Assessing efficiency and resilience in the Dewathang Thromde water distribution system

Abstract

Dewathang Thromde, a subdivision of Samdrup Jongkhar Thromde, faces a significant challenge in its drinking water supply. The region relies on a gravitational water supply system from Lemtshorong and Zalakhe. This study aims to assess the current system and determine its adequacy for the future population. The study employs manual methods, such as bucket and stopwatch techniques, to determine discharge at the water source, complemented by field observations for pipe size measurements. Utilizing EPANET software and a Demand Driven Analysis (DDA) approach, distribution network’s pressure and velocity requirements are analyzed. Elevation data from the My Elevation mobile app, validated by Google Earth images, contribute to a comprehensive evaluation. During peak season, a discharge of 35.92 l/s is documented, contrasting with 9 l/s during the lean season. The population, recorded at 2644 in 2005, surged to 3881 in 2017, with a forecast anticipating 7170 people by 2035 using the Incremental Increase Method. Average water consumption per person is approximately 113.35 lpcd, exceeding the WHO standard, influenced by climatic conditions. With a population of approximately 4389 in 2021, the current water demand in Dewathang Thromde is 13.72 l/s, surpassing the discharge capacity of 9 l/s during the lean season. By 2035, the projected water demand is expected to reach 22.41 l/s, exceeding the current source discharge by over 100%. Simulation results for the upstream and downstream networks of the Break Pressure Tank (BPT) reveal pressure-related challenges, with over 20 percent of nodes experiencing excessive pressure along HDPE pipes. Bursting incidents and negative pressure at more than 10 percent of nodes emphasize the need for network improvements, especially during reduced source discharge. The final segment of the pipe network surpasses the prescribed maximum flow velocity due to the direct proportionality between velocity and pipe diameter. Smaller pipe sizes, while limiting velocity, paradoxically contribute to actual velocities exceeding specified limits. Addressing these challenges is crucial for ensuring a sustainable and reliable water supply system in Dewathang Thromde.