Overview of climate change effects which may impact the urban water cycle

Abstract

Climate changes can have impact in all areas of the water industry, including quality and availability of water sources and water infrastructure robustness. Water utilities will have to adapt to the impacts of climate change; the choices of today, particularly regarding investments in infrastructure, will significantly influence the ability of the water industry to react to the impact of climate changes of tomorrow. In addition to the need to plan investments, new issues related to water utilitiy services, health, safety and environmental protection will have to be accounted for. This report brings into light the need for evaluating the relationship between climate changes and their impacts on urban water components, such as, river flow, groundwater level and salinity, reservoir level, water quality, demand for water and resilience of assets and infrastructures. For instance, it is envisaged that climate changes have a significant likelihood of influencing water quality, consequently acting in reducing the efficiency of current water treatment plants, affecting quality at the reservoirs, and during water transport. In terms of receiving water bodies, increased rainfall intensity and rainfall amount, together with unfavourable runoff conditions can cause more frequent and longer CSO operation periods in combined sewer systems. On the other hand wastewater treatment plant discharges can be the majority of flow in streams and rivers, especially during droughts. The impacts on the availability of the resource will be experienced at the catchment, reservoir and groundwater levels. Reliability during the transport of water or wastewater/stormwater will be reduced by factors that will accelerate the structural and operational urban water infrastructure deterioration. These factors, such as corrosion, breaks and blockages will consequently cause service failures, such as leakages, contamination and flooding. In this report the impacts of the expected climate changes on the urban water cycle are characterised. This report is based on the climate change assessment carried out by SINTEF and LNEC within the PREPARED Work Area 2. The report starts by summarising the projected climate changes in four different European climate regions and their effects, regardless the specific impact on the water industry. After this first overview, the attention is driven to understanding how climate changes can impact urban water assets, both in generic terms, with a summary of the main impacts on the integrated water cycle, water supply (drinking and non-drinking water systems) and wastewater/stormwater systems, and in detail, describing impacts at single asset groups for each climate region. This report aims to be a starting reference for PREPARED Work Areas 2, 5 and 6.