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Modelling regional water demand for agriculture with stakeholders : an example in the Drôme basin.

IWRA World Water Congress 2008 Montpellier France
1. Water availability, use and management
Author(s): Ph. Le Grusse
J.C. Poussin
P. Ruelle
M. Le Bars
L. Brunel
J.M Gonzalès-Camacho
J.C. Mailhol
J. Granier
UMR G-eau

Keyword(s): integrated management, agricultural water demand, participative modelling, regional model

AbstractThe “integrated management of water resources” tries to convey the functioning of the “hydro-systems” which brings together a group of resources and uses of water. This group of resources and uses interacts within a territory, which itself includes various administrative or political units. In order to develop this integrated management, some countries have chosen decentralization: water management is then given to basin institutions within which representatives of the various key interests sit. These institutions emphasize the poor support they get to encourage the dialogue. Available tools emphasize biophysical process but provide a very simplified representation of uses, and particularly of farm uses. These uses are not only linked to water availabilities and to its conditions of access, but also to the technological, economic, and institutional background in which the farmers operate. With the local stakeholders, we suggest to build a model of the system in which they act. At the same time, this model includes the technical, economic, and environmental sides. Therefore, this regional model includes (i) a hydrological model, which enables to assess as input the initial resource availabilities and to measure the impacts of withdrawals, (ii) a biophysical model which enables to assess crop water needs, yields and environmental impacts according to agricultural practices and agro-climatic conditions, and (iii) a technical and economic model which conveys the technical choices of farmers and theirs economic consequences. The construction of the hydrological and biophysical models can be limited to the parameterization of pre-existing models. The technical and economic model of farm activities at the regional scale relies on a typology of farms and of farm production units; its structure has been designed to enable an aggregation and a desegregation of the results between various scales, which provides a detailed analysis of the studied scenarios. The participative construction of the regional model relies on the creation, from the start of the study, of a “steering group” compound of the representatives of local stakeholders. This steering group takes part in the modelling by supplying the necessary data and by validating each stage of the model construction. The model, build and validated by all the stakeholders, can then contribute to help the local or regional decision-makers to develop reasoned scenarios in order to define strategies of integrated and sustainable water management. We have implemented this approach in the Drôme basin within the framework of the APPEAU project funded by the "Agriculture et Développement Durable" program of the French National Research Agency, and by relying on the works of the MIPAIS project funded by the Programme Interreg III Medoc of the European Union. This paper presents the first results obtained.
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