Yaroslavl Oblast's greatest natural resources are water and forests. This part of Russia has enormous water reserves; Yaroslavl Oblast has 4327 rivers with a total length of nearly 20,000 km. There are also 83 lakes with total area of nearly 5,000 km2. The largest lakes are Nero Lake in Rostovsky District and Pleshcheyevo Lake in Pereslavsky District. Pleshcheevo, Somino, Vashutinskoe, Chashnikovskoe, Ryumnikovskoe, and Lovetskoe lakes are located in the State Natural History Park. These lakes were formed from melting glaciers about 70,000 years ago. The region's mineral resource base includes brick clay and clay aggregate, gravel and sand-gravel mix, peat, and sapropel.Yaroslavl Region, Kommersant
