Prediction of hydrological events for planning rainfed rice

Daily rainfall and evaporation data of 30 years (1969-1998) are analysed for prediction of hydrological events, such as occurrence of effective monsoon (EM) and withdrawal of monsoon (WM), for planning rainfed rice in Eastern India. Those hydrological events are treated with normal (ND), lognormal (LND), Pearson type 111 (PTD), and log-Pearson type 111 (LPTD) distributions. The historical data of hydrological events are also transformed by power and modified SMEMAX transformations and ND is fitted. Normal distribution fitted to power transformed data is found to be the best for both the events. Accordingly, these events are predicted at various probabilities of exceedence (PE). At 50% PE level, the monsoon is effective in the region for 110 days. The study reveals that short-duration rice will face less drought stress than long-duration rice during the critical growth stage and will produce higher yield under rainfed conditions. At 50 and 70% PE levels, the simulated yield of shortduration rainfed rice is observed to be 2265 and 1890 kg ha", respectively, that is 6.7 and 7.6%o more, respectively, than the yield of long-duration rainfed rice.