Abstract:
Agriculture still the leading source of livelihood
and contributes a great percentage to national income
for most developing countries around the world. Since
agriculture is the major user of water, improving
agricultural water management is essential to any
irrigation management approach specially to apply the
exact amount of water to the field in order to meet crop
water requirement. This study aims to estimate water
requirement of rice by using the model CROPWAT. In this
study, water requirement of rice for the two seasons were
studied. The results show that, Batticaloa district receives
around 1060mm effective rainfall per year. ETO value
ranged between 3.07 and 4.57mm/day during December
to April respectively. ETC value recorded as 1.76 to 3.66
mm/day during November to January respectively. In
Maha season, crop water requirement of rice increases
at the rate of 1.85 mm/day at initial stage to 3.3 mm/
day in the mid stage of growth. The water requirement
of rice decreases from 3.46 mm/day in the late- season
to 3.03mm per day during the period of harvesting. In
Yala season, ETC values were recorded as in between
2.13 to 4.5 mm/day during the period of May to July.
The water requirement of rice decreases from 4.5 mm/
day to 3.29 mm per day during the late season to the
period of harvesting. According to the study, effective
rainfall were found to be 601.4 and 298.5 mm/ decade in
Maha and Yala season respectively, and total crop water
requirement are 349.2 and 436.7 mm/ decade in Maha
and Yala season respectively. Therefore the model for
planning of irrigation water requirements of rice is very
important for efficient utilization of water and to meet the
possible change of climate in agricultural sector
