Subbasin Overview

The Colusa Subbasin is a portion of the larger Sacramento Valley Groundwater Basin covering approximately 723,823 acres. The subbasin spans Glenn and Colusa Counties. It is generally bounded by Stony Creek to the north, the Coast Ranges to the west, to the east by the Sacramento River and the Reclamation District 1004 western boundary, and to the south by the Colusa-Yolo County boundary and the Colusa County Water District boundary.

map of colusa subbasin groundwater sustainability agencies

Click here to download the map.

Glenn County: Colusa Subbasin Factsheet

Please contact the Groundwater Sustainability Agencies below for more information on subbasin activities and meeting information.

Groundwater Sustainability Agency
Phone Number
Glenn Groundwater Authority 530.934.6540
Colusa Groundwater Authority 650.587.7300 X17