Predicting, monitoring and modelling nutrients and algae

Eutrophication, the nutrient enrichment of freshwaters, resulting in excessive growth of algae, is a significant challenge to the water industry.

Algal blooms can affect lakes, reservoirs and rivers resulting in ecosystem wide impacts such as: deoxygenation and fish kills, the production of toxins harmful to humans and animals, and other problems associated with water treatment such as the production of compounds affecting taste and odour.

Our scientists have innovative tools for identifying nutrient pollution sources, and use monitoring and modelling techniques to study how freshwater bodies are impacted by nutrient enrichment in combination with other threats such climate change.

Case study: Bloomin’ Algae

Algae. Photo: Shutterstock

UKCEH scientists, with the EA, SEPA, Public Health England and Health Protection Scotland, have developed the Bloomin’ Algae app. People can use the app to submit a photo of a suspected bloom; our scientists then gauge the risk to people and animals.

Water managers can receive alerts of blooms and take prompt action. The app's data help the water industry quantify the risks of algal blooms in reservoirs, in response to catchment management measures or climate change.

Tool: PROTECH model

Our PROTECH model (Phytoplankton Responses to Environmental Change) simulates the dynamics of phytoplankton in lakes and reservoirs, specialising in predicting the daily growth of mixed phytoplankton communities, including filamentous algae and cyanobacteria (blue-green algae). PROTECH has been used to research climate change impacts (drought, temperature increases) and nutrient pollution for the Environment Agency and Natural England, and to assess the likely impact of sewage treatment work (STW) upgrades for the water industry.

Case study: Modelling nutrients and algae in Thames Water’s reservoirs

UKCEH carried out work on future water quality for Thames Water, modelling nutrients and algae in their reservoirs and rivers under different drought scenarios. We used our long-term river flow and water quality records for the reservoirs’ supply rivers to estimate nutrient concentrations during major droughts of the past century, based on current-day wastewater treatment levels, using our Load Apportionment Model. We then applied our PROTECH model to predict impacts on the algal community in the reservoirs, to help determine how Thames Water would cope if different kinds of droughts were to occur in future.

Case study: Microbiology monitoring on the Thames

UKCEH have been using flow cytometry as a proxy measurement to quantify and characterise algal populations across the river catchment as a part of the Thames Initiative project. This analytical method produces cell counts for ten different classes of phytoplankton. A staining technique is used to enumerate and differentiate bacteria with high and low nucleic acid content. This generates a unique high resolution, multi-site overview of the populations of the major eukaryotic and prokaryotic plankton groups across this critically important river catchment. This rich dataset has advanced understanding of the causes of algal blooms in rivers, and is being incorporated into predictive models.


QUESTOR (Quality Evaluation and Simulation Tool for River Systems) is an in-stream water quality model. It has been used extensively in Europe to investigate issues such as the impacts of climate change, sewage discharges, and land management. The model was developed to help catchment managers assess the impact of actions they might take, for example changing discharges consents, abstracting more water from a river, establishing river-bank tree coverage or building a flood relief channel. The model produces a realistic representation of a number of important measures of river water quality while being practical to run using widely available datasets.