Sacramento Valley – West Butte (consolidated into Sacramento Valley – Butte subbasin 5-021.70)

2003: Bulletin 118 basin description

2014: Basin prioritization – high. Comment: Declining GW levels within the City of Chico and Durham areas (30-40′ decline in mid-aquifer GW levels since 1998). High Nitrates in north and west Chico area. High density of GW contamination plumes surrounding City of Chico. GW serves as a source of underflow to Butte Creek, which has endangered spring-run salmon. GW Use based on B118-03 and 2005 Butte County Inventory data

2016: Basin Boundary Adjustment (2016 Final Modifications): Reclamation District No. 1004 – 5-021.58 Sacramento Valley – West Butte, 5-021.59 Sacramento Valley – East Butte  2018: Draft basin prioritization – high. Groundwater level decline, subsidence comments: 1) CASGEM/WDL/GWIDS: Longterm hydrographs show groundwater level decline. Source: DWR. Report of subsidence occuring SW of Chico. Area has experieced long-term declines in GW levels. – Subsidence in California, March 2015 – September 2016, California Institute of Technology Per 2018 draft basin prioritization: Groundwater-related transfer  “Type A” in which local groundwater is pumped to compensate for exported surface water Butte County basin boundary/consolidation request for West Butte and the Wyandotte Creek  5-021.69, Corning 5-021.51, Colusa 5-021.52, Vina 5-021.57, East Butte 5-021.59, Sutter 5-021.62 subbasins pending

2019: Approved basin boundary modification reassigns basin to neighboring basins. Per DWR: It “consists of four parts. The first part revises and expands the Vina subbasin to cover groundwater dependent areas currently included in the northern portions of East Butte and West Butte subbasins. The modification extends the Butte County portion of Vina Subbasin southerly to the northern boundary of Western Canal Water District. The resulting Vina subbasin includes the City of Chico, unincorporated Durham, and the Durham Irrigation District. The second part modifies the western boundaries of the existing Butte County portion of Vina, and West Butte subbasins, near the Sacramento River to align with the Butte County line. The third part revises the southern boundary of the East Butte subbasin to follow the Butte/Sutter County line except for the Biggs-West Gridley Water District and Reclamation District 1004 jurisdictional boundaries; which results in these Districts being entirely within the resulting Butte subbasin. The fourth part consolidates the remaining East Butte and West Butte subbasin areas to form the Butte subbasin.”