The basin stretches in a generally north and then northeast direction from its headwaters located south of the Lake Tahoe Basin and just north of Sonora Pass in the Sierra Nevada Mountains to its terminus in the Nevada desert.
Even so, major issues still remain relative to interstate water rights in the Carson River Basin and the failure to secure Congressional approval of the California-Nevada Interstate Compact.
Major hydrologic characteristics of the upper Carson River Basin include the Sierra Nevada Mountains, which serve as the basin's primary source of precipitation, snowpack, and runoff, a number of relatively small high alpine lakes and reservoirs, the East and West forks of the Carson River, the mainstem Carson River running through the northern portion of Carson Valley and, to the north, Eagle Valley, containing the state's capitol, Carson City.
The lower Carson River Basin may be considered as beginning at the head of Dayton Valley and ending at the furthermost extent of the Carson Sink (Desert).
[See Table 1, Nevada Hydrographic Areas in the Carson River Basin, for a description of the hydrographic areas and sub-areas contained within the Nevada portion of the Carson River Basin.] Similar to the adjacent Truckee River Basin and the Walker River Basin, the vast majority of the Carson River Basin's surface area, and certainly most of its demands for water resources, lie within the State of Nevada.
However, most of the basin's precipitation and high alpine storage reservoirs are located in the State of California.
Not surprisingly, this extreme geographic separation between the Carson River Basin's principal supply of water and its principal demands for water has tended to exacerbate some of the controversies surrounding the rights to, and the uses of, water resources within the Carson River Basin and shared between these two states.According to the California-Nevada Interstate Compact, approved by the respective state legislatures in September 1970 (California) and March 1971 (Nevada), Nevada is entitled to 80 percent of the additional (future) yields developed within the Carson River Basin (i.e., new water yields in excess of those required to satisfy existing beneficial uses), with the remaining 20 percent belonging to the State of California.This interstate compact also specifically states that the waters of the Carson River shall not be used in areas outside the Carson River Basin.Although this compact was never ratified by Congress, thereby making it law, its terms have been enforced through a "gentlemen's agreement" and individual state legislative action.Furthermore, many of the provisions of this compact pertaining to the allocation of the waters of Lake Tahoe and the Truckee and Carson rivers have been incorporated into the 1990 Negotiated Settlement Act (Public Law 101-618).While flowing a relatively short 184 miles from the headwaters of its East Fork, located below Sonora Pass in the Sierra Nevada Mountains, the Carson River has experienced more than its share of controversy and holds the dubious distinction of being the cause of the longest-running litigation (1925-1980, 55 years) over water rights adjudication ever waged by the United States Government against private interests.