Estimating the impacts of a reservoir for improved water use in irrigation in the Yarabamba region, Peru

The pressure on irrigation is increasing worldwide, not only because of – perceived or real – high water consumption in the irrigated sector, but also because an increased world population puts stress on food production. Numerous irrigated areas around the world face similar issues of water scarcity, disparity in water distribution and deficient infrastructure. As a result, farmers are typically restricted in their production strategies. A general strategy in the irrigation sector is the introduction of so-called modern techniques in existing irrigation systems, with the aim to increase agricultural production. This paper discusses such a modernization effort in the sub-basin of Yarabamba, Arequipa, Peru, in which a reservoir is being constructed to improve water use and stimulate economic development. Based on fieldwork, including interviews and scenario modeling with WEAP, the relationships between water users, their irrigation systems and the water balances in the basin were studied. Scenario studies showed that the reservoir might alleviate the current water shortages in the sub-basin, but that restrictions in the current infrastructure and management of irrigation may be of more importance than the reservoir. Especially existing interests and actions of upstream and downstream areas appear to be important factors; these will not be automatically solved with the new reservoir.