Adapting to Dryness
Raising the water productivity of the global crop base is also critical. Actual strategies used will vary by crop, climate, and the type of water-control system, but the basic aim will necessarily be the same in each: to optimize the timing and amount of moisture in the root zone and to enhance the crops’ ability to use that moisture productively.Through plant breeding, for example, biologists can hasten the process of plant adaptation to dryness. Studies have shown that if no other factors are limiting plant growth total production is proportional to the amount of water a plant transpires. Larger or deeper root systems that allow plants to take in more moisture can thus increase yield. New genetic techniques are making it possible to screen crop varieties for water-efficiency traits. And developing varieties with shorter growing seasons or the ability to grow in cooler periods, when evaporation and transpiration are lower, could also help improve crops’ water-use efficiency.
The International Rice Research Institute in the Philippines, for one, is focusing on developing more efficient irrigation operations, technologies that reduce water consumption, and changes in the rice plant itself to improve water-use efficiency. Breeders have already shortened the maturation time for irrigated rice from 150 days to 110 days, for example, a major water-saving achievement.
Matching crops to varying water quality can also enhance supplies for irrigated agriculture. In the western Negev of Israel, for example, farmers successfully grow cotton using highly salty water from a local saline aquifer. The Israelis have also found that certain crops-such as tomatoes grown for canning or pastes-may actually benefit from somewhat salty irrigation water. The varying salt tolerances of crops raise the possibility of multiple reuse of irrigation water. In California, for instance, moderately salty drainage water from a crop of average salt tolerance is used to irrigate more highly tolerant cotton. In turn, the drainage from the cotton fields, which is even saltier, is used to irrigate salt-loving crops, a number of which scientists have made considerable progress toward commercializing. For example, when a variety of Salicornia, a seed-bearing plant, was irrigated with seawater in a coastal desert near Mexico’s Sea of Cortez, its yield was equal to or greater than freshwater oilseed crops such as soybean and sunflower.
Like more realistic water pricing, water marketing can create incentives both to encourage efficiency and reuse, as well as to allocate water more productively. Instead of looking to a new dam or river diversion to get additional water, cities and farmers can purchase supplies from others who are willing to sell, trade, or lease them water or water rights. The Metropolitan Water District of Los Angeles, for example, is investing in conservation measures in southern California’s Imperial Irrigation District in exchange for the water those investments will save. The annual cost of the conserved water is estimated at about 10 per cubic meter, far lower than the water district’s best new-supply option. In Chile, where water policy encourages marketing, water companies that serve expanding cities frequently buy small portions of water rights from farmers, most of whom have gained surpluses through efficiency improvements.
The setting of efficiency standards has also proven to be an effective policy tool for stretching supplies. U.S. legislation passed in late 1992 requires manufacturers of toilets, faucets, and showerheads to meet specified efficiency standards as of January 1994. U.S. residential water use for these three fixtures is expected to drop by more than 35 percent as the more efficient models replace existing stock over the next 30 years.
A number of other governments, including Mexico and the Canadian province of Ontario, have also adopted standards for household plumbing fixtures. The National Community Water Conservation Program in Cairo is working with the Egyptian government to introduce water conservation standards into the plumbing code. Although efficiency standards have so far mainly been applied to household fixtures, they offer potential for water savings in agriculture, industry, and other municipal uses as well.
Here and there, promising efforts inspire hope that the consequences of water shortage can at least be delayed. Yet so far, concerted national and international efforts to bring all the pieces of a sustainable water strategy together are few. One notable exception, however, may be South Africa. In early 1996, the Minister of Water Affairs and Forestry laid out principles for a fundamental overhaul of the nation’s water law and management. Among the top priorities are providing each South African with access to at least 25 liters of water a day to meet the minimum need for drinking water and sanitation, pricing water at levels that reflect its value, encouraging water marketing, mandating that water suppliers adopt conservation measures, allocating water to the environment to prevent the loss of ecosystem functions, and reserving water for countries downstream in order to promote regional cooperation and integration.
Although these principles are promising, turning them into actual laws, policies, and actions will not be easy because it will involve dismantling decades of apartheid-era water legislation. Moreover, the country is still pursuing the socially and environmentally destructive Lesotho Highlands Water Development Project, an $8 billion dam-and-diversion scheme aimed at supplying the Johannesburg region with water from the tiny mountain kingdom of Lesotho. Nonetheless, the nation’s new water plan, which could be taken up by the parliament in early 1997, may emerge as one of the stronger national water strategies thus far.
Beyond the adoption of similar strategies in other nations, there is also an urgent need at the international level to assess and monitor the availability of water for food production. A basic blueprint for satisfying human and ecological needs as well as using and allocating water more efficiently will not guarantee agriculture the water supplies needed to meet the world’s future food demands. For example, many of the policies and strategies to promote more sustainable water use-such as raising water prices and expanding water markets-will likely shift resources away from agriculture toward higher valued uses.
The time may not be far off when a global grain bank will be needed to guard against food shortfalls induced by water shortages. Particularly in Africa, Asia, and the Middle East, water deficits will widen markedly in the coming decades. Together these regions are projected to grow by nearly 2.3 billion people by 2025, accounting for 87 percent of projected population growth over the next 30 years. Many African and Asian countries are unlikely to have the financial resources to balance their water books by purchasing surplus grain on the open market.
Finally, reining in demand for water offers the best hope of preventing scarcity from leading to more hunger, poverty, widespread ecological decline, and social instability. Living within the limits of nature’s water supply will require reduced consumption among the more wealthy social groups and smaller family size among all groups.