Model study for rehabilitation planning of water supply network
Inefficient delivery and inadequate coverage of water supply and sanitation services are major concerns for public health in the urban regions of developing countries. The contamination of the treated water within distribution system leads to frequent outbreaks of waterborne diseases. This demands a proactive approach that is based on risk assessment and a management methodology to ensure water safety. In this context, the paper presents a model study undertaken for the water supply network of a pilot area in Hyderabad city, India. The risk assessment methodology uses geospatial databases of the water supply network, sewer network, open drains, groundwater table, pressure in pipes, and soil data with a number of system-specific attributes. Fuzzy multi-criteria evaluation approach with qualitative and quantitative domain knowledge is employed in pipe condition assessment model. The physical parameters viz. pipe age, material, diameter; operational parameters viz. intermittency, number of breaks and bursts, and leakage in the system; and environmental parameters viz. workmanship, bedding condition, and traffic determine the vulnerability of pipes to contaminant intrusion. The zones of contamination formed in the soil near open drains and sewer crossings (i.e., hazards) are delineated using a contaminant ingress model. The risk of contaminant intrusion is assessed as a function of vulnerability and hazard. The results indicate that roughly 3% of pipes in the network are in Bad condition and require rehabilitation on a priority basis; about 46% of pipes are in Medium condition. The study describes a techno-economically feasible approach to assist water managers and policy makers in delivering safe drinking water.
risk assessment multi-criteria evaluation pipe condition assessment contaminant ingress water distribution system