Implications of urban development for water demand, wastewater generation and reuse in water-stressed cities: case studies from South Asia and sub-Saharan Africa

Urbanisation has become one of the strongest drivers of growing challenges in the fields of food security, human health and water resources management. Water management is especially more difficult in rapidly growing cities in non-industrialised countries where local authorities typically have insufficient financial and managerial capacities to respond to the basic needs of its citizens. This PhD thesis addresses the research needs for growing cities in non-industrialised countries and their impact on current and future urban water demand, wastewater generation and reuse. It is argued that demographic growth and investments in water supply and sanitation infrastructure are increasingly influencing upstream and downstream water users and the environment in the water basin. Cross-comparative case study methodology was applied, having quantitative and qualitative research components. The qualitative research involved data collection through semi-structured interviews of local experts while the quantitative research consists of data collection from literature and simple urban water balance modelling. The cities of Accra [Ghana], Hyderabad [India] and Addis Ababa [Ethiopia] were selected as case studies. The cities share a number of characteristics typical for the current state of the water system and are detrimental factors for future development. A series of water supply expansion projects were carried out in an effort to keep up with fast rising water demands. Similar investments in sanitation and wastewater disposal, however, were not made, due a lack of priority and indistinct governmental responsibilities. Despite considerable expansion of wastewater treatment to be expected in all cities, the untreated wastewater volume will continue to rise in two cases. Depending on the downstream setting, a considerable fraction of this wastewater is reused in urban agriculture (up to 90%). This has not only brought huge benefits to many farmers but also entailed health risks from exposure to pathogens and environmental degradation. Cities have shifted their use from groundwater to surface water and moved away further from the city to exploit new water sources. However, the latter crucially depends on the financial capacity of the water utility to invest in expansion projects. The presented cases have shown that cities are increasingly influencing the upstream and downstream areas through urban water withdrawal and disposal of wastewater and stormwater. The institutional environment and state of water resources are considered detrimental in the future development of water supply and sanitation in these cities. The combination of tools applied in this research is found to be an appropriate and effective methodology to investigate the urban water balance of fast growing water-stressed cities in developing countries. Urban water balance modelling and scenario development are very suitable tools for local planners and decision makers to adopt and apply in their respective cities.