Preview

Contaminants and numbers

Nitrogen

The estimated reduction in nitrogen to achieve just the national bottom lines is 47%. To achieve the proposed Southland Water and Land Plan standards the reduction required is 66%, and to achieve the draft Murihiku Southland freshwater objectives it is 70%.

Find out more about what nitrogen and some of the modelled results here.

Phosphorus

The estimated reduction in phosphorus to achieve just the national bottom lines is 21%. To achieve the water quality standards detailed in the proposed Southland Water and Land Plan the reduction is 69%, and to achieve the draft Murihiku Southland freshwater outcomes it is 70%.

Find out more about phosphorus and the modelled results here.

E. coli

The modelling shows E. coli load reductions of around 90% are required to achieve the draft Murihiku Southland freshwater outcomes. To achieve the standards in the proposed Southland Water and Land Plan was only slightly less, 82% reduction in E. coli.

Find out more about E. coli and the modelled results here.

Sediment

The total regional reductions in sediment load needed to achieve the draft Murihiku Southland freshwater objectives are: 24% - to achieve the suspended sediment objective in rivers; and 32% - to achieve the visual clarity objective in rivers.

Find out more about sediment and the modelled results here.

For each of these contaminants you'll also find the estimated reductions catchment by catchment.

Find out more about the work and reports of the draft Murihiku Southland Freshwater Objectives here.

How these estimates were developed

The estimates of reductions have been completed using the best possible science and models that have been published in peer-reviewed international science journals.

The models used are the same as those used by the Ministry for the Environment to inform the National Objectives Framework in the National Policy Statement for Freshwater Management and are either similar or are more recent updates to those used to inform limit setting processes in other regions.

Fiordland and Stewart Island are not included in the modelling as no reductions need to be achieved in these areas. This is where the recent national work on nitrogen reductions differs from the results we’ve found for Southland. The national work modelled the whole country, including all national parks. We’ve done a more appropriate, closer look at our Southland river catchments, and therefore, have removed the modelling information for Fiordland and Stewart Island.

You can read the full reports here:

Report - E. coli load reduction modelling in rivers (LWP) (PDF, 3.7MB)

Report - E. coli state and rainfall effects (ESR) (PDF, 2.4MB)

Report - Microbial indicators and Faecal Source Tracking (ESR) (PDF, 1.2MB)

Report - Nutrient load reduction modelling - lakes, rivers, estuaries (LWP) (PDF, 3.3MB)

Report - Nutrient load reduction modelling - estuaries (NIWA) (PDF, 1.7MB)

Report - Sediment load reduction modelling (Manaaki Whenua) (PDF, 3.6MB)

Table of load reductions needed for each of the reporting catchments:

Reporting catchment

Total Nitrogen reduction (%)

Total Phosphorus reduction (%)

E. coli reduction in rivers (%)

Sediment reduction in rivers (%)

Visual clarity

Suspended sediment

Waiau catchments

Waiau Catchment (Waiau Estuary)

66 (38-83)

92 (89-95)

86 (64-96)

25

6

Te Waewae Bay Western Coastal Zone

1 (0-4)

3 (0-7)

64 (40-85)

3

1

Aparima catchments

Aparima & Pourakino Catchment (Jacobs River Estuary)

64 (34-81)

34 (18-43)

74 (38-93)

6

22

Waimatuku & Taunamau Catchments

69 (50-82)

43 (3-71)

86 (71-95)

55

33

Orepuki Coastal Zone

42 (32-52)

28 (14-48)

85 (77-90)

20

10

Ōreti catchments

Bluff Zone (Bluff Harbour & Awarua Bay)

14 (8-21)

94 (91-95)

65 (49-78)

40

2

Ōreti & Invercargill Catchments (New River Estuary)

62 (54-79)

75 (61-86)

89 (73-100)

48

29

Matāura catchments

Waituna Catchments (Waituna Lagoon)

90 (85-95)

62 (37-80)

78 (50-93)

84

61

Matāura Catchments (Toetoes Estuary)

79 (67-89)

58 (37-70)

89 (76-98)

35

49

Tokanui Coastal Zone

23 (11-43)

13 (5-26)

91 (79-102)

48

15

Waikawa Catchment (Waikawa Harbour)

50 (12-74)

32 (0-63)

86 (72-95)

54

16

Catlins (Longbeach) Zone

2 (0-8)

0 (0-0)

69 (46-86)

22

0

Total

70 (61-78)

70 (62-77)

90 (80-96)

32

24

Note: the numbers in brackets provide the top and bottom of the 90% confidence interval. The figures in this fact sheet use a 20% exceedance criteria.