20.-Hilltop impounding reservoir for rain water harvesting- A case study from Garhwal Himalaya

Abstract

In Garhwal Himalaya, water resources are inadequate. Most of the villages are located over the spurs between the river valleys, these spurs and ridges, because of uncontrolled deforestation and rapid soil erosion, lack of vegetation cover and consequently have few springs as only source of water. Since the rivers are far away such springs are generally drying up. As a result, the villages located on these spurs are facing acute scarcity of water. This problem further aggravates, as the rock formations are generally metamorphosed in nature viz. phyllites, schists and quartzites, there is hardly any possibility for underground water except along the valleys. The data collected for precipitation in this area suggest that the altitudes between 1,200-2,000 m a.s.l. receive a high rainfall viz. over 400 cm per annum. But because of low infiltration capacity of the ground, due to thin soil cover, impervious rocks and lack of vegetation, this water flows away down the slopes into the valleys. Therefore, a scheme was envisaged to collect this rainwater into some hilltop impounding reservoirs. Geomorphological studies carried out in the Pauri district, revealed that there are several hill tops lying between 1,800-2,000 m a.s.l. Such hilltops are some times flat with adequate soil cover. Three such hilltops were chosen viz. Ghandiyaldhar near Pauri, Tarakund near Chakisain and Gurkhal near Pokhra. Small ponds were dug up over such hilltops, and compacted mud pebble linings were made using locally available stones and sticky clays. During rainy season, it was noticed that such reservoirs are able to store adequate water. The loss of water on evaporation was checked by planting trees around the ponds. Some seepage through the floors and sides of the reservoirs was permitted. It was noticed that such seepage reactivate the springs located on the down slopes. In this way, a successful attempt was made to provide some additional source of water to the villages, mainly for irrigation purpose.