IWRA Proceedings

AbstractIntroduction MoGIRE is a model for integrated water management at the river basin level, allowing to optimise water use under several possible scenarios (agronomic, climatic or economic). This model is currently under development by an interdisciplinary team within the APPEAU project (2007-2010) funded by the French National Research Agency within the “Agriculture and Sustainable Development” program. An application of the model is proposed for the Neste system located in South-West of France. Objective The main objective of the MoGIRE is to develop an interdisciplinary integrated framework based on mathematical programming in order to evaluate scenarios for a better planning of agricultural and non-agricultural water use at the river basin level. Architecture of MoGIRE MoGIRE may be viewed as a multi-use water allocation model with an explicit representation of the water network at the river basin level. Agricultural, urban (domestic and industrial) and environmental water uses are represented in the model. Agricultural production functions are derived from a biophysical models of crop growth, STICS (Brisson et al., 1998). The crop growth model allows to characterize the relationships between agricultural water use and crop yields. Those relationships are used as inputs in a regional agricultural production model that determines the optimal allocation of land among possible crops and the resulting agricultural net profit. The urban water value is derived from econometric estimations of water demands, see for instance Garcia and Reynaud (2004) for such a derivation in France. MoGIRE then operates the network facilities and allocates water so as to maximise the river basin agricultural and urban economic value from water use, under water delivery constraints resulting from the characteristics of the water network and the minimum flow requirements. We make the distinction between two minimum flow levels: the Crisis Minimum Flow (CMF) and the Target Minimum Flow (TMF). The CMF (in French, débit de crise) defines the minimum flow under which biological life is not possible. When the water flow is lower than CMF, no irrigation is allowed. The TMF (in French, débit objectif d’étiage) defines the water flow level above which biological life is not constrained. When the water flow is greater than TMF, irrigation is not limited. This pursuit of economic objectives (aggregated social surplus resulting from water consumption in agricultural and non-agricultural regions) is then limited only by water availability, water network characteristics, and minimum flow constraints. Application of MoGIRE to the Neste sytem (France) Within the APPEAU project, MoGIRE is currently applied on the Neste system located in South-West of France. The Neste system is a system of rivers artificially recharged by upstream reservoirs located in the Pyrenees mountain. This system has been chosen first because it is managed by a single operator, the Compagnie d’Aménagement des Coteaux de Gascogne (CACG). Second there are significant water scarcity issues in that area that make the development of an integrated water management model relevant. For instance, the relationship between the CACG and farmers is defined by a contract. This contract specifies first, a discharge rate and second, a quota associated to each unit of discharge rate (l/s) subscribed by a farmer. Given the current price for the discharge rate, the demand of discharge rates by farmers exceeds the flow capacity of the system. The CACG must then manage a waiting list for quota allocation We then plan to use MoGIRE in order to optimize and simulate various agronomic, climatic or economic scenarios on the Neste system. For instance, a set of scenarios concerning various spatial distributions of cropping systems within the Neste system chosen to reach a compromise between minimising the irrigation demand and maximising the farm and the regional income is currently under development. Reference List Brisson, N., Mary, B., Ripoche, D., Jeuffroy, M. H., Ruget, F. e. al., 1998. "STICS : a generic model for the simulation of crops and their water and nitrogen balances. Theory and parameterization applied to wheat and corn". Agronomie, 18: 311- 346. Garcia, S. and A. Reynaud, 2004. "Estimating the benefits of efficient water pricing in France" , Resource and Energy Economics, (26), 1-25.