Trends in River Health of the Manawatu-Wanganui Region 2008 with Comments on the Soe Biomonitoring Programme
Total Page:16
File Type:pdf, Size:1020Kb
Trends in river health of the Manawatu-Wanganui region 2008 with comments on the SoE biomonitoring programme Stark Environmental Report No. 2008-07 August 2008 Cover Photograph: Whanganui River at Te Maire (Ohinepa Reserve). J.D. Stark, 11 December 1988. © Copyright: Apart from any fair dealing for the purpose of study, research, criticism, or review, as permitted under the Copyright Act, this publication must not be reproduced in whole or in part without the written permission of the Copyright Holder, who, unless other authorship is cited in the text or acknowledgements, is the commissioner of the report. Trends in river health of the Manawatu- Wanganui region 2008 with comments on the SoE biomonitoring programme John D. Stark Prepared for Horizons Regional Council Stark Environmental Limited P.O. Box 1831 Nelson 7040, New Zealand. Ph. +64 3 545 1766 [email protected] Recommended citation: Stark JD 2008. Trends in river health of the Manawatu-Wanganui region 2008 with comments on the SoE biomonitoring programme. Prepared for Horizons Regional Council. Stark Environmental Report No.2008-07. 61p. Stark Environmental Report No. 2008-07 August 2008 TABLE OF CONTENTS INTRODUCTION ...................................................................................................................... 1 METHODS ............................................................................................................................... 2 Timeline of SoE monitoring in Manawatu-Wanganui ......................................................................................... 2 Macroinvertebrate sampling methods ................................................................................................................. 4 Sampling sites ....................................................................................................................................................... 4 Trends testing methodology ................................................................................................................................ 7 Benjamini & Hochberg FDR..................................................................................................................................... 7 RESULTS ................................................................................................................................. 8 Trends in river health based on MCI and QMCI .................................................................................................. 8 Whanganui River ................................................................................................................................................... 10 Oroua River ........................................................................................................................................................... 11 Manawatu River ..................................................................................................................................................... 12 Makakahi River ...................................................................................................................................................... 14 Are these trends in biotic indices significant or not? ...................................................................................... 14 Evaluation of river health in the Manawatu-Wanganui region ......................................................................... 15 DISCUSSION ......................................................................................................................... 19 PRESENT STATE AND TRENDS IN RIVER HEALTH ........................................................................................ 19 GENERAL COMMENTS ON SOE MONITORING ................................................................................................ 24 Design criteria ...................................................................................................................................................... 24 Collect data that provide information for water managers .............................................................................. 25 Statistical requirements ...................................................................................................................................... 25 Statistical power .................................................................................................................................................... 25 Coping with variability ............................................................................................................................................ 26 How much precision do you really need? .............................................................................................................. 27 Methods consistency .......................................................................................................................................... 28 Sampling strategies ............................................................................................................................................ 28 How many SoE monitoring sites should there be? .......................................................................................... 30 Scope of SoE monitoring ....................................................................................................................................... 30 SPECIFIC COMMENTS ON HORIZONS’ SOE MONITORING ............................................................................ 31 Recommendations for future SoE monitoring .................................................................................................. 31 Number of sites ..................................................................................................................................................... 31 Site selection ......................................................................................................................................................... 32 SoE sampling strategies ........................................................................................................................................ 32 SoE sampling methods and indices for reporting .................................................................................................. 32 Compatibility with existing methods and existing data ........................................................................................... 33 Responses to additional questions ................................................................................................................... 34 ACKNOWLEDGEMENTS ...................................................................................................... 38 REFERENCES ....................................................................................................................... 38 LIST OF FIGURES Figure 1 Macroinvertebrate biomonitoring sites in the Manawatu-Wanganui region with an indication of the number of sampling occasions. .............................................................. 5 Figure 2 Significant positive trend in MCI for the Whanganui River at Te Maire. ....................... 10 Figure 3 Significant positive trend in QMCI for the Whanganui River at Te Maire. .................... 10 Figure 4 Significant positive trend in QMCI for the Whanganui River at Pipiriki. ....................... 11 Figure 5 Significant positive trend in MCI for the Whanganui River estuary. .............................. 11 Figure 6 Significant negative trend in QMCI for the Oroua River at Nelson St upstream of the MBP discharge. ............................................................................................................... 12 Figure 7 Significant negative trend in QMCI for the Oroua River at Awahuri (SH3 bridge). ...... 12 Figure 8 Significant negative trend in MCI for the Manawatu River at Maxwells Line / Teachers’ College. ............................................................................................................................ 13 Figure 9 Significant negative trend in QMCI for the Manawatu River at Maxwells Line / Teachers’ College. ........................................................................................................... 13 Figure 10 Significant positive trend in MCI for the Makakahi River at Konini. ............................. 14 Figure 11 The relationship between sampling method, sample replication, and fuzzy boundaries on the ability to unambiguously assign sites to quality classes. ........................................... 60 LIST OF TABLES Table 1 SoE monitoring sites in the Manawatu-Wanganui region that have been sampled on six or more occasions since 1999. .................................................................................................... 6 Table 2 Summary of Mann-Kendall p-values for MCI and QMCI for 21 rivers in the Manawatu- Wanganui region .................................................................................................................... 9 Table 3 Interpretation of MCI and QMCI according to (a) Stark & Maxted (2007a), and (b) Wright- Stow & Winterbourn (2003). ............................................................................................... 15 Table 4 Evaluation of river health based on average MCI and QMCI values (1999 – 2007) for 21 sites in the Manawatu-Wanganui region according to the interpretive guidelines in Table 3. ............................................................................................................................................