Lake Waiporohita MANAGEMENT PLAN CONTENTS
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Lake Waiporohita MANAGEMENT PLAN CONTENTS 1. PURPOSE .....................................................................3 2. INTRODUCTION ...........................................................3 3. LAKE LOCATION MAP ..................................................5 4. LAKE OVERVIEW ..........................................................6 5. SOCIAL AND CULTURAL DIMENSION ...........................6 6. PHYSICAL CHARACTERISTICS ......................................7 7. CHEMICAL CHARACTERISTICS .....................................15 8. BIOLOGICAL CHARACTERISTICS ..................................22 9. LAND USE ....................................................................26 10. MONITORING PLAN .....................................................27 11. WORK IMPLEMENTATION PLAN ...................................28 12. BIBLIOGRAPHY ............................................................28 13. APPENDIX 1. GLOSSARY ..............................................29 2 LAKE WAIPOROHITA MANAGEMENT PLAN | Introduction LAKE WAIPOROHITA MANAGEMENT PLAN 1. Purpose The1. PURPOSE purpose of the Outstanding Northlandformed Dune between Lakes stabilised Management sand dunes along Plans the westis to implementThe purpose of thethe Outstanding recommendations Northland Dune of the Northlandcoast, represent Lakes a large Strategy proportion ofPart warm, II lowland(NIWA 2014)Lakes Management by producing Plans is toLakes implement Management the Plans,lakes in New starting Zealand with which the still have12 ‘Outstanding’relatively good valuerecommendations lakes, and of the by Northland facilitating Lakes Strategy actions withwater mana quality whenua and high ecological iwi, landowners values. and other stakeholdersPart II (NIWA 2014) in by theproducing lake Lakescatchments Management to deliver priority work which will protect water qualityPlans, starting and with mitigate the 12 ‘Outstanding’ current pressures. value The outstanding dune lakes are grouped on the lakes, and by facilitating actions with mana whenua Aupouri, including Sweetwater, Karikari and Pöuto 2.iwi, landownersIntroduction and other stakeholders in the lake Peninsulas and the Kai Iwi group North of Dargaville. catchments to deliver priority work which will protect Thewater qualityfollowing and mitigate text currentis taken pressures. directly fromThe the lakes Northland vary in size, withLakes the majority Strategy being. Northland dune lakes and their associated wetlandsbetween 5 andare 35 ofhectares national in area andand generally international less significance.2. INTRODUCTION These lakes, most of whichthan have 15 metresbeen deep. formed Lake Taharoabetween of the stabilised Kai Iwi sand dunes along the west coast, represent aGroup large is one proportion of the largest of and warm, deepest lowland dune lakes lakesin in The following text is taken directly from the Northland New Zealand which still have relativelythe goodcountry, coveringwater anquality area of 211.07and highhectares ecological and Lakes Strategy. Northland dune lakes and their values. being 38.81 metres deep. Lake Taharoa also has the associated wetlands are of national and international deepest recorded submerged vegetation of any lake significance. These lakes, most of which have been The outstanding dune lakes are groupedin the onNorth the Island, Aupouri, to 24 metres. including Sweetwater, Karikari and Pōuto Peninsulas and the Kai Iwi group North of Dargaville. The lakes vary in size, with the majority being between 5 and 35 hectares in area and generally less than 15 metres deep. Lake Taharoa of the Kai Iwi Group is one of the largest and deepest dune lakes in the country, covering an area of 211.07 hectares3 and being 38.81 metres deep. Lake Taharoa also has the deepest recorded submerged vegetation of any lake in the North Island, to 24 metres. The dune lakes generally have little or no continuous surface inflows or outflows, being primarily fed by rainfall directly onto their surfaces and surrounding wetlands. As a result, their levels fluctuate considerably with climatic patterns. As most of the lakes are relatively small and shallow, they have limited capacity to assimilate any contaminants. They are prone to nutrient enrichment from stock and fertiliser, 4 LAKE WAIPOROHITA MANAGEMENT PLAN | Introduction The dune lakes generally have little or no continuous Recreational and commercial activities on or around surface inflows or outflows, being primarily fed by some of the lakes can affect water quality, lake rainfall directly onto their surfaces and surrounding ecology and increases the risk of introduction of pest wetlands. As a result, their levels fluctuate considerably weeds and fish. with climatic