Water use efficiency in an arid watershed: a case study |
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Authors: | Damaris Orphanopoulos Koen Verbist Alvaro Chavez and Guido Soto |
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Institution: | Rodhos Consulting, Vaticano 4026 B, Santiago, Chile;UNESCO-International Hydrological Programme, 1 Rue Miolis, Paris, France;Rodhos Consulting, Vaticano 4026 B, Santiago, Chile;Centro del Agua para Zonas áridas y Semiáridas de América Latina y el Caribe (CAZALAC), Benavente 980, La Serena, Chile |
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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. |
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Keywords: | integrated water resources management drought arid zones Chile |
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