Hydroclimatic variability and change in the Chesapeake Bay Watershed

The Chesapeake Bay (CB) Watershed is undergoing changes in climate, hydrology, and land use. The assessment of hydroclimatic impacts is important for both water quantity and quality management. This study evaluated the hydroclimatic changes using the Coupled Model Intercomparison Project 5 (CMIP5) data which provided statistically downscaled daily precipitation and temperature. An increase of 3.0 to 5.2 °C in temperature was projected between 2070 and 2099 when compared with the baseline period of 1970–1999. However, precipitation projections showed a modest increase with an average of 5.2 and 8.4% between 2070 and 2099. The northern part of the CB Watershed was expected to be wetter and warmer than the southern region. The average changes in flow were projected between −12 and 6% and −22 to 5% between 2070 and 2099, respectively, under two scenarios. Minimum changes in winter and highest flow reduction in fall with a high degree of variability among the ensemble members was expected. Greater decrease in flows in the northern region of the CB Watershed was projected. Despite the wetter future projections at the end of the century and uncertainties in our evapotranspiration (ET) estimation, reductions in the land surface runoff partly were attributed to increased ET.