Mustjõgi/Koiva

River Koiva is 452 km long – it’s the longest river in Latvia (Daugava is about 100 km shorter. As the crow flies, the springhead of Koiva is only 90 km from its estuary. The surface area of the catchment basin of the river is 9800 km². The drop of river Koiva is 234 meters, that makes it 0,52 m/km.
For 18 km, the river flows as a border river between Latvia and Estonia. On Estonian side, the river flows past the Koiva-Mustjõe Landscape Protection Area.
The biggest affluent of River Koiva in Estonia is River Mustjõgi that is 84 km long and with a relatively large watershed – 1820 km², half of which is located in Estonia and the other half in Latvia. The drop of River Mustjõgi is only 29,7 meters or 0,35 m/km but as its rather rich of water, the current becomes faster downstream.
After River Koiva and Mustjõgi conjoin, River Koiva abruptly becomes very wide, reaching up to 40 meters. After that, River Koiva flows through the territory of Karula National Park. The river is suitable for calmer hikers who don’t need constant adrenaline rush from rapids and other extremities. The flow is relatively slow, shores low, riverbed sandy and with smooth curves, especially near Mustjõe. On River Koiva, the shores turn into scenic wooded meadows, later high sandstone outcrops. River Koiva is perfect for multi-day hikes due to long distances and nice camping and recreation areas on the shores.