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Assessment of the effectiveness of innovative agricultural water demand management instruments in Charente river basin (France)

Congress: 2008
Author(s): Sťbastien LOUBIER, Guy GLEYSES, Marielle MONTGINOUL, Pierre Olivier MALATERRE and Fabien CHRISTIN
Cemagref UMR G-EAU

Keyword(s): Water demand, irrigation, economic instrument, Charente river basin, cost effectiveness analysis, dam management
AbstractIn period of low water level, some river basins face an imbalance between available water resource and water uses. In France, the development of irrigation since 1970ís is an important cause of this imbalance. Favoured by the 1992 French water act, rending water metering progressively obligatory and recommending dialogue among water actors, a volumetric management (VM) mechanism has progressively been implemented. A VM consists to find an equitable water distribution among users and to define water access rules, taking into account the water scarcity level. VM already exists in systems where water supply is foreseeable with a good probability (aquifer or dam). The Upstream Charente river basin in France faces an important imbalance added to high sensitivity of water resource to climatic conditions. However, a VM is implemented in this basin since the creation of a new dam (Mas -Chaban) in year 2000, which allows to resupply the river. This article presents VM instruments implemented in this basin, discusses their effectiveness and proposes an economic and hydraulic evaluation of innovative water demand management instruments. A first chapter is dedicated to the river basin presentation regarding its geographical, hydrological, economical and agronomical characteristics and the main water resources issues. In a second chapter, we expose the VM principles in Charente river basin and identify some explanatory factors for this structural water shortage. We highlight how the current control and sanction systems are non-incentive and then ineffective: no management instrument is able to limit the effects of the farmersí over-equipment in pumping capacity (farmers have a pumping capacity at least twice higher than the maximal discharge capacity of dams) and water allocation calendars do not coincide anymore with corn water needs whose varieties are more and more precocious. In a third chapter, we investigate economic instruments that can match simultaneously two objectives: to prevent the effect of farmerís over-equipment and to control farmerís withdrawals. Among the possible solutions, we focus our attention on the substitution of an electronic mechanism allowing to store farmerís volume and / or discharge data all along the irrigation campaign to the actual system based on farmerís declarations. Next, we compare the actual pricing mechanism to an optional pricing, where water is cheep if farmers accept to spread their consumption in order to prevent peak abstractionís periods and costly if they do not engage in such an arrangement. The last chapter is dedicated to a cost effectiveness analysis of the proposed instrument, i.e. the combination of an optional pricing system and an automatic metersí reading system: investment, operation and maintenance costs of the data storage mechanism are estimated and impact on farmersí income of water bill and of changes in corn yield (using PILOTE software) are calculated. The existing Charente decision support system is then used to estimate water savings either for the environment or the dams. We then conclude by highlighting that under certain conditions, farmers would have interest to change corn varieties for later ones. We also provide recommendations for Charente decision makers to restore supply and demand balance and then reach the Water Framework Directive objectives in 2015. These recommendations concern economic instruments, financial transfersí mechanism allowing a better social acceptability of the program and water release strategies.
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