Long-Term Data Collection Provides Insight to Changes in Water Resources in New England

Science Center Objects

Primarily through the efforts of Glenn Hodgkins and Robert Dudley, the New England Water Science Center has been studying historical changes in streamflows, groundwater levels, and lake ice in New England and across the country for 20 years. Glenn and Rob have analyzed a wealth of historical data, including 100+ years of streamflow data and 150+ years of lake-ice data at some locations. Understanding historical changes in water-resource conditions helps us understand possible future changes in response to climate change.

The timing of snowmelt-related runoff in New England is sensitive to small changes in air temperature; Rob, Glenn, and others have documented significant changes in the timing of snowmelt-related runoff, which is happening earlier than in past years as temperatures in New England have increased. For example, between 1940 and 2014, they observed that, with air temperatures between winter and spring increasing by 1.7 degrees Fahrenheit, average snowmelt-related timing in the northeast happened nearly 8 days earlier (Dudley and others, 2017). This can be seen in the figure below, which was prepared as part of a collaborative project with the U.S. Environmental Protection Agency. Lake ice-out dates in New England also are sensitive to air temperature changes, and ice-out dates have become earlier in recent decades (Hodgkins, 2013). Earlier lake ice-out dates likely contribute to lower dissolved-oxygen concentrations in lakes in late summer, which can adversely affect the survival of cold-water fish.

Figure 4 Timing of Winter-Spring Runoff in the United States, 1940–2018

Timing of winter-spring runoff in the United States from 1940 to 2018; from the U.S. Environmental Protection Agency climate change indicators (https://www.epa.gov/climate-indicators/climate-change-indicators-streamflow; Public domain.)

The amount of summer precipitation affects the magnitude and duration of low streamflows in New England (Hodgkins and Dudley, 2011). Changes in low streamflows can affect water supply and aquatic ecosystems. In general, low streamflows have increased or not changed substantially in New England in recent decades (Dudley and others, 2020). Groundwater levels also are affected by the amount of precipitation, and, as with low streamflow conditions, have increased at most monitoring sites in New England in recent decades (Hodgkins and others, 2017).

Figure 1 Seven-Day Low Streamflows in the United States, 1940–2018

Seven-day low streamflow in the United States from 1940 to 2018; from the U.S. Environmental Protection Agency climate change indicators (https://www.epa.gov/climate-indicators/climate-change-indicators-streamflow; Public domain.)

In contrast to low-streamflow and groundwater-level conditions, peak streamflows have generally not shown substantial changes in New England in recent decades for relatively natural watersheds (Hodgkins and others, 2019). However, rivers with large reservoirs can show large decreases compared with periods before the rivers were dammed, and streams in urban areas can show large increases; changes in peak flows for rivers affected by development often are due to a combination of factors. Future changes in flood flows are important to State transportation agencies and the Federal Highway Administration, who have supported recent research on peak-streamflow trends.

Figure 2 Three-Day High Streamflows in the United States, 1940–2018

Three-day high streamflow in the United States from 1940 to 2018; from the U.S. Environmental Protection Agency climate change indicators (https://www.epa.gov/climate-indicators/climate-change-indicators-streamflow; Public domain.)

These studies of historical climate-related changes are based on long-term hydrologic data collected at U.S. Geological Survey monitoring networks funded by many Federal, State, local, and Tribal partners. These partnerships provide data collection and interpretation vital to understanding climate variability and changes in water resources throughout New England.

 

References

Dudley, R.W., Hirsch, R.M., Archfield, S.A., Blum, A.G. and Renard, B., 2020, Low streamflow trends at human-impacted and reference basins in the United States: Journal of Hydrology,  v. 580, article 124254, 13 p., https://doi.org/10.1016/j.jhydrol.2019.124254.

Dudley, R.W., Hodgkins, G.A., McHale, M.R., Kolian, M.J., and Renard, B., 2017, Trends in snowmelt-related streamflow timing in the conterminous United States: Journal of Hydrology, v. 547, p. 208-221, https://doi.org/10.1016/j.jhydrol.2017.01.051.

Hodgkins, G.A., 2013, The importance of record length in estimating the magnitude of climatic changes—An example using 175 years of lake ice-out dates in New England: Climatic Change, v. 119, p. 705-718, https://doi.org/10.1007/s10584-013-0766-8.

Hodgkins, G.A., and Dudley, R.W., 2011, Historical summer base flow and stormflow trends for New England rivers: Water Resources Research, v. 47, no. 7, article W07528, 16 p., https://doi.org/10.1029/2010WR009109.

Hodgkins, G.A., Dudley, R.W., Archfield, S.A., and Renard, B., 2019, Effects of climate, regulation, and urbanization on historical flood trends in the United States: Journal of Hydrology, v. 573, p. 697-709, https://doi.org/10.1016/j.jhydrol.2019.03.102.

Hodgkins, G.A., Dudley, R.W., Nielsen, M.G., Renard, B., and Qi, S.L., 2017, Groundwater-level trends in the US glacial aquifer system, 1964-2013: Journal of Hydrology, v. 553, p. 289-303, https://doi.org/10.1016/j.jhydrol.2017.07.055.