataqua estuarine system. Continuous, in situ water-quality monitoring at several locations in the Lamprey River watershed, in concert with regular grab sampling, provides an opportunity to view the spatial and temporal patterns of water quality as affected by the landscape.

The U.S. Geological Survey (USGS) and the University of New Hampshire (UNH) have installed water-quality sensors in both headwaters and the main stem of the Lamprey River to measure temperature, pH, conductance, turbidity, and concentrations of nitrate, dissolved oxygen, and dissolved organic matter. These values are recorded every 15 minutes year-round and transmitted to a USGS or UNH database for near real-time access on the web. One station, which incorporates about 90% of the watershed, is a half-mile upstream from the USGS Lamprey River streamflow gage near Newmarket, NH; thus nutrient fluxes can be computed from the combined streamflow and water-quality data. Other stations in headwater streams provide simultaneous measurements of the water quality from different landscapes that contribute to the total fluxes in the Lamprey River. Grab samples, regularly scheduled and ad hoc during runoff events, supplement the in-situ continuous data with greater spatial coverage and additional water-chemistry analyses.

Examples of the data will demonstrate how the continuous water-quality sensors and regular sampling can together increase our knowledge of how nitrogen loads in the Lamprey River watershed vary through the seasons of the year and the range of flow conditions from baseflow to storm runoff. Temporal variations in spatial patterns of water quality may also be evidenced by the continuously-recorded data.