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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, 13 November 2017 10:19

The new green scene

Harnessing wetlands as green infrastructure solutions to our water woes
For one weekend every July in Canada, the village of St. Pierre-Jolys hosts the National Frog Jumping Championship. It’s part of the annual Frog Follies Festival. The thriving Franco-Manitoban community is also proud of its parks, a new residential compost pickup service and the Trans-Canada Trail that runs along the nearby Rat River. It’s about as green as it gets here. And it’s about to get greener.

Seeing wastewater through a green lens

Standing on a grassy berm overlooking St. Pierre-Jolys’ current wastewater treatment lagoon, Janine Wiebe points to an adjacent muddy field.
“In a few months, this field will be full of heavy equipment,” she says, smiling. The village’s chief administrative officer describes how their wastewater treatment system will expand to include a new tertiary treatment wetland.

Like all communities, St. Pierre-Jolys must anticipate the current and future needs of their wastewater treatment system. Future growth depends on it. Their system needs to remove pollutants, deliver clean water, handle increased volume and cope with the uncertain timing of storm water events.

Traditional, concrete treatment plants are expensive to build and maintain. St. PierreJolys found a better solution.

Staff from Native Plant Solutions (NPS) proposed the tertiary treatment wetland; a sustainable, cleaner, cost-effective and greener way to reduce nutrient levels in the village’s wastewater.

“In this system, a third cleansing cell – the wetland – is added to the primary and secondary treatment cells to reduce phosphorous levels,” says Glen Koblun, manager of NPS. NPS is a consulting branch of Ducks Unlimited Canada (DUC) and a leader in science-based treatment wetland systems.

“There’s lower maintenance and management costs to this system compared to chemical or mechanical treatment options,” adds Koblun. 

The treatment wetland system takes advantage of the natural functions of wetland plants – a process called phytoremediation – that transforms common pollutants into harmless by-products or essential nutrients. This comes from the sheer amount of biological activity that occurs in a wetland system including sunlight, wind, water, air, plants and soils.

“This project fits our vision,” says Wiebe. “We are leaving a legacy that will make it easier for future generations. It allows room for expansion and will cost less in the long run.”

Green infrastructure: it’s only natural

Green infrastructure is a buzz word that’s infiltrating conversations about making communities more resilient to disasters like floods. DUC research scientist Pascal Badiou, PhD, believes green infrastructure is essential. Wetlands, he says, are one of the most powerful systems available to us.

Traditional built infrastructure such as dry dams or water treatment systems serve an important role but typically address only one issue and come with high maintenance costs,” says Badiou.

“Green infrastructure, which includes natural areas, vegetation and wetlands, captures and treats stormwater and runoff at its source. It’s building with nature instead of concrete.” 

Communities from coast to coast are finding that nature has an effective and efficient way to deal with wastewater: wetlands. These cost-effective, natural powerhouses provide benefits and services that reduce the need for costly built (grey) infrastructure such as dams, water diversions, water treatment plants and engineered carbon sinks. Green infrastructure like wetlands can also reduce pressure on and extend the life of grey infrastructure. ©DUC

Wetlands hold rainwater, snowmelt and floodwaters. They filter pollutants, store carbon, replenish groundwater, reduce erosion and provide habitat for wildlife as well as places for people to enjoy the outdoors.

“Other types of flood control are not able to deliver the additional benefits that wetlands provide,” says Badiou, who has conducted extensive research across the Prairies about the role of wetland drainage on water quality and quantity.

Seeing the green light through restoration

Getting people and governments to appreciate green infrastructure can be difficult. In Alberta, it took the devastating floods of June 2013 for the provincial government to reach a watershed moment. Southern Alberta was inundated. Downtown Calgary shut down. These events cost millions of dollars in damage.

The government responded with a number of funding programmes to address a wide range of recovery activities, including the Watershed Resiliency and Restoration Programme (WRRP). As its name implies, the WRRP aims to improve watershed functions to build greater long-term resiliency to droughts and floods. Resiliency would be improved through restoration, conservation, education and stewardship.

Traditional mitigation projects involve largescale construction or engineered structures (“grey” infrastructure). Watershed restoration supported by WRRP focuses on natural solutions. This includes conserving and restoring wetlands.

Tracy Scott, DUC’s head of industry and government relations in Alberta, and other DUC staff presented a business case for the use of wetland restoration for flood mitigation in southern Alberta. Their efforts helped inform the government’s development and implementation of the WRRP.

