Urban water cycles
Introduction
Integrated Urban Water Management (IUWM) is the practice of managing freshwater, wastewater, and stormwater as components of a basin-wide management plan. It is based on existing water supply and sanitation considerations within an urban settlement by incorporating urban water management within the scope of the entire basin.[1].
IUWM is commonly considered as a strategy to achieve the goals of water-sensitive urban design. It seeks to change the impact of urban development on the natural water cycle, based on the premise that by managing the urban water cycle as a whole, more efficient use of resources can be achieved, providing not only economic benefits, but also better social and environmental outcomes.
One approach is to establish an internal urban water cycle through reuse strategies (see Reclaimed Water). The development of this part of the urban water cycle requires an understanding of both the pre- and post-natural water balance. Accounting for flows in pre- and post-development systems is an important step in limiting urban impacts on the natural water cycle.[2].
IUWM within an urban water system can also be carried out by evaluating any new intervention strategy using a holistic approach covering several criteria, including sustainability, where the integration of water system components – water supply, wastewater and stormwater – would be advantageous.[3].
The simulation of metabolic-type flows in the urban water system can also be useful to analyze processes in the IUWM urban water cycle.[3][4].
Components
Activities within the IUWM include:[5].
• - Improve water supply and water efficiency.
• - Improve water quality of drinking water and wastewater treatment.
• - Increase the economic efficiency of services to sustain operations and investments for water, wastewater and stormwater management.
• - Use alternative water sources, such as rain or reclaimed water.
• - Involve communities to reflect their water management needs and knowledge about it.
• - Establish and implement policies and strategies to facilitate the above activities.
• - Train staff and institutions participating in the IUWM.
According to the Commonwealth Scientific and Industrial Research Organization (CSIRO), IUWM requires management of the urban water cycle in coordination with the hydrological water cycle, which is significantly altered by urban landscapes and its correlation with increased demand. Under natural conditions, the inputs of water at any point in the system are precipitation and surface flows, while the outputs are through surface flows, evapotranspiration and groundwater recharge. The large volumes of piped water introduced with the shift to an urban environment and the introduction of vast impermeable (paved) areas have a strong impact on the water balance, increasing inflows and drastically altering outflow components.[2].