Major Rivers of Uruguay

Uruguay is a **water-rich nation** defined by **four major river basins** and **at least 11 principal rivers**:

1. Río de la Plata Basin (South — Atlantic Outlet)

• Río de la Plata — **Estuary (funnel-shaped)**, **world's widest "river" (220 km / 137 mi at mouth)**. **Border with Argentina**. **Montevideo, Buenos Aires** on shores. **Salinity gradient** → **freshwater wedge**.
• Río Santa Lucía — **Montevideo's water supply** (Paso Severino Dam). **~230 km**. **Agricultural pollution challenges**.
• Río San José — **Tributary of Santa Lucía**. **~120 km**. **Dairy/ag region**.

2. Río Uruguay Basin (West — Border with Argentina)

• Río Uruguay — **1,838 km (1,142 mi)** total; **~800 km forms border**. **Fast, clear, rocky** — **hydroelectric: Salto Grande (binational), Itá (upstream BR)**. **Golden Dorado fishery**. **Fray Bentos (pulp mill conflict)**.
• Río Cuareim / Quaraí — **Border river (north)**. **Tributary of Uruguay**. **Basalt canyons**.
• Río Arapey — **Thermal springs (Salto, Termas de Arapey)**. **Tributary of Uruguay**.
• Río Daymán — **Thermal springs (Termas de Daymán, Salto)**. **Tributary of Uruguay**.

3. Río Negro Basin (Central — Largest Entirely in Uruguay)

• Río Negro — **~750 km (466 mi)**. **Longest entirely within Uruguay**. **Three mega-dams: Rincón del Bonete (largest reservoir, 1,140 km²), Baygorria, Constitución** — **~30% Uruguay's electricity**. **Agriculture, tourism, fisheries**.
• Río Yí — **Main tributary of Negro**. **~200 km**. **Trinidad (capital of Flores Dept.)**. **Gold mining history**.
• Río Tacuarembó — **North-central**. **Tributary of Negro**. **Basalt, grasslands, cattle**.

4. Laguna Merín / Lagoa Mirim Basin (East — Border with Brazil)

• Río Cebollatí — **Main feeder of Laguna Merín**. **~250 km**. **Wetlands, rice irrigation (major), birdlife**.
• Río Tacuarí, Río Yaguarón — **Border streams**.

5. Atlantic Coastal (Southeast)

• Río Queguay — **North coast, Río de la Plata**. **Queguay Grande / Chico**. **Basalt, fossils, rock art**.

Management: **DINAGUA (National Water Directorate)**, **Binational Commissions (CARU — Uruguay River, CIC — La Plata)**. **Water quality, allocation, flood control, ecosystem health** — key challenges in **agro-export economy**.