Evaluation of Gridded Meteorological Data for Calculating Water Balance Cover Storage Requirements

Abstract

Core Ideas Required storage is a critical design parameter for water balance soil covers. Gridded meteorological data and station data result in consistent required storage. Gridded data result in higher required storage for sites with significant snowfall. Modeled cover system performance based on station and gridded data is consistent. Gridded data tend to result in conservative or higher estimates of required storage. Water balance cover (WBC) systems are attractive for waste management facilities in arid to semiarid environments because they are a lower cost alternative to conventional geotechnical soil or composite barrier-style covers. The required storage (Sr) for a WBC is dependent on climatic conditions, with the most influence from the seasonal balance of precipitation (P) and potential evapotranspiration (PET). Gridded meteorological datasets provide long-term, continuous, and accessible sources of P and PET for Sr estimation. Six sites in Nevada were analyzed for the agreement among P, PET, and Sr calculated from station and gridded meteorological data (gridMET). Two sites each at elevations of 0 to 1000 m asl, 1000 to 1500 m asl, and 1500 to 2000 m asl were considered during a 21-yr period. The gridMET and station-based P and Sr were generally not significantly different for sites between 0 and 1500 m asl. For sites above 1500 m asl, the differences in P were significant. For the sites analyzed in this study, gridMET typically resulted in equivalent or more conservative estimates of WBC Sr. Percolation rates from hypothetical WBCs were also simulated in the flow model HYDRUS to evaluate WBC performance when using station-based or gridMET-based atmospheric model boundary conditions. Simulations indicate that percolation rates are higher when gridMET atmospheric data are used vs. station-based data for five out of the six sites. This suggests that gridMET-based model boundary conditions provide a degree of conservatism in calculating WBC Sr. This trend was not ubiquitous for all sites (one out of six did not follow), indicating that further study is required before applying these findings generally.