5. Findings to date

5.1 Temporal and spatial distribution of sampling

Sampling and measurement of E. coli and Enterococcus sp. was infrequent throughout the watershed before 2001 and since then has been consistently in the summer with less frequent first-flush and winter/wet-season sampling (Figures 5 & 6). Sampling stations for the 4 primary monitoring programs are fairly spread out throughout the watershed, with most sites being in the lower and Southern parts of the watershed (Figure 1). Enterococcus sampling was much more restricted temporally and spatially than E. coli. The highest Enterococcus concentrations were in Santa Rosa Creek/Prince Memorial Greenway. Interestingly, after the high concentrations were found in 2001, Enterococcus concentrations were not measured again in Santa Rosa Creek, even though E. coli concentrations were measured at the same sites and thus grab samples could have been available.

5.2 Daily and monthly concentrations

Concentrations of fecal bacteria can change dramatically over short time periods (e.g., during storms) necessitating frequent sampling during those periods. Meays et al. (2006) found that measured E. coli concentrations could vary over

24 hour periods by as much as 30-fold, depending on when samples were taken. Previous sampling in the Russian River watershed shows that summer concentrations don’t vary as much among days in a given week or month, but wet season concentrations can vary widely (Figure 5). There is also considerable variation between the mean monthly E. coli concentrations in spring/summer and fall/winter (Figure 7). This is probably due to storm runoff and high in-stream flows causing the most input and suspension of fecal matter and bacteria. There were insufficient Enterococcus data to justify calculation of monthly mean concentrations.

5.3 Event loading and sampling

Storm events may contribute to water quality issues by overwhelming control facilities (e.g., ponds) or by suspending settled material in the channel benthos and floodplain. Non-storm events (e.g., exceptionally low flows) may have different time-spans than storms, but may provide exceptional conditions that contribute to overall water quality problems and require special sampling approaches.

5.4 Seasonal loading and sampling

Seasonal fluctuations in flow, water temperature, land-use practices, recreational uses, and in-stream biotic conditions and processes may all affect the storage and potential propagation of live pathogens. Winter conditions will tend to not contribute to in situ growth of pathogens, but may provide disturbing and flushing flows. Summer conditions will tend to contribute to both in situ growth and sources of pathogenic bacteria. In the Russian River watershed, fecal bacteria concentrations are highest in the late fall and early winter, when the first large storms occur. The measured concentrations are well above federal limits, but there is also not much contact recreation in waterways at this time. The high concentrations after storms may be due to inputs of fecal material from overland flows, or disturbance of existing sources in-stream, or in newly inundated areas.

5.5 Long-term change and sampling

In order to track deteriorating conditions or conversely to measure performance of management programs, specific measures should be consistently taken during a long-term monitoring program. The number and frequency of samples and variation in measurements will determine the accuracy of reporting of effective management of pathogenic bacteria. Currently, the sampling program in the watershed includes consistent sampling on the main-stem Russian River during all times of year and inconsistent sampling in sub-watersheds. This will make performance of control programs difficult to ascertain due to the fact that sub-watersheds are the sources of fecal matter and that wet season loading from sub-watersheds may be the cause of summer/recreational season problems.

5.6 Spatial distributions of mean concentrations

Because of the varied potential point and non-point sources of pathogenic bacteria in the watershed, the sampling site selection should efficiently capture the sources as separately as possible. This means identifying the lowest number of sites that also provide information about sub-watershed sources and particular watershed uses. Existing sites provide the highest resolution in the lower, more developed areas of the watershed (Figures 1 and 8). Mean concentrations at tributary sites in the lower watershed (e.g., Laguna de Santa Rosa) are regularly above federal limits, whereas mean concentrations on the mainstem Russian River are generally below the limits.

5.7 Sub-watershed loading

Spatial distribution of sampled sites should capture inputs from

individual sub-watersheds, with resolution at least at the Santa Rosa Creek scale. Figure 9 shows one possible grouping scenario, with relatively gross resolution. When means of all E. coli concentrations are calculated for each group, there appear to be differences among them (Figure 10). However, because the ranges of values used include dry-season baseflows (low concentrations of E. coli) and wet season storm flows (high concentrations), there is overlap among the groups. In general, tributary concentrations are higher.

Land-use association

5.8 Association with benthic algae

E. coli and Enterococcus have been found to be associated with Cladophora sp. in surface waters and beach sands (Whitman et al., 2003). These bacteria can survive 6 months at 4oC in dried algae, suggesting that these algae are an important secondary source of fecal bacteria.

In the Russian River, E. coli were found associated with live benthic algae and benthic sediments at recreational beaches during the summer (Figure 9). Although this association was not characterized fully, it is consistent with associations reported in the scientific literature.