Using Earth Observation to Monitor Water Quality and Improve Wastewater Systems in Lake Ypacaraí, Paraguay

Lake Ypacaraí is a primary water resource and recreational destination in Paraguay, however pollution from bacteria and toxic algae has rendered the water unsafe for consumption or recreational use, impacting the local economy. To help revitalise the lake, ESA’s GDA Water Resources thematic activity and the Inter-American Development Bank (IDB) are using Earth Observation (EO) to monitor water quality parameters and guide the improvement of the waste water system.

The approach focuses on monitoring nutrient concentrations in the water, particularly nitrogen and phosphorus, as these are the primary drivers of algal blooms when present at elevated levels. These nutrients are typically introduced through wastewater discharges and runoff, and they contribute to the development of harmful algae and pathogenic microorganisms in the lake. Chlorophyll is then used as a proxy indicator of biological activity in the water column. As chlorophyll reflects phytoplankton abundance, it serves as an indicator of overall water quality, with higher concentrations generally associated with nutrient enrichment and degraded conditions. Examining these signals over time also makes it possible to observe changes in the lake, including seasonal variability driven by rainfall and river inflows, as well as longer-term trends influenced by climate variability. These insights provide a stronger evidence base for managing pollution and supporting long-term lake restoration and water quality improvement strategies.

You can find out more about this Case Study on the GDA Impact Sphere: EO helps turn the tide on Lake Ypacaraí’s polluted past

Related Use Case

• Water Pollution and Water Quality Assessment and Monitoring