IWRA World Water Congress 2008 Montpellier France
1. Water availability, use and management
- Pablo ALVAREZ, Centro de Estudios Avanzados en Zona Áridas
(CEAZA), La Serena, Chile, - Pablo.Alvarez@ceaza.cl, Phone: 0056- 51-204378, Fax: 0056 – 51- 334741
Sandrine CORSO, University of Aix-Marseille III/ LPED, Marseille, firstname.lastname@example.org,
Drought, Water Rights, Vulnerability, Water allocation, Decision Making,
Extreme Events, Resistance, MAGIC.
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
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
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)
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.