Abstract
Transplanted Aman rice is very often confronting drought in Bangladesh. A study was conducted with a view to find some means for minimizing drought in T. Aman cultivation. With this aim this study at first developed a drought simulation model to simulate drought severity as well as drought duration. Daily water balance method was used in simulation. Drought amount (severity) and drought day (duration) were simulated at different growth stages (vegetative, reproductive and ripening) and the entire growing period of T. Aman rice. Northwest region of Bangladesh was selected for the study area, as this region is the driest part of the country. During study period (30 years), maximum drought of 367.8 mm and minimum drought of 5.8 mm occurred during the crop season in existing practice in the study area. The study area experienced of maximum drought of 93 days and minimum drought of 3 days during the crop season. Three transplanting periods were identified and were classified them from the point of risk of drought namely low, medium and high risk transplanting periods. Drought was the minimum when the short duration variety was transplanted in its low risk transplanting period. The model computed that the maximum and the minimum of total water losses (cumulative losses of seepage, deep percolation and spill) are 68.34 and 57.81% with an average of 61.57% for the short duration variety during the crop season in the study area. About 50% of seepage loss could be reduced through lining the bund with clay. Based on drought amount and drought day a practice for T. Aman cultivation was proposed in which drought influence was less than existing practice in the study area. The Kolmogorov Smirnov test showed that gamma distribution fitted the drought amount data better than lognormal distribution. It was found that for proposed practice, at 90% non-exceedence probability, drought was 72.84 mm during reproductive stage in Dupchachia. This amount was the highest in the study area at 90% non-exceedence probability. On the other side, chance of no drought was 20% i.e. at 80% exceedence probability, drought exceeded zero during reproductive stage in the study area. The return period analysis showed that drought of 10 mm occurred once in 2.2 years during reproductive period in Lalpur. This was the shortest return period of 10 mm in the study area. Some regression models were developed for predicting drought at different stages of the crop for a particular location where only rainfall data is available. In this study, interpretations of drought in T. Aman cultivation were given through Geographic Information System (GIS). For this, some thematic maps were developed with the help of GIS software of Bangladesh Country Almanac (BCA) and ARCVIEW3.5.