233-Modifying the Canal Delivery Schedule during the Periods of Limited Water Availability.

Abstract

An alternative canal delivery schedule during the dry season to improve the water regime in the canal command is suggested through model study. A distributary of Pun main canal system (a run-of-the-river scheme) in the state of Orissa was chosen for simulation study. The design discharge of the distributary is 6.045 m3/sec at its head regulator. Historical daily flow data of the distributary was analyzed to study the feature of the prevailing delivery schedule which is observed to be Continuous with variable flow rate. The modeling approach adopts a procedure of daily water balance/moisture balance simulation in the root zone of paddy and other dry season crops. In addition to Continuous schedule, five alternative rotational (variable discharge, constant duration and constant frequency) schedules were considered. The major crops considered are winter rice, groundnut, potato, tomato, cabbage, cauliflower, brinjal, green gram and black gram. Two tentative dates of canal water supply for the dry season i.e., and 151" of December were considered. Daily water balance simulation was performed for the dry season (145 days from the beginning date of canal water supply) for 15 years period. The results reveal that during the dry season canal closure of more than seven days will have moisture stress on crop fields. Considering both paddy and non-paddy crops to be grown in the command during dry season, 7 days canal operation followed by 7 days canal closure rotational schedule was found to be the best alternative amongst the schedules considered.