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abstract 287

Deficit irrigation reliability analysis:

Author(s): application of constraint state formulation and AFOSM
Author(s): Maryam Shekarrizfard, Arman Ganji

Keyword(s): deficit irrigation, reliability analysis, AFOSM, constraint state formulation

Article:

Poster:

Session: Poster session 2

AbstractDeficit irrigation has been thought as a strategy to increase overall system benefits watercrop production

scheme. However, as a common practice in deficit irrigation, the inherent uncertainty in crop water demand has been

largely ignored. In the present study, two types of uncertainty namely demand side uncertainty and allocation side

uncertainty are considered. A
constraint state formulation for stochastic optimization of weekly irrigation strategy

is used to incorporate the effects of the above uncertainties in deficit irrigation scheduling. This
formulation is

based on the first and second order moment analysis of the stochastic soil moisture state variable, considering soil

moisture at both saturation and deficit cases as the maximum and minimum bounds, respectively. As a result, mean

and variance of actual evapotranspiration are used for reliability analysis of the relative net benefit based on

the
Advanced First Order Second Method (AFOSM) for deficit irrigation case. This method is widly used in

engineering applications. The optimization and simulation results are indicative of the importance of crop water

demand uncertainty consideration when determining optimal deficit irrigation strategy. Also the probability of intra-

seasonal crop water stress index is determined based on the moment analysis and using the double bounded density

function methodology. The
results indicate that achieving a high long-term expected relative net benefit by

decreasing the crop water allocation and increasing the irrigated land may fail as a strategy when crop demand

uncertainty is ignored in the optimization process.

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Deficit irrigation reliability analysis: