Hello everyone and welcome to Episode 38 in the series which focuses on water and some of the critical issues for the sustainable use of this vital, global resource. We will focus in this episode on what is called fresh water – that is not salt water as in the seas and oceans. Here in Ireland we lie on the western edge of Europe and face the wide Atlantic ocean and rain is a very regular occurrence for us and so of course we complain about it all the time. It is hard for us to really appreciate the critical water shortages in so many parts of the world. I am delighted to have Tim with me to help with this episode.
Hi everybody. The phrase ‘Water is Life’ is commonly used but when we witness how threatened the world’s water resources are, you would wonder, do we really believe that statement. Although about 70% of the earth’s surface is water, most of that is saline water – that is salt water – in the seas and oceans. Much of the planet’s fresh water resources are in the form of glaciers and snow and so actually less than 1% of water is in a form that humans can easily access and use.
The earth is a closed system and sunlight is the only resource which comes into the system from outside. The planet has a natural water cycle that replenishes itself through a vast interconnected mechanism where water flows from the air to the earth and back to the atmosphere. Water evaporates from lakes, rivers and other sources and under certain conditions in the atmosphere it forms clouds and falls back to earth as Precipitation – that is rain and snow. Of this water, some of it immediately evaporates back into the atmosphere because of the heat at ground level. More of it is absorbed by plants’ roots and returns to the atmosphere, in a process known as Transpiration. These terms are sometimes combined as Evapotranspiration which is a really big word that can be used to impress your friends. The amount of water that evaporates each year and the amount that falls back to the ground are virtually constant, meaning that the amount of water on Earth does not change. So if a drought occurs in a specific region, it is not because the world’s rainfall for the year is less, but because the water is falling somewhere else on Earth.
Fresh water is also held in snow and glaciers which act as reservoirs and release this water as the summer melting occurs. For example, the Himalayan glaciers supplying much of India and China or the snow packs in the Sierra Nevada flowing to California and other states. The rest of the precipitation water seeps into the ground to form wetlands such as bogs, marshes and lagoons and as much as forty percent of these have been drained or developed over the past few decades.
Water flows and collects beneath the Earth’s surface also, gathering in soils, crevices and rocks and the term Groundwater is used to describe these sources even though they are underground. Where there is a body of rock saturated with water it is referred to as an Aquifer and these are the sources of water for a large portion of the world’s population using wells and pumps. The process of water entering into the groundwater or aquifer supplies is called the Re-charging of the supply. The level at which the ground is saturated is called the Water Table and this level is dropping in many areas as the sources are being used at a faster rate than nature can re-charge them causing a Falling Water Table. As the water table falls, deeper and deeper wells are required to access water and this affects the poorer populations greatest as they do not have the finances to build and maintain such systems. Giant aquifers such as the San Joaquin in California have been damaged by over extraction of the water to the extent that the ground has collapsed and destroyed access to the supply. The Ogallala aquifer in the centre of the United States is being over-used to supply the crops in several states.
The other major issue is water services – that is the management and control of water use. This covers issues such as pollution and wastewater treatment. The obvious above ground water sources such as rivers and lakes are used as reservoirs for easy access sources of supply. The biodiversity in rivers and lakes are real indicators of the health of an ecosystem and in many parts of the world this is falling drastically. Whilst in some areas of the world the pollution from industry has been controlled there are still huge areas with very bad outflows causing damage to water sources. These piped outflows from a factory or industrial area are called Point Source Pollution. The worst industrial pollutants can damage the underground water sources we depend on so heavily.
Agriculture has become not just a massive user of water but also a major pollutant through what are called Run-offs of the synthetic chemical fertilizers and pesticides which are used to increase crop yields. A percentage of the chemicals used are not taken up by the plants and instead enter the water system underground. These are called Non-Point Source Pollutants. This is a major source of water pollution even in countries which have now got industrial pollution under control. Efforts are being made to design agricultural systems which promote better use of or even eliminate the use of such chemicals. Furthermore, run-off nutrients from fertilizers and farm animals can result in excessive growth of algae called Algal Blooms in water bodies causing what is called Eutrophication. This is where the algal bloom greatly reduces the oxygen in the body of water and so damages or kills other plant and animal life.
It is estimated that up to 50% of water in our cities is wasted through leaking pipes. The huge supply needed for many cities has seen the development of Recycled Water which is treated domestic wastewater that is used more than once before being returned into the water cycle. Reclaimed water is similar and is where used water is stored for other uses such as in industry or public parks. Relatively clean waste water from sinks in a house or a building is sometimes reclaimed and used to flush the toilets and this is referred to as a Greywater system. Catching the rain off the roof and storing it for use in the garden or non-drinking water is called Rainwater Harvesting. This has been common practice in many dry countries for years but is now being considered in countries where water scarcity is not so acute. These are some of the examples of efforts to reduce how we are wasting water in many countries.
Similar to the term eco-footprint the term Water Footprint is a measure of the amount of water used by an individual, a business, a community or a nation. It is often measured in relation to the Earth’s capability to supply water – so the developed world’s water footprint far exceeds the Earth’s capacity to supply this should everyone in the world use water at that rate. The water footprint is far greater than the amount of water you drink or use in your home. The majority of any water footprint is made up of the water used in the manufacture and supply of the products consumed – this is called Invisible Water and it can represent over 90% of the water footprint figure. For example, a half litre of beer takes around 80 litres to produce. This rate of water use is true of many other products also and so measuring our invisible water use is a critical factor in understanding the limitations of our current system.
Within Ireland where water flows freely there is still the ancient tradition of the sacredness of water, recognising the life giving properties it contains. Many villages still have ‘holy wells’ and some locals respect and honour the waters. Despite this our modern lifestyle disconnects us from nature and many of our activities undermine the supply of this sacred water. Some of this is done through ignorance, some through the primacy of economics over other considerations. We all need to learn, understand and respect how dependent we are on nature’s resources despite our technological brilliance and seeming dominance over nature.
That concludes this episode in the series. My thanks to Tim for his help with this today and to you for listening. I hope you found it useful and informative and that you can join us for other episodes in the series. Thank you.