Figure 1. Stanislaus River Weir.

The Stanislaus River Weir fall-run Chinook salmon migration monitoring near Riverbank (RM 31.4) began immediately after installation was completed on September 7 (Figure 1). A total of 66 Chinook were detected by the Vaki Riverwatcher as they passed upstream through the weir between September 7 and 22 (Table 1). Daily passage ranged between zero and thirteen Chinook (Figure 2). The number of Chinook passages observed so far this year is greater than the numbers observed during this period in previous years (Table 1).

Instantaneous water temperature measured at the weir ranged between 62.4˚F and 72.0˚F and daily average water temperature at Ripon (RPN; RM 15) ranged between 67.4˚F and 74.1˚F (Figure 3), instantaneous turbidity ranged between 0.07 NTU and 1.21 NTU (Figure 4), and instantaneous dissolved oxygen ranged between 8.09 mg/L and 9.31 mg/L and dissolved oxygen at Ripon (RPN; RM 15) ranged between 7.8 mg/L and 9.3 mg/L (Figure 5).

Daily average flow in the Stanislaus River at Goodwin Dam (GDW; RM 58) remained stable between 200 cfs and 206 cfs. Flows at Ripon (RIP, RM 15) fluctuated between 185 cfs and 215 cfs (Figure 2). Note: flows downstream of Goodwin Dam may fluctuate from dam releases due to irrigation and other factors.

Table 1. Annual Fall-run Chinook passage prior to September 22, 2003-2010.

 

Figure 2. Daily upstream Chinook passage at the Stanislaus River Weir in relation to daily average flows (cfs) recorded in the Stanislaus River at Goodwin (GDW) and Ripon (RIP), and in the San Joaquin River at Vernalis (VNS), 2010.

 

 

Figure 3. Daily upstream Chinook passage recorded at the Stanislaus River Weir in relation to instantaneous water temperature recorded at the weir, and daily average water temperature recorded in the Stanislaus River at Ripon (RPN) and in the San Joaquin River at Vernalis (VER), Mossdale (MSD) and Rough & Ready (RRI),  2010.

 

Figure 4. Daily upstream Chinook passage at the Stanislaus River Weir in relation to instantaneous turbidity recorded at the weir, 2010.

 

Figure 5. Daily upstream Chinook passage at the Stanislaus River Weir in relation to instantaneous dissolved oxygen recorded at the weir, and daily average dissolved oxygen recorded in the Stanislaus River at Ripon (RPN), and in the San Joaquin River at Mossdale (MSD) and Rough & Ready (RRI), 2010.

The Tuolumne River Weir monitoring downstream of Fox Grove Fishing Access (RM 24) began immediately after installation was completed on September 9 (Figure 6).  A total of 19 Chinook were detected by the Vaki Riverwatcher as they passed upstream through the weir between September 9 and 22. Daily passage ranged between zero and four Chinook (Figure 7).

Figure 6. Tuolumne River Weir fish passage modifications.

Instantaneous water temperature measured at the weir ranged between 66.0˚F and 70.1˚F (Figure 8), instantaneous turbidity ranged between 0.22 NTU and 1.20 NTU (Figure 9), and instantaneous dissolved oxygen ranged between 8.21 mg/L and 9.55 mg/L (Figure 10).

Daily average water temperature at Modesto (MOD; RM 17) ranged between 67.8˚F and 69.5˚F (Figure 8). Daily average flow in the Tuolumne River was stable between 287 cfs and 295 cfs at La Grange (LGN; RM 50) and fluctuated between 417 cfs and 481 cfs at Modesto (MOD; RM 17) (Figure 7). Note: flows downstream of La Grange may be higher than dam releases due to accretion and Dry Creek inflow.

Figure 7. Daily upstream Chinook passage at the Tuolumne River Weir in relation to daily average flows (cfs) recorded in the Tuolumne River at La Grange (LGN) and Modesto (MOD), and in the San Joaquin River at Vernalis (VNS), 2010.

 

Figure 8. Daily upstream Chinook passage at the Tuolumne River Weir in relation to instantaneous water temperature recorded at the weir, and daily average water temperature recorded in the Tuolumne River at Modesto (MOD) and in the San Joaquin River at Vernalis (VER), Mossdale (MSD) and Rough & Ready (RRI), 2010.

 

Figure 9. Daily upstream Chinook passage at the Tuolumne River Weir in relation to instantaneous turbidity recorded at the weir, 2010.

Figure 10. Daily upstream Chinook passage at the Tuolumne River Weir in relation to instantaneous dissolved oxygen recorded at the weir, and daily average dissolved oxygen recorded in the San Joaquin River at Mossdale (MSD) and Rough & Ready (RRI), 2010.