1. Ecology and water quality of lowland lakes
Collaborative Stakeholder Group Workshop 6
Ecology and water quality of lowland lakes
in the Waikato region
David Hamilton
Environmental Research Institute, University of Waikato

2. Meeting the bottom line for chlorophyll a in the NOF
mg m-3 D
Bottom Line

3. Total N Meeting the bottom line for total nitrogen in the NOF mg m-3 D

4. Total P Meeting the bottom line: total phosphorus in the NOF mg/m3 D

5. LakeSPI index: indicator for submerged plant health
Lake Waahi
NIWA Report No: HAM

6. Nutrients in Lake Whangape
Wood et al. (2010) Harmful Algae

7. Comparison with N and P in lakes internationally
Waikato
lowland lakes
Abell et al. (2010): Ecosystems

8. Cyanobacteria in Lake Whangape
Wood et al. (2010) Harmful Algae

9. Storm event – Rotopiko South (September 2013)
4 tonnes ‘additional sediment’ delivered in 24 hours
11 kg ‘additional P’ delivered in 24 hours

10. Lake Ngaroto monitoring buoy dissolved oxygen
Chris McBride (University of Waikato)

11. Chlorophyll a in four shallow, lowland Waikato lakes
Hamilton et al. (2010): Waters of the Waikato

12. Applying ecological theory to changes in lake state
Photo: G. Tempero
Hobbs and Harris (2001). Restoration Ecology: Repairing the Earth’s Ecosystems in the New Millennium
Photo: J. Clayton (NIWA)

13. Re-engineering of existing systems
A Bruere
R Eivers
R Eivers
R Eivers

14. Native vegetation (%) in peat lake catchments
Ohinewai
1.3
Waahi
5.8
Waikare
6.7
Whangape
6.3 {

15. Can we reverse the trend and improve the current state?
> 20% native vegetation in catchment (threshold for regime shifts?)
> 5% of catchment in wetlands (N, P and SS removal)
Koi carp and invasive macrophyte removal (biological effects)
Re-engineering (physical effects)
Sediment treatment in some cases (addressing legacies)