Hydrography of the Russian River Estuary - Sonoma County Water ...

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still strong, due to continued trapping of high-salinity water at depth (Figure 3.31). Ri remains low in the surface mixed layer, down to -2m NGVD, but increases below that due to stratification in the upper pycnocline. Figure 3.31. Profiles of density, velocity, and Ri at Heron Rookery on 6 October. Where continuous vertical profiles of density or velocity are not available, one can calculate the bulk Richardson Number from top-bottom differences in current speed and water density: Ri Δ = Δρ g h / ρ 0 U 2 [Eq. 8] where Δρ is the surface-bottom difference in density, h is the depth of the water column, and U is the vertically-averaged flow velocity – and the critical value is taken as 1. Hourly density data are available from sondes deployed at the bottom, middle, and top of the water column at Paddy's Rock, and at the bottom and two mid-depth locations at Heron Rookery. Hourly velocity data are available from ADCPs at these sites. Ri Δ estimates were made at Heron Rookery only when the surface was known to be fresh, on the basis of surface salinity observed at Sheephouse Creek. This approach allows a time-series of Richardson Number estimates, although it does not resolve differences over depth. The Paddy's Rock time-series confirms that the water column was stratified during the entire June-July 2009 period, despite spring-neap variations in tidal amplitude and river inflows that varied from 70-140 cfs (Figure 3.32). While Ri Δ never approached 1, it does vary strongly with the tide, changing by two orders of magnitude, most noticeably as 48
diurnal variations during the spring tides in mid-July. Although velocity data are not available at the mouth, the observation of an isopycnal water column at the mouth (e.g., Figure 3.28) suggests that indeed Ri Δ would decrease below 1 at that station. Figure 3.32. Time-series of bulk Richardson Number Ri Δ at Paddy's Rock during July 2009. Dashed line indicates Ri Δ = 1. The Heron Rookery time series shows the tendency for mixing during inlet breach events (Figure 3.33). At all other times, Ri Δ is well over 100 (in contrast to Paddyʼs Rock). Weak diurnal fluctuations in Ri Δ are observed during the September closure events, a response to wind-driven seiche. Figure 3.33. Time-series of bulk Richardson Number Ri Δ at Heron Rookery during September-October 2009. Dashed line indicates Ri Δ = 1. 49
Page 1 and 2: HYDROGRAPHY OF THE RUSSIAN RIVER ES
Page 3 and 4: Executive Summary Circulation, stra
Page 5 and 6: Table of Contents 1. Introduction .
Page 7 and 8: 1. Introduction The Russian River B
Page 9 and 10: The study was conducted from June t
Page 11 and 12: attached to each ADCP, and a third
Page 13 and 14: 3. Data Analysis The results from s
Page 15 and 16: existing SCWA-management protocol t
Page 17 and 18: 7. Loss to aquifers: This term quan
Page 19 and 20: Figure 3.7). A concurrent drop in e
Page 21 and 22: Histograms of the probability of fl
Page 23 and 24: Figure 3.8. Observed flow losses du
Page 25 and 26: easily over denser estuarine waters
Page 27 and 28: 3.2.2 - Current velocities at Heron
Page 29 and 30: Figure 3.14. Water levels (top pane
Page 31 and 32: This diurnal cycle in winds results
Page 33 and 34: Figure 3.18. Observed water levels
Page 35 and 36: All water properties are subject to
Page 37 and 38: 3.3.2 - Salt intrusion into inner e
Page 39 and 40: Figure 3.22. Water temperatures dur
Page 41 and 42: On closer inspection, one can see t
Page 43 and 44: Preliminary biochemical oxygen dema
Page 45 and 46: 3.4 - Stratification and water-colu
Page 47: Figure 3.29. Profiles of density, v
Page 51: Using CTD profiles of ρ(z), time-s
Page 54 and 55: Figure 3.36. Decreasing bottom sali
Page 56 and 57: Figure 3.37. Estuary bathymetry fro
Page 58 and 59: water) or it may reflect vertical m
Page 60 and 61: Figure 3.40. Nearshore wave height,
Page 62 and 63: Figure 3.41. Change in dissolved ox
Page 64 and 65: • Instrument precision The error
Page 66 and 67: Table 3.3. Error estimates for estu
Page 68 and 69: unaffected and remains resident for
Page 70 and 71: 5. Literature Reviewed Battalio, B.
Page 72: Simpson, J., J. Brown, J. Matthews,

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