This water is around 95 million acre feet and while most of it is absorbed by the forests and rangelands, some 16 MAF goes into rivers and creeks from where it is supplied to 4.6 million people in Colorado alone.
Colorado has a legal obligation to serve other states and thus 8.8 MAF of water goes to south western states including Utah, Nevada, California, New Mexico, Arizona, and Mexico. Even though California is dependent on Colorado for water supply, it needs to understand that water resources of the state are limited and droughts are common in Colorado causing even faster absorption of water.
Colorado finds it increasing hard to serve a state as big as California and there are concerns about possible water shortage. California is a huge state and in order for Colorado to supply water, it needs to extract additional 6 MAF of water from reservoirs and storage systems. This has largely had a huge burden on Colorado's water system and during some heavy droughts, its agriculture, recreation, municipalities, and the environment suffered a serious blow.
But Colorado is legally obligated to supply water to California due to several interstate compacts, international treaties, and court ordered apportionment. While the state is suffering because of heavy demand of water and not adequate supply, it has managed to somehow been the main supplier for decades. However this will increasingly become difficult as Colorado's population increases.
Colorado's population is expected to increase by another 2.8 million by 2030. And this would mean greater demand for water. Colorado would then need an additional 630,000 AF of water supplies to meet its new obligations. Colorado is working on different plans to increase its water supply. Some of these include planning for new reservoirs and dams, expanding existing storage systems and conservation.
Summers also place an additional burden on Colorado's water supply. As summer arrives, not only the demand for water increases, the supply also shrinks due to evaporation and heat. This puts Colorado in a precarious situation. We need to understand that while many neighboring states depend on Colorado water, the supply is still not enough and these demands are placing a huge burden on Colorado's capacity to generate water. 1 ("Colorado wrestles", 2007)
California needs to exploit other ways in which in can meet the water demands of its people. Placing excess burden on one state is highly dangerous for the health of the state and its people. California has also been warned to limit its dependence on and use of Colorado water. The state is currently drawing much more water than it has been allotted but promises to reduce its dependence by 2015. In a news article, it was reported that, "Dubbed the "4.4 Plan," it lets California receive surplus Colorado River water that would otherwise go to the other states, in return for California's pledge to reduce reliance on the river within 15 years. California is entitled to 4.4 million acre feet of water a year under the 1928 Boulder Canyon Project Act. That agreement was upheld by the U.S. Supreme Court in 1964. Nevada is allotted 300,000 acre feet. Arizona gets 2.8 million acre feet. An acre foot of water is about 326,000 gallons, or roughly the amount needed for an average family of five for one year. In recent years, California's annual draw has grown to as much as 800,000 acre feet above its allotment."2