Geology for Global Development

hydrogeology

The importance of wetlands

The importance of wetlands

World Wetlands day is celebrated on 2nd February, marking the adoption of the Convention on Wetlands, also known as Ramsar Convention, in the Iranian city of Ramsar on 2nd February 1971. It “provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources.

Today 170 countries have adopted it and 2,341 Ramsar sites covering over 2,5 million km² are designated as Wetlands of International Importance. But what are wetlands and why should we care about them? I’ll address these questions and other important points in this article.

First, what are wetlands?

Basically, a wetland is an area of land that is covered with water, whether natural or artificial, permanent or temporary. This water can be salt, fresh or somewhere in between, and have a maximum depth of six metres. Mangroves, marshes, ponds, peatlands, swamps, deltas, estuaries, low-lying areas that frequently flood are all wetlands and they can be found on every continent. Some of the largest ones are the Sundarbans mangrove forest in the Ganges-Brahmaputra delta in Bangladesh, the Amazon River basin (figure below), and the Pantanal, both in Brazil.

Wetlands cover about 3% of world’s surface. A web-based map shows the global distribution of wetlands and peat areas. It was launched in 2016 by researchers from Sustainable Wetlands Adaptation and Mitigation Program – SWAMP and is based on satellite images acquired by the  Moderate Resolution Imaging Spectroradiometer (MODIS) instrument.

Why should we care about wetlands?

Wetlands are rich but also fragile environments. They can provide water, fish/biodiveristy, recreational areas and help to regulate the climate.

  • Biodiversity: Wetlands function as wildlife refuge, supporting high concentration of mammals, birds, fish and invertebrates, being nurseries for many of these species.
  • Resources: Further, they can be a huge resource for humans, supporting rice paddies (Figure 2), a staple food. They also help purify water by trapping pollutants and heavy metals in the soil and neutralizing harmful bacteria by breaking down suspend solids in the water.
  • Geohazards: Wetlands provide flood control and storm protection in coastal areas acting like a sponge during storm events such as hurricanes, reducing their power of destruction.
  • Climate change: Here is another important point that I would like to highlight about wetlands. They play an important role in climate change mitigation and adaptation, since they store huge amounts of carbon. If you are curious about this topic, see this post where Heather [a regular contributor to the GfGD Blog] discusses how carbon is stored in peat soils in the tropics and the main threats to these areas.

Wetlands in Amazon river basin during the dry season (Oct 2017), close to Santarém, Brazil – Photo: Bárbara Zambelli

Threatened environment

Despite their social and ecological importance, wetlands are continuously being degraded and even destroyed worldwide. According to this research the world has lost 64-71% of their wetlands since 1900 AD. Here is a list of the main threats towards wetlands:

  • Pollution: Generally located in low-lying areas, they receive fertilizers and pesticides from agricultural runoff, industrial effluents and households waste or sewage. These pollutants have detrimental effects on water quality and threaten the fauna and flora of wetlands. As I mentioned before, wetlands work as water filters, therefore there is a growing concern about how pollution will impact drinking water supplies and wetland biological diversity.
  • Agriculture and urbanization: One of the biggest threats to this environment is its drainage to make room for agriculture and human settlements. Such activities are an increasing threat and they destroy the ecosystem and all the benefits wetlands can provide.
  • Dams: The construction of a dam alters the natural flow of water through a landscape. This alteration may lead to an increase or decrease of water flow through a wetland, being potentially harmful for wetland ecosystems. Thus, it is essential to choose the location of a dam wisely, to reduce the impact on existing ecosystems.
  • Climate change: Climate change is shifting the world’s temperature and precipitation patterns. Wetlands are getting lost due both too much and too little water. Shallow coastal wetlands such as mangroves are being swamped because of sea level rise. In areas affected by droughts, estuaries, floodplains and marshes are drying up. Wetlands and climate change are the theme of World Wetlands Day in 2019.

Opportunities – taking action

Wetlands are a critical environment and their effective management can give a substantial contribution to biodiversity conservation and restoration, maintaining its bioecological characteristics and allowing the using of resources economically.

According to SWAMP, “carbon-rich mangroves and peatlands are high priorities in climate change adaptation and mitigation strategies throughout the world.”

