A Water Balance Study of Four Landfill Cover Designs Varying in Slope for Semiarid Regions
- J. W. Nyhan *,
- T. G. Schofield and
- R. H. Starmer
The goal of waste disposal in landfills is to reduce risk to human health by isolating contaminants until they no longer pose a hazard. To achieve this, the performance of a landfill cover design without an engineered barrier (Conventional Design) was compared with designs containing either a hydraulic barrier (USEPA Design) or two capillary barriers (Loam and Clay Loam Capillary Barrier Designs). Water balance parameters were measured at 6-h intervals for these designs in 1.0 by 10.0 m plots with downhill slopes of 5, 10, 15, and 25%. Whereas runoff generally accounted for only 2 to 3% of the precipitation losses on these designs from December 1991 through July 1995, similar values for evaporation ranged from 86 to 91%. Evaporation usually increased with increases in slope in our field plots; the Conventional Design at slopes of 5 and 25% exhibited 139 and 162 cm of evaporation, respectively. Consequently, interflow and seepage usually decreased with increasing slope: interflow decreased from 10.7 to 1.5 cm for the Clay Loam Capillary Barrier Design at slopes of 5 and 25%. Although seepage comprised up to 10% of the precipitation on the Conventional Design, seepage did not occur in either the USEPA design or the capillary designs at the larger slopes.
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