Indicator 24.
Percent of Water Bodies in Forest Areas (e.g., Stream Kilometers, Lake Hectares) with
Significant Variation from the Historic Range of Variability in pH, Dissolved Oxygen, Levels of
Chemicals (Electrical Conductivity), Sedimentation, or Temperature Change
100%
Sedm ( > 1sd)
Sedm ( > 1sd)
90%
pH ( < 2sd)
pH ( < 2sd)
80%
pH ( < 1sd)
70%
Cond ( > 2sd)
pH ( < 1sd)
Cond ( > 2sd)
Cond ( > 1sd)
60%
Cond ( > 1sd)
Temp (s > 2sd)
Temp (s > 2sd)
50%
Temp (s > 1sd)
40%
Temp (w > 2sd)
Temp (w > 2sd)
30%
Temp (w > 1sd)
Temp (w > 1sd)
20%
D.O. (s < 2sd)
10%
Temp (s > 1sd)
D.O. (s < 2sd)
D.O. (s < 1sd)
West
North
D.O. (w < 2sd)
North
0%
South
South
D.O. (w < 2sd)
D.O. (s < 1sd)
D.O. (w < 1sd)
West
D.O. (w < 1sd)
0
10
20
Figure 24-2. The relative contribution of each variable to the
effects on aquatic systems within forested watersheds in
counties of each Resources Planning Act region.
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Figure 24-1. Percentage of counties with HUC8 watersheds
that were significantly different from other counties within
each Resources Planning Act region. (Sed=sediment;
pH=water pH; EC=electrical conductivity; T=temperature of
water; DO=dissolved oxygen in water; s=summer; w=winter;
sd=standard deviation of mean).
What Is the Indicator and Why Is It Important?
What Does the Indicator Show?
This indicator measures key chemical and physical
attributes of aquatic health and water quality. Water
temperature (T) is an important aspect of aquatic
habitat and influences metabolism, behavior, and
mortality of aquatic species. Dissolved oxygen (DO) is
essential for most aquatic life. Electrical conductivity
(EC) represents the amount of total dissolved salts
(ions) in the water. The pH of a water sample measures
the concentration of hydrogen ions, and determines
the biological availability of nutrients and heavy metals.
Sediment (SED) is composed of finely divided solid
particles (larger than 0.062 mm) that are transported
by wind, water, or ice and deposited in water. Declines
in water quality indicated by the above variables often
indicate that forest-related management activities and
conversions are having adverse effects on aquatic
ecosystem health, and are affecting drinking water
quality, fisheries, industry, recreation, agriculture,
and other uses.
Generally, high T, low DO, high EC, low pH, and high
SED are indicators of the major problems affecting
aquatic systems. Since nationally standardized data
is available only since 1990, problem areas were
identified by looking at differences in forested counties
within a Resources Planning Act (RPA) region, using
standard deviations (sd) from the mean as a statistical
method to identify abnormal conditions. Greater than
1 (poor) or 2 (bad) sd above or below the mean,
depending on whether low or high values were of
concern, were evaluated for all indicators. DO and T
were the only indicators that showed marked seasonal
differences, so values for both winter (w) and summer (s)
were given. Each RPA region had a significant
proportion (greater than 10 percent) of forested counties
in the poor or bad condition. For example, the west
region’s biggest issues were DO (winter), T (winter and
summer), and SED. The north region’s biggest issues
were T (winter and summer), and EC. The south
region’s issues were DO (winter), T (winter and summer),
EC, pH, and SED.
38