Climate-related changes on northern New England rivers and lakes during the last century

Presentation (pdf document)

Glenn A. Hodgkins, Robert W. Dudley, Thomas G. Huntington
U.S. Geological Survey, Augusta, ME, 207/622-8201, gahodgki@usgs.gov, rwdudley@usgs.gov, thuntington@usgs.gov

Researchers from the U.S. Geological Survey and other organizations have analyzed trends over time in many hydrologic variables in New England that are sensitive to climatic variability. Spring has become earlier in northern New England in the last 30-40 years, based on several lake and river data sets. Lake ice-out dates at many lakes have become significantly earlier in northern New England since the 1800’s. The overall change in dates at Moosehead Lake between 1850 and 2000 was 9 days and for Damariscotta Lake was 16 days; much of the change toward earlier ice-out dates occurred from about 1968 to 2000. River ice-out dates at 12 out of 16 rural, unregulated rivers in northern New England became significantly earlier during the 20th century. Most of the 11-day average change for 9 rivers, from 1936 to 2000, occurred from the 1960’s to 2000. Winter/spring high river flows became significantly earlier during the last century at all 11 rivers in areas of northern New England where snowmelt runoff has the most effect on river flows. Most of the one to two week change (depending on the site) occurred in the last 30 years. Lake and river ice-out dates and river high-flow dates were highly correlated with March through April air temperatures (r = -0.7). There have been few changes over the last century in summer low flows or in fall river ice-in dates.