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Water use efficiency in an arid watershed: a case study
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Citation of this paper:Damaris Orphanopoulos,Koen Verbist,Alvaro Chavez,Guido Soto,2013.Water use efficiency in an arid watershed: a case study.Sciences in Cold and Arid Regions,5(1):0016~0026.
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Author NameAffiliationE-mail
Damaris Orphanopoulos Rodhos Consulting, Vaticano 4026 B, Santiago, Chile  
Koen Verbist UNESCO-International Hydrological Programme, 1 Rue Miolis, Paris, France k.verbist@unesco.org 
Alvaro Chavez Rodhos Consulting, Vaticano 4026 B, Santiago, Chile  
Guido Soto Centro del Agua para Zonas áridas y Semiáridas de América Latina y el Caribe (CAZALAC), Benavente 980, La Serena, Chile  
 
Abstract:Integrated Water Resource Management (IWRM) becomes increasingly important in arid watersheds, where water resources are scarce and demands are rising under increased population pressure. In this case study, we present the results from the Elqui Valley in Chile, where water resources are shared between agriculture, mining operations, hydropower generation and drinking water for nearby cities. An IWRM model was applied to visualize water resources distribution in the catchment and determine irrigation and water use efficiencies. After calibration with observed surface and groundwater measurements, the model showed large differences in efficiencies between different irrigation sectors. Most notably, irrigation sectors with the highest irrigation security, i.e., higher water rights per hectare, were characterized with lower water use efficiencies. Frequent water deficits were present in sectors downstream of the main reservoir, which was related to limited water rights per hectare, lower irrigation efficiencies and higher water demands due to larger agricultural areas. In subsequent scenario analyses, the model was used to evaluate the impact of improved irrigation and water use efficiencies in these downstream sectors, to confirm an important reduction in water deficits, except for drought years when surface water resources are insufficient. In a third scenario, groundwater resources were allowed to compensate for water deficits, effectively reducing these in most irrigation sectors, especially during droughts. Expansion of the current agricultural area by 37% was evaluated, as a future scenario, and was found to be unsustainable, as aquifer levels are lowered to such levels that make annual recharge insufficient.
keywords:integrated water resources management  drought  arid zones  Chile
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