The Water Quality of Sinking Creek and the Missouri River

The Water Quality Index

A comparison of the quality of different water resources is possible using the Mitchell and Stapp index (8). Their index uses nine weighted indicators of water quality. The value of each indicator measured is converted, by interpolation from a graph, into a Q-value. The indicator's Q-value is then multiplied by a weighting factor to yield a total point value for the indicator. In an ideal world the nine indicator point values would add up to 100. The total value is the Water Quality Index. Streams with indexes of: 90-100 are considered excellent, 70-90 good, 50-70 medium, 25-50 bad and 0-25 very bad.

2004 Sinking Creek Water Quality Data Table

 Measurement

 Test Results

 Q- Value

 Weighting

 Total Points

 Dissolved Oxygen (%Sat.)

 112, 117

94, 93

0.17

 15.98, 15.81

 Fecal Coliform (cells/100ml)

130, 50

41, 58

0.16

6.56, 9.28

 pH

7.4, 7.3

91, 92

0.11

10.01, 10.12

 B.O.D. mg/L

3, 3

65, 63

0.11

7.15, 6.93

 Temperature Change

0.3, .33

91, 92

0.10

9.1, 9.2

 Total Phosphorus mg/L

.91, .08

20. 61

0.10

2.0, 6.1

 Nitrate mg/L

<.25, <25

95, 95

0.10

9.5, 9.5

 Turbidity JTU

10.6, 30,6

75, 52

0.08

6.0, 4.16

 Total Solids mg/L

100, 100

84, 84

0.07

5.88, 5.88

 Overall Water Quality Index = 72.2, 76.98 Ave. = 74.6

 General Rating = Good

200`4 Missouri River Water Quality Data Table

 Measurement

 Test Results

 Q- Value

 Weighting

 Total Points

 Dissolved Oxygen (%Sat.)

 91

97

0.17

16.49

 Fecal Coliform (cells/100ml)

5400

12.5

0.16

2.0

 pH

7.7

89

0.11

9.79

 B.O.D. mg/L

6

47

0.11

5.17

 Temperature Change

1

90

0.10

9.0

 Total Phosphorus mg/L

0.18

49

0.10

4.9

 Nitrate mg/L

<,25

95

0.10

9.5

 Turbidity JTU

27.8

53

0.08

4.24

 Total Solids mg/L

450

40

0.07

2.80

 Overall Water Quality Index =63.89

 General Rating = Medium

 

WQI and River Condition, Years 1987 to 2004
 

Missouri River

Sinking Creek

 Year

 WQI

 Condition

 WQI

 Condition

 1987

-

-

86

Good

 1989

64

Medium

88

Good

 1990

 -

-

87

Good

1991

79

Good

86

Good

1992

78

Good

82

Good

1993

69

Medium

84

Good

1994

63

Medium

78

Good

1995

66

Medium

81

Good

1996

61

Medium

87

Good

1997

70

Medium-Good

91

Excellent

1998

60

Medium

82

Good

 1999

 63

 Medium

 89

 Good

 2000

 62

 Medium

 78

 Good

 2001

 63

 Medium

 84

 Good

 2002

 58

 Medium

 81

 Good

 2003

 67

Medium 

 82

 Good

 2004

 64

 Medium

 74.6

 Good
         


1991-2004 Water Quality Graph


 

Biological Indicators of Water Quality

Besides using abiotic factors to determine water quality, sampling the biological community can help determine how healthy or polluted a stream is. Different organisms have varying tolerances to degraded environments and degraded environments usually support fewer types of organisms. Macroinvertebrates are used more frequently than other animals for biomonitoring because they cannot easily move from a place when conditions change. An advantage of biological sampling (versus chemical testing) is that it looks at indicators of conditions which are present in the stream over a period of time, rather than just at the moment which a water sample is collected.

Biological monitoring uses a table containing lists of sensitive, somewhat-sensitive and tolerant organisms. Checkmarks (X) in the following table show which type of organisms were found to be present in Sinking Creek. To obtain an estimate of the creek's water quality the number of different kinds of organisims in each category was multiplied by a weighting factor. Then the three products were added together to give a total water quality value. Based on the rating scale used the water quality of Sinking Creek is excellent.

Water Quality Rating Scale: excellent (>22), good (17-22), fair (11-16) and poor (<11)

 2004 Macroinvertebrate Count - Sinking Creek
 Sensitive Organisms

 X
 Caddisfly Larvae

 X
 Helgramites

 X
 Mayfly Nymphs

 X
Right-Handed Snails

 X
 Riffle Beetle Adults

 X
 Stonefly nymphs

 6
 Total Kinds of Sensitive Organims X 3 =

 18
 Somewhat-Sensitive Organisms

 X
 Other Beetle Larvae

X
 Clams

 X
Cranefly Larvae 

 X
 Crayfish

 X
 Dragonfly Nymphs

 X
 Damselfly Nymphs
   Scuds
   Sowbugs

X
 Fishfly Larvae

 X
 Alderfly Larvae

8
 Total # of Kinds of Some-what Senitive Organims X 2 =

 16
 Tolerant Organisms

 X
 Aquatic Worms
 Blackfly Larvae

 X
 Leeches

 X
 Midgefly Larvae
 Left-Handed Snails

3
 Total # of Kinds of Tolerant Organisms X 1=

3

   Sinking Creek Water Quality Biotic Value

37

   Sinking Creek Water Quality Rating

 excellent

 




Seasonal Characteristics of Sinking Creek
Drey Land Page
JBS Home Page