Shallow lakes are highly valued but often degraded in New Zealand.
Recent research indicates degradation has occurred due to combined stresses from wastewater discharge and intensive agricultural land use in lake catchments, and invasion by exotic plants, that are prone to mass-collapses, and exotic coarse fish, that feed on lake plants or disturb lake bed sediments during their feeding.
In December a workshop of “Shallow Lake Restoration” was held in Hamilton to review the state and values of Waikato shallow lakes and the policy and science tools available to restore them (workshop flier). It involved a morning information session and an afternoon discussion session at the Serpentine Lakes where participants explored their key goals for restoration, key barriers to progress and innovative ways to make progress.
- Workshop flier (PDF 1.1 MB)
- Summary outcomes (PDF 242 KB)
Shallow lake management policy, status, recreational values and pressures
The Julian Williams outlined the Tainui tribe’s area of management in the Waikato and their vision for management of the restoration process for the Waikato River and its lakes and wetlands.
- Tainui (PDF 2.4 MB)
Dr Keith Thompson, recently retired from University of Waikato, evaluated the current framework for shallow lake management.
Keri Neilsen (Environment Waikato) reviewed the state of Waikato shallow lakes.
- The state of the Waikato shallow lakes (PDF 1.8 MB)
Rob Pitkethly (Fish and Game NZ) reviewed shallow lakes’ recreational values.
- Recreational value of shallow lakes (PDF 1.4 MB)
Dr Marc Schallenberg (Otago University) described the results of a national survey of the pressures associated with shallow lake flipping from a clear vegetated state to a turbid de-vegetated state.
- Pressures on shallow lakes (PDF 1.1 MB)
Tools for restoring lakes
Dr Gail Tipa (Ngai tahu, Tipa and Associates), described the Cultural Opportunity Mapping and Assessment tool she has developed to deliver outcomes to Maori through shallow lake restoration.
Dr Chris Tanner (NIWA) reviewed the tools for reducing and treating the external nutrient loads to waterways.
- Reducing & treating external nutrient loads (PDF 6 MB)
Dr Chris Hickey and Max Gibbs (NIWA) reviewed approaches to controlling internal lake loads of nutrients.
- Options for reducing in-lake nutrient loads (PDF 2.9 MB)
Mary de Winton and Dr Piet Verburg (NIWA) reviewed the opportunities and limitations of biomanipulation to restore lakes.
- Biomanipulation for lake resotration (PDF 6.7 MB)
Framework for decision making
Dr John Quinn (NIWA), Dr Marc Schallenberg (Otago University) and Prof David Hamilton (University of Waikato) overviewed the key messages from a science workshop on Shallow Lakes Management at the NZ Freshwater Sciences Society Conference on 25 November 2008 and presented a proposed framework for restoration illustrated using the Lake Hakanoa case study.
- Framework for restoration decision making (PDF 233 KB)
They conclude that greatest progress with lake restoration will occur by engaging all key stakeholders so that policy and practice are based on the best science information and the community is well-informed and motivated to act.
