Water erosion caused by accelerated anthropogenic activities has been perceived as the major source of sediment flow in Himalayan catchments. Keeping this in view, the sediment flux data measured at the outlet
of the Sainj and the Tirthan watersheds in the Lesser Himalayan region was analysed.

Gaumukh is the snout of the Gangotri glacier located at an altitude of 4000 m in the Himalayas from where the snow and glacier-fed Bhagirathi River emerges.

The two most important hydrological extremes are floods and droughts. These events pose serious hazards to human populations in many parts of the world. These water related disasters are caused because of large diversity in climate and topography of the country. Climate change in future is expected to have severe implications on river flows in South Asia including India. Global climate change is likely to result in severe droughts and floods in India, with major impacts on human health and food supplies.

Irrigation is human being's efforts to substitute for any deficiency in natural rainfall with the objective of a steady expansion in crop output. The impact of irrigation on income/output is a difference between the magnitude of irrigated and un-irrigated income/over all crop yield per hectare.