Table 1 Summary statistics for biophysical parameters describing the 77 catchments of the National River Water Quality Network.

From: The implications of lag times between nitrate leaching losses and riverine loads for water quality policy

Variable

Mean

SEM1

Minimum

Quartile 1

Median

Quartile 3

Maximum

Data source

Area (km2)

2640

423

15

435

1130

3229

20,540

75

Population

13,393

4403

3

240

2513

7227

297,098

76

Mean slope (degrees)

4.2

0.3

0.7

2.3

3.3

6.1

12.6

75

Mean altitude (m)

621

33.0

63

370

638

815

1424

75

Mean monthly rainfall (mm)

148

4.8

69

126

139

160

308

75

Mean monthly runoff (mm)

77

4.6

5

55

69

90

228

77

Baseflow fraction

0.36

0.02

0.03

0.19

0.29

0.48

0.88

2

Olsen P (mg kg−1)

32

0.8

23

27

32

36

60

78

Intensive agricultural land (%)

41.7

3.6

0

14.0

34.8

66.8

99.9

79

Forest (%)

53.7

3.7

0.1

24.8

57.6

81.2

100.0

79

Rangeland (%)

4.4

1.0

0

0.3

1.2

3.8

52.2

79

Strahler stream order

5

0.2

2

5

6

6

8

80

Potential monthly evapotranspiration (mm)

51.2

0.5

39.6

47.3

51.5

54.9

61.4

81

  1. Geology was added as a categorical variable assigned to either sedimentary, metamorphic or volcanic74.
  2. 1SEM standard error of the mean.
  3. 2Calculated according to the method of Pelletier and Andréassian55.
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