Estimation of Crop Water Requirement and Irrigation Scheduling of Rice in Southeastern Region of Bangladesh Using FAO-CROPWAT 8.0

Abstract

Water resource is scarce in most of the areas of Bangladesh during dry period due to changing climate impact. The shortage of water resources is endangering the recently achieved self-sufficiency of food production of Bangladesh. Thus, further research is necessary to increase water use efficiency and preserve the e-flow of rivers during the dry season while sustaining the stability of food production even at low usable water supply. The study was conducted to estimate irrigation requirements and irrigation scheduling for rice crop. The study area involved four districts (Cumilla, Brahmanbaria, Chandpur, and Feni) of the southeastern region of Bangladesh since 46.92% of the total land area is used for rice cultivation in this region. FAO developed CROPWAT 8.0 model was adopted for estimating irrigation water requirement, effective rainfall, and irrigation scheduling during Aus, Aman, and Boro rice. Historical climatic data including temperature, humidity, sunshine hours, wind speed (1981–2010) from three weather stations, and rainfall data from four rainfall stations were used as input to the model. The model calculated reference evapotranspiration (ET_o) using the FAO Penman–Monteith method and USDA soil conservation method was used to find effective rainfall. Results showed that, Boro rice required the maximum irrigation than other seasons due to less seasonal rainfall. T. Aus rice estimated irrigation water in its early growing period, whereas T. Aman rice estimated it in later growing period because of ununiformed rainfall distribution. Boro rice demanded irrigation in its whole growing period in each study location. Practically, farmers applied more irrigation water to their rice field than the model estimated amount. This was the result of lack of farmers’ knowledge about water management technologies. This study found the model suitable for generating irrigation schedule with the necessary split application dates without yield reduction. CROPWAT model has the potentiality to make appropriate irrigation scheduling and save irrigation water. It will save huge energy, cost of production and reduces pressure on water sources.