ONLINE MEETING, GRA NorCal: A Tale of Two Waters? Groundwater and Surface Water-an Interconnected Resource

November 19, 2020 @ 12:00 pm – 1:00 pm

Groundwater and surface water are often treated as two different water resources, but groundwater and surface water regularly interact with one another, and should be managed as a single interconnected resource.

Big Chico Creek (BCC) is an important ecological and recreational feature for the Chico area. The City of Chico and the majority of the surrounding agricultural lands are fully dependent on groundwater as a water source. To improve our understanding of stream-aquifer interactions between BCC and the underlying aquifer we took bi-weekly to monthly streamflow measurements at six locations between Bear Hole in Upper Bidwell Park to the confluence with the Sacramento River (i.e. BCC01 through BCC06). From June through November 2020, BCC was an entirely losing stream (i.e. water flowed from the stream to the aquifer) from BCC02 (5 Mile Bridge) to the confluence of the Sacramento River. By late June, BCC no longer reached the Sacramento River. By mid-July, BCC went dry just downstream of the Rose Drive bridge in west Chico. For the duration of the study to date, losses were roughly 0.05 m3 s–1 km–1 from BCC02 to BCC05.

We recommend that student-led efforts should both continue and expand stream flow measurements (including other creeks) to better understand spatial and temporal trends in stream-aquifer interactions in the region. Installing dedicated shallow groundwater monitoring wells would nicely supplement the streamflow data by measuring adjacent groundwater levels and temperature.

Additionally, characterizing groundwater-surface water interaction is essential and a required component of Groundwater Sustainability Plans. The presentation will include how this topic surfaces in the Basin Setting work of the Vina and Butte Subbasins related to Groundwater Dependent Ecosystems and interconnected surface waters.

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