The Colorado River is a major source of water in the Southwest and many dams, such as the Hoover Dam, form reservoirs along it. So much water is drawn for drinking water throughout the West and irrigation in California that in most years, water from the Colorado River no longer reaches the Gulf of California. The Columbia River, the largest river in volume flowing into the Pacific Ocean from North America, and its tributary, the Snake River, water the Pacific Northwest. The Platte runs through Nebraska and was known for being a mile (2 km) wide but only a half-inch (1 cm) deep. The Rio Grande forms the border between Texas and Mexico before turning due north and splitting New Mexico in half.