The Lamprey River Hydrological Observatory: Suburbanization and Changing Seasonality

Key Findings

For 20-plus years, the Lamprey River Hydrological Observatory (LRHO) has been collecting data on the chemistry and hydrology of the 212-square-mile Lamprey River watershed, providing a baseline of information on river/stream discharge, levels of nitrogen and greenhouse gases (including methane and nitrous oxide), and dissolved organic matter to compare with future climate change-based measurements and to offer a historic look at how a developing landscape and warming climate have affected the river to date.

The length of the study has allowed the researchers to observe changes in surface water chemistry (such as increases in nitrate levels) due to suburban development within the watershed.

From its headwaters near Northwood Meadows State Park in Northwood, NH, the Lamprey River meanders for more than 50 miles until it empties out into New Hampshire’s largest and most culturally significant estuarine environment, the Great Bay. Long-term research of the Lamprey River can provide particularly impactful insights. Its partial protection under the National Wild and Scenic Rivers Act and passage through areas growing in population density— where most households use on-site waste disposal, like septic systems, that can pass nitrogen into water runoff—offer conditions for studying the impact of suburbanization on a water body. The Lamprey’s location, in a temperate region where winters are experiencing less snow and more rain than they did two decades ago and the transitional seasons between winter (spring and fall) are lengthening, make it an ideal watershed for studying climate change.

Long-term research of the Lamprey River can provide particularly impactful insights. Its partial protection under the National Wild and Scenic Rivers Act and passage through areas growing in population density— where most households use on-site waste disposal, like septic systems, that can pass nitrogen into water runoff—offer conditions for studying the impact of suburbanization on a water body. The Lamprey’s location, in a temperate region where winters are experiencing less snow and more rain than they did two decades ago and the transitional seasons between winter (spring and fall) are lengthening, make it an ideal watershed for studying climate change.

The length of the study has also allowed Wymore, McDowell and their colleagues to gather data that characterize river dynamics after extreme weather events, including multiple record-breaking winter and summer droughts, back-to-back 100-year-scale floods (in 2006 and 2007) and shifting seasonal changes, like shorter winters and longer springs. Additionally, LRHO researchers have identified changes in the chemistry of surface water within the watershed over time, such as that nitrate levels within the river and tributaries are slowly rising while dissolved organic nitrogen is steadily decreasing. However, how this will impact downstream critical waterbodies, like the Great Bay estuary, remains to be seen.

“Because Great Bay estuary is impaired by too much nitrogen, being able to quantify the impacts of potential future development in the Lamprey watershed is essential for developing future-oriented management strategies for Great Bay,” said McDowell. “At the same time that we have documented the impacts of land use patterns on nitrate levels, we have also shown that rain and snow have actually gotten cleaner over the last 20 years or so.”

This material is based on work supported by the NH Agricultural Experiment Station through joint funding from the USDA National Institute of Food and Agriculture (under Hatch award number 1022291 and 1019522) and the state of New Hampshire. Co-authors include A. Wymore, M. Shattuck, J. Potter, L. Snyder and W. McDowell.