ABSTRACTCATCHMENT SCALE RUNOFF FROM EARTHEN LANDFILL FINAL COVERSByTryambak KaushikEarthen landfill final covers (EFCs) offer cheap alternative to the conventional covers for isolating municipal solid waste underlain with a liner system, from precipitation and render minimum deep percolation. Earthen covers or alternative covers as they are often referred to in the literature, do not function as a hydraulic barrier similar to conventional covers. EFCs store precipitation water in storage layers during winter season and release it back to atmosphere in summer season. Although surface runoff had been long identified as one of the most important design variable of EFCs which controls predicted percolation, yet minimum literature is available on the catchment scale measurement and modeling of surface runoff from EFCs. The primary aim of this dissertation was to identify 1) critical factors governing the measured surface runoff from catchment scale EFCs, 2) accuracy of water balance and unsaturated flow models in predicting catchment scale hydrology of instrumented EFCs and 3) change in surface runoff from EFCs of different soil types and soil thicknesses at a regional scale in different climates of Texas. Two catchment scale EFCs were instrumented at Austin Community Landfill (ACL) in semiarid climate of Austin, Texas. Surface runoff from each catchment was collected with a custom designed storm water collection system consisting of high capacity tanks fitted with automated actuator valves. Soil water contents were monitored at several locations of both catchments for twenty three months. Upper catchment with smaller runoff length generated higher runoff than lower catchment. Seasonal variation in total precipitation, average precipitation intensity, precipitation return period, antecedent soil water content, PET/P and vegetation cover resulted in relatively high runoff in Winter 2012 and Fall 2013 than intermediate seasons. UNSAT-H was able to predict annual runoff from both catchments relatively accurately than RZWQM. UNSAT-H was not able to accurately predict daily runoff at ACL. Validated UNSAT-H model was subsequently used to predict surface runoff in different climatic regions of Texas. Annual and daily surface runoff-precipitation correlated better for wet regions than dry regions.
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