Water Quality

Background and Problem

According to a report funded and published by the State Water Resources Control Board in 2010 (Roadmap to Watershed Management, 2010) protecting the high quality waters of the Fall River remains a high priority management issue for the state.

YSI Testing Equipment
Photo Credit: Val Atkinson

From 2001 to 2005, the Pit River Alliance and the Central Valley Regional Water Quality Control Board (RWQCB) conducted a water quality study, which established the following baseline conditions:

  1. temperature range: 9C to 18C
  2. pH: 8 to 9
  3. turbidity: 2 to 4 NTU (with occasional spikes)
  4. fecal coliform bacteria: 20 to 100 MPN (with occasional spikes)
  5. nitrate: 0.1 to 0.22 mg/l

Findings from this study indicated that existing bacteria levels in the river have decreased from levels reported in the 1980’s. Minimizing bacteria concentrations, however, should remain the primary management objective for conservation groups and state and federal regulators. According to the study, “Other water quality-related issues on the Fall River include bank erosion from livestock trampling, irrigation tailwater discharge, and channel and riparian habitat impacts from muskrat burrowing.

Additional Fall River water quality data can be found here:


Key Findings from this report:


  1. Fall River summer temperatures show significant warming from near the headwaters (Fletchers Bridge – FR1) to near the PG&E Diversion (Fall River Ranch Bridge – FR7)
  2. Daily maximum river temperatures increase through this reach by about 15°F
  3. All Fall River and tributary sites monitored show year round temperature regimes supportive of trout and other cold water species except for Tule River above the Fall River confluence, and Fall River pond in the town of Fall River Mills
  4. Both seasonal and diel (daily) temperature variation in the Fall River and tributaries is low relative to other typical surface water bodies (diel temperature variation ranged from 3 to 7°F during the summer period)


  1. Turbidity in Fall River generally ranged from 0 to 5 NTU and is typically less than 2 NTU
  2. One elevated turbidity event occurred on 19 Feb 2004 throughout Fall River from a heavy rainfall event in the watershed
  3. Elevated turbidity at the Tule River sites probably results from the presence of algae rather than soil particles in the water column

Fecal Coliform Bacteria:

  1. Fall River and tributary sites infrequently exceeded the Basin Plan fecal coliform objective (maximum of 400 MPN for protection of contact recreation)
  2. Only 2 of 271 samples exceeded 400 MPN. There were 10 individual exceedences of the 200 MPN (mean) objective, however, when all sites are averaged, none of the monthly sample dates exceeded 200 MPN during the study period
  3. Fecal coliform bacteria concentrations in Fall River are commonly in the range of 20 to 100 MPN and this should be a concern for residents that take their domestic water supply directly from the River
  4. Management practices that minimize bacteria transport to the River should continue to be promoted
  5. A seasonal trend in fecal coliform bacteria showed higher levels in summer and lower
  6. levels in winter
  7. The levels and duration of fecal coliform exceedance of the Basin Plan objective do not appear to justify listing the Fall River system as ‘water quality impaired’ for this parameter

E. Coli Bacteria

  1. As with fecal coliform bacteria, E. coli infrequently exceeded recommended water quality criteria for protection of contact recreation, however the levels and frequency of exceedance do not appear to justify an impaired waterbody listing for E. coli concentrations
  2. E. coli findings are similar to that for fecal coliform bacteria, i.e. seasonal trends show higher summer concentrations as compared to winter, and typical Fall River E. coli concentrations are at levels which should at least be a concern to those taking domestic household water supplies directly from the river
  3. Bacteria concentrations (both fecal coliform and E. coli) in ambient waters are highly variable and one must use caution in determining the significance of any single sample results

Nitrate Nitrogen

  1. Nitrate levels were about twice as high in the fall/winter months as the spring/summer months at the River and tributary sites
  2. This likely results from weed and algae uptake during their period of high growth
  3. Upstream Fall River sites (FR1, FR2, & FR4) averaged about twice the levels of nitrates as downstream sites (FR 6, FR7, & FR8), based on limited data from the latter sites
  4. This again is probably the result of nutrient uptake from weed growth
  5. The relatively low nitrate values – sometimes non-detectable – indicates that nitrogen may be a major limiting factor in growth of weeds and algae


Leave a Reply