Between September 19 and October 2 a total of 119 Chinook salmon were detected by the Vaki Riverwatcher as they passed upstream of the Tuolumne River weir, increasing the season total to 128 (Figure 1). Daily passage ranged between 2 and 14 Chinook. While monitoring began a week later this year relative to 2010, the number observed so far in 2011 exceeds the annual count as of the same date in 2010 (Table 1).

Daily average flow in the Tuolumne River ranged from 264 cfs to 342 cfs at La Grange (LGN; RM 50) and from 465 cfs to 562 cfs at Modesto (MOD; RM 17) (Figure 2). Note: flows downstream of La Grange may be higher than dam releases due to accretion and Dry Creek inflow.

Instantaneous water temperature measured at the weir ranged between 64.5˚F and 69.6˚F and daily average water temperature at Modesto (MOD; RM 17) ranged between 66.4˚F and 69.6˚F (Figure 3). Instantaneous turbidity ranged between 0.17 NTU and 2.11 NTU (Figure 4), and instantaneous dissolved oxygen ranged between 8.29 mg/L and 10.57 mg/L (Figure 5).

Table 1. Annual Fall-run Chinook passage at the Tuolumne River Weir prior to October 2, 2009 - 2011.