GSP Annual Report
1-004 SHASTA VALLEY
2022 (OCT. 2021 - SEP. 2022)
Single Annual Report
GSP Annual Report Information Comments
03/28/2023 8:20 AM
2022 (OCT. 2021 - SEP. 2022)
Single Annual Report
A Groundwater Extraction
Total Groundwater Extractions (AF)
38,000
Water Use Sectors
3,500
0
34,500
0
0
0
0
B Groundwater Extraction Methods
Meters
0
Electrical Records
0
Land Use
0
Groundwater Model
34,500
Estimate
60-70 %
Shasta Watershed Groundwater Model
Historical groundwater level and stream flow observations were used to calibrate the model which make it a 'Likely' representation of the basins hydrology. However, there is still variation of the model from observations and there are significant data gaps in observations throughout the basin thus we estimate the model accuracy falls in the range of 60-70%.
Other
3,500
Direct
70-80 %
Population data from (https://gis.water.ca.gov/app/bp-dashboard/final/) to estimate urban water demand
Data source 2010 US Census. Dataset comes from US Census based on input from residents and may not be completed by all residents. Per capita use is based on statewide average which may vary locally.
C Surface Water Supply
Total Surface Water Supply (AF)
50,416
Methods Used to Determine
The Scott Valley and Shasta Valley Watermaster District keeps records of surface water supply that are summarized in an annual report for each standard year in March.
Water Source Types
0
0
0
50,416
0
0
0
0
D Total Water Use
Total Water Use (AF)
88,400
Methods Used to Determine
Groundwater flow model output, urban population per capita water use, Watermaster records
Water Source Types
38,000
50,400
0
0
0
Water Use Sectors
3,500
0
84,900
0
0
0
0
E Change in Storage
Method used to calculate change in storage
Change in storage was calculated by taking the difference between the Fall 2022 groundwater contour and the Fall 2021 groundwater contour to estimate change in groundwater levels. This change in groundwater level was then multiplied by the aquifer storage coefficients to estimate change in aquifer storage. However, there are still data gaps in the groundwater level network that impact the accuracy of the groundwater contours thus there is still uncertainty in the calculated change in storage. This is important to note because an erroneous depth to water measurement at one of the monitoring points can estimate a much larger change in groundwater level that in reality and this error is multiplied because that change in groundwater level is used over a large spatial distance due to data gaps in the basin. In water year 2022, the State Water Resources Control Board authorized Emergency Regulation Curtailments in Shasta Valley which limited surface water diversions. This may have decreased groundwater recharge from ditches and other unlined depressions, mostly on the western side of the valley. However, the impact of the curtailments on the water balance of Shasta Valley will be a target of future study. This year, the majority of wells in the network (18 out of 36) experienced over 3 feet of decline from Fall 2021 and twenty-seven wells had at least a decline of 0.5 ft.
