Changes in the timing of high river flows in New England over the 20th Century

Abstract

The annual timing of river flows is a good indicator of climate-related changes, or lack of changes, for rivers with long-term data that drain unregulated basins with stable land use. Changes in the timing of annual winter/spring (January 1 to May 31) and fall (October 1 to December 31) center of volume dates were analyzed for 27 rural, unregulated river gaging stations in New England, USA with an average of 68 years of record. The center of volume date is the date by which half of the total volume of water for a given period of time flows past a river gaging station, and is a measure of the timing of the bulk of flow within the time period. Winter/spring center of volume (WSCV) dates have become significantly earlier ðp , 0:1Þ at all 11 river gaging stations in areas of New England where snowmelt runoff has the most effect on spring river flows. Most of this change has occurred in the last 30 years with dates advancing by 1 -2 weeks. WSCV dates were correlated with March through April air temperatures ðr ¼ 20:72Þ and with January precipitation ðr ¼ 20:37Þ: Three of 16 river gaging stations in the remainder of New England had significantly earlier WSCV dates. Four out of 27 river gaging stations had significantly earlier fall center of volume dates in New England. Changes in the timing of winter/spring and fall peak flow dates were consistent with the changes in the respective center of volume dates, given the greater variability in the peak flow dates. Changes in the WSCV dates over the last 30 years are consistent with previous studies of New England last-frost dates, lilac bloom dates, lake ice-out dates, and spring air temperatures. This suggests that these New England spring geophysical and biological changes all were caused by a common mechanism, temperature increases. Published by Elsevier Science B.V.

Has urbanization changed ecological streamflow characteristics in Maine (USA)?

“…Although the intent of the authors was to utilize the relatively similar climate in northern Maine as a point of comparison to southern Maine, Hodgkins et al (2003) found that the timing of peak streamflows in northern Maine over a similar study period changed significantly, while those in southern and coastal Maine, and much of southern New England did not. Peak streamflows, measured as winter/spring centre of volume, were found to occur earlier in northern Maine and these changes were correlated with warmer temperatures and earlier snowmelt.…”

Resistance and Resilience of A Stream Salamander To Supraseasonal Drought

“…Higher temperatures mean that a greater proportion of the winter precipitation falls as rain rather than snow, and the snowmelt season begins earlier. Snowmelt in parts of New England shifted forward by 1 to 2 weeks between 1936 and 2000 (Hodgkins et al, 2003), although this has had little discernible effect on summer flows (Hodgkins et al, 2005). [WGII 1.3.2]…”

Defining high-flow seasons using temporal streamflow patterns from a global model

“…Despite this broad attention to annual streamflow and its connections to global climate processes and precursors, there has been relatively little attention paid to the intra-annual timing of streamflow, emphasizing the need for analysis of seasonal streamflow patterns to further improve understanding of large-scale hydrology and atmospheric behaviors in the main (flood) streamflow season globally (Dettinger and Diaz, 2000). Moreover, better assessment of streamflow timing and seasonality is important for addressing frequency and trend analyses, flood protection and preparedness, climate-related changes, and other hydrological applications that possess important sub-annual characteristics (Burn and Arnell, 1993;Burn and Hag Elnur, 2002;Cunderlik and Ouarda, 2009;Hodgkins et al, 2003). This motivates further investigation of intra-annual temporal streamflow patterns globally.…”