An analysis of continuous rainlcss days (CRD) within the monsoon period (18 June to 17 October) was made to investigate the possibility of irrigation using the runoff obtained and stored in the water harvesting ponds during rainy days. The CRDs were reckoned as those occurring between rainy days yielding at least 2.5 mm rainfall. Three study site representing low, medium, and high rainfall regions were selected for the study. Daily rainfall records for 29 to 34 years were used inthe analysis. The longest CRD spells were selected in each of the four about 30-day long periods within the monsoon season, from 18 June to 17 October, for each year. Probability of being equal to or exceeding 5, 10 and 15 CRDs were determined for all the sites using Weibull formula. Irrigation could be planned on the basis of probability of equaling or exceeding 10-CRD or 15-CRDs. It was revealed that there were possibilities of irrigating kharif crops within the monsoon period, using the water stored in the water harvesting ponds.
Rain-fed agriculture is practiced over an estimated 75% of the cultivated area (Dwivedi, 1981). About 29% of the geographical area receives high annual rainfall (> 1125 mm), 36% receives medium rainfall (750 -1125 mm), 22% receives low rainfall (350 to 750 mm) and 13% receives very low annual rainfall of < 350 mm (Singh, 1990). Most of the rain-fed areas under all the above classes suffer from short or long duration drought and short duration intense rainfall leading to soil erosion, nutrient loss and floods. To mitigate drought, to moderate floods, to conserve soil and to develop water resources, harvesting runoff water for temporary storage and its subsequent use for irrigation holds a promise to enhance and stabilize crop production in the rain-fed areas. After meeting the irrigation need during monsoon breaks in the kharif season, balance water (if any) can meet initial water need in the following rabi cultivation season also.
