A paired-watershed study is conducted by using two similar watersheds and evaluating them for differences. One watershed is a control and the other has a management change applied to it. You can then measure the differences in flow and water quality exiting the watersheds, and have a pretty good idea of how the management change influenced any flow or water quality changes. Or in this case, with no management applied, the differences reveal natural differences in the watershed.
February 2020 was the driest February since 1864 in San Francisco. No rain fell there, as well as here in San Geronimo Valley (except for one weather station (WDAC1) that picked up 0.01 inches of precipitation on February 24th). December precipitation was 200% of average, however January was only 37% of average. February was 0% of average.
San Geronimo Creek peaked at a respectable 210 cfs in December--the highest December flow in 3 years, but less than 1/10th the peak flow in 2016--a good situation for Coho salmon redds, which got plenty of water but wouldn't have been washed out by flows high enough to scour the streambed. Since there weren't that many redds this year, a higher survival rate would be nice. January's peak flow was 70 cfs. February's was 6 cfs--perhaps the lowest February flow since 1864.
