Incorporation of Water Distribution Network Costs in Water Supply System Design Highlighting the Strength of Raster GIS Modelling

Abstract

Design of Water Supply Scheme is very complex and challenging with the numerous options for source, Towers and Network Layout. It demands a several map based analysis to determine suitable layout with intake locations and intermittent storages. Spatial modelling in GIS using a raster format enables a water supply engineer to incorporate the spatial variability, parameter uncertainty, changes to decision objectives, exploring the conceptualizations, and time saving while providing the facility to not only visually explore the result but also to quantify in a meaningful manner. Raster model was developed to demonstrate the strength of GIS and to analyze tower locations and water distribution network layout options in Hanwella DSD area, Sri Lanka. Demonstrating a simple method to incorporate tertiary level pipe networking costs, this case study demonstrates the evaluation of the least cost distribution network for the two alternative tower locations that would produce the same revenue. To demonstrate raster GIS potential in the Water Supply and Drainage sector through a case study application of cost based tower location selection combining the impact of terrain features and consumer settlement distribution. In the present study, three options were considered in order to supply water to the project area with proposed two source points. After obtaining lease cost paths to lay distribution network under each options considered, path costs were compared in order to identify best alternative. There is a 36% Variation of cost between options and Out of three options, third option with the lowest cost will not be an effective option since even though both source points were used, source 1 will be used supply only for two destination points. Both have capability to supply water effectively and economically to particular area. But supplying water with S2 tower will be the best option with 33% less cost compared to highest cost option and only 2% higher than least option.