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Intensive agricultural activities favor eutrophication and harmful phytoplankton blooms due to the high export of nutrients and damming of rivers. Productive watersheds used for water purification can have multiple reservoirs with phytoplankton blooms, which constitutes a high health risk. In general, water quality monitoring does not cover small and medium-sized reservoirs (0.25–100 ha) of productive use due to their large number and location in private properties. In this work, the in-situ trophic state of fourteen reservoirs was simultaneously assessed using Sentinel-2 images in the Santa Lucía River Basin, the main drinking water basin in Uruguay. These reservoirs are hypereutrophic (0.18–5.22 mg total P L-1) with high phytoplankton biomasses (2.8–4439 µg chlorophyll-a L-1), mainly cyanobacteria. Based on data generated in-situ and Sentinel-2 imagery, models were fitted to estimate satellite Chl-a and transparency in all the basin reservoirs (n = 486). The best fits were obtained with the green-to-red band ratio (560 and 665 nm, R2 = 0.84) to estimate chlorophyll-a and reflectance at 833 nm (R2 = 0.73) to determine transparency. The spatial distribution of the trophic state was explored by spatial autocorrelation and hotspot analysis, and the variation in spatial patterns could be determined prior and subsequent to a maximum cyanobacteria value in water treatment plant intakes. Therefore reservoirs with greater potential for phytoplankton biomass export were identified. This work provides the first fitted tool for satellite monitoring of numerous reservoirs, and strengthens the country's ability to respond to harmful phytoplankton blooms in its main drinking water basin.

Intensive agricultural activities favor eutrophication and harmful phytoplankton blooms due to the high export of nutrients and damming of rivers. Productive watersheds used for water puri cation can have multiple reservoirs with phytoplankton blooms, which constitutes a high health risk. In general, water quality monitoring does not cover small and medium-sized reservoirs (0.25-100 ha) of productive use due to their large number and location in private properties. In this work, the insitu trophic state of fourteen reservoirs was simultaneously assessed using Sentinel-2 images in the Santa Lucía River Basin, the main drinking water basin in Uruguay. These reservoirs are hypereutrophic (0.18-5.22 mg total P L -1 ) with high phytoplankton biomasses (2.8-4439 µg chlorophyll-a L -1 ), mainly cyanobacteria. Based on data generated in-situ and Sentinel-2 imagery, models were tted to estimate satellite Chl-a and transparency in all the basin reservoirs (n = 486). The best ts were obtained with the green-to-red band ratio (560 and 665 nm, R 2 = 0.84) to estimate chlorophyll-a and re ectance at 833 nm (R 2 = 0.73) to determine transparency. The spatial distribution of the trophic state was explored by spatial autocorrelation and hotspot analysis, and the variation in spatial patterns could be determined prior and subsequent to a maximum cyanobacteria value in water treatment plant intakes. Therefore reservoirs with greater potential for phytoplankton biomass export were identi ed. This work provides the rst tted tool for satellite monitoring of numerous reservoirs, and strengthens the country's ability to respond to harmful phytoplankton blooms in its main drinking water basin.

El cambio en el régimen de eventos de inundaciones en espacios urbanos es una problemática global. Para identificar posibles causas de las inundaciones en San José de Mayo, se analiza a nivel de cuenca los factores que favorecen este fenómeno, considerando el cambio climático y las transformaciones en los usos del suelo. Se evalúa la incidencia de la variabilidad de eventos fuertes de precipitación, precipitaciones acumuladas e intensificación productiva en relación al caudal del río, con el fin de comprender la ocurrencia de eventos de inundación en la ciudad. Se identificaron en los últimos 30 años aumentos en las precipitaciones; una asociación entre las precipitaciones y los niveles del río; y además un cambio en la matriz productiva en el territorio. Donde los procesos de impermeabilización del suelo, frente al cambio climático, generan una situación de mayor vulnerabilidad para la población en áreas inundables. Se muestra la importancia de crear una estrategia territorial a nivel nacional para actuar en los espacios urbanos inundables, teniendo en cuenta toda la cuenca.Palabras clave: cambio climático, cambio uso de suelo, precipitaciones, transformaciones territoriales.