Abstract
Studies estimating the value of irrigation water as a function of river discharge are rarely found in the literature; however, discharge‐based valuation carries significance when the in‐ and off‐stream uses are evaluated for optimal water allocation. This paper develops the total and marginal benefit functions of the key off‐stream water use, irrigation, as a function of flow in the Teesta River of Bangladesh. The field water balance approach and CROPWAT modelling are used to calculate irrigation water requirements for rice and other crops respectively. The residual imputation method is employed to estimate the value of irrigation water. In the cases of insufficient flow in the river, several scenarios based on (i) conjunctive uses of groundwater, (ii) reduction in irrigated land area and (iii) yield loss due to water stress, form the basis for establishing the total and marginal benefit functions for river water use in irrigation in the study area. Estimated marginal benefits as a function of river discharge are found to be linear with zero slopes for the first two scenarios and sloping downward for the third. Results of the study will assist water planners and managers with equitable and efficient allocation and sustainable management of the river water. Copyright © 2010 John Wiley & Sons, Ltd.