Tracing groundwater/surface water interactions

Tracing groundwater/surface water interactions

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Understanding the origin of our water sources has grown increasingly important with the concerns of future shifts in climate. The Fairfield Osborn Preserve is located on a faulted, erosion- dominant hillslope environment underlain by basalt and other volcanic formations. During the wet and dry seasons, the preserve contains a combination of ephemeral and perennial channels, as well as perennial groundwater springs.  We investigated water chemistry to better understand the relative percentages of groundwater and surface water on Sonoma Mountain, and make more accurate predictions of groundwater storage within Sonoma Mountain.

Obrien et al 2019: When water makes contact with rocks, material is taken off the rocks and put dissolved solids into the water source. We tested spring and creek water at the Fairfield Osborn Preserve for conductivity content and ion concentrations.

Ivani et al 2019: In a previous study, we used total dissolved solids to show the higher conductivity present in groundwater compared to rainwater; we determined Copeland Creek to be a mixture of both. Basalt groundwater systems are known to have higher concentrations of calcium ions, while having lower concentrations of potassium ions. In this study, we observed the change in ion composition along Copeland Creek on the Fairfield Osborn Preserve on April 13th. We used a chloride, calcium, and potassium ion selective probe to track ionic composition while sampling downstream along the creek. Where the ion concentration increased, we conclude that groundwater is being discharged into the creek. Having the ability to track our sources of groundwater can prove helpful in water management to ensure that we use our limited supply consciously and efficiently.

Lawrence and Glas 2019: We monitored the shallow groundwater response to precipitation events near a perennial spring on the west side of a “mole track” ridge at the Fairfield Osborn Preserve. Preliminary results show a strong response to precipitation in the shallow subsurface.

A Watershed Year is a freshman year experience that introduces students to local watersheds as they learn about science. The course focuses on teaching students how to conduct their own research. Course development was funded by National Science Foundation.


Project Results
Title Format Download Students
"Water sources and flow paths on Sonoma Mountain: tracing groundwater- surface water interactions with dissolved ion chemistry" poster Justin DiGennaro, Matt Ivani, Ethan Herlihy, Bradley Ancora
"Evidence of Water-Rock Interactions in FOP" presentation Matt Ivani, Justin DiGennaro, Soledad Ortiz, Michaela O’ Brien
"Investigating Groundwater-Atmosphere Connectivity in a Headwater System" poster Lawrence Thompson
Osborn rainfall data data Lawrence Thompson
Osborn well data data Lawrence Thompson