1. Shallow Lake Management & Restoration
A WRC Management Perspective
Presentation to CSG Meeting #11
Introduction
Here to talk today from a management perspective about the shallow lakes in the Waikato region, and specifically in the Waikato/Waipa River catchments
Understand that you have already received presentations from Prof David Hamilton about the condition of the lakes, and from Tony Petch regarding Lake Waikare – so I have tried not to duplicate that information.
Will cover
a brief introduction to the lakes
a summary of the planning work that has been undertaken for shallow lakes at WRC
Overview of interventions and lake management programme to give you an insight to some of the practical work that is being undertaken on the lakes

2. Waikato/Waipa River Catchment
59 natural lakes in Waikato/Waipa River catchment
30 peat
17 riverine
4 dune
7 volcanic
1 geothermal
54 of 59 are shallow lakes
13 lakes currently monitored
59 natural lakes in the Waikato/Waipa River catchment
Locations on map – peat, riverine, dune, volcanic
Shallow lakes – less than 10m deep (most <5) and most would have supported submerged aquatic plants in their original state
Many shallow lakes are heavily modified & susceptible to further change
 Shallow lakes are particularly vulnerable to the effects of landuse, and require a targeted management approach.
Shallow lakes function differently to deep lakes in that their depth provides for them to be:
Capable of supporting submerged aquatic plants over most of the lake bed due to their shallow depths that allow light penetration to allow plant growth;
Regularly stirred up by wind and wave action due to their shallow nature which prevents thermal stratification and serves to recycle nutrients from the bottom sediments of shallow lakes;
Susceptible to changes in catchment land uses and hydrology due to the large interface between the lake bed and water column that amplifies the influence of lake bed sediments; and
More heavily impacted by invasive species

3. Peat Lakes Dune Lakes Riverine Lakes Volcanic PEAT LAKES
Internationally rare & important lake type – concentrated in Waikato & Waipa Districts
Associated with formerly extensive peat bogs
Mostly small to moderate in size (1-33 ha) with catchments < 200 ha.
Rotokauri (42 ha), Rotoroa (55 ha) and Ngaroto (108) are the largest of the peat lakes. Lake Ngaroto has the largest catchment size at 1856 ha.
All peat lakes in the Waikato Region are located within predominantly pastoral catchments and few have extensive marginal wetlands.
Maratoto has the largest area of adjoining wetland (22 ha).
DUNE LAKES
Dune lake - small to moderate in size 0.2 – 22.4 ha. Catchment sizes are small <134 ha
Most data poor of all of the lakes
Otamatearoa – exceptional water quality
VOLCANIC
Many of the volcanic lakes have formed in explosion craters associated with volcanic activity.
Shallow volcanic lakes are less than 10ha in size with moderate to large catchment sizes ( ha) and variable amounts of forest cover
RIVERINE LAKES
part of the extensive wetland/floodplain system in lower Waikato
All of the Waikato riverine lakes are naturally shallow (<5m depth) Are the largest shallow lakes in the region including Waikare (3442 ha), Whangape (1450 ha) and Waahi (522 ha).
All riverine lakes have poor water quality and most experience regular algal blooms.
Their large wind fetch have led to increased internal sediment re-suspension and reduced water clarity, especially following collapse of submerged vegetation. The interconnectedness of the riverine lakes facilitates the spread of pest fish and weeds
 The riverine lakes are particularly difficult to restore due to their large size, highly modified hydrological regimes and large catchment sizes.
Emphasise range of lakes types and their catchment sizes – different scales (& COST) of restoration intervention

4. Shallow Lakes - Values Indigenous fauna and flora; Wildlife & game
Commercial & traditional fisheries;
Culturally & recreationally significant;
Ecosystem processes (incl. nutrient cycling)
Economic benefits (e.g. water supply & flood control)
Intrinsic values
Shallow lakes support a wide range of values, even in their modified states....
Remaining natural values – including threatened and specialised species
ALSO SIGNIFICANT CULTURAL, SOCIAL & ECONOMIC VALUES
And INTRINSIC VALUES IN AND OF THEMSELVES

5. Shallow Lakes - Pressures
Hydrological modification & drainage
Habitat modification (esp. wetland loss)
Invasive (plant & animal) species;
Diffuse & direct catchment inputs (stored up over long periods & re- suspended)
Shallow lakes are vulnerable to “flipping” & experiencing algal blooms
These lakes have been, and continue to be threatened by:
Nutrient enrichment – “flipping” to alternative (turbid, de-vegetated) stable state & algal blooms
Many lakes no longer support submerged aquatic plants
Many monitored lakes fail to meet the NOF bottom lines for water quality
Many of the lakes are vulnerable to the effects of land use changes
Privately owned lakes are particularly vulnerable due to inadequate protection and unanticipated land use changes

