25 Apr Thal-what? Thalweg?

Hello! I’m Joseph Batom, GOGA Hydrology intern, welcome back to my blog. Learning and exciting experiences continue at the beautiful Golden Gate National Recreation Area. I’ve found myself getting excited to talk and learn about streams!

I went out on a field day with Alex Iwaki of SFAN I&M to complete water quality sampling at Point Reyes. We drove around to multiple sites in the area with bottles to collect water samples, and we put a fancy computer with a probe, known as a YSI, into the water to read water quality metrics like temperature, dissolved oxygen, turbidity, and conductivity. After collecting all of our samples, we took them back for processing and testing. While out sampling, Alex mentioned the “Thalweg” of a creek, which I discovered was the deepest portion of a channel. I quite liked the word the first time I heard it, and I knew I had to include it in my next blog post. I’ve been trying to learn all of the associated vocabulary with my study systems, as well as trying to incorporate the words into conversations. “Thalweg” is a great conversation starter for sure, and it brings me joy whenever I hear someone else use it and I understand what it is that they are describing.

I was also able to participate in winter habitat mapping at Muir Beach! Each year, potential habitat for wildlife, primarily turtles and salmon, is assessed at Muir Beach. What we search for are pools with depth, cover (proximity to vegetation/woody debris), and relatively low flow. Ideal habitat is typically characterized by log jams, undercut banks, and low flow pools. Log jams are areas where woody debris has built up to create lots of nooks and crannies that a salmon may reside in. Undercut banks are typically created by erosion from high flow–water impacts the bank at a high velocity and scours out sediment, creating a pocket that is covered. Low flow pools provide good habitat in tandem with woody debris or overhanging vegetation. To assess the area for potential habitat, I walked around with hydrologist Karl Kindall and we looked for these various habitat features, and added them to an existing map in order to produce an updated map with all of the new habitat features included. We walked from the beach upstream in our waders, measuring various habitat features with transect tape and a rangefinder. Given the recent rainfall, the water was quite turbid, so a wading stick was essential. Before each step, I poked around to ensure that I wouldn’t submerge myself in a deep pool upon moving forward. The day was long, but I learned a lot about wildlife habitat in creeks. Since mapping, I’ve found myself identifying habitat in all the creeks I end up in for work.

Thank you for reading my blog post! As always, I have some more cool pictures to share: