Revised Version September 2010 Resource Consent Application and Assessment of Environmental Effects for the Okere Gates and Ohau Channel Weir Structures Okere Gates and Ohau Channel Weir Structures: Application for Resource Consents Assessment of Environmental Effects Revised Version September 2010 Contents Executive Summary ........................................................................................................................ 1 1 Introduction .......................................................................................................................... 10 1.1 Purpose of the Project .................................................................................................. 10 1.2 Timeline to Obtain New Consents ................................................................................ 10 1.3 Background .................................................................................................................. 11 1.4 Resource Consents Sought ......................................................................................... 11 1.4.1 Resource Management Act .............................................................................. 11 1.4.2 Bay of Plenty Regional Council Floodway and Drainage Bylaw 2002 .............. 15 1.5 Project Objectives ........................................................................................................ 15 1.6 Processes Followed to Date ......................................................................................... 15 2 Existing Situation ................................................................................................................ 17 2.1 Explanation of Relative Levels in Existing Resource Consents for Lake Rotoiti .......... 17 2.2 Description and Location of Structures ........................................................................ 18 2.2.1 Location ............................................................................................................ 18 2.2.2 Ownership of the Lake Beds and Land beneath the Weir and Gates ............... 19 2.2.3 Ohau Channel Weir .......................................................................................... 20 2.2.4 Okere Radial Gates .......................................................................................... 20 2.3 Existing Resource Consents ........................................................................................ 21 2.4 Description of Existing Lake Operating Regimes ......................................................... 21 2.4.1 Lake Rotorua .................................................................................................... 21 2.4.2 Lake Rotoiti ....................................................................................................... 22 2.5 Ohau Diversion Wall ..................................................................................................... 22 2.6 Existing Resource Consent Compliance ...................................................................... 23 2.6.1 Operation of Ohau Channel Weir...................................................................... 23 2.6.2 Operation of Okere Gates ................................................................................. 23 2.7 Summary of Key Existing Issues .................................................................................. 24 3 Description of the Existing Environment .......................................................................... 25 3.1 Recreational and Commercial Tourism ........................................................................ 25 3.1.1 General ............................................................................................................. 25 3.1.2 Lake Rotorua .................................................................................................... 25 3.1.3 Lake Rotoiti ....................................................................................................... 27 3.1.4 Kaituna River .................................................................................................... 30 3.2 Lake Navigation ............................................................................................................ 30 3.2.1 General ............................................................................................................. 30 3.2.2 Lake Rotorua .................................................................................................... 31 3.2.3 Lake Rotoiti including the Ohau Channel ......................................................... 31 3.3 Tangata Whenua Context and Cultural Values ............................................................ 32 3.3.1 Context ............................................................................................................. 32 3.3.2 Cultural Values ................................................................................................. 34 3.4 Archaeology ................................................................................................................. 35 3.5 Property Ownership ...................................................................................................... 36 3.5.1 Jetty, boatshed and boat ramps ....................................................................... 36 3.6 Local Stormwater Drainage and Utility Services .......................................................... 36 89030.07 September 2010, Final Version 3 i Okere Gates and Ohau Channel Weir Structures: Application for Resource Consents Assessment of Environmental Effects Revised Version September 2010 3.6.1 Lake Rotorua .................................................................................................... 36 3.6.2 Lake Rotoiti ....................................................................................................... 37 3.7 Catchment Description, Hydrology and Hydraulic Behaviour of Lakes System ........... 39 3.7.1 Physical Environment ....................................................................................... 39 3.7.2 Lakes Hydrology ............................................................................................... 42 3.7.3 Kaituna River Hydrology ................................................................................... 46 3.7.4 Hydraulic Aspects ............................................................................................. 47 3.7.5 Wave Climate.................................................................................................... 50 3.7.6 Sedimentation Effects in the Ohau Channel ..................................................... 50 3.7.7 Mixing Characteristics of Ohau Channel Outflow into Lake Rotoiti and Ohau Diversion Wall .............................................................................................................. 52 3.8 Ecological Health and Habitat Values .......................................................................... 53 3.8.1 General Ecology ............................................................................................... 53 3.8.2 Water Quality .................................................................................................... 53 4 Options Considered ............................................................................................................ 54 4.1 Description of Options .................................................................................................. 54 4.1.1 Lake Rotorua .................................................................................................... 54 4.1.2 Lake Rotoiti ....................................................................................................... 54 4.2 Key Finding of the Aurecon Report 2009 ..................................................................... 55 4.3 Review of Aurecon Modelling ....................................................................................... 56 4.3.1 Summary of Additional Work Undertaken ......................................................... 56 4.3.2 Broad Trends Reported in the Original Aurecon Report ................................... 56 4.3.3 Further Work Undertaken for Options 1 and 4 .................................................. 56 4.3.4 Results .............................................................................................................. 57 4.4 Optimisation Modelling ................................................................................................. 57 5 Development of the Proposed Options (as at June 2010) for Lake Levels for Lake Rotoiti and Lake Rotorua .................................................................................................... 59 5.1 Lake Rotorua ................................................................................................................ 59 5.2 Lake Rotoiti .................................................................................................................. 60 5.3 Historical and Anecdotal Data ...................................................................................... 68 5.4 Mauri Model .................................................................................................................. 69 5.5 How Consultation Was Used to Develop the Lake Rotoiti Starting Point Operating Range (December 2009) and the Proposed Option (D7) (June 2010) ......................... 70 5.6 Use of Multi-Criteria Option Evaluation Matrix for Lake Rotoiti