Evaluation of Evapotranspirative Covers for Waste Containment in Arid and Semiarid Regions in the Southwestern USA (original) (raw)

2005, Vadose Zone Journal

Performance evaluation of evapotranspirative (ET) covers is critinicipal solid waste recommended by the USEPA (Koercal for waste containment. The purpose of this study was to evaluate ner and Daniels, 1997). Resistive barriers rely on low ET covers at sites in Texas and New Mexico representative of arid hydraulic conductivity to minimize water movement into and semiarid regions in the southwestern USA using water balance monitoring during 4-and 5-yr periods and water balance simulations the underlying waste; however, previous studies have using short-term (1-5 yr) and long-term (25 yr) climate forcing. Esti-shown that many resistive covers, particularly compacted mated drainage at the Texas site was related to irrigation while meaclay layers, leak because of desiccation, which can occur sured drainage at the New Mexico site was restricted to the first even in humid settings (Melchior, 1997; Dwyer, 2001; 2 yr of the 5-yr monitoring period. Evapotranspirative covers work Albrecht and Benson, 2001; Albright et al., 2003). Inextremely well in these regions because of the dominance of summer creasing emphasis is being placed on optimal cover deprecipitation (62-80%) that corresponds to periods of highest ET. sign for arid and semiarid regions because they are gen-Strong relationships between decreases in soil water storage and vegeerally considered more suitable for waste disposal than tation productivity at both sites underscore the importance of vegetahumid regions (Reith and Thompson, 1992) and many tion in controlling the water balance in these systems. Simulations of contaminated sites are located in these regions. A varithe Texas site indicate that drainage can occur in response to high preety of alternative cover designs have been proposed for cipitation near the end of the growing season, but such drainage can waste containment in arid and semiarid regions, includbe eliminated with a capillary barrier. Inclusion of a capillary barrier ing monolithic ET covers, capillary barrier ET covers, increased available water storage by a factor of about 2.5 at both and anisotropic barrier ET covers, which all rely on insites. The capillary barrier effect of drainage lysimeters can result in creased water storage rather than low hydraulic conducunderestimation of drainage and overestimation of water storage relativity to minimize water movement into waste (Albright tive to covers not underlain by capillary barriers. The data from this study indicate that a 1-m-thick ET cover underlain by a capillary bar

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