“The expansion of the WRRP programme to include natural green infrastructure was an excellent example of how we helped the Government of Alberta align wetland conservation with provincial and societal priorities, including Alberta’s Wetland Policy,” says Scott. “Few people recognise that the new Alberta Wetland Policy represents an important implementation tool to support Alberta’s flood, drought, water quality and biodiversity management goals.”

During the first round of the programme’s implementation in 2014, DUC has received $11.6 million to fund restoration of 1,380 acres (558 hectares) of wetlands in flood- and drought-prone areas in the southern part of the province

“A significant proportion of that money is going directly into the pockets of participating landowners, rewarding them for their contribution to ecosystem services, with the balance being used for the actual restoration work,” says Scott.

This puts the natural power of the landscape to work, instead of relying only on traditional engineered infrastructure,” says Scott. It’s a proactive approach that’s safeguarding the long-term future of water, wildlife and people across the province.

“The WRRP is the first chapter of DUC’s green infrastructure story in Alberta,” says Scott.

St. Pierre-Jolys CAO Janine Wiebe stands near the future site of the village’s tertiary treatment wetland.

St. Pierre-Jolys CAO Janine Wiebe stands near the future site of the village’s tertiary treatment
wetland. The village consulted with DUC’s Native Plant Solutions on the project, will be an
additional treatment step to clean wastewater. This form of green infrastructure uses natural
wetland processes to clean the water before it enters the Rat River. ©Leigh Patterson


Pairing green with grey

As Alberta has learned, flood control is a key environmental benefit provided by wetlands. But little research exists specific to Ontario. The need to fill information gaps has escalated in recent years as the province has been hit with bigger storms and floods.

In 2016, DUC and several partners conducted research in the Credit River watershed, a densely-populated region vulnerable to extensive flooding. They used a hydrological model that quantified the consequences of wetland loss and gain on flooding under a variety of storm events. 

This past fall, the results came in.

Not surprisingly, in modeling scenarios where researchers removed wetlands from the landscape, flooding was worse. When wetlands were restored the intensity of flooding diminished.

The research supports the idea that when combined with built infrastructure like storm water retention ponds, green infrastructure like wetlands can provide another layer of flood defence. Green infrastructure like wetlands can also reduce the pressure on and extend the life of grey infrastructure.

“The research identifies areas where wetland restoration will have the greatest impact on flood reduction,” says Mark Gloutney, PhD, DUC’s director of regional operations, eastern region. “DUC can work with municipalities, conservation authorities and others to better plan for extreme weather and flooding by helping build up their inventory of natural infrastructure assets, like wetlands.”

Building climate-resilient communities in Ontario will require strategic investments in wetland restoration, says Gloutney. DUC, he adds, “is prepared to come to the table.”

Coast to coast: more shades of green

Janine Wiebe is looking forward to the final implementation of her village’s green vision. They plan to add educational signage and trails around the new tertiary wetland site. They also want to invite environmental science students to conduct research there.

As they wait, cities like Moncton, N.B. are reaping the rewards of investing in green infrastructure.

By working with NPS staff, Moncton has integrated wetland-like naturalised storm water retention ponds into urban developments. These urban wetlands are able to store and filter vast amounts of water, which improve water quality as a result.

Elaine Aucoin, Moncton’s director of environmental planning and management found that these systems are functional, and add to the quality of life for residents. “Wetlands look a lot nicer, and provide the community with a place to gather around, unlike dry ponds that are often fenced off, and a waste of space,” says Aucoin.

In March, DUC president Jim Couch recognised the City of Moncton with a special “Ducks Unlimited Canada Order of Conservation” for its wetland conservation leadership.

Leading the green infrastructure revolution on the opposite side of the country is Gibsons on B.C.’s sunshine coast. The town gained national recognition when the Globe and Mail profiled it for declaring Nature its “most valuable infrastructure asset”. Their 2015 financial statements read: The Town is fortunate to have many natural assets that reduce the need for man-made infrastructure that would otherwise be required. This and filtration), creeks, ditches and wetlands (rain water management) and the foreshore area (natural seawall).

What gets measured gets managed. So important are these green infrastructure assets, the town made a pioneering decision to include them under the same asset management system as engineered infrastructure.

Walking over a footbridge spanning the springswollen Rat River, Wiebe says she understands why Gibsons values the potential of green infrastructure solutions that exist around us.

“Instead of working against nature, we should be working with it.”

Leigh Patterson

Leigh Patterson

Leigh Patterson is editor of Conservator 

Published in Issue 173