Waimakariri Zone water quality and ecology: State and trend Report No. R17/18 ISBN 978-1-98-852039-1 (print) 978-1-98-852040-7 (web) Michael Greer Adrian Meredith April 2017 Waimakariri Zone water quality and ecology: State and trend Report No. R17/18 ISBN 978-1-98-852039-1 (print) 978-1-98-852040-7 (web) Michael Greer Adrian Meredith April 2017 Name Date Michael Greer 01/08/2016 Prepared by : Adrian Meredith 01/05/2019 Shirley Hayward 20/09/2016 Reviewed by : Greg Burrell 23/09/2016 Helen Shaw April 2017 Approved by: Tim Davie April 2017 Report No. R17/18 ISBN 978-1-98-852039-1 (print) 978-1-98-852040-7 (web) 200 Tuam 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 Zone water quality and ecology: State and trend Executive summary Background This report has been prepared to provide science input into the Waimakariri Land and Water Solutions programme; the Waimakariri Zone Committee are developing methods to manage the resources in the Waimakariri zone in order to meet community outcomes for freshwater. In this report, the current state of the zone’s waterways in terms of ecology and habitat values are summarised, and state and trends in water quality discussed. This report is not only intended to inform the zone committee of current state, but also of the key drivers of ecosystem health in the zone so that these factors can be managed appropriately through the Waimakariri Land and Water Solutions Programme. What we did Comprehensive water quality and ecology data for the Waimakariri Zone were collated, and the results compared with the Canterbury Land and Water Regional Plan (LWRP) limits and objectives, and established guideline values from national limits and the literature. Current state was assessed from data collected over the five years between 2011 and 2015, and trend analyses were undertaken across the entire data set where more than five years of data were available. Where comprehensive data (intensive sampling and/or 5 years or more of data) were not available, a qualitative assessment was undertaken to acknowledge and briefly comment on their current state or issues. What we found and what does it mean? Many of the rivers in the Waimakariri Zone, particularly spring-fed streams, have ecological communities in poor condition, poor habitat conditions, and degraded water quality. These degraded conditions are considered to largely result from excessive nutrient and sediment inputs into the streams, associated with the high intensity land use and development in many parts of the zone. In many of the hill-fed rivers in the Ashley River catchment macroinvertebrate communities are also in a degraded state. Deposition and accumulation of fine sediment is a likely dominant cause although a sustained drought period, and high nutrient concentrations are also likely to have exacerbated the degraded results. Faecal contamination has only occasionally been recorded as being so high as to pose a risk to contact recreation in the Ashley River, the Glentui River and the Grey River in the past five years. Toxic cyanobacteria have not been recorded as posing a significant or consistent health risk in most hill-fed rivers. The only exceptions are the main-stem of the Ashley River, between Rangiora/Loburn Road and SH1, where significant Phormidium growths were recorded during the summer months. These may pose a significant health risk to recreational users and detract from river uses. In the spring-fed rivers in the Ashley and Kaiapoi River catchments macroinvertebrate communities are also in a degraded state. Deposited fine sediment cover is high in all spring-fed streams in both catchments and is likely a key driver of poor ecosystem health and high macrophyte cover in these systems. Nitrate toxicity may be another important driver of degraded invertebrate health in the zone’s spring-fed rivers, particularly where there are high nitrate-N concentrations in the Silverstream, the Cust Main Drain and the Ohoka River. Spring-fed streams in the Ashley and Kaiapoi River catchments are generally unsuitable for primary contact recreation due to significant faecal contamination. Environment Canterbury Technical Report i Waimakariri Zone water quality and ecology: State and trend ii Environment Canterbury Technical Report Waimakariri Zone water quality and ecology: State and trend Table of contents Executive summary ............................................................................................... i 1 Introduction ................................................................................................ 1 1.1 Key drivers and indicators ........................................................................................ 2 1.1.1 Macroinvertebrate health ............................................................................. 2 1.1.2 Habitat as a driver of ecosystem health ....................................................... 3 1.1.3 Water quality as an indirect driver of ecosystem health .............................. 4 1.1.4 Water quality as a direct driver of ecosystem health ................................... 4 1.1.5 Water quality and plants as a determinant of recreation value .................... 5 2 Methods ...................................................................................................... 6 2.1 Data sources ............................................................................................................. 6 2.2 Analysis ................................................................................................................... 11 2.2.1 Current state of macroinvertebrate communities ....................................... 11 2.2.2 Current state of cyanobacteria, periphyton and macrophyte coverage ..... 11 2.2.3 Current degree of bed sedimentation ........................................................ 11 2.2.4 Current state and trends in dissolved oxygen (DO) and water temperature ................................................................................................ 12 2.2.5 State and trends in nutrient concentrations in terms of plant growth and toxicity ........................................................................................................ 12 2.2.6 Current state and trends in total suspended solids concentrations ........... 14 2.2.7 Current state and trends in faecal contamination ...................................... 14 2.2.8 Comparison with National Policy Statement (2014) attribute states .......... 14 3 Results ...................................................................................................... 15 3.1 Ashley River catchment - hill-fed streams .............................................................. 15 3.1.1 Ecology and habitat ................................................................................... 15 3.1.2 Current state of water quality ..................................................................... 22 3.1.3 Trends in water quality ............................................................................... 28 3.1.4 Comparison against the NPS ..................................................................... 28 3.1.5 Summary .................................................................................................... 29 3.2 Lower Ashley River catchment - spring-fed streams .............................................. 30 3.2.1 Ecology and habitat ................................................................................... 30 3.2.2 Current state of water quality ..................................................................... 36 3.2.3 Trends in water quality ............................................................................... 41 3.2.4 Comparison against the NPS ..................................................................... 43 3.2.5 Summary .................................................................................................... 43 3.3 Kaiapoi River spring-fed streams ............................................................................ 44 3.3.1 Ecology and Habitat ................................................................................... 44 3.3.1 Current state of water quality ..................................................................... 49 3.3.2 Trends in water quality ............................................................................... 56 3.3.3 Comparison against the NPS ..................................................................... 58 3.3.4 Summary .................................................................................................... 58 3.4 Upper Ashley River – Lees Valley .......................................................................... 59 3.5 Lower tidal Kaiapoi River ........................................................................................ 59 3.6 Courtenay Stream and Kaikanui Stream ................................................................ 59 3.7 Eyre River and hill fed tributaries, and View Hill Stream ........................................ 60 3.8 Losses to the Waimakariri River ............................................................................. 60 Environment Canterbury Technical Report iii Waimakariri Zone water quality and ecology: State and trend 3.9 Cust River ..............................................................................................................