6. Shallow Lakes Management Plan
Part I: Shallow Lakes Management Plan
High level – focus on WRC role, 10 year term
Identifies 9 objectives, and associated strategies & actions within 3 areas
Policy & Planning
Information & Monitoring
Lake Restoration & Rehabilitation
Part 2: Resource Statement
Summarises available information about each lake and their relative priorities
Identifies management options & recommendations for future WRC work
Given the number of lakes in the region and the complexity of issues that affect them at such large scale – NEED TARGETTTED APPROACH FOR THEIR MGMT
WRC has recently developed a SLMP
Plan is currently in draft form but has been endorsed by the Integrated Catchment Management Committee for approval by Council at their next meeting.
SLMP summarises
Legal and policy framework for shallow lake management
Covers the range of interventions that are required at different levels to manage shallow lakes – from policy development and implementation of non-regulatory policy provisions, through to operational and tactical planning for individual lakes
Part 1 - strategic component that identifies 9 key management objectives within 3 areas
Part 2 – Operational Component

7. Inter-Agency Agreements
Non-statutory Agreements
Recognise the values of the lakes and wetlands in the Waipa and Waikato Districts
Promotes improved collaboration and co-ordination of effort between DOC, Fish & Game, Iwi, District Council, and WRC
Non-statutory Agreements
Recognise the ecological, scientific, recreational, cultural and aesthetic values of the lakes and wetlands in the Waipa and Waikato Districts
Promotes improved collaboration and co-ordination of effort between DOC, Fish & Game, Iwi, District Council, and WRC to restore and enhance the lakes and wetlands in the Waipa and Waikato Districts (using the tools available to each agency)
Waipa Peat lakes Accord has existed for more than 10 years and has successfully facilitated a considerable amount of collaborative work on the peat lakes in district – both private and public lakes
Waikato District Lakes & Freshwater Wetlands is relatively new and in the early stages. Modelled on successful Waipa Accord
Development was timed to incorporate the Waikato River settlement and the vision and strategy for the Waikato River catchment
At this stage the group has undertaken
a stocktake of work being undertaken on the lakes and future agency priorities, and identfying options for collaboration.
Progressed the development and implementation of a restoration plan at Lake Areare
collaborative project to develop CMP for Lake Waikato & Whangamarino wetland

8. Resources & Best Practice Available
Other Parties
Industry, Iwi, NGOs (Landcare Trust), Researchers, Landowners, Caregroups
Resources & Best Practice Available

9. Lake Restoration Interventions
Usually undertaken to improve specific lake attributes and/or uses Lake & outcome specific
Have typically involved:
Improved access (recreation& management)
Restoration/protection of lake levels & hydrology;
Fencing & riparian retirement;
Enhancement of marginal habitat, including re-vegetation and weed control;
Control of pest fish and weeds;
Reduction of nutrient and sediment inputs;
Catchment Management Planning (including Farm Plans)
Adaptive Management Approach
Usually undertaken to improve specific lake attributes (e.g. cultural, historic, recreation, biodiversity, water quality) and/or uses (e.g. swimming, hunting, fishing, water source)
Have typically involved a range of actions including: (list)
I think of these as being grouped into 4 main outcomes
Access – to facilitate appreciation, public enjoyment and management
Hydrology – to secure the lakes (particularly the peat lakes) in the medium term
Works undertaken to improve biodiversity, wildlife , and amenity values
Initiatives to improve water quality (LONG GAME)
At a regional scale – real focus on the peat lakes because they are vulnerable to further change, are smaller, have smaller catchments, and as a consequence are perceived as being more achievable

10. Lake Level Setting
Lake Level Setting Programme - “to determine appropriate minimum water and/or bed levels for the purpose of promoting the sustainable management of significant peat lakes and wetlands in the Region”
Process
Vulnerable peat lakes in WRP
Establish minimum summer level
Install a structure in the lake outlet, or survey existing control level
Incorporate new levels in WRP
Lake Mangakaware
Regional Plan lists 17 shallow lakes that (at the time) were seen as the most vulnerable to further lowering of levels and provides for a process to set a minimum control level for these lakes. 
The Regional Council works with stakeholders and landowners to agree on a minimum lake level and “protect” this via the construction of a weir
The weirs are designed to prevent lakes going below an undesirably low level during summer, but allow for natural fluctuations over winter.
Process involves – surveys and monitoring or modelling to set a level,
Successful at a number of lakes but more complex at other lakes where there is a large groundwater component or complex hydrology, and more detailed studies are required.

