Water Pollution and Water Quality Assessment and Monitoring

Long-term monitoring of water quality changes across large areas is essential for detecting pollution and managing freshwater and marine ecosystems. Tracking trends and shifts in water quality over time provides crucial insights into the impacts of human activity and climate change. Earth Observation (EO) data enables continuous assessment of key water quality indicators in coastal, estuarine, and inland water bodies.

Parameters such as turbidity, chlorophyll-a concentration, water temperature, and transparency are vital for evaluating the condition of aquatic ecosystems, supporting public health, and guiding economic activities such as aquaculture and tourism. The extensive spatial coverage offered by satellite data aids decision-makers in developing effective water management strategies, mitigating public health risks, and reducing the vulnerability of freshwater and marine ecosystems.

Using EO for water pollution and water quality assessments offers several significant advantages. These include the provision of information across vast areas and multiple water bodies—something not feasible through in-situ measurements alone—access to historical datasets, and the ability to detect spatial patterns and track changes over time. EO platforms can deliver near-real-time data, enabling authorities to detect pollution events, monitor seasonal variations, and evaluate the effectiveness of environmental policies. For example, persistent turbidity may indicate erosion, dredging, or stormwater runoff, while elevated chlorophyll-a levels could signal nutrient pollution or harmful algal blooms.

A reliable and continuous EO-based water quality service provides the objective evidence necessary for informed decision-making and timely alerts to emerging problems. By reducing reliance on field-based sampling, EO enhances monitoring capabilities, enabling more frequent and consistent assessments over large areas.

Identifying, characterising, and monitoring sources and impacts of water pollution involves both point-source pollution (such as wastewater discharges or oil spills) and diffuse sources (such as agricultural runoff or urban drainage). EO data assists in tracking pollution plumes, sediment loads, and chemical indicators, providing early warnings of contamination. It also supports backtracking to probable pollution sources and evaluating their environmental impacts. In coastal areas, EO is particularly valuable for managing marine litter, monitoring plastic drift, and understanding the fate of pollutants transported by rivers.

Beyond environmental benefits, pollution monitoring through EO supports public health protection, particularly in regions reliant on coastal waters for drinking, recreation, or fisheries. Combined with modelling and ground observations, EO-derived data enables decision-makers to take swift, targeted actions to reduce pollutant loads, restore water quality, and enforce environmental standards.