A Simplified Climate Change Impact Assessment Tool (SCIAT) addresses the specific needs of the water industry, translating climate change projections into real world impacts. A recent study in CIWEM’s Water and Environment Journal demonstrates its application in assessing the impacts of climate change on the reservoir water quality and water treatment plant (WTP) operations at Grafham Water in the east of England.
Whilst many studies consider the implications of climate change on water quantity, little emphasis has been placed on possible changes in reservoir water quality and the risks posed to WTP operations. Many studies have a strong emphasis on event risks as opposed to outcome risks, or adopt a standard scenario-driven impact assessment approach that does not provide information that can be incorporated into risk-based decision making. The SCIAT’s primary aim is to provide WTP operators with knowledge of the potential impacts and associated probabilities of occurrence of climate change, enabling them to make informed decisions.
The water industry, with its direct reliance on the hydrological cycle, is particularly vulnerable to the variable weather patterns associated with climate change. Changes in precipitation, temperatures and catchment hydrology may lead to alterations in the concentration of natural organic matter (NOM); changes in the thermal structure of the reservoir, leading to the invasion of temperature-sensitive exotic species and increased incidences of algal blooms; transformation of the physical, chemical and biological processes that govern water quality, affecting chemical reaction rates and aquatic flora and fauna growth rates; or the decrease in the oxygen-carrying capacity of the water, increasing anoxia in eutrophic waters. And more intense rainfall events will lead to increased levels of suspended solids because of fluvial soil erosion, whilst decreased reservoir water levels due to increases in evaporation will further concentrate pollutants within the reservoirs.
The application of the SCIAT at the Grafham Reservoir showed that whilst changed raw water quality will not render the water untreatable, the water treatment costs increased due to decreased filter run times and increased chemical dosing. The projections were consistent with the regional projections in AR4, but differed from those of the UKCIP02 studies, which have been used in many climate change impact assessments in the United Kingdom, highlighting the importance of considering an ensemble of models as opposed to a single model.
Whilst the paper’s focus was on understanding the possible changes in the Grafham Water water-quality regimes, their aim was to provide a more general framework by which WTP operators can assess the impact of climate change on WTP operations, enabling them to make more informed, risk-based planning and adaptation decisions.
Source: The Chartered Institution of Water and Environmental Management (CIWEM)
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