Climate Change and Water in New England: What the USGS Is Studying

The U.S. Geological Survey has long studied how climate change affects water in New England. Recent USGS studies in the Northeast have found substantial evidence of change over the past 100 years: snowmelt runoff coming earlier in the year, less river ice and less winter snowpack. Its work falls under five themes:

• collecting long-term data that can detect and track climate-related changes in water;
• relating past climate variation to past hydrologic variation, and connecting those relations to future conditions projected in the Intergovernmental Panel on Climate Change's emissions scenarios;
• building climate scenarios into assessments of how streamflow and aquifer levels may change;
• describing climate change's effects on floods, droughts and long-term water supplies for people and nature;
• developing consistent regional tools to forecast ecosystem change and manage water.

Cold after rain formed an ice layer on Libby Brook near Northfield, Maine, which stayed as the water dropped, February 2005. Photograph by the USGS.

Collecting climate-response data

The USGS has expanded its networks to meet present and future information needs: new stations for general monitoring, new measurements such as water temperature at key sites, and joint climate work with other federal and state agencies and universities at its stations.

• A climate-response network for New England. Many climate-sensitive hydrologic measures in the region changed over the last century and are expected to keep changing, with consequences for water supply, hydropower, transport infrastructure and river ecology. A USGS framework identifies which inland measures are sensitive to climate, which regions respond alike, and which basins suit detailed study, and proposes a fixed network built from existing streamflow, groundwater, lake-ice, snowpack and weather stations.
• NorEaST stream temperature. A multi-agency web portal maps and stores continuous stream-temperature records for New England, the Mid-Atlantic and the Great Lakes: nearly 7,900 stations in 22 states, from 41 organisations. The project sets common data standards, refines the portal with users, and shows through models how consistent, large-scale temperature data can inform decisions.

A USGS scientist checks an automated water-level system with a steel tape at the Mirror Lake groundwater research site, Hubbard Brook Experimental Forest, North Woodstock, New Hampshire. Photograph by the USGS.

Past climate and past water

• Snowmelt and groundwater in northern New England. Maine, New Hampshire and Vermont are ideal for watching climate effects on groundwater: their water is dominated by snowmelt, and little development means little pumping. Snowpack, snowmelt runoff and summer base flows there have changed substantially over the last 100 years. The project correlated year-to-year groundwater levels across the region with seasonal air temperature and precipitation to measure how sensitive groundwater is to each.
• Peak flows in Maine. There is evidence that peak river flows in Maine have risen over the past 50 years, so some bridges and culverts may now be too small. With the Maine Department of Transportation, the USGS examined trends at 28 gauges with at least 50 years of data. Because flood estimates are sensitive to very rare floods, it is hard to say whether recent years or the whole record give better estimates; one cautious approach is to compute both and use the higher.

Effects on people and nature

• Salt marshes and sea-level rise at Acadia. Coastal wetlands, above all salt marshes, give wildlife places to breed and raise young, feed migrating birds, improve water quality and check shoreline erosion. The USGS studied the salt marshes of Acadia National Park to find which are threatened by rising seas and which could adapt by moving into low-lying land next to them.
• Cape Cod's aquifers. A study of the four freshwater lenses of the lower Cape Cod aquifer looked at how changes in pumping, recharge and sea level affect groundwater. The depth to the boundary between fresh and salt water varies across the area in direct proportion to the water table's height above sea level; simulated sea-level rise raised water levels and streamflows but brought the saltwater boundary closer to the surface. A study with the Cape Cod Commission is modelling more sea-level scenarios.

The coast at Acadia National Park. Photograph from the National Park Service.

Projecting the future

Models such as the Precipitation-Runoff Modeling System and MODFLOW, combined with long-term data and fieldwork, test how projected changes in rainfall and temperature would affect New England's water.

• New Hampshire. As part of the state's effort to prepare for climate change, a test study of the Ashuelot, Oyster, Pemigewasset and Souhegan River basins simulated 21st-century streamflow, base flow and snowfall. On average, streamflow is likely to rise and base flow to fall, though with wide differences by place and season. Streamflow is likely to become more variable, with more high flows and more low flows; the largest increases come in winter, with small decreases in summer. Snowfall declines in every basin on average, most in the northern Pemigewasset, though any given winter could still bring more snow than expected. The work is being extended statewide.
• Rhode Island. Models of the Chipuxet and Chickasheen River basins in southern Rhode Island mapped the areas that recharge supply wells and projected groundwater's response to 21st-century climate. Under continuing high emissions, winter recharge could rise by as much as 15 percent and fall recharge drop by as much as 24 percent, though annual recharge would change little.

Tools for managers

The USGS uses statistical and process models to forecast seasonal and long-term change, assess the effects of water use, improve biological population and survival models, and help emergency agencies plan. With the Massachusetts Department of Environmental Protection it built the Massachusetts Sustainable-Yield Estimator, a statewide tool giving screening-level estimates of a basin's sustainable yield: the difference between natural streamflow and the amount a user specifies must stay in the stream for recreation, habitat and other needs. Because the water available in a basin varies over time and faces competing demands, a new version is in development with the state.

Sources

• Robert Lent, Climate Change Science Activities of the U.S. Geological Survey in New England, USGS Fact Sheet 2016–3011, March 2016. https://doi.org/10.3133/fs20163011
• The photographs are taken from the fact sheet's PDF.
• Corrected: "Interagency Panel on Climate Change" to "Intergovernmental Panel on Climate Change", as in the fact sheet's own reference.