The term ‘water tower’ has been widely adopted to express the importance of mountains in providing freshwater to downstream areas. In fact, more than half of humanity relies on freshwater from mountain regions (UN's Food and Agriculture Organisation).
Sikkim is unique in that it is one of the highest rainfall zones in the country and it also has a dense network of drainage channels, which take away the surplus water. This not only helps to mitigate floods but also equally distributes the surplus water across the region. Unfortunately, the state has never been able to fully utilise or conserve its water sources.
84 glaciers cover an area of about 440 sqkm of which 251 sqkm is permanent snow fields. A large rainforest covers more than 76% of the total area. The annual rainfall varies from less than 400 mm in the north to more than 3,400 mm in the southeast. The main drainage channels for this are the rivers Teesta and Rangit.
Natural springs serve 80% of the rural population but the constraints of terrain do not allow piped water to be transported to homes nor can canals be dug for water to reach every farming plot as it is done in the plains. These springs were preserved traditionally as sacred and protected 'Devithans', which were protected from tree felling and construction. However, this religious approach is losing its influence and spring sheds which earlier comprised of well-forested catchments are increasingly being reduced to a few trees or a bamboo clump.
Alterations in water availability for drinking and irrigation, either due to climate change or reduction in forest cover, can threaten water security and agricultural productivity. Around 10 of the total 26 blocks in the state have been identified as drought-prone areas. These fall fully on the side of the Darjeeling Himalayas, which gets little rain and has rocky terrain with little or no forest cover in the upper regions.
Community observations on recent climate change impacts also indicate that in the subtropical belt (less than 1000 m) there is hardly any rainfall for the six months from October to March resulting in frequent and ascending forest fires, drying of spring water sources and decline in the production of winter crops and vegetables. The average seasonal rainfall has decreased at the rate of 53.43 mm over 30 years in winter, whereas the decrease was higher during monsoon period at 139.01 mm.
Sikkim registered a decadal population growth rate of 12.36% (2001-2011) against 33.07% in the previous decade (1991-2001). Studies reflecting per capita availability of water has not been conducted in Sikkim in the past and so should be initiated now and projected till the year 2050 based on the projected population database and the water availability from different sources. Around 7.6–10.4 lakh tourists would visit Sikkim during the year 2017, which would also have implications on the infrastructure, environment and natural resources of the state.
Urban centres like Gangtok, the capital of Sikkim, which is visited by 90% of the tourists coming to Sikkim, would experience shortage of drinking water. In this regard, the Sikkim government has enhanced water works at Selep from 13.5 MLD to 25 MLD with state-of-the art treatment for solving the perennial water scarcity problem Gangtok and adjoining areas to a significant extent.
We need to generate and analyse extensive scientific data on groundwater exploration in the state. The quantity of surface water to be recharged is around 44 million cubic metres annually using spring development, nullah embankments to increase water percolation, rock dam walls for moisture retention, and roof water harvesting.
Stream gauging stations, which keep records of water flow in streams for many years, are one of the most important tools to estimate water availability. There are 11 gauge and discharge observation sites being maintained by the Central Water Commission on Teesta river but the runoff data, which isn't analysed at the moment, must be used on a consistent basis.
This post was based on a paper submitted for the Sustainable Mountain Development Summit held at Kohima, Nagaland, on September 25-27. The original submission can be downloaded from below.