Studies on Rainfall-Runoff Relationship for Assessment of Rainwater Harvesting Potential under Marathwada Region

Abstract

The rainfall available in the watershed is key factor for determining the availability of water to fulfill the different demand mainly for agriculture, hydropower water supply, industry, etc. A watershed is that contributes runoff water to a common point Runoff is one of the important hydrologic variables used in most of the water resource applications. Runoff is the total surface flow from a given drainage area. Rainfall duration, intensity and aerial distribution influence the rate and volume of runoff. Watershed characteristics such as slope, shape and size, cover of soil and duration of rainfall have a direct effect on the peak flow and volume of runoff from any area (Chandler and Walker, 1998). Rainfall and runoff are significant constitute the sources of water for recharge of ground water in the watershed. Estimation of runoff in a watershed is very important to manage the water resources efficiently. Most of the part of the Marathwada region is comes under assured rainfall zone. The region receives mean annual rainfall of 880 mm. Rainfall in uncertain and erratic in this region and sometimes suffers from severe droughts. The rainfall data for Aurangabad, Parbhani and Nanded stations were collected from the Agro-meteorological station under VNMKV, Parbhani. Runoff was estimated using SCS curve number method considering the all parameters like soil type, vegetation etc. The rainfall runoff relationship was worked out for further planning of small water harvesting structures like farm ponds. The runoff potential for Aurangabad, Parbhani and Nanded station is found to be 20.07 %, 28.31 % and 31.69 % respectively, indicating a good scope for rainwater harvesting and thereby, many more rainwater harvesting structures can be constructed based on site specific conditions. A relation between rainfall and runoff for Aurangabad, Parbhani and Nanded stations were worked out as Y = 0.301X - 55.711 ( R2 value - 0.75), Y = 0.4043X - 88.882 (R2 value - 0.8687) and Y = 0.6018X - 209.2 (R2 value -0.9575) respectively. The linear rainfall-runoff relation obtained can be used for finding out runoff corresponding to any rainfall occurring in the area. The rainfall runoff relationship will be useful for determination of rainwater harvesting potential and its reuse for enhancing production potential of various rainfed crops.