Water wheel turns slowly in China

01-12-2009 | David Oliver

Climate change may be seen as a major threat to global food production, but water looms as the biggest limiting factor for China's arable sector.

Lower rainfall, increasing temperatures and desertification are issues facing many parts of the country. In 2008-2009, drought struck many parts of northern China while record snowstorms were experienced both last year and in November of this year.

The southern province of Guangdong is experiencing a drought that is threatening the water supplies for major cities including Hong Kong. It gets a lot of its water supply from the mainland.

Despite all this a joint United Kingdom-China study into the impacts of climate change on cereal production concluded that provided adequate measures were taken, China could maintain its per capita cereal production to 2050.

Making predictions that far into the future is difficult, but the study concluded that increased CO2 levels combined with advances in technology would mitigate adverse effects.

The biggest problem is likely to be access to water. It is estimated that 40% of grain production relies on groundwater irrigation but there is increasing non-agricultural demand for water from growing cities and industries.

Half of the country's arable land has access to irrigation with 90% being flood-irrigated.

Simon Appleby, an Australian irrigation consultant, says much of China's northern regions waste more than 75% of their irrigation water by using outdated irrigation methods, instead of using spray or trickle systems.

"This amounts to more than 50% of northern China's total water consumption (for agriculture, industry and housing) being needlessly wasted through primitive irrigation systems."

The Yellow River, the northernmost of China's two major rivers that runs through many grain-growing regions, now runs dry most years before reaching the sea. During a drought in 1977 it failed to reach the sea for 226 days.

China has over 1.3 billion people, about 20% of the world's population, but only 7% of the world's arable land, yet it has managed to not only feed its population but also be a substantial exporter of agricultural produce.

Since 1980 grain production has increased by 89%. The challenge of feeding everyone will only increase because the population is forecast to peak at 1.5 billion in 2033. By then an extra 150 million tonnes of grain will need to be produced.

At the same time diets are changing. Chinese are eating more meat as they get wealthier, requiring Chinese farmers to produce a wider range of food off a declining arable base.

Government officials estimate that in 1996 there were 130 million hectares of cultivated land in China; by 2006 this had shrunk to 120 million hectares - considered the minimum necessary. In a country where statistics can be manipulated, it is not clear if this area of arable land really exists.

Factors contributing to the loss of arable land include rapid urbanisation, desertification and illegal land seizures by local governments who then on-sell the land at a premium for other purposes.

Around Beijing it is easy to find large areas of quality arable land that have had walls erected around them and are not being farmed. Quite often the land rights were transferred to a developer for a real estate project that failed to materialise.

In 2007, almost 106 million hectares were sown in grain crops with a total grain output of 501.6 million tonnes. Rice, wheat and corn are the major grain crops as well as soybeans and barley. Other crops include 6m hectares of cotton and 2m hectares of sugarbeet. In 2007, exports of farm produce were $US37 billion while imports were just over $US41 billion.

China exported 10 million tonnes of grains (excluding soybeans) while importing 1.56m tonnes of grains. Grain exports included wheat, corn and barley.

It imported 32 million tonnes of soybeans and eight million tonnes of vegetable oils In a study for the World Bank Australian hydrologist Ray Evans estimated that the North China Plains groundwater will last only 20-40 years, at most, under current usage.

He also said shallow aquifers which replenish have dropped 10m to 50m since the 1960s. Deeper aquifers which don't replenish had dropped by up to 90m.

Before the 2008 Olympics farmers in regions around Beijing had their access to water reduced to ensure there was enough water for the city. Competition for water from growing cities and industry will only grow. This will potentially lead to more cuts in irrigation around cities. On top of this the irrigation infrastructure has been neglected with many dams silted up and ditches not being maintained.

Change is happening, if only slowly.

While flood irrigation is still widely used, pivot irrigators and drip irrigation techniques are also being implemented. Dryland farming systems that make efficient use of natural precipitation have been developed that reduce water consumption by 30-50%.

Changing land use could also save water. It doesn't make much sense to grow thirsty crops like rice in arid regions. Winter cereal crops require more irrigation in areas where most of the rain falls in summer.

Appleby says a major impediment to irrigation reform in China is pricing. Water usage is charged by the area instead of by the cubic metre, so no incentive exists for farmers to rationalise their water use.

Weather modification is another, sometimes controversial way of inducing rainfall and snow by firing silver iodide into clouds. The technical know-how has been around since at least 1946.

Silver iodide is blasted into clouds using either modified anti-aircraft guns or from aircraft. The silver iodide causes cloud condensation that then falls as either snow or rain depending on the temperature.

• David Oliver is an adviser based in China. His email is: david@orienz.com

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