Water Technology
Understanding Lake Eutrophication: Causes and Remediation Approaches
Eutrophication is the enrichment of a water body with nutrients, principally nitrogen and phosphorus, that stimulates excessive growth of algae and aquatic plants. In urban lakes, the main nutrient sources are wastewater inflows, stormwater runoff carrying fertilisers and organic matter, and the release of nutrients stored in bottom sediments, a process known as internal loading.
The consequences extend beyond unsightly algal blooms. Dense surface growth blocks sunlight, submerged vegetation dies back, and decomposing organic matter consumes dissolved oxygen. The result is a simplified ecosystem dominated by a few tolerant species, with periodic fish kills and odour problems in severe cases.
Remediation follows a hierarchy. The first priority is always reducing external nutrient loads: intercepting wastewater discharges, managing stormwater, and controlling runoff from surrounding land. Only then do in-lake measures, such as sediment capping or removal, hypolimnetic aeration, and biomanipulation, have a chance of lasting success. Skipping the source-control step is the most common reason lake treatments fail.
Monitoring underpins the whole process. A nutrient budget that quantifies inflows, internal loading, and outflows tells practitioners where to focus effort, while ongoing water-quality data verifies whether the lake is actually recovering.