WATER BALANCE STUDY IN A HILLY WATERSHED

Abstract

In modern era, owing to population explosion, rapid, industrialization, urbanization and many diversified reasons, availability of water has reduced considerably. Water is not available adequately and timely. For successful planning, design, construction, operation , maintenance and sustainability of any project or human activity , specially , irrigation , a reasonably realistic water balance study of the area is necessary to achieve proper co- ordination between surface and sub- surface water use. On the basis of conceptual model of Ben Zvi and Gold Stoff, a soil-water balance method is used to compute the rainfall recharge. Soil Conservation Services method is used to get initial abstraction. Rainfall minus initial abstraction gives effective rainfall amount, a fraction of which infiltrates into root -zone and this is calculated by using Green & Ampt 'infiltration ,R ethod. Thus rainfall minus initial abstraction minus infiltration gives the amount of water that emerges out as surface run-off. Infiltrated water increases the soil moisture. Soil moisture in excess of field capacity is deep percolation and regarded as recharge to ground water To take into account of slope of a catchment in a hilly watershed, the opportunity time for infiltration after stoppage of rainfall is computed from time area diagram. Assuming that the infiltration rate towards the end of the rainfall is equal to saturated conductivity, the quantity that infiltrates from the entire catchment during post rainfall is computed....