Agriculture Reference
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maximum capacity of the reservoir is in the two cases. The second
system is simulated on the basis of data from the first, considering that its
demands are one half (except for the minimum flow, where it seems
reasonable to assume that this will be the same throughout the length of the
river). The data on cultivated surface area and agricultural profits have
been taken from the real situation found in our area of study and translated
to the second system, copying the share of crops and the net margin per
hectare corresponding to the upstream system.
Figure 11.3 represents a supply-demand equilibrium for a given
upstream flows regime (that of the Vadiello Reservoir in an average water
year). As we can see, all the water rights are satisfied in the place and time
established; that is, there is no deficit for any sector.
On the basis of a situation of equilibrium such as that described
above, we can consider two types of problem that might arise as a
consequence of changes in the supply and/or demand conditions: first, a
situation of drought, assuming a fall in the water supply of 30% ( i.e., a fall
in upstream inflows); secondly, an increase in the surface area under
irrigation of 700 hectares within system 2 ( i.e., an increase in the system 2
irrigation needs). In this latter case, the irrigation-based farmers operating
within this system wish to have as much surface area under cultivation as
their counterparts operating within system 1 (we assume a constant
distribution of crops). It should be noted that we are dealing with an
optimisation problem based on an annual time horizon.
3.2 Specification of the theoretical model
We reduce both problems (drought and increase in downstream
requirements) to the same terms: calculate the changes in the operational
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