Abstract:
Service area achievement in a run-of-the-river type irrigation
project depends upon the available flow which can be
diverted from the river to the canal system through the
headworks. But the available flow of the river varies from year
to year~ If we can forecast the available flow ahead of time, it
- will lead to proper planning and operational management of the
project. This study was aimed at developing a methodology for optimum
use of water in a run-of-the-river type irrigation project
and to demonstrate of its usefulness by applying it to Manu River
Project.
A low flow prediction model of Manu river at Moulvibazar
has been developed for forecasting the available flow before
start of the irrigation season. The available flow can be better
used if we consider various workable alternative strategies and
select the one which gives the highest net return. The alternatives
are: reducing the service area and applying the water at
yield maximizing level; staggering of planting date to minimize
the irrigation demand during the critical period; crop
diversification; and deficit irrigation and water delivery according
to crop sensitivity to water stress.
The irrigation demand with the proposed cropping pattern of
Manu River Project has been compared with the available flow (75
percent probable). The result shows that the available supply is
v
in deficit in most of the irrigation seasons. The dry period
(November to April) flow of the Manu river during the period
1966-'85 has been divided into a number of categories. A linear
programming model has been developed to determine the optimum
acreages of different crops under the option of crop diversification
The net returns from the above four alternatives have been
calculated for each deficit flow category. Crop diversification
was found to give the highest service area and net return among
the four alternatives considered. The project management should
consider that the lands having light textured soils are cultivated
with other Rabi crops instead of Boro rice.
The present status of water use in the Manu River Project
has also been studied. Major constraints were the communication
gap between the BWDB staff and water users, lack of extension
personnel, absence of farmers' association, lack of field channel
and lack of canal system in most fertile land. The project performance
could be increased by providing' sufficient of extension
workers to the project, forming farmers' effective association
and constructing the field channels under Food for Works
Programme. Such improvement works would encourage the farmers to
irrigate the lands and improve the utilization of the existing
facilities.
