Watershed health — Lower Columbia update

We investigated the health of stream habitats in the Lower Columbia Status and Trends Region in 2010, 2014, and 2023. Data from 2010 and 2014 show a majority of good biological conditions, but there is widespread poor relative bed stability. 2023 data are under review.

Photo of large wood spanning the stream

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Regional summary

  • B-IBI scores in the Lower Columbia Region show a similar number of streams in good biological condition, but the proportion of streams in poor condition appeared to increase.
  • The most prevalent stressors for streams in the Lower Columbia Region were poor relative bed stability, elevated nitrogen concentrations, low dissolved oxygen, and elevated sand/fines percentages.

Biological condition

Invertebrate biological condition of streams, as assessed with B-IBI scores, did not change significantly from 2010 to 2014 in the Lower Columbia Region. However, the proportion of streams classified as fair decreased, and those classified as poor increased. These results were not significantly different and will require another round of sampling to see trends.

From 2010 to 2014, the percentage of 'Good' qualifying streams stayed the same, while 'Fair' streams decreased and 'Poor' streams increased.

We used B-IBI ratings from 2010 & 2014 to obtain the percentage of stream kilometers in good, fair, and poor conditions for the Lower Columbia Region. Error bars represent 95% confidence intervals.

Significant physical and chemical stressors

In the Lower Columbia Region, the number of stream kilometers with poor riparian shade cover at the stream bank improved between 2010 and 2014. Similar to many other regions, substrate-related attributes were among the worst stressors. These included bed stability, sand/fines, embeddedness, and suspended solids. High nitrogen and poor dissolved oxygen, chemical stressors, were also prevalent in the Lower Columbia Region.

To interact with this graph and learn more about these physiochemical stressors, hold your mouse over each bar.

This interactive graph shows the percentage of stream kilometers assessed with poor physiochemical conditions in the Lower Columbia Region for 2010 and 2014. The x-axis represents the percentage of river extent in poor condition. Error bars show 95% confidence intervals.

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