Water

So commonplace and yet so important. It is thought by exobiologists that water is so essential that searches for extraterrestial life are focussing on finding water. There is great excitement as water is on Mars and not just at the poles as ice, but strongly salty solutions thought to be flowing in the Martian summer. While conventionally too briny for life it is remarkable that elementary life can exist under extreme conditions of temperature, pressure and saltiness. Whether there is elementary life on Mars now or in the past is one of the main drivers of Martian exploration.

Water is funny stuff. While its molecular nature is well known as H2O what is rather less known is that there is a slight electric dipole with oxygen slightly negatively charged and the hydrogen slightly positive. This means that water forms loose aggregates as the hydrogen is slightly attracted to adjacent oxygen. It is this weak bonding which ensures water is mostly a liquid on earth because without this attraction it would be a gas.

This property of water to form aggregates led scientists astray for a while in the late 80’s. It was thought that under special circumstances water could form massive long lasting aggregates. One of the proponents of this idea came to work at Unilever’s Research Lab. While I was there. There was some alarmist suggestions that this massive aggregate ( polywater ) could catalyse ordinary water to turn into a polymeric form thus rendering life impossible with the complete extinction of life. However it all turned into a gigantic false alarm. The polymeric water didn’t exist but was an artefact of dissolving the fine tubes in which it was examined.

The phase changes of water are of great importance for life on earth. Ice is immobile and cannot support life although the change to ice at zero degrees can be beaten to a limited extent by some organisms which can supercool themselves.

There is a lot of water on earth but the vast majority is in the sea and is too salty for life. The amount of freshwater is limited and it is apparent that inefficient usage is leading to problems. These difficulties are likely to be made much more severe by climate change. The UK should be alright provided we adjust to milder, wetter winters and hotter, drier summers. Water storage to allow for this needs to be expanded. Winter flooding must be expected and flood defences planned accordingly. However there are many parts of the world where severe problems can be expected.

Food is dependent on water supply. In fact agriculture takes up much of the world’s supply of freshwater. There are areas which are living in a “fools paradise” where agriculture is taking from groundwater which is just not being replenished. There are areas where water hungry crops are grown where they should not. Groundwater sources as they are depleted require ever deeper wells. At depth the water tends to be contaminated by heavy metals and this then poses a risk to health. Tragically in some places relying on deep groundwater children are growing up stunted and deformed from this type of contamination.

It sounds easy to say that desalination to turn seawater into freshwater is the panacea. This isn’t the case for two big reasons. Firstly a lot of arid areas are a long way from the sea. To transport seawater any distance would be hugely expensive. Rivers are, of course, no solution because they flow downhill ending in the sea. Secondly the energy involved in desalination is huge and expensive. The most efficient process is reverse osmosis and the best plants ( in Israel) produce water for about a half dollar per ton. These plants are  only found in rich areas such as the Middle East Gulf states.

While river flow is a major source of water it also is a big source of conflict. Big rivers tend to flow through several countries so upstream users are often in dispute with downstream ones.  For example Egypt, reliant on the Nile, is worried about Sudanese dams upriver.

As mentioned above climate change is a very big problem. It is reckoned that the UN agreed +1.5 degree rise will not have a big effect on river flow while a 2 degree rise would have a major effect. Also at this degree of change life may become impossible just because peak temperatures will be so high.

As far as can  be seen at present there is no early prospect of a global shortage of water. The issue is that water resources are unevenly distributed. There are plenty of places where every bit of water technology will be needed