Freshwater wetland management

Hey guys,

Recently, I’ve been to the Florida everglades during one of my school trips, it was amazing!

Firstly, let me introduce what a wetland is!

Wetland is an area of land whose soil is saturated with moisture either permanently or seasonally e.g swamps, marshes and bogs in which Florida Everglades is one of it.

Today let’s briefly talk about what happened in Florida Everglades, United states and their channelisation with the Kissimmee River. 

Here is a hand drawn map of Everglades that I did during our trip. In this map it clearly shows that the Kissimmee River flows south into the Lake Okeechobee in which during the wet season it will overflow, causing a slow-moving river of grass that extends to the Florida Bay. 

picture of the old and new channel

Channelisation

Basically during the 1960s, Kissimmee was being channelised with the aim of reducing flooding for flood management, however, it caused both negative and positive impacts on the environment.

The positive impacts are mainly for nevigation and flood control.

Aim:  Flood management ( reduce flooding)

Impacts: 

Positive Impacts :

– Navigation

Flood control

Negative Impacts :

– Flood plain dried up after channelization and no longer reaches bankfull discharge

– reduction of the floodplain → reduction in waterfowl habitat by 90% (especially Herons and Egret)

– Catches of Largemouth bass are reduced

– Increasing in the level of pollution with 25% of nitrate and phosphate pollution  downstream flowing into the Lake Okeechobee 

– Reduce in water quality

– Decline in fishing, bird watching and hunting tourism

– Reduce in the amount of oxygen in rivers

– Increase in invasive species such as crocodiles and wild boars

Restoration in 1990s (also called dechannelization)

Aim: Restore over 100km squared of river and floodplain wetland

Impacts:

Positive impacts

– Reduction in nutrient loads (phosphate, nitrate) to downstream Lake Okeechobee (Bacteria living in wetland can purify and clean the river)

– River flows freely and no longer stagnant → dissolved oxygen levels improve

– Restoration benefits avian species (e.g. Bald eagle, wading birds and water fowls) with the habitat and food provided

– High water levels increases support for a natural river ecosystem

– Game fish activities attracts recreational fishermen and boosts tourism industry → providing employment opportunities

Negative impacts

– Expensive project ($578 million) – costs almost twice as much as channelizing the river!

– Benefits of navigation are lost

– Shallow body of water created → more water is lost through evapotranspiration

Kissimmee river restoration

Formations of Wetland :

wetlands are formed when a river overflows its banks or when changes in sea level make once dry areas saturated where the river meets the sea / ocean. In addition, climate can impact wetland formations as high rainfall in normally dry areas with poor drainage causes ground to become saturated.

Wetlands now only cover 6% of the earth’s surface. This is roughly half the amount of the planet that was covered in wetlands 100 years ago. The most important are:

Bogs (30%): A wetland area that accumulates acidic peat, a deposit of dead plant material. Bogs occur where the water at the ground surface is acidic, either from acidic groundwater, or where water is derived entirely from precipitation Water flowing out of bogs has a characteristic brown color.

Fens (26%): Low land that is covered wholly or partly with water unless artificially drained and that usually has peaty alkaline soil.

Swamps (20%): A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of dry-land areas, covered by aquatic vegetation or vegetation that tolerates periodical inundation (being covered by water).

Floodplains (15%): All rivers have floodplains. They are the valley floors that get covered in water when a river exceeds bankfull discharge. However, with an increasing amount of rivers being managed e.g. levees and dams, floodplains are spending less time underwater.

Lakes (2%): Lakes are surface stores that are fed by rivers. Some lakes e.g. Caspian Sea are being drained because of unsustainable use.

Values of Wetlands :

Importance of Wetlands

• Flood control: Many wetlands are covered in vegetation which can intercept precipitation, absorb rainwater and transpire water. Wetland vegetation can also reduce the velocity of rivers flowing into them or from them and act as natural stores of water. If you remove or drain areas of wetland more pressure is placed upon the main river channel. Coastal and marine wetland areas can also absorb the energy of tropical storms, tsunamis etc.
• Groundwater recharge: Wetlands can collect large areas of precipitation and river discharge. As this water is held in storage it will infiltrate and percolate into the ground to recharge groundwater.
• Transport Network: Wetland provide many natural waterways that people can move around on easily.
• Tourism and Leisure: Some wetlands, like the everglades in Florida or the fens in East England become tourist attractions. They also become popular locations to bird watch, fish and hunt.
• Flora and Fauna: Many wetlands are unique habitats that support indigenous aquatic plants and animals. Many wetlands support rare reptilian and amphibian species. Many migratory birds also rest in wetlands flying to and from nesting and breeding grounds.
• Fisheries: Wetlands can support large numbers of fish which can support local populations. Wetlands are not normally viable commercial fisheries.
• Water purification: The soils, geology and vegetation of wetlands can help clean and purify water.
• Storage of organic matter: Wetlands support large areas of organic matter that can hold large stores of methane (greenhouse gas).
• Coastal stabalisation: Wetlands that occur along the coastline and on river banks have prevent erosion from the sea or by rivers.

Factors Causing Loss and Degradation of Wetlands

Increased demand for agricultural land: As the world population grows there is an increasing demand for food. With the amount of viable agricultural land decreasing, increasingly areas of wetland are being artificially drained to make ways for agricultural land e.g. the draining of the fens in East England.

• Population growth: As the world’s population grows, it demands more water, more food and more land. The increasing demand for water can mean wetlands are drained of their water or their source of water. This problems is made worse as the world’s population develops and uses more water e.g. showers and toilets.
• Urbanisation: With the world population growing, there is a greater demand for housing. Increasingly this demand for housing is in urban areas. With urban areas growing more and more wetland areas are being drained or inhabited. Urbanisation on or near wetlands can cause pollution, changes in river flow and river channels and disturbance of wildlife. Land reclamation is the process of reclaiming land from the water.
• Sea level rises: Global warming is causing glaciers and ice sheets to melt causing sea levels to rise. These rising sea levels can flood coastal and marine wetland areas. Even if the whole wetland is not flooded, water conditions can be changed from fresh to brackish.
• River flow changes: Many rivers have been channelised and straightened, reducing the amount of wetlands. Others have been drained or dams have altered flow. Some have been polluted or redirected. All these natural changes are removing or changing the ecosystems of many wetland areas.
• Pollution: Any form of pollution, but particular chemicals and metals can change the delicate ecosystems of wetlands. Process like eutrophication, caused by fertiliser run-off can completely kill whole wetland areas by preventing the wetland oxygenating properly and receiving sunlight.
• Infrastructure projects: As populations grow and we become more mobile, there is an increasing demand for new roads, airports, railways. etc. Unfortunately wetlands are often drained or disrupted (bridges, dykes and causeways) to make way for these projects.
• Alien species invasion: Many alien species like the cane toad in Australia or the American mink in the UK have been introduced to wetlands and devastated indigenous species. The introduction of any alien, however small can disrupt food webs and ecosystems.
• Tropical storms: Although wetlands can be a natural defence against tsunamis and tropical storms, they can also been damaged by them. Freshwater wetlands in particular can be flooded by storms surges associated with tropical storms, changing the salinity of water and damaging vegetation.