A Groundwater Extraction

Total Groundwater Extractions (AF)

Water Use Sectors

Rural Residential

B Groundwater Extraction Methods

Meters

Metered Municipal Wells

Metered connection maintained by City of Biggs 

Electrical Records

Land Use

Land use estimates were derived from crop mapping and CropScape survey results

Typical uncertainty for water balance calculation

Groundwater Model

Other

Rural residential groundwater extraction is estimated based on California Water Service Company's 2020 Urban Water Management Plan 2020 usage of an average per capita water use of 181 gallons per capita per day. Population data from the 2020 census was coupled with water district boundary data to identify total population not serviced by municipal supplies

Uncertainties are from population estimates and gallon per capita per day estimates

C Surface Water Supply

Total Surface Water Supply (AF)

Methods Used to Determine

Diversions for local supplies are estimated based on historic State Water Resource Control Board eWRIMS (Electronic Water Rights Information Management System) data for total diversions. Surface water delivery estimates are based on historic deliveries in the area that have occurred in dry and critical years

Water Source Types

D Total Water Use

Water Source Types

Water Use Sectors

Rural Residential

E Change in Storage

Method used to calculate change in storage

Spring measurements used to calculate the change in groundwater storage were computed as the average
of all available groundwater level measurements from March and April of the respective year. The
representative storage coefficient was established by roughly calibrating the estimated change in storage
based on changes in observed groundwater levels (i.e., calculated using groundwater level data,
representative area, and a storage coefficient parameter) with estimated change in storage outputs from
the BBGM, as reported in the GSP to aggregate characteristics across all zones of the Primary Aquifer
system. A total of 20 pairs of concurrent annual storage changes assembled from both methods over the
period from WY 1999 through WY 2018 were used for calibration. Determination of a representative
storage coefficient allows for estimating the change in volume of groundwater storage based on the
measured change in groundwater levels and known representative area (i.e., Thiessen polygon)
associated with each groundwater level measurement.
Negative changes in storage values indicate lowering groundwater levels and depletion of groundwater
storage, whereas positive changes in storage values represent rising groundwater levels and accretion of
groundwater in storage. As shown in Figure 4-2, the change in storage for each representative area (i.e.,
Thiessen polygon) in the Primary Aquifer over the previous year ranged from a loss of roughly 400 AF to
a gain of roughly 800 AF. The representative areas in the northern and western portion of the Subbasin in
close vicinity to the Sacramento River and in the eastern portion adjacent to the Thermalito Afterbay and
Feather River had a relatively larger positive change in storage compared to most other areas in the
Subbasin. Total groundwater storage change in the Primary Aquifer was estimated to be approximately
12,700 AF between spring 2023 and spring 2024.

F Monitoring Network Module

G PMA Module