Vulnerability assessment of urban water and wastewater systems facing high groundwater level using fuzzy decision-making approach

Arid cities in Iran have neither sufficient nor efficient sewage system. The water returned to surface cesspools and leakages from insufficient sewage system makes internal groundwater recharge within the urban area.... [ view full abstract ]

Arid cities in Iran have neither sufficient nor efficient sewage system. The water returned to surface cesspools and leakages from insufficient sewage system makes internal groundwater recharge within the urban area. Additionally, water supply system leakages further raise the groundwater level which produces several potential danger and risks for the infrastructure / foundations and parts of water and wastewater systems. In this paper, a modelling framework based on fuzzy decision making has been developed for vulnerability assessment of water and wastewater collection systems to manage their performance while facing high ground water level under natural or man-made critical conditions. In this model, certain criteria were defined, fuzzy MADM techniques were exploited, and an inference check list was employed to measure such risk parameters as the probability of threats, the severity of their impacts, and the vulnerability of the network components. Based on the calculated magnitude of the risks, the threats and hazards in urban cities facing high ground water level were classified into groups ranging from low-risk to high-risk threats. This procedure was employed for the water and wastewater collection system in Kerman city as a case study in Iran. Kerman city has encountered with high groundwater level causes flowing of wastewater in underground spaces, corrosion of infrastructures and etc. ‘Introduction of chemical pollutants into the sewers’ and ‘drastic changes in wastewater quality’ were identified as the most threatening crises for the district and the ‘risk reduction strategy’ was proposed for combating the critical conditions in this area.