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Gross Margin (€/ha)

1,023.94

When planning strategies for the economic optimization of water used in irrigation, different gross irrigation depths must be considered. The results of MOPECO are very useful for economic analysis of the irrigation strategies in the different pilot areas, establishing the economic optimum for each scenario. This irrigation strategy, associated with a different deficit for each crop (objective relationship ETa/ETm) will be recommended for each experimental area.

3.3.2 Bayesian Networks Applied to Water Management

CREA built a Bayesian network (Bn) applied to water resource management in the HU of 08.29. This model was developed within Project MERIT (Management of the Environment and Resources using Integrated Techniques, Ref. EVK1-CT-2000-00085) funded by the EU from June 2001 to June 2004. The aim of MERIT was to construct Bns for four study areas that have different problems in terms of water use. These networks, regardless of the way in which they may be used in the management of each hydrographic catchment, are intended to act as a pilot program for the construction of any Bn geared towards water resource management, within the framework of the EU or elsewhere.

Bayesian networks (Cain, 2001; Jensen, 2001; Díez, 2003) are directed, acyclic graphs, in which nodes represent random variables and arcs the cause-effect relationship among these variables. Each node has a conditional probability table (CPT) associated with it that quantifies in probabilistic terms how much that node is related to its parent nodes.

The objective was to build a Bn that helps in defining a sustainable strategy for the management of the HU 08.29. Long-term sustainability can be obtained only if the consumptions are balanced, on a yearly basis, by the average recharge volume.

The construction of a Bn follows a well-defined procedure, the main stages of which are:

• Identification of the variables which affect and describe the state of the Unit.

• Identification of the relationships among these variables.

• Discretization of the states and population (filling up) of the CPT tables.

The Bn that describes the "Eastern Mancha" aquifer and its concerns is divided into five large groups (Fig. 28) and is composed of 56 variables. In turn, the group of variables that describe the agricultural consumption are partitioned into five sub-groups, the reason being that the largest consumer, i.e. agriculture, has to be described in greater detail than the other factors (Domínguez, 2004).

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