SOME HYDROLOGICAL ASPECTS IN A NATURAL FOREST IN THE MID COUNTRY INTERMEDIATE ZONE OF SRI LANKA

Abstract

Forests are considered to be hydrologically important land uses since forest environment influences significantly two main hydrologic processes, namely evapotranspiration and infiltration. These two processes are mainly responsible for overland flow and soil water storage in a forest. Understanding of the behaviour of these processes is very important for proper management of watersheds of the country. However, information on these aspects are very rarely available. Therefore, an experiment has been initiated in a natural forest in the mid-country of Sri Lanka to study the relationships among rainfall, runoff, and water storage in the soil profile. The data of the first year of work was analyzed to estimate the water loss from the forest vegetation, change of water storage in the soil profile and water extraction pattern from the different soil layers. The results showed that most of the rainfall was stored and used by the vegetation thus minimizing run off. Water loss by vegetation (evapotranspiration and interception ) varied with the rainfall and the soil water conditions.