A Glass of Water - Part 2

In my last post, I explored how increases in temperature and rainfall as a result of climate change may affect the drinking water that we rely on as humans. There are some more factors to consider though, which I will cover in this post. Before we start though, why not go to the kitchen and pour yourself a glass of water from the tap? Drink it while you read this post. While you do that, I will run through some more potential effects of climate change on drinking water.

Drought

While it is never a good thing for water to contain pollutants, it’s best to have a small amount of pollutant in a large amount of water. This means the pollutant is more diluted in the water, with less pollutant per unit of water. Think of it in terms of a glass of orange squash – the ratio of the squash to water influences how strong the taste is, and it is the same with water pollution. You are more likely to get sick from drinking water concentrated with pollutants, rather than water in which the pollutant is more diluted.

Droughts reduce the amount of water in a hydrological system, due to a lack of rainfall and increased evaporation, but the amount of any pollutants in water remains the same. As such, droughts reduce dilution of pollution, increasing pollutant concentrations in water. The IPCC suggests it is likely that the frequency of droughts will increase in presently dry regions by the end of the 21^st century, and this could have significant implications for drinking water. There are still high levels of uncertainty in the quantification and projection of drought at a regional scale using climate models, but we know that droughts have increased in the Mediterranean, Central America and South Africa, and it is projected that they will increase into the future (Orlowsky and Seneviratne, 2013). 

The effect of drought in reducing the dilution is well documented. van Vilet and Zwolsman (2008) use existing water quality data to show a decline in the water quality of the Meuse river in north-west Europe during drought conditions, with increases in heavy metals, major elements, and the amount of algae in the river (the river flowing more slowly allows algae to develop, along with an increased nutrient concentration). As we saw in the previous post, algae have a negative effect on water quality. Bonte and Zwolsman (2010) show a similar effect for two man made lakes in the Netherlands, but in this instance using modelling to attempt to predict to effect of climate change induced changes in water quality. Using climate change predictions for 2050, the model suggests an intense salinisation (the water becoming more salty) of the two lakes due to increased chloride concentration as a result of low river flows, evaporation, and reduced rainfall. 

All of these effects are not good for human drinking water - hopefully that glass of water you are drinking isn't rich in heavy metals, algae and salt. They are not good things to put into your body. 

Sea level rise

Sea level rise is perhaps the most discussed topic in all of climate change, and as we all know is a major consequence of climate change and global warming. It could have significant impacts on drinking water quality as a result of a process called saline intrusion, which involves salty sea water workings its way into a freshwater aquifer, causing groundwater to be contaminated with salt. Take a look at this before and after diagram:

On the left is the normal state of things - the freshwater (light blue) separated from the salty water (dark blue). Remember that these are not bodies of water, but just the water that is stored in rock, deep beneath the sea bed. The well will be pumping up only fresh groundwater.  On right, is a situation likely to occur as a result of sea level rise - the sea level has risen, and as a result there has been an intrusion of salt water (towards the left, in this case). As a result, the same well will now be pumping up somewhat salty water. If we assume this well is used to supply a coastal village with drinking water, you can see the problems this process of sea level rise may create. 

This isn't just a process that will happen in the future - it is already happening in Bangladesh. Here drinking water in coastal areas has become contaminated with salty, as a result of rising sea levels causing saline intrusion, along with storm surges from extreme weather systems. Khan, et al. (2011) suggest that this explains a seasonal excess of hypertension (high blood pressure) in pregnancy in the area, as the estimated salt intake of the local population is exceeding recommended limits. The level of saline intrusion will only increase in the future, potentially causing long term health problems for the area - imagine that glass of water you are drinking with extra salt added, and think of the effects it would have on your body!

Disruption of water treatment facilities

This is a short but important point that I somewhat mentioned in the previous post, but warrants re-addressing here. Increased rainfall and resultant flooding means drinking water supply systems are vulnerable to climate change, as they may be unable to cope with the increased amounts of water, particularly if that water has become polluted. Howard, et al. (2010) make the assessment that that very few current water supply technologies are resilient to climate change. It is essential that we update these technologies. My view is that access to safe drinking water is a universal human right. We must work to preserve universal access to drinking water, both through trying to reduce the effects of climate change, and preparing technologies and infrastructure for these effects.