Assessment of Water Shortage and Potential for Rooftop Rainwater Harvesting in Rural Development Training Centre, Zhemgang Town, Bhutan

Abstract

Rainwater harvesting is one of the promising alternatives to supplement surface water resources in areas where existing water supply is inadequate to meet the demand. The water shortage in Zhemgang is a recurring problem. This study was conducted to assess the water shortage in Zhemgang town and the potential for Rainwater Harvesting (RWH) in the Rural Development Training Centre (RDTC). A total of 318 households were assessed for the water shortage and knowledge, attitude and practices on RWH. Additionally data were collected once in 24 hours in the rainy season from June through September from five rooftops in RDTC premises. The study revealed that the Zhemgang Municipal supplies 469.02 litres of water per day per household resulting in residents facing potable
drinking water deficit of about 54.48 litres/ day/ household as the average requirement is 523.50 ± 110.48 (mean ± SD) litres/day/household. Zhemgang town receives a mean annual rainfall of 1,412.50 ± 208.90 (mean ± SD) mm with an intra-annual variability range of 0.95 and 0.97 mm and interannual variability of 0.15 mm. The low variability in rainfall, ranging from 0.29 mm to 0.41 mm
during the rainy season, indicates a reliable condition for RWH and guarantees the return on investment. The RWH potential for RDTC was 7,790,220.00 m3 and the average rainwater runoff collection from the experimental sites was 633,000 L during the rainy season from the rooftop catchment area of 456.14 m2. The daily collections of rainfall in 1,000 L from the month of June through September were 3.4 L, 8.9 L, 3.6 L, and 4.9 L respectively. The water was used to irrigate field crops such as maize, oats, vegetable, pasture field and fruits trees. The study identifies RWH as an alternative means to supplement the water supply scheme. The quality of RWH from CGI roofing after the
first flush had all physical parameters within the permissible limit.