IWRA Proceedings

AbstractChile’s water allocation is regulated by a permanent and spot market, which is more active in the semi-arid North, due to less water availability. Private regulation and collective management inside and among organizations of water rights are prevailing. Studying the resistance of an allocation system driven by physical and social constraints against extreme hydrological events will serve to improve decisions making for future climate pressures. The strategies and its impacts due to the drought period from 1993-1997 in an agriculture dominated catchment will be presented. The province of Limarì is located in the semi-arid North of Chile. Here the normal average annual rainfall does not exceed 120mm whereas the potential evapotranspiration exceeds 1,000mm. Additionally the region has to cope with strong inter- and intra annual variations of water availability. The main activity in the catchment is irrigated agriculture which is possible through a regulated hydrological and social system known as the “La Paloma System”, which is in operation since 1972. It is composed by three reservoirs storing 1,000MCM and the associated channel network. An important part of the regulated irrigation dedicates its production to pomiculture for exportation; just a small part is used for annual crops. Nine private organizations as well as the State are participating in the system. In this context, integrated water management is quite complex. The study includes the analysis and evaluation of indicators of decision, diverse strategies (individual and organizational), their motivation and impacts. Different indicators of vulnerability and resistance were considered: perceptive indicators, demand satisfaction, irrigation security among others; the aim was to define different levels of a drought (depending mainly of the duration), their affiliated risks and possible management reactions. Furthermore the resilience of the system under the historical operation has been studied and evaluated. The results of a simulation of the historical operation between 1990 and 2004 is been analyzed. The simulation has been conducted with the model MAGIC: “Modelación Integrada de Cuencas y Acuiferos”; a generic, object oriented model developed by the national water authority (DGA). Furthermore an investigation with questionnaires developed for the farmers of two organizations (individual strategies) as well the realization of interviews with all administrators and people of the boards of the nine organizations has been carried out in order to access the strategies at different decision making levels. This is being supported by an analysis of secondary information (e.g. Census, registers of water right property) Two main zones can be identified as zones of high vulnerability; in one zone, non-regulated by reservoirs, mitigation through reallocation of water is no option, whereas in the other zone, located downstream a reservoirs the spot water market during the season of 1995/96 increased up to around 20%. Despite this increase the demand satisfaction didn’t reach 40%. This shows the necessity of identifying different levels of risk (vulnerability due to a drought), their indicators and possible mitigations and methods of resolution for similar future events, taking the physical and social constraints into consideration.