Water – 80% to 90% of Global Freshwater Used for Irrigation; Sustainable?
The global picture for freshwater use is fairly grim. Water supplies, as we discussed previously, are large but finite – and we currently tap pretty much all of the easy and cheap sources for freshwater. A relatively recent paper on the use of freshwater in agriculture around the world puts the blame, if blame is the word, on irrigated agriculture, which worldwide accounts for between 80 and 90 percent of freshwater use. (Abstract here).
Currently, about 1.1 billion people lack adequate access to fresh water, and almost half of the world’s population doesn’t have adequate access to water for sanitary purposes. The impact of this lack of fresh water on disease and health is complex but negative, as you can probably imagine. As incomes rise globally, we can expect a demand for better water conditions from the formerly impoverished citizens of many nations – a demand that is likely to redirect water use from agriculture in the short run, as wealthier people are able to bid up what they are willing to pay for clean drinking and cleaning water and thus outcompete local agricultural sectors.
As farmers around the world are forced to pay more for water, governments and land-use planners are likely to have to shift their priorities for land use, including greater use of naturally-watered land for agriculture. It is unlikely that we are going to see many governments tearing down housing developments in order to return the land to agricultural use, but over time the market will make it economically rational to farm where the water is.
In the long run, it is likely that it will require human intervention into the freshwater system to produce more of a now-scarce resource. Remember we said that water is finite? Well, it is – but it is a finite resource that we can create more of, if we really need to. Except for rarities like the Gulf states, nations which are energy rich and water poor at the same time, nations have “made do” with the freshwater supplies available through nature and a modicum of dam-building, river-rerouting civil engineering. The only way we currently can increase our freshwater supply is to desalinate sea water, which is effectively infinite in quantity. Desalination is enormously expensive in terms of energy, however, meaning that even in situations where freshwater is very difficult to acquire, desalination is, at current prices for fresh water and for energy, an option of last resort.
How expensive is desalination? Some analysts say that it is easier to raise a gallon of water vertically by 2000 meters, or to ship it across 1600 kilometers of terrain, than it is to desalinate a gallon of seawater – the most efficient modern plants can desalinate water for about fifty cents per cubic meter. That sounds cheap – and it is, if you just need a drink of water. If you need a billion cubic meters a day for your agricultural irrigation or for your metropolis, it’s another story.
However, the existence of desalination does mean that water is, over the long term, a problem to be solved rather than a crisis that we do not have a solution for. The difference between a crisis and a problem is that problems usually have known solutions; some problems remain problems because we don’t want to do what’s necessary to fix them. In the case of the water problem, there are solutions, desalination among them – they just require us to do things we don’t really want to do. Next week we will conclude our look at water and agriculture with a review of the possible solutions to the problems we face.