Evaluating the influence of land cover on seasonal water budgets using Next Generation Radar (NEXRAD) rainfall and streamflow data

Abstract

Accurate estimates of fluxes between different components of the hydrosphere are needed for water resources management at the watershed scale. Runoff and evapotranspiration are critical fluxes that are heavily influenced by land cover characteristics; however, our understanding of the interactions between land cover attributes and these fluid fluxes is generally limited by inadequate regional data to capture variations in both climatic conditions and landscape characteristics. This limitation is largely avoided by integrating data from Next Generation Radar (NEXRAD) precipitation systems with widely available streamflow, land cover, and other Geographic Information System data sets. Such data integration facilitates development of rapid and reliable methods for estimating hydrologic fluxes at desirable temporal and spatial scales. In this study, we calculate ratios of streamflow to NEXRAD rainfall over the peak growing season for 40 watersheds across Michigan and use these to evaluate the landscape factors that influence groundwater recharge rates. Results indicate that ratios of streamflow and baseflow to rainfall are strongly influenced by land cover attributes. Stream baseflow analyses indicate that approximately 5% of the July to September rainfall becomes recharge in high‐intensity agriculture (>70%) watersheds compared to 15% in moderate‐intensity agriculture (<50%) watersheds across our study region during the same period. A strong negative correlation was also found between intensive agriculture and the streamflow:rainfall ratio during summer and early fall periods.