Tributaries of the upper San Juan River above Navajo Dam include the Rio Blanco and the Navajo River, and the Piedra River and Los Pinos River (Pine River) which join the San Juan in Navajo Lake. In addition to the Animas River, several major tributaries join below Farmington including the La Plata River and Mancos River in New Mexico, and McElmo Creek in Utah. The San Juan also has a number of seasonal tributaries that drain arid regions of the Colorado Plateau. These include the Cañon Largo and Chaco River in New Mexico, and the Montezuma Creek and Chinle Creek in Utah. The northern tributaries of the San Juan River, which originate in the San Juan Mountains, are snowmelt-driven with the highest flows between March and June. Southern tributaries such as the Chaco River are mostly ephemeral but can carry large volumes of water during flash floods.