The influence of climate variations on an irrigation water resources system performance strategy

Abstract

The influence of climate change on the performance strategy of an irrigation water resources system (WRS) containing a reservoir cascade is discussed as a decision-making problem under uncertainty. There are: (1) a set of climate change scenarios and (2) a set of river runoff sequences and a set of irrigation demand sequences with various statistical characteristics (sets (2) correspond to every scenario (1)). The function of transfer from the scenarios to the sequences is defined as certain subjective probabilities. The probabilities reflect the degree of the expert confidence in the plausibility of hydrology and moistening hypothesis. There is an index showing the degree of departure of WRS performance from the normal and from the worst values. The proposed technique allows us to (a) generate hydrology and water demand scenarios; (b) calculate the subjective probabilities; (c) compute the irrigation rates as a function of precipitation, radiation balance, etc., and then to compute of irrigation demand schedules; (d) to simulate the WRS. The algorithms of water resources distribution between the users and of WRS operation with stochastic water demands were implemented in a simulation model. The Terek river basin (North Caucasus, Russia) was taken for sample computations.