Risk Assessment for Urban water Supply in a developing Country: a case study of Dhaka City

Abstract

Water supply access in most developing countries like Bangladesh is complex. Expanding safe drinking water and sanitation services would drastically cut the loss of life from water-related illness and free up scarce health resources in developing countries. According to the UN-Water report (2008) five thousand children die each day from diarrhoea alone or one every 17 seconds. Upgrading water supply and sanitation services based on risk assessment can reduce vulnerability of people being affected by water borne diseases. In quantitative risk assessment, an attempt is made to numerically determine the probabilities of various adverse events and the likely extent of the losses if a particular event takes place. Risks can be identified at various stages, and prioritized in terms of likelihood and seriousness (ADB, 2010). A risk-ranking matrix should be developed to address both likelihood and severity. Most approaches use some form of semi-quantitative ranking system by allocating numbers to different levels of likelihood and different levels of severity. A risk score is then calculated by multiplying these two numbers together as shown : Risk = Likelihood * Severity. For the purpose of risk analysis of different zone of Dhaka city, we collect leakage value of different zones of previous 7years (2007,2008, 2009,2010,2011,2012,2013). Then we plot the data in graph for determine the monthly variation of leak for various zones of Dhaka city. Then we find out the average of leakage of each zone for different years. Then we create a risk analysis matrix from the weighting value of leakage and number of connection for risk ranking .We found that zone 4 is at higher risky position. From DWASA we know that zone 4 is included area Agargoan,West Agargoan, East Symoli,kallanpor, Paekpara,Pererbag,Taltola,West Sewreapara, West Kazipara. Some reasons behind this : Unplanned urbaniztion, Densly popullated, Narrow roads, Poor sewerage system, Lack of mintainance, Old pipe. Some risk reduction options for zone 4 are: Regular maintenance, Replacing old age pipe, Regular water quality test , Less joint in the pipe, Take proper safety when other construction works is done near to the pipe line ,Public awareness. We measured risk only for leakage. Further risk should be measured from pipe age, pipe diameter , pipe length and jointing , pipe material. We measured severity from the number of connection .Further if population data can be found then risk analysis can be more accurate.