Integrated water strategy uses principles of centralised sustainable drainage as well as strategic and site level approaches to managing surface water and disposing of wastewater including grey water usage and rainwater harvesting, which can also be used to achieve as close as possible neutrality in water usage.
This approach could be particularly relevant for large scale new developments that require a step change in the provision of water supply, wastewater treatment and water infrastructure. This could address several issues including a lack of capacity in the drainage infrastructure, areas of surface water, sewer flooding risk and an increasing deficit of available water to meet an ever-growing population. In this situation, integrated water management could help to limit the waste and surface water discharge to a sewer to a point where the runoff of the site would match that of an equivalent undeveloped or greenfield site. Demand on the centralised water supply would also be minimised by re-using water resources and wastewater resource. In an ideal world, this would all be done in the most sustainable way.
Water companies already work to reduce a water supply deficit through a combination of measures for existing properties to tackle leakage, manage (and reduce) water demand and implement new water supply schemes. The addition of innovative water supply solutions for new developments will further help to reduce the water supply deficit.
Distribution of annual flows
Water demand varies seasonally with the weather. In hot dry weather more water is used for outdoor uses such as garden watering and in very cold weather water leakage may increase due to burst pipes. Rainfall also varies seasonally across the year with the majority of fall in the autumn months. The volume of rainfall that falls in a short space of time will also have a significant impact on local drainage systems. The impact of high intensity storms is further increased by catchment urbanisation which removes the natural process of infiltration, interception and evapotranspiration on vegetated surfaces. Increasing green, permeable areas within the catchment and providing attenuation storage and SuDS features will assist in reducing the peak surface water flows entering the combined sewer system.
Sustainability is key in ensuring that water management measures have a positive impact on climate change as well as key measures such as biodiversity which in turn will also often have benefits for local communities. The sustainability of any integrated water management strategy will be affected by carbon intensity which includes both the embedded carbon and ongoing requirements for energy e.g. for water pumping. Provision of blue-green spaces can enhance the are for the local community whilst also providing habitat and increasing biodiversity, improving air quality and reducing the impact of the urban heat environment. Consideration should also be given to whether an integrated water strategy is resilient to climate change itself.
Opportunities for integrated water management are summarised in the list below:
- Water efficient fixtures and fittings
- Use of toilets with cyclonic flow to reduce water usage without loss of performance
- Monitoring of usage to support behavioural responses e.g. smart meters
- Network sensing including leak detection optimisation of water pressures for potable water transmission networks
- Microclimate controlled irrigation to tailor irrigation requirements to different parts of the same site.
- Green roofs combined with roof water harvesting systems
- Green source control including bio retention and manufactured soils, tree pits and rain gardens and thirsty concrete.
- Below ground storage including underground geocellular storage
- Streetscape strategic SuDS networks
- Modification of waterway storage and discharge
- Downstream stormwater retention ponds or wetlands
- Building scale grey water recycling
- Strategic scale waste water recycling
- Strategic scale stormwater recycling
- Rainwater harvesting
When creating an integrated water management strategy and selecting which elements to include, key considerations could include the cost and technology requirements, potential water savings, potential discharge reduction, potential attenuation contribution, spatial requirements, maintenance requirements, regulatory and public acceptability, flexibility and scalability, carbon intensity, blue-green space, climate resilience and surface water quality. Measures can be both retrofitted and planned for new developments to maximise impacts. A clear framework laid out for both developers and stakeholders will help to ensure the effectiveness of the plan.
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