PLANNING INTRASEASONAL WATER REQUIREMENTS IN IRRIGATION PROJECTS

The problem of planning intraseasonal irrigation requirements for the reservoir based projects with an extensive water distribution network is addressed. The network is hierarchical and consists of canals, dist ributaries or laterals and field turnouts or outlets. irrigation requi rements are estimated by considering the problem at two levels. At the first level, the intraseasonal weekly and biweekly irrigation require ments of crops at the field turnouts are estimated by a daily two laye r soil water balance model. At the second level, the field level water requirements are transferred to the upstream nodes of the water distr ibution network after accounting for conveyance losses by a simple hyd raulic model for flow in canals. The main questions examined are (i) w hether there are significant year to year fluctuations in intraseasona l field level irrigation requirements of crops and (ii) whether a reli able sequence of target weekly/biweekly reservoir releases can be deri ved for irrigation planning at the project level. This is done in the context of a case study irrigation project in India. (C) 1998 Elsevier Science B.V. All rights reserved.