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Draft Final Report Acwa-08-05 - Continuation Of Lower Nushagak River Fecal Coliform And Water Quality Assessment - Alaska Department Of Environmental Conservation - 2008 Page 13

DRAFT Final Report ACWA-08-05

8 October 2008

Between 1979 and 1986, the USGS recorded turbidity in the lower Nushagak River at Ekwok on 36

separate occasions (USGS, 2008). The May 2008 turbidity levels in the lower Nushagak River, on

average, showed a three-fold increase from the highest turbidity reading of 8.1 NTUs on June 6, 1985 by

the USGS over that time period (Table A1). The elevated turbidity in the river in May, accompanied with

the spike in fecal coliform concentrations suggest that more intensive monitoring of the river

immediately following breakup may be warranted.

It is also interesting to note that the sampling period when water quality was at its lowest did not

correspond with one of the assumptions in our study design, which was that water quality would decline

during peak human activity on the river (in August, September and June). During those times, fecal

coliform concentrations in the lower Nushagak were relatively low as compared to the May sampling

event, although they were not as low as they were in October, when recreational activities on the river

had waned for the year. Again, the magnitude of the May spike in turbidity and corresponding spike in

fecal coliform concentrations may warrant further investigation.

Recommendations for future monitoring

The results of this study add additional data to a growing water quality data set on the lower Nushagak

River. In light of the results of this latest study, we make the following recommendations for future

monitoring efforts:

1) Investigate the duration and intensity of the spike in turbidity and fecal coliform concentrations

in the lower Nushagak River after breakup. Infrequent sampling to date has painted a hazy

picture of the temporal changes in water quality in the river. More concentrated sampling

efforts during times when conditions are most degraded may help to determine the causes of

degradation.

2) Continue to involve local monitors and guides in water quality monitoring. These folks have

developed expertise in collecting data and have invaluable knowledge of the region. They have

the largest vested interest in monitoring Nushagak River water quality, as the river is the

lifeblood of their communities.

3) Collection of bacteriological information, in addition to fecal coliform, to help determine the

source(s) of the fecal bacteria in the river. Fecal coliform has many sources, including all warm-

blooded wildlife, whereas E. coli may prove to be a better estimator of human sources of fecal

bacteria in a waterbody.

Page 13

Draft Final Report Acwa-08-05 - Continuation Of Lower Nushagak River Fecal Coliform And Water Quality Assessment - Alaska Department Of Environmental Conservation - 2008 Page 13

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