Quantifying the impacts of climate change and land use/cover change on runoff in the lower Connecticut River Basin

摘要

Climate change and land use and cover change (LUCC) have had great impacts on watershed hydrological processes. Although previous studies have focused on quantitative assessment of the impacts of climate change and human activities on decreasing run-off change, few studies have examined regions that have significant increasing run-off due to both climate variability and land cover change. We show that annual run-off had a significant increasing trend from 1956 to 2014 in the U.S. lower Connecticut River Basin. Abrupt change point years of annual run-off for four subbasins are detected by nonparametric Mann-Kendall-Sneyers test and reconfirmed by the double mass curve. We then divide the study period into 2 subperiods at the abrupt change point year in the early 1970s for each subbasin. The Choudhury-Yang equation based on Budyko hypothesis was used to calculate precipitation and potential evapotranspiration, and landscape elasticities of run-off. The results show that the difference in mean annual run-off between 2 subperiods for each subbasin ranged from 102 to 165.6mm. Climate variations were the primary drivers of increasing run-off in this region. Quantitative contributions of precipitation and potential evapotranspiration in all subbasins are 106.5% and -3.6% on average, respectively. However, LUCC contributed both positively and negatively to run-off: -18.6%, -13.3%, and 10.1% and 9.9% for 4 subbasins. This may be attributed to historical LUCC occurring after the abrupt change point in each subbasin. Our results provide critical insight on the hydrological dynamics of north-east tidal river systems to communities and policymakers engaged in water resources management in this region.