The effects of natural water level fluctuations on N and P cycling in A great lakes marsh

<p>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 ten 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 different 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 are located at the eastern edge of Lake Wairarapa in the Wellington Region. They formed as a result of the deposition of sanddunes 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% 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% 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.</p>

Vegetation Dynamics, Buried Seeds, and Water Level Fluctuations on the Shorelines of the Great Lakes

Coastal Wetlands ◽

10.1201/9781351070720-3 ◽

2018 ◽

pp. 33-58

Author(s):

P. A. Keddy ◽

A. A. Reznicek

Keyword(s):

Great Lakes ◽

Water Level ◽

Vegetation Dynamics ◽

Water Level Fluctuations ◽

Buried Seeds

The contribution of lake benthic algae to the sediment record in a carbonate mountain lake influenced by marked natural water-level fluctuations

Freshwater Science ◽

10.1086/676471 ◽

2014 ◽

Vol 33 (2) ◽

pp. 499-512 ◽

Cited By ~ 11

Author(s):

Marco Cantonati ◽

Graziano Guella ◽

Daniel Spitale ◽

Nicola Angeli ◽

Andrea Borsato ◽

...

Keyword(s):

Water Level ◽

Natural Water ◽

Benthic Algae ◽

Mountain Lake ◽

Water Level Fluctuations ◽

Sediment Record

Water-level fluctuations in Lake Ontario over the last 4000 years as recorded in the Cataraqui River lagoon, Kingston, Ontario

Canadian Journal of Earth Sciences ◽

10.1139/e90-143 ◽

1990 ◽

Vol 27 (10) ◽

pp. 1330-1338 ◽

Cited By ~ 8

Author(s):

Robert W. Dalrymple ◽

John S. Carey

Keyword(s):

Great Lakes ◽

Water Level ◽

Lake Ontario ◽

Organic Content ◽

Water Level Fluctuations ◽

Great Lakes Basin ◽

Radiocarbon Dates ◽

Western Great Lakes ◽

Low Levels

The modern sediments in the Cataraqui River lagoon and marsh (Kingston, Ontario) consist of mixtures of organic material and clayey silts, the organic content of which increases as water depth decreases; gyttjas are accumulating in the deeper water parts of the lagoon, whereas peat is the dominant sediment in the very shallow water portion of the lagoon (< 0.7 m) and in the adjacent marsh. Cores show that one partial (modern) and two complete depositional cycles (gyttja passing upwards into peat) have formed within the last 4000 years. The contact between cycles (gyttja over peat) is abrupt. These cycles are interpreted as resulting from fluctuations in the level of Lake Ontario about the long-term rising trend. Radiocarbon dates show that relatively low levels prevailed from 4100 to 3300 BP and from 2300 to 1900 BP; rapid rises in water level, which are indicated by the abrupt contact between cycles, occurred at 3300–3100 BP and some time between 2000 and 1500 BP. These water-level changes are synchronous with those shown by other studies in Lake Ontario and with century-scale paleoclimatic events. The high stands correlate with wet periods, and perhaps also with warm periods in the eastern part of the Great Lakes basin, but an inverse relationship between precipitation and temperature in the western Great Lakes suggests that the Great Lakes basin does not respond uniformly to climatic changes.