a river in Smolensk Oblast, RSFSR, and Vitebsk Oblast, Byelorussian SSR; a left tributary of the Zapadnaia Dvina. Length, 136 km; basin area, 5, 410 sq km.
The Kasplia River originates in Lake Kasplia in the Vitebsk Upland. It is fed by a mixture of sources (predominantly snow). The average annual water discharge at the village of Lepino (13km from the river’s mouth) is 39.6 eu m per sec. The city of Demidov is located on the Kasplia.