Climate Proof Cities
What can cities do to become resistant climate proof? Let’s give an overview.
Water scarcity in Cities
To become climate-ready, cities need to manage both demand for scarce water and extreme weather events. Demand management is the better use of existing water supplies before plans are made to further increase supply.
Demand management promotes water conservation and efficiency through changes in practices, cultures and people’s attitudes towards water. In addition to balancing demand with supply, demand management enables water utilities to lower energy costs in providing water.
Re-using rain and greywater
Only 20 % of water used by the sectors receiving a public water supply is actually consumed. The other 80 % is returned to the environment, primarily as treated wastewater. Concreted and sealed surfaces in cities typically direct the rainfall to the sewer networks where it is merged with wastewater. This prevents the rainfall from infiltrating the soil and forming part of our groundwater storage that can benefit us at a later date. Rain runoff and wastewater often pass through water treatment plants before being returned to rivers, usually far away from the cities. With some changes to urban water systems, both rain water and less polluted wastewater could be returned to the city’s water users.
One of these changes is the reuse of greywater. Read all about it.
The loss of water through leakages can be considerable; in a lot of cities all over the world, more then 40 % of the total water supply is lost in the water transportation network.
Leakages can be prevented through maintenance and water network renewal, and also through the use of new technologies.
Such technologies may involve sensors that recognise and locate the noise from a leak or devices that use radio signals to detect the presence of flowing water. With the application of these technologies, public water systems no longer need to face the extra burden of water loss through leakages when fulfilling water demands with limited supplies. Read all about it here.
Meanwhile, green infrastructure is the use of natural or semi-natural systems to manage stormwater at its source, keeping it away from the built environment while delivering multiple economic, social and environmental benefits such as reducing damage to property from localized flooding and reducing energy costs, and carbon emissions, of treating wastewater. Read all about it here.
Water Demand Management
It is estimated that in the Water Services Sector water loss and inefficient usage could be as high as 45%. The Integrated Resource Planning process can determine at what rate and cost these inefficiencies can become an increased supply
Demand management promotes water conservation and efficiency – in times of both normal conditions and uncertainty – through changes in practices, cultures and people’s attitudes towards water. In addition to balancing demand with supply, demand management enables water utilities to lower energy costs in providing water.
Instead, it can involve simple actions that enable households to reduce their water consumption and lower the amount of runoff from their properties into the stormwater system. Two examples of which are South West Water’s free water-fixtures program and New York City’s free rain barrel program.
So the scope of a city includes both distribution management and customer or end use Demand Management measures.
How is Integrated Resource Management (IRP) different from traditional planning?
It is wrong to regard IRP as something completely new or as the “same old thing” from what many water institutions are currently doing. The are four differences of IRP from the current planning practises that are worth identifying:
- Integration of planning to achieve the best results to society (end consumer).
Current planning practises focus on the best-perceived solution from the institution perspective
- Evaluation criteria must be comprehensive and include social, economic, and environmental
- Water demand-side management measures are considered as an alternative resource option and not a separate campaign
- Evaluation criteria must be looked at from the life cycle of the different measures and not just on implementation
Evaluation criteria in an IRP process
The are six key evaluation criteria that should be considered in the evaluation process to determine the best combination of demand-side and supply-side management measures:
- Environmental impact
The environmental index is a composite of four types of environmental impacts. These are Wetlands, Scenic resources, endangered species, and environmental water reserve.
- Social impact
The social impact index is a composite of five types of social impact. These are affordability, job creation, sustainability of services, public acceptability, and service delivery to new consumers.
Risk is measured in terms of forecasting uncertainties. An index that indicates the uncertainty of a specific measure to supply or make water available must be determined for each option.
- Technical feasibility
The technical index is a composite of four types of technical criteria. Time constraints, availability of appropriate technology, availability of capacity to implement and overall practicality to implement.
- Economic (Cost)
IRP can only be achieved through the ethos of partnerships and customer focus.
The economic criteria and financial evaluation considerations are described in more detail in the section below.
Participating Customer Test
The net present value (NPV) from the participating customer perspective (PCT) is given by:
PCT = RB – CC
- RB = PV of all benefits to all participating customers from reduced bills;
- CC = PV of customer costs (all net costs excluding rebates, incurred by all participating customers)
- PV means the present value of the stream of costs and benefits over time
- Schools use cleaned rainwater for toilets
- 3 steps to save water leakage in domestic areas
- Reduce risks storming water
- Lessons learned from Hurricane Sandy
- The Netherlands Roadmap to wastewater management
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