The effects of land cover and climate change on wetness and runoff partitioning of small catchments

Abstract

Climate change has altered precipitation patterns increasing annual precipitation and the frequency of short duration storms. In addition, urban areas have expanded altering the distribution and transport of water within a catchment. In this study, I examined temporal relationships in water balance components, focusing on inter-annual variations in runoff and wetness partitioning for 25 Maryland USGS gaged sites with varying urban, forest, and agricultural land cover. First, I quantified systematic inter-annual variations of baseflow and stormflow as a function of land use. Forested catchments exhibited the largest baseflow inter-annual variations, associated with variations in cold season precipitation. Urban catchments have lower inter-annual variations in baseflow due to limited infiltration caused by impervious cover. Next, I examined the response of groundwater and baseflow to the timing and magnitude of 2 precipitation inputs: 2012 Hurricane Sandy and 2018 wet year. These data indicate that both groundwater and baseflow in forested catchments respond directly to small, more frequent storms, but not large, isolated warm-season storms. Urban basins had reduced seasonal baseflow and groundwater cycles and were not responsive to either storm type. Groundwater and baseflow recharge were only present during the 2018 wet year, but in subsequent years, groundwater and baseflow peaks steadily declined although annual precipitation was near normal. The decline may reflect the shift in precipitation events to short duration, high magnitude storms suggesting that storm characteristics may affect groundwater recharge and stream baseflow.