GSP Annual Report
5-021.52 COLUSA
2021 (OCT. 2020 - SEP. 2021)
Single Annual Report
GSP Annual Report Information Comments
04/01/2022 11:57 AM
2021 (OCT. 2020 - SEP. 2021)
Single Annual Report
A Groundwater Extraction
Total Groundwater Extractions (AF)
977,230
Water Use Sectors
10,230
0
933,000
34,000
0
0
0
B Groundwater Extraction Methods
Meters
4,030
Direct
5-10 %
Flowmeter records of groundwater extraction for urban use, from the Cities of Orland, Williams, and Willows
Estimated based on the typical field accuracy of meters, and the typical combined accuracy of volumes in urban distribution systems (accounting for metered groundwater, metered deliveries, unmetered deliveries, and apparent losses)
Electrical Records
0
Land Use
967,000
Estimate
20-30 %
Groundwater extraction for agriculture and managed wetlands was estimated through a land use-driven water budget approach based on applied water demand within corresponding land use areas (Land IQ 2018 informed by jurisdictional areas and GSP land use analyses), after accounting for available surface water supplies. Total water demand was quantified based on OpenET ET data. The portion of ET met by precipitation (ETPR) was quantified from total ET, PRISM gridded precipitation data, and representative soil/crop parameters. The portion of ET met by applied water (ETAW) was quantified as the difference between total ET and ETPR. Total applied water and the portion met by groundwater were estimated based on efficiencies calculated from the GSP groundwater model in recent years, considering ponding operations in managed wetlands.
Typical uncertainty when calculated from a land surface water budget approach, considering the combined uncertainty of other water budget flow paths following the procedure described by Clemmens and Burt (1997). The uncertainties of other flow paths are quantified based on measurement device accuracy, technical literature, or professional judgment.
Groundwater Model
0
Other
6,200
Estimate
10-20 %
Estimates of groundwater extraction in urban areas where flowmeter records were unavailable were estimated based on annual population data and monthly per capita water use requirements. Annual population data were obtained from the California Department of Finance. Average monthly per capita water use rates in 2016-2021 were quantified from population data and available pumping data in the Cities of Orland, Williams, and Willows, and then adjusted according to the relationships between cities/unincorporated areas identified during GSP development.
Typical uncertainty when calculated from population and per capita water use data, considering the combined uncertainty of those data sources.
C Surface Water Supply
Total Surface Water Supply (AF)
918,000
Methods Used to Determine
CVP supply and local supply (Orland Project) surface water deliveries were summarized from Farm Gate Delivery records, where available, or were estimated from USBR records of deliveries to contractors, adjusted for distribution losses quantified during GSP development for the GSP groundwater model. CVP supplies available to managed wetlands were summarized from CVPIA Refuge Water Supply Program contract quantities and reported annual allocations to National Wildlife Refuges in the Colusa Subbasin.
Water Source Types
895,000
0
0
23,000
0
0
0
0
D Total Water Use
Total Water Use (AF)
1,895,000
Methods Used to Determine
Groundwater is determined following the methods described in Part B.
Surface water is determined following the methods described in Part C.
Totals are rounded to nearest TAF, except urban water use which is rounded to nearest 100 AF (substantial meter records).
Water Source Types
977,000
918,000
0
0
0
Water Use Sectors
10,200
0
1,782,000
103,000
0
0
0
E Change in Storage
Method used to calculate change in storage
Annual change in groundwater storage was calculated based on change in measured spring-to-spring groundwater elevations multiplied by the area of the Thiessen polygon associated with each groundwater level RMS well and a storage coefficient of 0.1. Change in groundwater storage in WY 2021 represents the Spring 2020-Spring 2021 annual change in groundwater storage.
