Rainwater harvesting is one of the promising alternatives to supplement the surface water resources in areas where existing water supply is inadequate to meet the demand. The residents of Zhemgang town currently face shortage of potable water, but so far the potential of Rainwater Harvesting (RWH) to supplement the existing water supply system has not been assessed. This study was conducted to assess the water shortage problem in Zhemgang town and potential for Rainwater Harvesting (RWH) in the Rural Development Training Centre (RDTC). A total of 318 households were interviewed to assess the water shortage problems and knowledge, attitude and practices on RWH. Data were collected once in 24 h every rainfall during the entire rainy season from five rooftop structures in RDTC premises to determine the potential for RWH and its usage. The study showed that the Zhemgang Municipal Office supplies 469.02 L of water per day per household resulting in residents facing potable drinking water deficit of about 54.48 liter/day/household as the average requirement is 523.50±110.48 L/day/household. Zhemgang town receives a mean annual rainfall of 1412.50±208.90 mm with an intra-annual variability range of 0.95 and 0.97 mm and inter annual variability of 0.15 mm. The low variability in rainfall, which ranges between 0.29 mm and 0.41 mm during the wet seasons, suggests a reliable condition for RWH and a guarantee for the return on investment. The RWH potential for RDTC was 7,790,220.00 m3and the average rainwater runoff collection from the experimental sites showed an overall collection of 633,000 L of rainwater during the wet season (June-September 2019) from rooftop catchment area of 91 m2. The study thus identifies a huge potential for RWH as an alternative means to supplement the water supply scheme. The quality of RWH from CGI roofing after first flush is fit for drinking as all physical parameters were within permissible limit.

Key words: Water quality, water shortage, rooftop rainwater harvesting, Zhemgang.