Waimakariri tributary report Report No. R09/11 ISBN 978-1-86937-927-8 Taryn Wilks Adrian Meredith February 2009 Report R09/11 ISBN 978-1-86937-927-8 58 Kilmore Street PO Box 345 Christchurch 8140 Phone (03) 365 3828 Fax (03) 365 3194 75 Church Street PO Box 550 Timaru 7940 Phone (03) 687 7800 Fax (03) 687 7808 Website: www.ecan.govt.nz Customer Services Phone 0800 324 636 Waimakariri tributary report 2008 Executive summary Water quality in the lower Waimakariri catchment, including Cam, Cust, Ohoka, Kaiapoi, Courtenay, South Branch/Otukaikino and the Styx Rivers have been monitored since 2000 by Environment Canterbury. Cessation of waste water discharge in 2005 and the initiatives to improve discharge methods of both Waimakariri District Council and Christchurch City Council have yielded significant water quality improvements in the Cam River and South Branch/Otukaikino. Water quality in the Ohoka, Cust and Styx Rivers has remained in a steady state, while water quality in the Kaiapoi River has shown signs of degradation. Concentrations of faecal indicator bacteria in Waimakariri tributary streams regularly exceed the contact recreation guideline of 550 MPN/100ml, resulting in very poor contact recreational grades. The sources are likely to be a mixture of natural (wildlife), agricultural (livestock), and discharges, but exclusion of livestock from stream banks and springheads hold most promise for reduced concentrations. High nitrogen concentrations are also an ongoing issue, and it is therefore recommended that monitoring of these tributaries (both water quality and ecosystem health) is continued. Additionally an investigation into declining water quality in the Kaiapoi River is recommended. Environment Canterbury Technical Report i Waimakariri tributary report 2008 ii Environment Canterbury Technical Report Waimakariri tributary report 2008 Table of contents Executive summary .................................................................................................... i 1 Introduction ..................................................................................................... 1 2 Methods ........................................................................................................... 1 2.1 Data analysis .................................................................................................................. 4 2.1 Trend analysis ................................................................................................................. 4 3 Results ............................................................................................................. 5 3.1 Water physico-chemistry ................................................................................................ 5 3.2 Nutrients .......................................................................................................................... 6 3.2.1 Dissolved Inorganic Nitrogen ............................................................................. 6 3.2.2 Ammonia Nitrogen ............................................................................................. 7 3.3 Microbial contamination - Escherichia coli ...................................................................... 9 3.4 Dissolved Organic Carbon ............................................................................................10 3.5 Turbidity ........................................................................................................................11 3.6 Trend analysis ...............................................................................................................12 3.7 Ecosystem health..........................................................................................................13 3.8 Contact recreation.........................................................................................................16 4 Discussion ..................................................................................................... 18 5 Acknowledgements ...................................................................................... 20 6 References ..................................................................................................... 20 Appendix 1: Summary of Waimakariri Tributaries water quality 2000-2008 ....... 23 Appendix 2: South Branch before and after the ocean outfall ............................ 24 Appendix 3: Cam River before and after the ocean outfall .................................. 25 Appendix 4: Photos of Waimakariri Tributaries .................................................... 26 Appendix 5: Guideline values for water quality determinands used in this study .................................................................................................... 27 Environment Canterbury Technical Report iii Waimakariri tributary report 2008 List of figures Figure 2-1: Map of Waimakariri tributary sampling site ....................................................................... 3 Figure 3-1: Distribution of Dissolved Oxygen Saturation (DOSAT%) 2000-2008, note outer edges of box are 20th and 80th percentiles. ..................................................................... 5 Figure 3-2: Distribution of Dissolved Inorganic Nitrogen concentrations 2000-2008. ....................... 6 Figure 3-3: Distribution of Ammonia Nitrogen (mg/L) concentrations 2000-2008 ............................... 7 Figure 3-4: Distribution of Dissolved Reactive Phosphorus concentrations 2000-2008. .................. 8 Figure 3-5: Distribution of Escherichia coli (E. coli) concentrations in the Waimakariri Tributaries 2000-2008.. ....................................................................................................................... 9 Figure 3-6: Distribution of Dissolved Organic Carbon (mg/L) concentrations in tributaries of the Waimakariri River 2002 -2008. ........................................................................................10 Figure 3-7: Distributions of Turbidity concentrations (NTU) in the Waimakariri Tributaries 2000- 2008. ..............................................................................................................................11 Figure 3-8: Invertebrate community diversity (%) of six tributaries of the Waimakariri River over summer 2008/09. ............................................................................................................14 List of tables Table 2-1: Waimakariri River tributary monitoring sites ...................................................................... 2 Table 3-1: Water quality trend analysis 2000-2008; showing Relative Sen Slope Estimator (expressed as % of data median yr)................................................................................13 Table 3-2: QMCI and Invertebrate Grade over summer 2008/09 ....................................................13 Table 3-3: Contact recreational monitoring sites in the Waimakariri catchment ..............................17 iv Environment Canterbury Technical Report Waimakariri tributary report 2008 1 Introduction The Waimakariri River has a number of lowland tributaries that enter the river near the sea. These tributaries drain extensive areas of both the Waimakariri District in the north and Christchurch City in the south. Some of the tributaries have historically received a number of industrial and municipal discharges that compromised the water quality of both the tributaries themselves and the lower reaches of the Waimakariri River. Most of these discharges have ceased in recent years through closure of major industries, alternative treatment, or alternative (ocean outfall) disposal options. However, urbanisation of Christchurch suburbs (Belfast, Northwood) and Waimakariri townships (Kaiapoi, Rangiora, and outlying settlements) has the potential to further compromise water quality through the infiltration of contaminants arising from initial land developments and stormwater discharges. Agricultural land use intensification (often associated with irrigation such as the Waimakariri Irrigation Scheme) has also developed rapidly in recent years, and has the potential to further compromise water quality. The Waimakariri River Regional Plan (WRRP) became operative in 2004 and contains controls on the use and discharge of water, and regimes for monitoring of the Waimakariri River and tributaries. The resulting quarterly monitoring of Waimakariri River tributaries over the past eight years (<32 samples per site) provides a useful data set to summarise the current state, trends, and changes following modification of major discharge activities. This reports main focus is on reporting the current state, trends and changes in water quality for seven major lowland tributaries of the Waimakariri River; Cam, Cust, Ohoka, Kaiapoi, Courtenay, South Branch/Otukaikino and Styx Rivers. A brief summary on invertebrate health and microbial quality related to contact recreation is also included in this report 2 Methods As part of Environment Canterbury’s (ECan) routine water quality monitoring programme, quarterly water quality data was collected from six rivers in the lower Waimakariri catchment over 2000 to 2008, with an additional site monitored monthly in 2007-2008 (Table 2-1; Figure 3-1). The microbial quality of six tributaries are monitored as part of Environment Canterbury’s contact recreational programme and results are discussed briefly (Table 2-1; Figure 3-1). Standard water quality guidelines where available were used in this report