Impact of climate variation and change on Mid-Atlantic Region hydrology and water resources

The sensitivity of hydrology and water resources to climate variation and climate change is assessed for the Mid-Atlantic Region (MAR) of the United States. Observed streamflow, groundwater, and water-quality data are shown to vary in association with climate variation; Projections of future streamflow, groundwater, and water quality are made using models determined from these associations and are applied to 2 transient general circulation model (GCM) scenarios. Regional streamflow increases in one scenario, but decreases in the other; both scenarios result in changes in the seasonality of peak flows. Response of groundwater to climate change depends on the GCM scenario used. Canadian Climate Center (CCC) scenarios suggest recharge will occur earlier in the year, and that seasonal fluctuations in groundwater levels will be less extreme. Hadley Center scenarios suggest recharge will occur earlier in the medium term, but later in the long term, with seasonal fluctuations in general being more extreme. Both scenarios show that nutrient loads can be expected to increase in winter and spring because of the expected increase in streamflow. Projected decreases in streamflow and associated nutrient fluxes in July and August could ameliorate problems associated with estuarine stratification and eutrophication in late summer. These projections demonstrate that future hydrology and water resources will be influenced by climate change, but that uncertainty in accurately projecting that influence will continue until model scenarios improve.