Historical weather data can be used to develop and modify the management practices to increase the production with the conjunctive use of rain and irrigation water as per the water needs of the crop. Regional scale crop and water resource planning needs determination of reference crop evapotranspiration (eto), probability distribution of rainfall and ETo, and estimates of magnitude and duration of water deficit and surplus which can promote crop production in both irrigated and dryland areas. Daily weather data of 16 years (from 1984 to 2001) for five locations i.e., Aurangabad, Beed, Nanded, Parbhani and Osmanabad of Marathwada region was used to determine reference crop evapotranspiration (ETo). The rainfall and ETo data were analysed to ascertain their fit to various probability distributions. The goodness of fit was determined by chi 2 tests. The developed crop coefficients were used to estimate crop water requirements of 8 major crops of the region. Effective rainfall was used to determine the weeks at which the rainfall exceed or fall deficit of crop water requirement. The study indicated that normal distribution gave the closest fit to the weekly rainfall and ETo data. The seasonal water requirement of cotton, groundnut, sugarcane and banana is higher at Parbhani whereas that of kharif sorghum, rabi sorghum, wheat and soybean is higher at Osmanabad than other places in the region, the effective rainfall meets the water need of kharif sorghum and soybean. The rainfall values during the critical growth stages of rabi (sorghum and wheat) and summer crops (groundnut, banana and sugarcane) are deficit than their water requirement in the respective weeks and hence require irrigation during those periods. Among the row crops, wheat and groundnut can only be grown under irrigation. Annual excess rainfall for various crops ranges between 561-749 mm for kharif sorghum, 124-195 mm for rabi sorghum, 0-15 mm for wheat, 624-808 mm for soybean, 633-786 mm for cotton, 453-609 mm for sugarcane and 526-703 mm for banana. If the excess rains are effectively harvested, the irrigation potential could be raised in the region.
