Planning for conjunctive use of surface and ground water for irrigated agriculture: a systems approach

Abstract

Attempts to control the occurrence of – waterlogging of agricultural land, spreading soil salinity and rising water-table in saline groundwater zones, has met with very limited success for most medium and major irrigation projects in the country. This is primarily because the solutions adopted to control such unwanted conditions from occurring have looked at the canal water supplies as distinct from the groundwater stored in the aquifer system in the command areas. In this study, an attempts has been made to establish adaptive control over the operating policies for water resource system, primarily meant for the enhancement of irrigated agriculture, keeping in mind the improved availability and efficiency of water usage, achieved through, conjunctive use of surface and ground water (under centralized control). The Mahikadana irrigation scheme was chosen for the purpose of familiarization with the operations and also as a source for the data need for modeling a complete system. A mathematical programming formulation embodying the various sub-system (reservoir system, canal distribution system, etc.) and the interactions between them was constructed to represent the operations of the complete system (except for the groundwater aquifer operations). This MIXILP formulation comprises of 1400 constraints including 41 binary variables. The groundwater system is represented separately in a simulation model which is used in conjunction with the MIXILP model to project the water-table movements in the entire command over time. Operating plans giving the period-wise water use allocation by source (group or surface) to provide for the crop water requirements in different parts of the command area are generated using a MIXILP-linked-simulation iterative procedure, with the objective of maximizing value of agricultural output over the plan period (spanning kharif and rabi cropping seasons). To provide for adaptability of these operating plans are generated to arrive at efficient operating schedules.