Monday, March 28, 2011

Water and Food

In much of the world food prices are rising. The effects of the current price spikes have not been significant in the United States where food represents about 10% of the income of a typical family and where the volatility in food and energy are accepted or at least tolerated. In the United States processing and advertising costs of foods often outweigh the cost of food ingredients themselves.

Food prices are being driven up in part by an increase in oil prices, affecting both fuel and fertilizer costs. But the primary cause is water. The recent droughts and flooding have both impacted food production. Russia has been hit with the worst drought in a half century. Australia has suffered years of drought only to be hit by torrential flooding so that the lack of water has been replaced by too much water. India’s falling water table and water shortages have been well documented in the world news. Even U.S. grain forecasts have been reduced due to adverse weather.

In countries where most residents purchase only basic foodstuffs and where food costs require a much larger percentage of household income, the cost of food has effectively skyrocketed. When food represents 50% of household income, a 10% increase cannot be absorbed. The outcry in India over the price of onions recently illustrated this. India’s food production regions are reportedly sitting atop groundwater aquifers that are being depleted. Irrigation accounts for 84% of India’s total water use. The population continues to grow, industrial demand for water grows and the demand for more water intensive food is growing. Generally, higher value crops such as sugar and vegetables are more water-intensive than cereals, and meat and dairy are even more water-intensive. So as populations move up the economic ladder beyond subsistence the demand for irrigation water explodes.

Overall, approximately 60% of all the world's freshwater withdrawals go to irrigation. Large-scale farming could not provide food for the world's large populations without the irrigation of crop fields by water from rivers, lakes, reservoirs, and ground water wells. Without irrigation, crops could never be grown in the arid and semi-arid lands of California, the Middle East, or India where irrigation consumes a much larger share of fresh water.

The majority of irrigated acres in the United States is in the west were where annual precipitation is less than 20 inches and is insufficient to support crops without supplemental water. In the western United States water used for irrigation exceeds 75% of the water supply. The system of water rights that developed in the west assured for generations the allocation of water to agriculture. The water rights system as conceived and administered in the western states was not designed to conserve water. It was developed in a time when population was still sparse, water supplies were believed to be plentiful and development and growth were to be encouraged. The system was designed to protect the water and work necessary to build farms in the west. This management scheme has resulted in non sustainable use of groundwater and unsustainable agricultural practices.

When agricultural land is irrigated, the water balance in nature is altered. Water is withdrawn from a river, spring, or groundwater and added to agricultural fields. The environmental impact of an irrigation system is dependent on the nature of the water source, the quality of water, the method of delivery and the local geology and climate. Withdrawing ground water beyond the recharge rate may cause the land to subside as happened in the Central Valley of California. In many parts of the world where water is often plentiful slash and burn agriculture is practiced and the land cultivated until it is exhausted then abandoned, more forest cut down and the climate impacted by the massive loss of trees. Irrigation of lands can destroy them.

Aquifers and the land may become saline. All water contains dissolved salts that attached to the water molecules as it washed over the land or percolated in the ground. Rain also contains some salts. The salts are generally at very low concentrations in “fresh” water’ however, evaporation of water from dry earth leaves much of the salts behind. Over time the salts concentrate. This problem has become acute in the Central Valley of California, in China’s North Plain, in Soviet Central Asia (the –istans), parts of the Middle East and the Colorado River Basin. These are all semi-arid areas where irrigation is the basis of agriculture that has used flooded irrigation for generations. Land is being irrigated before planting to reduce the salt levels. At least 20% of all irrigated lands are salt-affected, with some estimates being as high as 50%.

To address these problems, more controlled types of irrigation have been developed and more salt tolerant crops need to be exploited. Micro-irrigation also known as drip irrigation has gained attention during recent years because of its potential to increase yields and decrease water, fertilizer, and labor requirements if managed properly. Drip irrigation systems can apply water and fertilizer directly to individual plants or trees, reducing the wetted area by wetting only a fraction of the soil surface; water is applied directly to the root zone.

In drip irrigation, water is run through pipes (with holes in them) either buried or lying slightly above the ground next to the crops. Water slowly drips onto the crop roots and stems. Unlike spray irrigation, very little is lost to evaporation reducing water waste. Subsurface drip irrigation is the slow frequent application of water below the surface to the root area of the pants. The goal is to maintain constant moisture content in the soil at the optimal plant growth level. This requires monitoring soil moisture and weather instead of a set irrigation schedule and in this way reduce net water use by 30%.

The costs involved in drip irrigation can be substantial, not just the $800-$2,000 for the tubing, filters and pumps, but also the irrigation infrastructure that would allow controlled constant delivery of filtered water. On demand water availability for irrigation may be an insurmountable hurdle within the current water allocation system. In addition, a University of California study concluded that a salt balance must be maintained in the root zone, irrigation without improved management practices cannot be sustained in the San Joaquin Valley. In addition, sensible choices will have to be made about water allocation, crop choices, and water pricing. Our political systems and human nature have not excelled in the past at sensible.

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