patterns. As most of the lakes are relatively small and shallow, they have limited capacity The Northland Lakes Strategy (NIWA 2012) presents a to assimilate any contaminants. They are prone classification and ranking system for Northland lakes to nutrient enrichment from stock and fertiliser, including assessment of ecological values and lake particularly where lakeside vegetation has been grazed pressures and threats. The 12 highest ranked lakes or removed, and where there is direct stock access from north to south are: to the lake. Further effects on the lakes result from Outstanding (12) forestry fertilisation, sediment mobilisation during • Lakes - Wahakari, Morehurehu, Waihopo, harvest and water budget dynamics. Ngatu, Waiporohita, Waikare, Kai iwi, Taharoa, Humuhumu, Kanono, Rotokawau These lake and wetland ecosystems are important and Mokeno habitats for a wide variety of plant and animal species, some of which are regionally or nationally significant Northland Lakes Strategy (NIWA 2012, 2014) because of their rarity. These include birds such as recommends that individual lake management plans the pateke/brown teal, banded rail, New Zealand should be developed for each high value lake. This dabchick, marsh crake, fern bird and Australasian would include: bittern, the aquatic plants Hydatella inconspicua and • Descriptions of each lake and lake catchment Myriophyllum robustum and native freshwater fish • Outline of lake values and significance including the giant kokopu, banded kokopu, short (including ecological and social) jawed kokopu, inanga, dwarf inanga and dune lakes • List of agencies and individuals involved in galaxias. management The most outstanding characteristic of these lakes is • Communications plan the limited impact of invasive species on their biota, • Monitoring plan which is unparalleled elsewhere on mainland New • Identification of gaps in knowledge/research Zealand. Despite these values, the status of these lakes plan is not secure and the overall trend has been gradual • Current threats and pressures deterioration. • Management actions to mitigate or ameliorate threats and pressures Northland Regional Council monitors water quality • Work implementation plan quarterly in 26 dune lakes and undertakes ecological monitoring, along with NIWA, for ~90 dune lakes on an annual rolling basis. Annual weed surveillance Key principals of lake management are: is undertaken at high value lakes with public access. • Balance between protection and utilization Threats and pressures include biosecurity (aquatic • Managing the environmental quality of the weeds, pest fish and the risk of invasion and spread), catchment, in particular water quality eutrophication from surrounding land use for farming • Integrated management of habitat and species and forestry, occurrence of algal blooms and water (including pests) level fluctuations, especially dropping lake levels. • Monitoring as a key environmental Natural events such as summer droughts and high management tool rainfall events place further pressure on these lakes. 4 LAKE WAIPOROHITA MANAGEMENT PLAN | Lake Location Map The plan takes the approach of presenting robust Further south within Northland, on the west coast information on all aspects of the lakes. This includes north of Dargaville, are the three Kai Iwi Lakes (Lake Kai social and cultural, physical, chemical and biological Iwi itself, and Lakes Taharoa and Waikare, sometimes summaries of information not generally available to referred to as Waikere). the public in a condensed format. This data is the best available at the time of writing and does not represent Finally, four outstanding lakes on the Pöuto Peninsula, peer-reviewed science in the sense that errors may be on the north head of the Kaipara Harbour, round out inherent in the raw data and presence and absence the final twelves lakes of covered in the Outstanding of species changes over time. Yet it offers trends for dune lake plans. These include the west Pöuto Lake further discussion among partners involved in protection Mokeno and the east Pöuto lakes Humuhumu, Kanono and restoration activities. The plan goes on to scope and Rotokawau (Pöuto). required work for the mitigation of threats and offers a communication strategy to implement this work. Most lake names come from te reo Mäori and, therefore, some names refer to several lakes around 2.1. Geographic Lake Groupings Northland. Rotokawau is a name given to several The outstanding dune lakes within these plans all sit lakes, with one in Pöuto, two in Karikari and one in within two broad ecological districts; Aupouri and Sweetwater. Additionally, the word “kawau” means Kaipara. Within these two districts there are further the waterbird shag or cormorant and two additional geographical associations of lakes, especially relevant