The Aiviekste is a river in Latvia. It begins at Lake Lubāns (the largest lake in Latvia) and drains into the Daugava (the largest river in Latvia). The Aiviekste is the largest tributary of the Daugava in Latvia. The Aiviekste, along with the Pededze, forms the unofficial border between two historical Latvian regions Vidzeme and Latgale, although the administrative border was slightly different. The river is 114 kilometers long, with annual drainage 1.81 km. The Aiviekste is between 10,000 and 12,000 years old, formed at the end of the last ice age. Nearly a quarter of the river's flow is unregulated, but most of the river has been excavated, including with explosions.
The Aiviekste flows from the northern end of Lake Lubāns, where it does a wide semicircle and then turns southwest. At this stage is the smallest drop, in addition, here Aiviekste receives the largest tributaries Pededze, Bolupe and Iča. Furthermore, it was straightened and deepened for 83 km. At the lower end, Aiviekste flows through a slightly undulating area. There are several islands, sandbars and about 15 stone sills here in the river. The small Aiviekste hydroelectric power plant (1.4 MW) was built on one of these island groups. After the construction of the Pļaviņu hydroelectric power plant, the lower end of Aiviekste is flooded with a reservoir. It flows through the towns of Lubāna and Pļaviņas (estuary). Near Krievciems - a dolomite quarry.