With their partners, SWAMP have developed a collaborative agenda expected to raise the awareness about sustainable management of wetlands in changing world and livelihoods of local communities. The Ramsar Convention, an international agreement, is still important today because it supports environmental policy development and it encourages countries to commit to it. It is also valuable as an international forum for gathering and sharing knowledge about sustainable wetlands management. Also international NGOs such as Worldwide Fund for Nature (WWF) and Wetlands International play an important role.

Finally, regarding the Sustainable Development Goals (SDGs), recently Ramsar published a briefing note of how wetlands can contribute to their achievement. Access it hereto find out more details.

World Water Day 2016

The 22nd March 2016 is World Water Day, an annual event organised by the United Nations to promote the vital importance of ensuring universal access to clean, safe water. Around 10% of the world (650 million people) still lack access to clean water. 

Water is essential for life. When communities don’t have clean water they are forced to drink dirty and dangerous water, causing illness and sometimes death. Communities may also have to walk several kilometres to collect their water, sometimes clean and in other cases dirty but the closest or only water source around.

Clean water can transform lives, having a direct impact on many other areas of development. As it is usually women and children who collect water, a sustainable, clean water supply close to homes means that children can attend school and enjoy an education. Women can engage in more income-generating activities, adult education and see improvements in gender equality. Health is also transformed across the community, with reductions in disease and premature deaths.

Daily collection of water in Tanzania (2014)

Daily collection of water in Tanzania (2014)

Great progress has been made in recent years in helping bring access to clean water to more and more people, but there is still a lot of work to do. Geologists in both research and practice have a significant role to play in identifying sources of water, managing water supplies and protecting them from contamination. The relevant and important knowledge that we already have needs to be effectively used to support local (often village level) water user committees, government water departments and NGOs operating in affected regions. Effective technical-capacity strengthening at all levels is vital to ensure that water supplies are sustainable and effective.

Find out more… At the EGU General Assembly, the Geological Society of London and Geological Society of America are co-organising a session on “Meeting the water needs of a growing global population: groundwater contamination, monitoring, mitigation and adaptation in developing countries (GSL/GSA sponsored session)”

The Impacts of Climate Change on Global Groundwater Resources (Part 4 of 4)

barry-christopherChristopher Barry is a doctoral researcher at the University of Birmingham. He has written for the GfGD Blog in the past – detailing his contribution to water projects in Burkina Faso and fundraising efforts to support such work. We have recently added a briefing note to our website, written by Christopher, describing the role of climate change on global groundwater resources. You can access the full briefing note here.

To help share the contents of this briefing note we are publishing a portion of it’s contents over a series of four blogs. This is the final instalment, with the rest available in our archives. At the end of each blog is a link to the full PDF, where you can read each section in its full context and find a full reference list.

6. Near-Surface Turbidity

6.1 How it Happens

Intense rainfall will lead to high-energy surface water.  This has the combined effect of flooding more ground due to higher river levels and picking up more material from the flooded land because of the higher energy of the water.  The material that is picked up will include sediment, but also harmful pathogens (harmful micro-organisms) that are found in excrement.  In short, much of the material on the ground is harmful for consumption and more intense water flow has a greater chance of picking this up and carrying it into the groundwater.  Turbidity of surface water has a detrimental effect on surface water and shallow groundwater.  Even when wells are covered, the effects of turbidity may be seen in shallow groundwater wells, though uncovered wells are affected more seriously.  It results from more intense wet seasons, as described in the previous section.

6.2 Threatened Areas

As this is an effect of shorter, more intense wet seasons, this is also a process to which semi-arid regions are vulnerable.  Human factors can also make a location particularly vulnerable, in particular poorly contained excrement, either from animals or humans.  Excrement placed near a drinking water source is always a hazard, but high-energy water flows make it increasingly likely that pathogens will enter the water source.  The type of water source is also important, with shallow wells, wells with improper casing and uncovered wells at the greatest risk.

6.3 Example

A study in Malawi (Pritchard et al., 2008) found that wells abstracting water from shallow groundwater were susceptible to contamination resulting from turbid water on the surface. The most serious form of contamination was microbiological, likely in many cases from nearby sites where human excrement had been dumped. Wells which were not covered at the surface consistently contained dangerous levels of pathogens, but many covered wells (about 90 % in the wet season) also failed to meet standards for safe drinking water for pathogens. Wet season results were worse than dry season and is likely to be due to intense discharge washing pathogen-carrying material into shallow groundwater. If climate change makes peak discharges more intense in the wet season, this problem is likely to worsen over time.

