RISK EFFICIENCY OF OPTIMAL WATER ALLOCATION WITHIN A SINGLE AND MULTI-STAGE DECISION-MAKING FRAMEWORK

作     者：PRIMROSE MADENDE 

作者单位：University Of The Free State 

学位级别：硕士

导师姓名：Bennie Grov

授予年度：2017年

主      题：Single-stage decision-making framework Multi-stage decision-making framework water use dynamics sequential irrigation decisions simulation evolutionary algorithms water restriction risk decision-making 

摘      要：The main objective of this research was to compare the results obtained from modelling irrigation water allocation decisions within a single-stage decision-making framework with the results obtained within a multi-stage sequential decision-making framework under a full water quota and a restricted water quota. A unified irrigation decision-making framework was developed to model the impact of the interaction between water availability, irrigation area and irrigation scheduling decisions as multi-stage sequential decisions on gross margin variability. An Excel ® risk simulation model that utilises evolutionary algorithms embedded in Excel® based on the Soil Water Irrigation Planning and Energy management (SWIP-E) programming model was developed and applied to optimise irrigation water use. The model facilitates the simulation of the economic consequences resulting from changes to the key decision variables that need to be optimised through gross margin calculations for each state of nature. Risk enters the simulation model as crop yield risk through different potential crop yields in each state of nature and stochastic weather which determines irrigation management decisions. Water budget calculations were replicated to include 12 states of nature within a crop rotation system of maize and wheat. The risk simulation model was applied in Douglas, a typical location of an irrigation farm. The results showed improved risk management within a multi-stage decision-making framework as indicated by higher gross margins and reduced variability due to improved irrigation scheduling decisions under both a full and restricted water quota scenario. Close to potential yields, if not full potential yields were achieved within both decision-making frameworks. However, a significant reduction in per state irrigation water use resulted within a multi-stage decision-making framework sequentially resulting in improved gross margins. A full irrigation strategy with reduced areas was fol