A Groundwater Extraction

Total Groundwater Extractions (AF)

Water Use Sectors

Rural Domestic and Small Public Water System

B Groundwater Extraction Methods

Meters

Metered Municipal Wells

The level of accuracy is rated on a qualitative scale of low, medium, and high. The Metered groundwater extraction accuracy rating is high.

Electrical Records

Land Use

Land use data along with climate and soil data were analyzed and processed using the soil-water balance model that was developed for the PasoRobles Groundwater Basin Model Update (GSSI, 2014).

The level of accuracy is rated on a qualitative scale of low, medium, and high. The Land Use accuracy rating is medium.

Groundwater Model

Rural Domestic and Small Public Water Systems groundwater extractions in the Subbasin were estimated using the groundwater model update completed for the GSP (M&A, 2019).

The level of accuracy is rated on a qualitative scale of low, medium, and high. The Rural Domestic and Small Public Water Systems groundwater extraction accuracy rating is low-medium.

Other

C Surface Water Supply

Total Surface Water Supply (AF)

Methods Used to Determine

Metered

Water Source Types

D Total Water Use

Water Source Types

Water Use Sectors

Rural Domestic and Small Public Water System

E Change in Storage

Method used to calculate change in storage

From PDF page 37 of Report [SECTION 7: Change in Groundwater in Storage (§ 356.2[b][5])]:

Annual changes in groundwater elevation in the Paso Robles Formation Aquifer for water years 2017, 2018,
and 2019 are derived from comparison of fall groundwater elevation contour maps from one year to the
next. For example, the fall 2016 groundwater elevations were subtracted from the fall 2017 groundwater
elevations resulting in a map depicting the changes in groundwater elevations in the Paso Robles Formation
Aquifer that occurred during the 2017 water year (see Figure 12). Similar calculations were made for water
years 2018 and 2019 resulting in groundwater elevation change maps in the Paso Robles Formation Aquifer
for water year 2018 (Figure 13) and water year 2019 (Figure 14). These groundwater elevation change
maps are based on a reasonable and thorough analysis of the currently available data. As stated in Section
3, groundwater elevation data for the Alluvial Aquifer are too limited to prepare annual groundwater
elevation contour maps. Therefore, the change in groundwater in storage analysis is limited to the Paso
Robles Formation Aquifer for this annual report. As discussed in the GSP, the monitoring network needs to
be expanded to more completely assess Subbasin conditions.

The groundwater elevation change maps presented above represent a volume change within the Paso
Robles Formation Aquifer for each water year. The volume change depicted on each map represents a total
volume, including the volume displaced by the aquifer material and the volume of groundwater stored within
the void space of the aquifer. The portion of void space in the aquifer that can be utilized for groundwater
storage is represented by the aquifer storage coefficient (S), a unitless factor, which is multiplied by the total
volume change to derive the change in groundwater in storage. Based on work completed for the GSP, S is
estimated to be 7 percent. Appendix F of the report includes derivation of the storage coefficient from the
GSP groundwater model files and a sensitivity analysis.

F Monitoring Network Module

G PMA Module