Why did Peter the Great survey the Don River?

Peter the Great initiated a hydrographic survey of the Don River as part of his broader efforts to secure Russia's southern frontier and expand access to the Black Sea.12

Following the failure of his first military campaign against Azov in 1695, Peter recognized the strategic necessity of naval power to achieve his objectives. He subsequently built a fleet at Voronezh to navigate the Don River, which proved successful in the capture of Azov in 1696. His interest in the river's geography and navigation was foundational to these military goals and his later attempts to connect the Don with the Volga River via a canal.132