Himalayan River systems: lifeline of fresh water supply
Rajiv Sinha, Indian Institute of Technology Kanpur, India
Rivers in the Indian subcontinents have long been the most important source of fresh water supply to the region. Not just the modern civilization is heavily dependent upon the rivers for the freshwater supply, the ancient civilizations such as the Indus Valley civilization also developed along the river valleys to meet the demands of fresh water. Out of the total available annual flow from rivers draining the Indian territory (~1870 km3/yr), the ‘utilizable’ flow is ~690 km3/yr out of which ~320 km3/yr comes from the Himalayan Rivers. The quantity of utilizable water in India has been constantly decreasing due to increase in demand for irrigation, industry and domestic use by an ever-increasing population. The current estimates of freshwater demand for the years 2025 and 2050 are 840 km3/yr and 1180 km3/yr respectively. In addition to the increased demand due to increasing population, the assessment of impacts of climate change and retreating glaciers on the river systems – and hence the freshwater supply – remains uncertain and unpredictable.
Looking at the uncertain availability of water and the escalating future demands, it would be pertinent to consider fresh water as a ‘limited resource’. Considering the role of Himalayan river systems as a critical source of freshwater supply, it is necessary to adopt a sustainable river management. More than the issue of ‘demand and supply’, there is now a strong realization and effort to maintain the ‘river health’ and ‘ecological flow’ which are significantly influenced by geomorphic characteristics and biotic association of the river. Anthropogenic modifications on the Himalayan river systems, mostly driven by increased demands for fresh water, have been extensive and any efforts towards maintaining sustainable flow and river rehabilitation must address these issues to derive a long-term benefit.