HomeMy WebLinkAboutTAC Minutes 5.13.20Technical Advisory Committee (TAC) Meeting
1:00 P.M. – Wednesday, May 13, 2020
Mendocino County Administration Center,
501 Low Gap Road, Room 1010, Ukiah CA 95482
Virtual Meeting via Zoom
Supporting Documents:
Agenda
UVBGSA TAC Presentation Agenda Items 2, 3, 4
Meeting Summary
CALL TO ORDER – ROLL CALL
Present: Glenn McCourty, Sean White, Beth Salomone, Ken Todd, Levi Paulin, Mike Webster, Laurel Marcus and Don Seymour
Absent: Sonny Elliot, Jr.
Discussion Regarding Historical Trends of Groundwater Elevation
Presenter/s: Laura Foglia, Larry Walker and Associates; Amir Mani, Larry Walker and Associates and Stephen Maples, Larry Walker and Associates
Introduction:
Relatively constant long-term historical elevations show that the alluvium aquifer recovers from quickly from seasonal changes.
There seems to be occasional errors that need to be adjusted.
Redwood Valley
Range : 718-792 ft.-MSL
Seasonal Change: ~12 ft. (4-7 ft.)
Central Ukiah Valley
Range : 542 -691 ft.-MSL
Seasonal Change: ~8 ft. (0-28 ft.)
Southern Ukiah Valley
Range : 518-650 ft.-MSL
Seasonal Change: ~8 ft. (1-16 ft.)
Groundwater direction is normally southward and towards the river showing recharge towards the river.
Mainstem Russian River, south of the lake, seems to be connected most of the year with the aquifer.
Similar pattern were shown for 2017-2019.
It seems west of the river and east of the river have different responses to the change in season. That may be due to the difference in land use.
North of Redwood Valley is very dependent on climate variability.
Discussion:
Is there long-term data in Redwood Valley?
No – earliest data is 2000 and there does seem to be more flux because of natural hydrology.
Committee Action: None.
Update and Discussion Regarding the Integrated Model and Preliminary Water Budget
Presenter/s: Laura Foglia, Larry Walker and Associates; Amir Mani, Larry Walker and Associates and Stephen Maples, Larry Walker and Associates
Introduction:
PRMS updates
PRMS is updated to the newer version PRMS 5.0 compatible with GSFLOW v2.0.
Ponds were included in the PRMS. SW diversions are estimated.
Reservoir operation methodology was developed to be incorporated into the PRMS.
IDC updates
IDC calculated percolation and ET are being used to adjust MODFLOW recharge and PRMS ET.
IDC’s role will be switched to recently released Ag Package within GSFLOW and IDC will be used to form Ag Package inputs and ground truth its results.
Review of model layers, model assumptions, hydrologic parameters, streamflow package, well package and Lake Mendocino modeling.
Observations from the MODFLOW initial calibration.
Groundwater pumping and recharge are the most sensitive parameters…while hydraulic properties are relatively less sensitive.
Pumping estimates are relatively well constrained, recharge is uncertain.
Parameters included in the calibration:
Recharge
Horizontal hydraulic conductivity
Stream conductance
Storage properties
Please see presentation for calibration result graphs.
Discussion:
How is the PRMS handling reservoir operation?
Went through information from Sonoma Water and incorporating PVP and Lake Mendocino operations.
Sonoma Water is concerned that the method to simulate Lake Mendocino is not robust enough (SPERO transition). LWA will be able to include changes to the operation method with the information
provided by Sonoma Water. Sonoma request to have a meeting with Sonoma modeling team to ensure we are on the same page for new management operation for the Lake and incorporate the
correct data and management values for future management simulation.
What is used for sensitivity?
LWA is using heads and flow in sensitively analysis.
Committee Action: Follow up with Sonoma Water regarding Lake Mendocino modeling.
Discussion Possible Action Regarding Sustainable Management Criteria Development for Surface Water Depletion and Subsidence
Presenter/s: Laura Foglia, Larry Walker and Associates; Amir Mani, Larry Walker and Associates and Stephen Maples, Larry Walker and Associates
Discussion:
Overview on the surface water-groundwater (SW/GW) interaction sustainable management criteria
SW/GW interactions discussion topics:
Possibly tailor in-stream flow studies to local conditions.
Correlating flow conditions with data from spawning surveys data or juvenile surveys.
Possibly define measurable objectives as functional flows, rather than constant flow rate.
Relate flow rates (at FJ gauge? elsewhere?) to tributary connectivity
Has this been done?
What does the model tell us about SW-GW interaction?
Key task moving forward:
Get informed on all aspects of SW beneficial uses
Options for defining:
Measurable Objectives for stream discharge/depletion and GDEs “healthy” basin condition
Undesirable Results “Significant and unreasonable” depletion of surface water
Minimum Thresholds – avoid undesirable results
What are the key questions that will help define the above?
Review of subsidence undesirable result for SGMA
InSAR satellite-derived subsidence data product is the only known dataset for Mendocino County to use for GSPs.
Data available from mid 2015-2018
Additional 2018-2019 data was expected by April 2019
The data shows there is no subsidence issues in the Ukiah Valley Basin. LWA can wrap up the subsidence in GSP chapter quickly.
Comments:
We need to look at scenarios to run for groundwater pumping effecting the amount of release from the reservoir.
We need to get a handle on surface water pumping from the river vs. groundwater pumping to understand magnitude of the pumping impact on the river.
The tributaries dry up backwards in Ukiah which is unusual (salmon getting trapped) – document that this seems to be natural and not related to groundwater use.
With the model comparing wet year vs. low water years, we should get insights on fisheries impacts. Would be interesting to look at the purple pipe and its long-term impact on groundwater/surface
water use.
One of the first things LWA will do is run climate scenarios.
Do we need to come up with an undesirable results and metrics for subsidence?
LWA checked other basins and it looks like it is enough to show it’s below the measurable thresholds and the GSA will check DWR data to make sure there are no other changes. May want
to check with DWR to confirm this is allowable. If there is no undesirable result to define before 2015, we can pass on establishing thresholds.
Committee Action: Provided direction to staff.
Action Items and Closing Comments
Presenter/s: None
Committee Action: None.
Public Comments on Items Not on the Agenda
This time is reserved for the public to address the Committee about matter not on the agenda and within the jurisdiction of the Advisory Committee. Persons wishing to speak on specific
agenda items should do so at the time specified for those items.
Public Comment: None.
Adjournment
The Meeting adjourned at 4:00pm.
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Glen McGourty, Chair
Attest: Sarah Dukett
UVBGSA Plan Manager
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