Water Quality Lake Waikare Presentation to Waikato District

Water Quality – Lake Waikare Presentation to Waikato District Council 24 June 2014

Presentation outline • Context - Lake Waikare and surrounding catchment • Lake Waikare water quality challenge • Existing governance arrangements • Future

Lake Waikare Context • One of many shallow lowland peat lakes in the Waikato delta • Lower Waikato Flood Protection scheme • Area of significance for Waikato-Tainui • Whangamarino wetland • Catchment land use and sedimentation • Shallow lakes accord (Waikato-Tainui, WDC, Do. C, WRC)

35 Lower Waikato Lakes 28 21 16 • 25 lakes in the 3 Lower Waikato zone 38 11 10 42 • 3 provisionally 40 ranked in Top 10 Waipa/Waikato/ Hamilton lakes • Lakes 9 13 Rotokawau (3), Areare (9) and Waahi (10)

Lake Waikare Context • A shallow lake, high sediment input • Flood control scheme lake level storage and management • Large sediment inflow from Matahuru catchment • Downstream impacts of sediment through the wetland • Current Waikare gate consent compliance review • Other consents to discharge to Lake Waikare

Rangiriri Spillway & 1971 when in operation

Lower Waikato Flood Protection Scheme

Lower Waikato Zone

Lake Waikare water quality • Nitrogen, phosphorus – promote algal growth • Sediment (reduced clarity impacts ecology and suitability for contact recreation) • Wind and pest fish disturb bottom sediments

Monoraphidium sp. Red pigment “zeaxanthin”

Water quality in some shallow lakes 2008 -12 Total P (mg/m 3) Total N (mg/m 3) Chlorophyll (mg/m 3) Secchi (m) Rotomanuka 20 1070 11 1. 4 Serpentine 30 1350 13 1. 3 Waikare 170 2640 110 0. 2 5 80 1 16 Taupo

Estimated phosphorus loads from lakes’ catchments Load of P (kg/ha/yr) Farming (%) Rotomanuka 1. 0 94 Serpentine 1. 0 93 Waikare 1. 0 88

Lake Waikare, P concentrations 1996 -2014

Matahuru Catchment • Soil stability • 65% of catchment unstable • evidence of past erosion on hill slopes • Erosion mainly landslides, gully erosion and stream bank erosion • Soil Conservation • Present on 4337 ha (42%) of catchment • Absent and required on 1340 ha (13%) • Upgrades to conservation required on 1445 ha (14%)

Matahuru Catchment

Matahuru Catchment

Existing Governance Arrangements

Land administered by DOC, WRC & Waikato –Tainui in the vicinity of Lake Waikare & Whangamarino Wetland

Land Ownership • Lake bed owners – Waikato-Tainui • Mixed ownership of lake margins (Fish and Game, Do. C, local Iwi, WRC, WDC, private) • Remainder of catchment upstream (mainly private) • Remainder of catchment downstream (Do. C, Fish and Game, private)

Governance Arrangements • Waikato District Council • Land use planning • Consent to discharge (Te Kauwhata waste water) • Waikato Regional Council • RMA - Effects of land use, Healthy Rivers – Wai Ora, Water • • allocation V 6 Lower Waikato Liaison subcommittee Lower Waikato Flood Protection Scheme and associated consents Project Watershed – Integrated catchment management Co-management (JMAs and co-managed lands)

Governance Arrangements • Joint management • Co-management • Waikato District Lakes Memorandum of Agreement • Waikato Tainui • Co-governors and owners of lake bed • Co-managed lands / Sites of significance • Do. C • Wetland Biodiversity management • Fish and Game • Wetland game bird management

Future • Management of upper catchment (soil conservation and water quality) • Scale of issues major impediment to in-lake restoration • Habitat enhancement of margins – ephemeral wetlands • Management of lake depth – WQ/sediment re-suspension, irrigation • Plant pest management (yellow flag, alligator weed)

Future • Management of the flood protection scheme • Local -1500 ha surrounding lake • Regional – 17, 000 ha protected land • National infrastructure – SH 1 protection • Lake Waikare an important part of the scheme • Challenge: • Maintaining viable flood protection scheme • Improving lake water quality • Protecting biodiversity • Managing future demands for water • All parties to act effectively towards a common goal

WRC Future Actions • Consent review Lower Waikato Flood Control Scheme • Lake Waikare discharge • Impacts on Whangamarino wetland • Long Term Plan 2015 -25 • Detailed assessment of high risk/opportunity sites in the zone • Project management for inter-agency catchment plan • Additional catchment management staff and incentives