Development of a climate resilient and sustainable approach for urban water cycle management

Abstract

Land-use change along with capital-centric development in the mega city Dhaka has resulted high population density, increased hard surface, reduced green and blue surface, increased runoff, reduced recharge and water stress with an imbalance in the urban water cycle (UWC) with quality and quantity. Unplanned urbanization withtraditional approach for water management is the root cause of water stress. In fact, there is no holistic approach to manage the UWC by coining the concept of climate resilience and sustainability. The traditional approach in general follows the typical ground water (GW) dependent urbanization with direct discharge of both stormwater and wastewater (black and grey water) into the combined sewer system without any rainwater harvesting (RWH) and use, reuse and recycle of the wastewater. The global philosophy of Integrated Water Resources /Urban Water Management (IWRM/IUWM) is arguably not internalized into the UWC management systems in Dhaka or elsewhere in the country to reap its benefits. This study has explored the gaps, pressures and challengers of UWC management to develop an approach with a case study area in greater Dhaka with three key analyses that are inevitable for any urban development and UWC management i.e., land-use change analysis, hydrogeological analysis integrating the climate change (CC) impacts and sustainability analysis. Results from all three analyses have identified the opportunities and challenges of UWC management with the options of decision-making towards achieving climate resilience and sustainability. The two important components of IWRM/IUWM, i.e., RWH and wastewater use/reuse/recycle are hardly practiced in Dhaka. Even with high average annual rainfall and legal compliance for its use, RWH systems are missing in any urban context. Alongside, no use/reuse of wastewater is noticeable. Widespread awareness generation, enforcement of compliance and streamlining the process of integration are the key imperatives to offset the challenges of UWC management. In essence; sensitivity, accountability and amenability of both beneficiary and functionary without involving too many stakeholders would help realize the climate resilient and sustainable UWC management in the water stressed Dhaka and elsewhere in the country including the megacities having similar climatic trend and institutional difficulties. In fact, the developed approach for UWC management has essentially involved two intertwined approaches, i.e., analytical and management approach. Analytical approach of land-use change addresses the identification and quantification of land-use change for its usability and helps make decisions for in urban water demand and distributed runoff management. Hydrogeological analysis broadly addresses the inclusion of CC effects in climate resilient urban drainage planning and avoid urban flooding and inundation and the decisions for sustainable temporal water management. The sustainability analysis identifies the overall environmental and socio-economic challenges, pressures and gaps of UWC management. The UWC management approach is the decision-based output of the analytical approach. All identified challenges from the analytical approach of UWC have been generalized, addressed and fixed through the management approach for low and high density urban development respectively towards achieving climate resilience and sustainability. Keywords: Climate change, climate resilience, hydrogeological analysis, integrated urban water management, land-use change, sustainability, urban water cycle.