11. Riparian Restoration & Enhancement
Riparian fencing, weed control and planting has been a key activity on lakes
Riparian margin extension has also been a key activity
Lakes are priority sites for funding incentives from WRC (35%) for fencing, planting and weed control
Stock exclusion also a requirement under the Dairy Accord for (certain sized) streams, lakes and wetlands
Obtained external funding for larger fencing, weed control and planting programmes at high priority lakes
Funding : WCEET, DOC BCF, WRA Clean Up Trust,
Sites: Maratoto, Mangahia, Ngaroto, Mangakaware, Areare, Harihari
Riparian fencing, weed control and planting has been a key activity on lake margins (including extending riparian areas)
Regional Plan provides for various non-regulatory means for encouraging private landowners to protect and enhance land and water including shallow lakes.  The Council will provide up to 35% of the costs of fencing, planting and weed control for projects at priority sites – all shallow lakes in the Region are eligible for this.  If the Council contribution to the project is more than $10,000 the works are required to be protected by way of a covenant.
Lakes are priority sites for funding incentives from WRC (35%) for fencing, planting and weed control - Stock exclusion also NOW a requirement under the Dairy Accord for streams (of certain size), lakes and wetlands
External funding opportunities for larger fencing, weed control and planting programmes at high priority sites
Funding : WCEET, DOC BCF, WRA Clean Up Trust,
Sites: Maratoto, Mangahia, Ngaroto, Mangakaware, Areare,
Nga whenua rahui also an option for lakes and land in Maori ownership

12. Lake Mangahia
Improvement to habitat/biodiversity & amenity values
What has been achieved at Lake Mangahia – privately owned with diverse native wetland vegetation (including regenerating kahikatea).
Programme has involved:
Development of a restoration plan
Majority landowner moved fences a further 20-30m from the lake creating a m wide margin
QEII convenant for lake margin
Willow control
Planting programme and ongoing maintenance
Council funding plus $50,000 from DOC BCF, and landowner contribution
Planting costs for a decent job – around $40k/ha to spot spray, purchase plants, planting and 2 follow up releases.

13. Pest Fish - Koi Carp
Koi, catfish and goldfish contribute to sediment & nutrient resuspension through benthic feeding habits
Testing of traps and gates to manage pest fish at specific lakes (Lakes Waikare & Ohinewai) – in conjunction with Waikato University
Work at Lake Waikare and Ohinewai looking at options to capitalise on the migratory movements of koi carp and other pest fish in order to remove the fish from the lake system
Options for more strategic approach to invasive fish management within the lower Waikato River system taking advantage of migratory bottlenecks and spawning behaviour
Bruno will be talking more about his work tat Lake Waikare this afternoon

14. Invasive Fish Management
DOC rudd control programme at Lake Serpentine to protect native submerged plant communities
Fish barriers are increasingly being considered for lakes that don’t contain pest fish
Experimental pest fish control on a lake-by-lake basis
J. Gumbley, DOC
J. Gumbley, DOC

15. In-Lake Nutrient Management
Options for Waikato peat lakes assessed:
Sediment capping & flocculation to reduce P availability
Dredging/sediment removal
Pest fish removal
Hypolimnetic treatments
Trials of flocculants/dredging not warranted until external nutrient loads are substantially reduced (>50%) and as part of integrated restoration programme
In some eutrophic lakes, internal nutrient loads can be comparable with the external loads.
In-lake restoration techniques have been used elsewhere to prevent release of nutrients from the bottom sediments in order to reduce algal blooms.
remove nutrients directly from the water column or
lock nutrients up in the bottom sediments.
Picture shows flocculants being applied to Lake Okareka (modified zeolite and clay trialled)
In 2006 Waikato University reviewed available methods for internal sediment/nutrient removal for peat lakes
EXTERNAL NUTRIENT LOADS ARE TOO HIGH FOR ANY OF THESE OPTIONS TO BE FEASIBLE IN THE MEDIUM-LONG TERM.
reduction of external nutrient load in the order of 50% would be required prior to a pilot study
Any pilot study should take an integrated approach – also involving pest fish control and re-establishment of submerged plants.
Andy Bruere, EBOP

