Abstract:
Land use and irrigation management
become vital for sustainable agriculture in the
context of climate change. The model CROPWAT
8.0 was used in this study for the determination of
crop water requirement and irrigation scheduling
with the objectives to optimize irrigation
scheduling under the Kapuwaththa irrigation tank
and to recommend better water management
options. Three years (2018-2020) of weather data,
soil data and crop data from relevant sources
were used as input in the model. The CROPWAT
automatically calculated the daily soil moisture
balance until the end of the growing season, the
totals of effective rainfall and irrigations applied.
Based on the modelling application, the respective
water requirements per season were 691 mm and
830 mm for Maha and Yala seasons, respectively,
whereas the actual amounts applied were 725 mm
and 967 mm. The study indicates that the farmers
over irrigated the fields by 5.0% and 16.5% in
Maha and Yala respectively, when the irrigation
efficiency of the scheme is 40%. If the actual
application efficiency of the scheme is more, the
over irrigation will be more than the amounts
given by the model. CROPWAT model can be used
as a good tool to schedule the irrigation for paddy
under a village tank. The model could be used in
optimizing the use of rainfall and saving water, but
the effective rainfall calculation method needs to
be applied with caution from place to place, and
the coefficients of the dependable rainfall method
needs to adjusted accordingly to get accurate
results.
