Water crisis

In recent years, one could possibly have forgiven the denizens of the Arabian Peninsula for forgetting that water was a scarce resource.

They have been obtaining it by tapping into aquifers - wet underground layers of permeable rock or unconsolidated gravel, sand, or silt from which groundwater can be extracted by means of a well or borehole.

This has enabled them to grow vast acreages of wheat and other crops. However, now it appears that the aquifers are running dry or becoming saline.

The problem is that most of them are non-replenishable fossil aquifers: they were filled by seepage from the surface during the last ice age. As they are tapped, the water-table drops and salt water seeps in from the surrounding seas.

Yangtze River. Picture courtesy: Google

Saudi Arabia was until recently self-sufficient in wheat, but the growing scarcity of groundwater has caused harvests to drop by two thirds. Three years ago, in order to conserve its groundwater, the Saudi government clamped down on pumping and removed subsidies for wheat production.

Food production

In neighbouring Yemen, water tables are falling by 2 metres per year, and harvests have fallen by one third. Water is set to replace petroleum as the Middle-East’s most valuable commodity.

This is not just an Arabian problem. In the USA the huge Ogallalla Aquifer, which irrigates farms from North Dakota to Texas - America’s breadbasket - is also running dry and food production could collapse.

In China, which is the world’s largest producer of grain, falling groundwater has affected harvests. Although the country has replenishable aquifers, water needs have exceeded the rate at which these get recharged.

The problem has been compounded by changing weather patterns and increased times of scarce rain. China is at present in the midst of a drought. It is the worst seen in the Yangtze River basin for 50 years, in Shangdong - a province 21/2 times the size of Sri Lanka - the worst in two centuries.

Irrigation systems

In the US breadbasket, the shortage of aquifer water has been exacerbated by a series of droughts over the past 13 years, the worst of which seems to be this spring’s. In Texas and the Southwest states, in Oklahoma and Kansas, this unprecedented dry spell is expected to bring harvests down by as much as 50 percent.

Meanwhile, the wheat heartland has not had significant rainfall since last July, not very far distant the Mississippi River has been flooding - an aberrant climatic pattern which is becoming familiar all over the world.

This is also a pattern which has been seen here in Sri Lanka. Despite the fact that our island is so tiny, it has a relatively large variety of climate zones. Historically, rains from the mountains fed the rivers and irrigation systems of the Dry Zone even in the absence of rain.

Now, however, rainfall patterns appear to be taking on a much more peculiar shape. This year there was increased rainfall in April, usually a dry month, leading to floods. Conversely, the South West Monsoon, the onset of which is usually in mid-May, has been delayed.

Rice varieties

An estimated quarter of the last Maha season’s harvest of paddy was destroyed by excessive rain and flooding. This pattern can be expected to repeat itself in coming years.

Aggravating the problem of erratic rains is the fact that deforestation has severely impinged on the water-retention capacity of the highland watersheds. The aftermath of heavy precipitation is that the rainwater, instead of being held by the soil on hillsides, flows down and into the rivers, causing floods.

There is also a developing shortage of groundwater. This is not so much a result of the depletion of the water table - Sri Lanka’s aquifers are replenished by water seepage from the surface - as it is of pollution.

Agriculture in this island, particularly the cultivation of rice - has come to be dominated by agro-chemical usage. The new rice varieties introduced since the beginning of the ‘Green Revolution’ in the ‘60s require large quantities of fertiliser. They are less resistant to pests and diseases, so they require huge amounts of pesticides.

These toxic chemicals trickle down through the soil and into the aquifers, which they contaminate. Over the past half-century, the accumulation of these noxious substances in the groundwater has led to decreased potability - so there is now a growing shortage of drinking water.

Rainwater harvesting

The crisis in water supply needs to be tackled immediately. There are several techniques by which the different aspects of the problem may be addressed.

Obviously, the best way to counteract increasingly erratic rainfall patterns is to make sure there is adequate storage for excess water when it rains so that it can be used in periods of drought. This was the system adopted by the ancient kings with their network of canals and tanks.

This rainwater harvesting can also be done on a small-scale or household level. Legislation has already been passed requiring rainwater harvesting to be catered for in new construction plans, but this does not affect existing buildings.

The reforestation of the highlands as part of an improved system of watershed management provides the best long-term solution to the dual problem of excessive flooding combined with drought.

Probably the most difficult issue is cleaning up the contaminated aquifers, which will require the minimising of agro-chemical usage. This will require new rice varieties (possibly by breeding versions of the old ‘Sinhala vee’) and greater use of organic manures and natural pest control.

The Government could set the ball rolling by targeting selected areas, in which the fertiliser subsidy could instead be used to fund organic farming techniques.