16. Sediment & Nutrient Mitigation
Monitoring sediment and nutrient inflows to peat lakes
Installation of constructed wetlands and silt traps to reduce nutrient and sediment inputs into lakes
Working with individual landowners in small peat lake catchments to reduce sediment and nutrient losses (farm plans)
Catchment Management Plans (e.g. Waipa CMP and proposed CMP for Lake Waikare & Whangamarino)
Management of external nutrient and sediment loads is key for shallow lakes – particularly ncreasing focus in lakes management as water quality becomes more of a focus.
Waipa CP – identifies Waipa lakes as priorities for WQ and biodiversity and identifies farm planning as a key tool for managing sediment and nutrient inputs to the lakes.

17. Farm Planning
Farm planning undertaken at several lakes (Kaituna, Tunawhakaheke/Lake E, Serpentine, Rotomanuka, Mangakaware, Ngaroto)
Farm planning approach promoted for more lakes in future (e.g. Waipa CP)
Promote:
More efficient use of fertiliser and effluent
Improved stock management to increase overall production
Best practice for peat soil management
Management of waterways and lake margins
Farm plans have promoted.....
Initial results suggest that there is scope for landowners to increase their nutrient efficiency, reduce nutrient and sediment losses to waterways and improve animal health to maintain their relative levels of production.

18. Scope for Nutrient Reductions through Land Use Improvements
Desktop assessment of potential nutrient reductions achievable for 44 lakes through land use practices in their catchments (Jenkins & Vant 2006)
Nitrogen 7- 36% reduction
Phosphorus 18-39% reduction
Average to best practice N 7% P 18%
Best practice to potential practice N 36% P 39%

19. Monitoring Inputs to Peat Lakes
Two years of baseflow & storm- sampling monitoring at 2 Waipa Peat lakes undertaken by University of Waikato
Large amounts of material transported during storm/flow events.
e.g. In 24 hrs at Rotopiko South
4 tonnes ‘additional sediment’
11 kg ‘additional P’
110 kg ‘additional N’
Project to try and quantify nutrient and sediment inflows to 2 high value peat lakes in the Waipa District.
Most of the drains were small and dried up during summmer.
Involved monitoring at baseflow and also during flow/storm events in several inflows/drains at the lakes
Results show
DISCHARGE FROM SMALL, EPHEMERAL FARM DRAINS DURIGN HEAVY RAINFALL EVENTS CAN BE A SIGNFICIANT SOURCE OF SEDIMENT AND NUTRIENTS FOR SHALLOW LAKES
These results highlight the challenge to manage nutrient and sediment sources on high flow events

20. Constructed Wetlands & Silt Traps
Lake Mangakaware – Waipa DC
Lake Kaituna – R.Eivers
Practical issues:
Size to accomodate peak flows
Area to locate the traps
Cost for landowners & care groups (e.g. resource consents)
Design for site
Lake Kaituna floating wetland trial

21. Catchment Retirement
76% of lake catchment is being retired & revegetated at Lake Waiwhakareke
Duggan (2012) modelled nutrient budgets for the lake and concluded that it could return to a mesotrophic state
10-15 yr timeframe to reach new P equilibrium
Lake Waiwhakareke is an interesting scenario where there is an opportunity to monitor and assess the effect of large scale catchment retirement and re-vegetation on the water quality of an extremely eutrophic – hypertrophic lake.
76% of lake catchment (50ha of a 66ha catchment) is being retired and revegetated as part of WNHP
Duggan modelled nutrient budgets for the lakes and concluded that it is likely to return to a mestotrophic state in time which would enable the lake to be used for contact recreation and be a suitable centrepoint for the park.
Study quotes overseas experience – in that it can take years for lakes to reach a new P equilibrium.
Opportunities to speed up by reducing internal nutrient loads – pest fish control, aquatic plants but need for long-term and integrated approach to reducing external loads for water quality improvements to endure.

22. Conclusions
Dealing with legacies of catchment management (nutrient sinks & sources)
Range of scales for issues and actions
Lake by lake approach
Adaptive management approach
Costs and uncertainties
Need for long-term interventions & monitoring
Realistic about timescales for improvements
But opportunities to build on existing work and make a long term difference!
I also want to give you a sense of the ground work that has been undertaken on the lakes to date, which sets a good platform for your work to establish policy to reduce inputs to the lakes, which is the critical step for improving water quality in these lakes in the long term.