Availability of water is seriously affected in most parts of the world by problems such as inadequate waste management, excessive consumption, contamination of water aquifers, lack of proper water-gathering and distributing technology, and excessive farming on marginal lands. Without more concerted action, these problems will only continue to grow worse since water consumption is doubling every 20 years, while as much as 50 percent of the water supply in some major Third World cities leaks away. Water withdrawals in 1950 were 1,365 cubic kilometers. Trends in population, urbanization, tourism, and standard of living are expected to increase this to 5,187 cubic kilometers by the year 2025, according to Dr. Shiklomanov, St. Petersburg Institute of Hydrology. At the same time, water tables and renewable water resources are falling.
Climate change is also a factor.
Global warming and its related changes in rainfall patterns are undermining the effectiveness of existing water control structures, storage, and distribution facilities, and will change areas affected by scarcity and floods. As a result mass migrations in heavily populated areas such as in Bangladesh, India, and China may occur. As urbanization, population, and economic growth continue, competition between urban and agricultural uses of water will increase, and this competition can become a source of political instability and conflict. Agricultural uses far exceed other uses of water, accounting for as high as 70 percent of total water usage in some regions. Because water is becoming more scarce, some countries are diverting water from rural agriculture to cities and importing grain to make up the difference.