Ducks Unlimited

Essential information for the decision making process of wetland restoration.

Abstract: Cheng Shi.

Wetlands are areas where lands transition  to water bodies. Because of this special geomorphological setting, wetlands play important roles in flood control, nutrient retention, and water storage. In New Zealand, less than 10 percent of the original wetlands have survived since human settlement. Many of the remaining wetlands are still under threat from water quality degradation, invasive species, and changes in hydrological regime. 

Wetland restoration is the process of bringing the structure and function of a wetland back to its original state. Although specific objectives may vary between projects, three major objectives of wetland restoration are restoration of wetland function, restoration of wetland structure, and restoration of traditional landscape and land-use practices.  In order to ensure the success of a wetland restoration project, a good understanding of the hydrological process in the wetland is the first step. 

Boggy Pond and Matthews Lagoon on the eastern edge of Lake Wairarapa in the Wellington Region were formed as a result of the deposition of sand dunes on the eastern shore and changes in river courses between floods. They were modified by a series of engineering works under the lower Wairarapa valley development scheme in the 1980s. 
As a result, Matthews Lagoon now receives agricultural outputs from surrounding farms; it is affected by water pollution and invasive plant species. 

Boggy Pond is cut off from Lake Wairarapa and surrounding wetlands by a road and stopbank, leaving a more stable water level compared to its original state. To analyse the water and nutrient balance in these two wetlands, factors such as surface flows, surface water levels, groundwater levels, rainfall, climate data, and water quality were assessed at various monitoring stations in this study. It is believed that Matthews Lagoon and Boggy Pond have completely different water regimes. Matthews Lagoon receives surface inflow from the Te Hopai drainage scheme and discharges to Oporua floodway, but Boggy Pond only has rainfall as the water input. 

The results from the water balance analysis seem to support this assumption. An unexpected finding in Matthews Lagoon suggests that water might bypass the main wetland, creating a shortcut between the inlet and outlet. As a result, the nutrient removal ability was considerably weakened by this bypass because of the short water retention time. 

In Boggy Pond, there may be an unknown water input which could adversely affect the 
water quality and natural water regime. Boggy Pond is expected to have better water quality than Matthews Lagoon as the latter receives agricultural drainage from surrounding farms. The results from water quality monitoring also support this hypothesis. The nutrient balance in Matthews Lagoon showed very limited removal ability for phosphate but much higher removal rate for nitrate. The removal rate in summer for phosphate was less than 5 percent while in winter more phosphate was discharged from Matthews Lagoon than it received from Te Hopai drainage scheme. For nitrate pollutants, the removal rate was as high as 17 percent even in winter. 

Some recommendations are given on the restoration of these two wetlands. First, set proper objectives according to their different functions. Second, enhance the nutrient removal ability of Matthews Lagoon by harvesting plants, removing old sediments, and creating a more evenly distributed flow across the wetland throughout the year. Third, restore the natural water level fluctuations and improve water quality in Boggy Pond by identifying any unknown water inputs first.

To view Cheng Shi’s full thesis go to:http://researcharchive.vuw.ac.nz/
handle/10063/3481
 

 

Published in Issue 162
Monday, 19 March 2018 07:22

Boggy Pond April rounds

Last April, I was able to complete the servicing round down at Boggy Pond, Mathews and the Wairio Restoration Block. The total predators trapped there for the month was :
 
1 cat, 5 ferrets, 1 weasel, 9 rats, 29 hedgehogs, 6 mice and 1 hawk.
 
While there I GPS’d another eight potential trapping sites on the new bund wall that was recently created.
 
A Timms trap was missing from the trap site by the Bridge to No Where and a Timms/ DOC 250 was missing past the second bridge  leading to the Viewing Hide. I suspect these  have been stolen as they were there when I serviced the gear in February. These missing traps will be replaced after duck shooting season. I am wary that more may disappear during that time with the influx of hunters to the area.
 
Steve Playle.
 
 

 

Published in Issue 164
Sunday, 25 February 2018 10:02

Keeping count at Boggy

Boggy trapping progress June, 2015.

Steve Playle completed two years of trapping at Boggy wetlands at the end of June this year.

He sent the following report:

Interestingly predator numbers have not reduced since the first year off trapping was completed. There is currently 94 trapping sites established around the project area now so trapping hours have increased substantially meaning that more traps have been available for predators to encounter than was the case in the first year.

Trapping Period Cats Ferrets Stoats Weasels Rats Hedgehogs Mice magpies Hawks Rabbits
2014/2015 20 60 2 18 87; 169 70 10 11 4
2013/2014 20 43 1 13 52 159 29 10 2 1
Over 2 years 40 103 3 31 139 328 99 20 13 5


Steve Playle
Biosecurity Officer
Published in Issue 165
Thursday, 22 February 2018 07:42

Spoonbills at Boggy Pond and surrounds

The photo is of spoonbill chicks in a nest early this year. The nest itself is a pretty loose affair of sticks placed in the base of a dead willow tree and surrounded by open water on all sides. As the chicks age the nest becomes a lot whiter, the result of droppings from both the chicks and their parents.

This was the first record of spoonbills nesting at Boggy Pond and only the second for Wairarapa.

They have been seen more often in the wider area over the past few years with the increased area of shallow wetland created by DU’s Wairio restoration project likely to be providing a good reliable food source.

I think, also, that the predator control in the area has been a big part of supporting these nests once they start and giving the youngsters a decent chance of fledging.

We hope that this is the first of many!

Earlier in the year a team took the canoe to  chase and spray purple loosestrife.

On the way out we noted a big flock of  spoonbills at the northern end of the lagoon and on the way back we came across some nests in the bases of sprayed willows. 

We didn’t approach too closely, but through the telephoto it looked like two chicks at least in each.

It was quite a shock to come across these, a  pleasant one too, as you’d imagine. This is the  second confirmed nesting site at Wairarapa Moana.

We plan to follow up the loosestrife work and will check on these chicks and have a look over a wider area to see if there are more.

I think this is a result of the combination  of willow spraying opening up the lagoon  and creating the right conditions for nest  building and the pest control keeping the nests alive instead of providing food for hungry mammals.

Tony Silbery

Kaiarahi- Koiora Rereketanga (Ranger,  biodiversity) DoC. 

Published in Issue 167
Monday, 04 September 2017 00:16

Hard Work at Boggy Pond

Steve Playle of the Greater Wellington Regional Council (GWRC) was on the job in early January getting trapping work done around Boggy Pond in the Southern Wairarapa.  
“I started back at GW on the 9th and my first job was to get the trapping work done over 10/11 January.
 
“Predators caught were 5 ferrets, 1 weasel, 8 rats, 21 hedgehogs, 4 mice, 1 magpie, 1 rabbit and 1 thrush. Water levels were still very high in the Wairio Restoration Block and at the southern end there were a couple of big flocks of Pied Stilts in residence. At Boggy Pond the Royal Spoonbills were back in residence where Tony Silbery took his photos of breeding birds last year. I am assuming there may be breeding taking place again this season.
 
“The total major predators taken since the trapping commenced in July 2013 now stands at:
  • 62 cats,
  • 140 ferrets,
  • 8 stoats,
  • 53 weasels,
  • 652 hedgehogs and
  • 295 rats.
There was a period prior to Christmas where it went quiet on the ferret scene but obviously there has been some movement over the festive break. It is great to see the water levels so good in the Wairio Restoration Block,” said Steve.
Published in Issue 170