www.sonomacountywater.org

Surface Water & Groundwater InteractionsMiddle Reach of Russian River

Marcus Trotta, PG, CHgWater Agency Hydrogeologistmarcus.trotta@scwa.ca.gov

6 Collector Wells

7 Vertical Wells

5 Infiltration Ponds

Inflatable Dam

Russian RiverRiverbank Filtration System

One of the largest riverbank filtration systems in the

world

Treatment accomplished via natural filtration.

Only chlorine added as a disinfectant

Groundwater MovementBetween Recharge and Discharge

U.S. Geological Survey Circular 1139

Groundwater Basin Characteristics

Unconfined alluvial aquifer filled with highly transmissive sands and gravels

Hydraulically connected with Russian River

Alluvial sediments Up to ~100 feet thick near River

Bounded on West by low permeability Franciscan bedrock

Bounded on East by older and less transmissive fluvial deposits (correlative with Glen Ellen Fm)

GainingandLosing

Streams

Stream gains water fromgroundwater

GroundwaterMounds beneaththe stream

Stream loses water togroundwater

US Geological Survey Circular 1139

Assessment Techniques and Methods

Temperature based streambed conductance estimates

Water-Level measurements & vertical gradient analysis

Seepage meters Surface and groundwater quality studies Riverbed sediment sampling program In-situ microsphere studies Geophysical Methods to Evaluate SW-GW

Interactions• Electrical Resistivity• Spontaneous Potential

Measurement of Temperature to Characterize

Surface and Groundwater Interactions

Since 1998, SCWA/USGS have measured temperature

trends of Russian River & shallow groundwater Estimate hydraulic conductivity & streambed conductance using VS2DH (USGS) Able to evaluate seasonal trends

Cost-effective method

Results compare favorably with seepage meters

Temperature data showing upward gradient

Water level data showing upward gradient

Groundwater Flow Models

Questions/Discussion