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Faecal Contamination of Rural Waikato Waterways: Sources, Survival, Transport and Mitigation Opportunities

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Report: TR 2010/38
Author: Helen Ritchie and Andrea Donnison (AgResearch)

Abstract

This report reviews information about the origins of faecal contamination in Waikato waterways and the mitigation options available to address this issue.

The focus is on rural farmland. Human sewage is not included in this review, although it affects water quality in some localities.

Faecal Contamination of Rural Waikato Waterways: Sources, Survival, Transport and Mitigation Opportunities (586 kb)

Table of contents

  Executive summary vii
1 Introduction 1
1.1 State of knowledge 1
1.2 Gastrointestinal disease 1
1.3 Water quality microbial indicators 3
1.4 Comparability of transport patterns with sediment transport pathways 4
2 Sources of faecal organisms 5
2.1 Direct deposition to water 5
2.2 Faeces deposited during grazing 7
2.3 Effluent irrigation 9
2.4 Effluent ponds 9
2.5 Wild animals 10
3 Survival and reservoirs 11
3.1 Conditions for survival 11
3.2 Growth and survival in animal faeces 13
3.3 Survival in soil 14
3.4 Streambed sediments 14
3.5 Survival in wetlands 15
3.6 Survival in effluent ponds  16
3.7 Stand-off pads 16
4 Transport and entrapment 16
4.1 Rainfall events and flow  17
 4.1.1 Subsequent events  17
 4.1.2 Flow affecting entrapment  18
 4.2 Topography  18
4.3 Soil types 19
4.4 Sub-surface flow 21
4.5 Laneways, tracks and yards 22
4.6 Drain transport and attenuation 22
5 What are the most important factors affecting faecal contamination? 23
5.1 Multi-variate analysis comparing Waikato catchments 23
5.2 Determining the relative importance of different sources 24
5.2.1 Stock type 25
5.2.2 Wild animals vs stock 26
5.3 Direct deposition vs run-off 28
5.4 Comparative loadings 30
5.5 Assessing critical source areas in a landscape 32
6 Mitigation 33
6.1 Land use change 34
6.2 Stock exclusion and crossings 34
6.3 Riparian buffers and grass filter strips 36
6.3.1 Flow characteristics 37
6.3.2 Buffer zone width 38
6.3.3 Vegetation 39
6.4 Management of lanes, tracks and other 'hotspots' 39
6.5 On-off grazing of crops 40
6.6 Avoiding high-risk practices on some soils and locations 40
6.7 Effluent management 40
6.8 Drain management, settling ponds and constructed wetlands 41
6.9 Can mitigation practices achieve water quality standards? 42
7 Relevance of practices in the draft Regional Policy Statement 43
8 Conclusions 46
  References 48
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