Medium to steep slopes characterise the topography of the area. Run-off has eroded surface drainage due to unconsolidated nature of the formations over which they flow. As a result of these features the drainage pattern is well developed. Well defined narrow stream channels of all orders drain the area. The project site is located in the catchment of river Twang. Gutur, Lunghmur and Dialdawk are the major perennial rivers that flow through the study area. Few wetlands and small ponds are other sources of water. The water table at the airport site is between shallow and very deep due to steep rolling terrain of hills, small peaks and valleys. The rivers flowing through the forest areas have some fish population and form vital breeding places for them.