Laguna–San Diego Coastal water resource basin
# Laguna–San Diego Coastal water resource basin

Laguna–San Diego Coastal water resource basin (HUC 180703) is one of three hydrologic basins within the Southern California Coastal water resource subregion and is one of approximately 2,200 water resource basins in the United States hydrologic unit system.

The Laguna–San Diego Coastal water resource basin is a third-level subdivision of the United States hydrologic unit system. The tiers of the classification system, in order from largest to smallest, are regions, subregions, basins (formerly accounting units), subbasins (formerly cataloging units), watersheds, and subwatersheds. These geographic areas contain either the drainage area of a major river, or the combined drainage areas of a group of rivers.

The Laguna–San Diego Coastal basin is approximately 3,860 sq mi (10,000 $km^2;$ 2,470,000-acre) and includes the drainage into the Pacific Ocean from Moro Canyon near Laguna Beach to the international border between the United States and Mexico. The Laguna–San Diego Coastal basin is composed of five fourth-level hydrological units called water resource subbasins (formerly known as water resource cataloging units), each with its own 8-digit hydrologic unit code.

## List of subbasins of the Laguna–San Diego Coastal basin

| Basin HUC | Basin name | Basin description | Basin location | Basin size |
| - | - | - | - | - |
| 18070301 | Aliso–San Onofre subbasin | San Juan Creek, Aliso Creek, Laguna Beach coastal streams, Dana Point coastal streams, San Clemente coastal streams | Orange County | 498 sq mi (1,290 $km^2)$ |
| 18070302 | Santa Margarita subbasin | Santa Margarita River, drains Fallbrook and Marine Corps Base Camp Pendleton | San Diego County, Riverside | 731 sq mi (1,890 $km^2)$ |
| 18070303 | San Luis Rey–Escondido subbasin | Sometimes called the San Luis–Carlsbad Watershed; includes San Luis Rey River, Escondido Creek, Buena Vista Lagoon, Agua Hedionda Lagoon, Batiquitos Lagoon, San Elijo Lagoon, Loma Alta Creek and the associated slough | San Diego County | 766 sq mi (1,980 $km^2)$ |
| 18070304 | San Diego subbasin | San Dieguito Creek, Peñasquitos Creek, San Diego River, Pueblo Watershed coastal streams including Chollas Creek, Sweetwater River and reservoirs, Otay River | San Diego County | 1,390 sq mi (3,600 $km^2)$ |
| 18070305 | Cottonwood–Tijuana subbasin | Tijuana River (international watershed, subbasin boundary is at the border) | San Diego County | 477 sq mi (1,240 $km^2)$ |