 

7. Parched Soil and Vegetation: Effects for Groundwater Recharge

7.1 How It Happens

The effect of climate change on the recharge of groundwater in semi-arid regions has not received enough scientific attention to be able to predict reliably.

On the one hand, longer and hotter dry seasons parches the topsoil, causing it to crack.  This actually assists the water from the next wet season in being taken into the soil and infiltrating into the groundwater, because water flowing over it ponds in the cracks, rather than flowing away and being lost into the sea.

On the other hand, the harsher dry season conditions lead to a loss of vegetation (plant life).  Vegetation helps groundwater recharge by holding rainwater in its leaves for a while before dropping it, and therefore reducing the intensity of water flow on the ground.  Tree roots also assist the infiltration of water through the soil into aquifers.

The interacting factors are depicted in Figure 3. Consequently, uncertainty exists as to what effect climate change will have on groundwater recharge with respect to surface conditions.

GWater4

Download the full briefing note (including a reference list) on the Water and Sanitation page of the GfGD website.

The Impacts of Climate Change on Global Groundwater Resources (Part 3 of 4)

barry-christopherChristopher Barry is a doctoral researcher at the University of Birmingham. He has written for the GfGD Blog in the past – detailing his contribution to water projects in Burkina Faso and fundraising efforts to support such work. We have recently added a briefing note to our website, written by Christopher, describing the role of climate change on global groundwater resources. You can access the full briefing note here.

To help share the contents of this briefing note we are publishing a portion of it’s contents over a series of four blogs. In this third instalment we focus on the effects of temperature and precipitation changes on groundwater recharge. At the end of each blog is a link to the full PDF, where you can read each section in its full context and find a full reference list.

4. Temperature Changes: Effects for Groundwater Recharge

4.1 What Happens

Groundwater recharge occurs by rainwater infiltrating through the soil.  Water at the surface will either enter the soil and groundwater, evaporate, run off into rivers and the sea, or be consumed.  The atmospheric rise in temperature increases the amount of surface water being evaporated, and therefore reduces the amount of water available for groundwater recharge.

In basins in which the groundwater is recharge from melting ice, the rise in temperature increases the rate of recharge by increasing the rate at which the ice melts.  But eventually the ice becomes depleted and then that source of water is lost.

4.2 Example

Tajikistan, in Central Asia, is a country that is highly dependent on melt water from glaciers as a source of water.  In the Pamir mountains of Tajikistan, a retreat of glaciers due to melting of 1% per year has been observed.  This raises concerns about the long-term security of this water resource.  In the short-term, increased rates of melting poses the risk of large outbursts of water.  Such an event occurred in 2005, killing 25 people (Mergili et al., 2012).

5. Precipitation Changes: Effects for Groundwater Recharge

5.1 What Happens

Climate change focuses the rainfall across the year into a shorter, more intense wet season.  In humid and temperate areas, much of the intense rain water may be wasted into the sea, because the soil has a limited capacity for infiltration.  In these areas, intense rainfall caused by climate change is likely to overwhelm the process of infiltration and therefore reduce annual groundwater recharge.

Conversely, in the arid and semi-arid climates of the sub-tropics, recharge is favoured by intense rainfall.  This is because rain water falling at a slower rate is likely to be largely evaporated.  More intense rainfall is too fast for a large proportion of rainwater to be evaporated, so a lot more of the water is able to infiltrate.

These factors are demonstrated in Figure 2.

GWater3

For basins containing ice or glaciers, the type of precipitation is also important.  Rising temperatures increase the amount of rainfall relative to snowfall.  The effect of intense rainfall is reduced if some precipitation falls as snow, because the run-off is delayed until the snow melts.  Therefore a reduction in snowfall compared to rainfall also increases the intensity of wet season run-off.

5.2 Example

In the UK, a set of climate change projections developed by the Meteorological Office called UKCP09 [1] have been used to assess the likely outcomes of changing climate on water resources.  UKCP09 consists of eleven equally likely climate scenarios projecting the next 150 years.  Simulations of river flows consistently show that we should expect a decrease in mean flow rates and even lower flows during droughts, although there is variability in the predicted results for high flow events.  Conversely, the effect on groundwater level is less pronounced – though for the UK a general decrease is more likely, some climate projections would give an increase with some groundwater models.

[1] http://ukclimateprojections.metoffice.gov.uk/21678

Download the full briefing note (including a reference list) on the Water and Sanitation page of the GfGD website. The final instalment, Part 4, will be published on this blog soon.