Optimal crop planning and water resources allocation in a coastal groundwater basin, Orissa, India

Abstract

Intensive rice cultivation in a coastal groundwater basin in Balasore district of Orissa province (eastern India) during monsoon and winter seasons has resulted in extensive pumping of groundwater by a network of shallow, mini-deep and deep tubewells. Particularly, shallow tubewell owners using centrifugal pumps are unable to lift groundwater during winter seasons due to rapid drawdown of groundwater table below suction lift caused by mini-deep and deep tubewell owners. The seawater intrusion front is also progressing inland in an alarming rate. To develop a long-term sustainable land and water management strategies for the aforementioned issues in humid regions, the district administration realized the need for crop planning and water resources management policies in deterministic and stochastic regimes. As non-structural measure, the Deterministic linear programming (DLP) and chance-constrained linear programming (CCLP) models were developed to allocate available land and water resources optimally on seasonal basis so as to maximize the net annual return from the study area, considering net irrigation water requirement of crops as stochastic variable. These models were solved using the quantitative systems for business (QSB) software package. Sensitivity analysis of the models has been carried out by varying three ranges of cropping scenarios (20, 40 and 50% deviation from the existing cropping pattern) and combinations of surface water and groundwater at various risk levels (10, 20, 30 and 40%). The total groundwater available and withdrawal in the region are 655.87 × 10 3 and 255.03 × 10 3 km 3, respectively. The study reveals that 40% deviation of the existing cropping pattern is the optimal that satisfies the minimum food requirement and maintain geo-hydrological balance of the basin. The sensitivity analysis of conjunctive use of surface water and groundwater shows that 20% surface water and 30% groundwater availability as the optimum water allocation level. The proposed cropping and water resources allocation policies of the developed models were found to be socio-economically acceptable that maintained the balance of the entire system, considering all the constraints and restrictions imposed.