Modelling future scenarios to prevent reservoir failure
UKCEH has pioneered a scenario modelling approach to inform water companies’ mitigation plans and alleviate the risks of reservoir failure.
Effective reservoir management involves building in flexibility to overcome both established and emerging challenges.
How resilient are current filtering systems against longer lasting issues caused by different types of algal blooms?
How adaptable are they to consequences of climate change?
UKCEH has pioneered a scenario modelling approach to inform water companies’ mitigation plans and alleviate the risks of reservoir failure. By simulating various environmental stressors and operational scenarios, water companies can also optimise and test reservoir design before finances are committed and construction commences.
Our PROTECH model (Phytoplankton Responses to Environmental Change) simulates the dynamics of phytoplankton in lakes and reservoirs, and can be used to predict the daily growth patterns of mixed phytoplankton communities, including filamentous algae and cyanobacteria (commonly known as blue-green algae). The model generates comprehensive data, which can be broken down into different groups of interest e.g. taxonomic distinctions (diatoms, cyanobacteria) or size related categories (filter blockers/penetrators), allowing for targeted analysis and insight.
PROTECH has been used to research climate change impacts, including drought occurrences and temperature increases, as well as to assess changes in catchment nutrient inputs for UK water companies, including Thames Water, Welsh Water, Scottish Water and Yorkshire Water.
Drought conditions can place extreme demands upon reservoirs, leading water supplies to be depleted to very low levels not encountered during in typical operating conditions. UKCEH scientists conducted research to investigate the impact of such low water levels on the algal communities of five Thames Water reservoirs. Employing the PROTECH model, they simulated the effects of extreme drawdown conditions, generating data to refine the size classification of filter blockers and penetrators and highlighting key issues.
The analysis revealed critical insights such as: blockers cause the Rapid Gravity Filter (RGF) mechanism used in the treatment works to malfunction, whereas penetrators are small enough to pass through the filter and enter the works. Modelling scenarios showed that penetrators can thrive in conditions of extreme drawdown, exacerbating the likelihood of operational issues within the treatment works . Reservoir managers can use these insights to be vigilant for this effect and respond accordingly.
Algal-related water quality problems in reservoirs are often caused by nutrients entering the reservoirs, triggering harmful causing blooms. To address this challenge, one possible solution is to use alternative water sources with lower nutrient concentrations.
Our team of scientists used the PROTECH model to test this proposed strategy and extended it to evaluate its sustainability as air temperatures rise. Our analysis confirmed that using the low-nutrient water sources improved the reservoir water quality, but raising temperatures generated a marked increase in the duration and magnitude of cyanobacteria blooms, (see figure).
Our scientists provided Thames Water with relevant data to test the design of a new reservoir prior to construction. Their goal was to optimise both the structural design and operational procedures in order to minimise potential problems. They were primarily interested in the impact of the design on algal bloom formation, but were also able to use the PROTECH tool to extend the research to assess the effects of various water pumping strategies.
