Sustainability of Water Supply in Hill Towns in The Himalayas
The Himalayas are often referred to as the ‘Third Pole’. This appellation acknowledges the fact that after the two poles – North and South – the Himalayas with their snowfields, glaciers and perennial rivers are the largest reservoir of freshwater on this planet. Reassuring as it may seem, this appellation pales when one looks at the paradox of water supply in towns and cities across the Himalayas.
Traditionally water supply in hill towns has been based on supply from natural springs, streams fed by springs, lakes and rivers. Over a period of time, increasing population, loss of forest cover, lower water availability from springs and streams have ensured that hill towns and cities face water stress especially during the summer season. Leakages in the distribution system and a drop in production efficiencies also contribute to water stress. Erratic supplies and leaky networks also result in system contamination during periods of zero or negative system pressure, thus compromising water quality. This is compounded by the fact that access and the distribution of water is extremely uneven across the Himalayan region. Lack of natural storage capacity in the case of towns located on ridges is also a limiting factor. Several hill towns are located at higher altitudes, whereas the natural water sources flow at a much lower altitude. The difference in altitude is sometimes so great that multistage pumping is required to lift water from the source to the towns.
Sustainability of water supply in hill towns is a function of both source sustainability and demand. Source sustainability itself is a function of bio-physical as well as socio-ecological factors that mediate the recharge of the natural water sources. This is controlled among others by a number of factors – duration of rainfall, residence time of snowpacks, forest degradation, landuse, protection afforded to the „critical‟ water zones and geology. Skewed seasonal availability and increasing demand impose severe strains on the water supply systems. More often than not the summer season, March to June, is one of extreme water stress. This imbalance is dealt with by lowering the water supply pressure, the duration of piped water supply and rationing. One of the technical fixes to deal with this has been to obtain water from new and more distant sources, often through the implementation of energy intensive pumping schemes, which where possible, pump up water from rivers. These schemes have high capital costs and lead to an increase in the cost of water which can potentially be unaffordable for small towns.
This paper presents the water supply scenario from six Himalayan towns in India and Nepal, which are the focus of collaborative research funded by the ESPA programme. The paper examines the drivers for the altered regimes of water supply in these towns and the mechanisms to deal with it. It focuses, especially, on current pressures on critical elements of the landscape which have the potential to alter hydro-geological regimes in the region.