Why are the world’s lakes disappearing?

By Tierney Smith

Something is going on with the world’s great lakes. Slowly but surely, some of them appear to be vanishing.

Iran’s Lake Urmia has become the latest lake to be categorised as under ‘serious threat’ from climate change, but it’s the latest in a long line of similar disappearances.

Some – like the dying Aral Sea – can be attributed to ill-conceived irrigation schemes. But for others the causes are less clear.

A recent report from the United Nations Environment Programme (UNEP) found that studies of Iran’s Lake Urmia have seen a decline in water levels of as much as seven metres between 1995-2011.

The most recent satellite image of Iran’s Lake Urmia demonstrates how drastically the lake has shrunk since 1998 (NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using Landsat data provided by the United States Geological Survey)

The main cause for the drying up of the lake is drought caused by climate change impacting the inflow to the lake – resulting in a 65% reduction in water levels.

Increased diversion for irrigated agriculture, the building of dams and reduced rainfall over the lake’s surface, are also named as contributing factors.

Scientists have warned that continued decline of Lake Urmia could have huge impacts on the area.

These include a changing local climate – hitting agriculture, livelihoods and heath, increasing the salinity of the water, destroying ecosystems and wetland habitats and increasing the chances of wind blown ‘salt storms’.

The story of Lake Urmia, however, is not new, and similar examples can be found at lakes and rivers across every continent in the world.

According to the World Preservation Foundation one third of the world’s major rivers and lakes are drying up, and the groundwater wells for 3 billion people are being affected.

The loss of rivers, lakes and underground water reserves are impacting the livelihoods of millions of people, hitting animals, farming and electricity production, as well as threatening to exacerbate climate change further through the release of CO2 and methane.

While climate change is playing a role, the building of dams, over extraction and mismanagement of water and over-fishing are all playing a part in the disappearing of the world’s lakes and rivers.

I’ve taken a look at some of the biggest examples of dying lakes and the causes behind them.

The Aral Sea

On the borders of Kazakhstan and Uzbekistan, the Aral Sea was once the world’s fourth biggest inland sea. Today it is mostly desert.

Over the last several decades the lake has receded by as much as 75% to 90% following moves from the former Soviet Union which diverted waters from the Ama Dariya river and the Syrdariya river – both of which fed into the Aral Sea – to grow cotton in the desert.

Satellite images show the decline of the Aral Sea between 2000 and 2011 (images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite)

The ecological disaster which followed left the seabed covered in salt – with winds blowing this salt into the surrounding regions – and changing the surrounding climate – with  shorter, hotter and rainless summers and longer, colder and snowless winters.

Fish stocks – previously a staple diet for those living around the Aral Sea – have diminished, drinking water is salinated and disease is rife.

While work is currently underway to change the farming methods said to cause the problem, the lakes may never fully recover.

Lake Chad

One of the best examples of what climate change is doing to lake and river systems, the world must look towards Lake Chad.

The fourth largest lake in Africa, Lake Chad is shared by Nigeria, Chad, Cameroon and Niger.

Global warming, with steadily reducing rainfall, and water extraction have seen it diminish around 80% in the last 30 years.

Plans to mitigate the effects of climate change on the lake include methods from planting more forestry in the immediate surroundings to building a dam and 60 miles of canals to transfer water from the Congo River to the River Chari which feeds into the lake.

RTCC VIDEO: Engr Sanusl Abdullahi from the Lake Chad Basin Commission explains why the lake is so vital to the area and what work is being done on the ground to protect it…

North America

The threats to rivers are in no way isolated to regions in Africa, Asia and the Middle East.

In North America a series of dams, and the diversion of water for large cities and agricultural irrigation has left the Colorado River – once one of the most prosperous wetlands in the North American continent – a dried up desert of salt flats.

In a recent blog on the Huffington Post one blogger, Zachary Podmore shared his experience of kayaking the length of the river, and reaching the final of the 11 dams – the Morales Dam.

“On one side of the dam was the Colorado River,” he writes. “On the other was a trickle of water – much too shall to float – which disappeared into the sane within a couple of miles.”

“The mighty river that had carried us across six states and into another country had been entirely diverted out of its former riverbed 90 miles from the sea.”

The same can be seen across the US. For example, the Rio Grande River completely disappears for much of its length, without reaching the sea.

Worldwide examples

The list doesn’t stop there. According to the World Preservation Foundation diminishing rivers spread as far as South America (Lake Cachet, Chile), Europe (the Mersey and the Severn, UK and the Rhine, Germany), Australia (Lake Colac), Asia (Mekong-Lancang) and Africa (the Nile).

Read more on: Nature |