Vidaga
Vidaga - the left tributary of the Gauja in Alūksne, Gulbene and Valka districts. Length 24 km, swimming pool 116 km2. Annual runoff 0.028 km3, drop 51 m (2.1 m / km).
Vidaga flows along the Trapene plain in the D - N direction. Lots of forests in the pool. The river is formed by the confluence of 2 rivers; one (Irbupīte) starts in the forest of Lejasciems parish of Gulbene district, ~ 3 km from the overgrown Lāči lake, the other (Baltupe) starts in the forest of Vaguļi and flows along the border of Gulbene and Valka districts (recently Baltupi is considered to be the upper reaches of Vidaga). The largest tributary - Niedrupe (14 km). Near the mouth of the Gauja, the river flows through the Vidaga mill lake.
The list of information source can be found here .