Vatma is an intermittent (seasonally drying) stream in the Nizhny Novgorod Region, a right tributary of the Vadok River. It flows into the Vadok directly within the waters of Lake Vad, on its southern shore.
Hydrography
The Vatma belongs to the basin of the Pyana (disambiguation), of which the Vadok is a tributary. The stream is characterized as intermittent: during low-water periods its flow is interrupted. The mouth of the Vatma lies on the southern shore of Lake Vad — a karst body of water with clear sulfate-calcium water, located in Vadsky District.
The entire system that includes the Vatma has a pronounced karst character: the Vadok itself loses water in sinkholes and depressions before flowing into the lake, and underground channels connect Lake Vad with neighboring karst water bodies. The area around the lake is dotted with karst sinkholes, both fresh and overgrown.