The California water resource region is one of 21 major geographic areas, or regions, in the first level of classification used by the United States Geological Survey in the United States hydrologic unit system, which is used to divide and sub-divide the United States into successively smaller hydrologic units. These geographic areas contain either the drainage area of a major river, or the combined drainage areas of a series of rivers.[1] [2]
The California region, which is listed with a 2-digit hydrologic unit code (HUC) of 18, has an approximate size of 168579sqmi, and consists of 10 subregions, which are listed with the 4-digit HUCs 1801 through 1810.[3]
This region includes the drainage within the United States that ultimately discharges into the Pacific Ocean within the state of California; and those parts of the Great Basin (or other closed basins) that discharge into the state of California. Includes parts of California, Nevada, and Oregon.[3]
| Subregion HUC[4] | Subregion Name | Subregion Description | Subregion Location | Subregion Size | Subregion Map | |
|---|---|---|---|---|---|---|
| 1801 | The drainage into the Pacific Ocean from and including the Smith River Basin to and including the Stemple Creek Basin | 24800sqmi | ||||
| 1802 | The Sacramento River Basin and drainage into Goose Lake | California, Oregon | 27600sqmi | |||
| 1803 | The drainage into the Tulare and Buena Vista Lake closed basins | California | 16200sqmi | |||
| 1804 | San Joaquin River Basin | California | 15600sqmi | |||
| 1805 | The drainage into the Pacific Ocean from the Stemple Creek Basin boundary to and including the Pescadero Creek Basin, excluding the Sacramento and San Joaquin River Basins | California | 4470sqmi | |||
| 1806 | The drainage into the Pacific Ocean from the Pescadero Creek Basin boundary to and including the Rincon Creek Basin | California | 11400sqmi | |||
| 1807 | Drainage within the United States that discharges into the Pacific Ocean from the Rincon Creek Basin boundary to the California-Baja California international boundary | California | 11100sqmi | |||
| 1808 | The drainage east of the Sierra Nevada and north of the Truckee River Basin, which includes the Lahonton closed basins that discharge into California | California, Nevada | 4480sqmi | |||
| 1809 | The Closed Desert Basins that discharge into South Central California, including Mono Lake, Owens Lake, Death Valley, and the Upper Mojave Desert | California, Nevada | 28000sqmi | |||
| 1810 | The closed desert basins in southeastern California, including the Lower Mojave Desert and the Salton Sea | California | 16000sqmi |