The XXI century is characterized by the strong growth of the world population and the development of urbanization. Nowadays, there are megacities with the population of over 10 million people. As a result of the development of industry, transport and energy as well as the industrialization of agriculture human impact on the environment has taken a global nature. It has led to the fact that fresh water consumption has increased by seven times, including that used for municipal drinking purposes, which increased by 13 times. Nowadays, water along with energy and food has become one of the major global problems. Nowadays, there is the lack of water resources in many regions of the world. The shortage of drinking water is obvious and extremely acute in some regions of the Earth.
Freshwater resources exist because of the eternal cycle of water. “Thus far, it is believed that water is indestructible and is recycled through the hydrologic cycle.” As a result of evaporation, there is a huge amount of water reaching 530 thousands of cubic meters per year. 85% of this amount falls on the salty waters of the oceans and inland seas. The rest of water evaporates on dry land. Each year, about 1250 millimeters of the water layer evaporates. The major part of it falls with precipitation into the ocean.
Only 2% of the hydrosphere accounts for fresh water. Nevertheless, it is constantly renewed. The rate of renewal defines the resources available to mankind. The largest amount of fresh water is concentrated in the ice of the polar regions and glaciers. The rate of water exchange is lower there than in the ocean. Thus, surface water on land is renewed about 500 times faster than ocean water. Water of rivers is renewed even faster. Therefore, freshwater rivers are of the greatest practical importance for humanity.
Nowadays, a great problem worldwide is wastewater. Rivers have always been a source of fresh water. However, in modern times, water is greatly contaminated by transport wastes. Wastes in the catchment area on river channels drain into seas and oceans. Most of water that is used from rivers returns to rivers and reservoirs in the form of wastewater. Until now, the construction of treatment plants lagged behind the increase in water consumption. However, even with a perfect treatment system, including biological cleaning, any dissolved inorganic compounds and up to 10% of organic contaminants remain in the treated wastewater. This water may again become suitable for consumption only after repeated dilution with pure natural water.
The global water balance showed that 2,200 cubic kilometers of water in all types of water consumption is wasted per year. Dilution of wastewater constitutes nearly 20% of the freshwater resources of the world. The calculations have showed that 30-35 thousand cubic kilometers of fresh water for dilution of wastewater is needed annually. It means that resources of the world’s river flow will be close to exhaustion. Moreover, in many parts of the world, they have already been exhausted. The amount of fresh water is not reduced. However, its quality is impaired sharply. As a result, it becomes unsuitable for consumption. In such a way, wastewater is a great problem nowadays because people have less access to fresh water.
Humanity will have to change the strategy of water use. There is a necessity to isolate anthropogenic water cycle from natural. In practice, it means transition to a closed water supply and non-waste technology accompanied by a sharp decrease in the volume of water consumption and treated wastewater.
The problem of water scarcity is becoming more urgent in many regions of the world. The reasons for it lie in population growth, climate changes, and a number of other factors. However, for many places on Earth, this problem is not new. It is due to climatic characteristics, namely low precipitation. “The worldwide distribution and management of water is very uneven, which partly explains why more than one billion people lack access to safe drinking water.” Dry areas are areas where rainfall is less than 400 millimeters per year. As a result, farming without additional water sources is not possible in such regions. They constitute about 35% of the planet’s surface. The aridest areas receive less than 100 millimeters of rainfall a year. Arid regions with 100-200 millimeters of rainfall per year constitute 15% of the land surface. Developing countries are mostly situated on the territories of arid lands. On these territories, the rate of water consumption differs from that of industrialized countries. According to the World Health Organization, in developing countries, only 25% of the rural population has reasonable access to fresh water. The territories of 36 countries of the world include dry areas. 11 countries are situated entirely in arid regions – Djibouti, Egypt, Yemen, Saudi Arabia, and others.
Reserves of fresh water are potentially large. However, in any part of the world, they may be depleted due to unsustainable water consumption and pollution. The number of these places is growing, covering the entire geographic areas. Water demand is not met in 20% of urban and 75% of rural population of the world. The volume of water consumption depends on the region and the quality of life. It ranges from 3 to 700 liters per person a day.
People try to eliminate the problem of water scarcity in the world in a variety of ways. The first one is the export of water. Thus, there exists an agreement on the water transportation between Turkey and Israel. The volumes of similar contracts are measured in hundreds of millions of dollars. The next way is the creation of artificial reservoirs. The reduction of water consumption is another way to save water recourses. In 1992, the US Congress passed a special law on reduction of the volume of water consumption for municipal needs by 70%. Desalination of sea water or salt water from underground sources is becoming very popular nowadays. The manufacture of fresh water is growing continuously and rapidly in the world.
Water Resources and Industry
Water consumption by industry also depends on the economic development of the area. For example, in Canada, industry consumes 85% of the total water intake while in India this number equals 1%. “The economies of all nations are dependent on access to water, and its use is indispensable across all economic sectors.” The most water-intensive industries are steel, chemical, petrochemical, and food. They spend almost 70% of the water consumed by industry. On average, industrial water use constitutes approximately 20% of all water consumed. However, the main consumer of fresh water is agriculture. It needs about 70-80% of all fresh water. “An aspirational goal for agriculture everywhere is to produce twice the yield of half the area and use no more water than at present.” Irrigated agriculture amounts to only 15-17% of agricultural land and gives half of all products. Almost 70% of cotton in the world was grown with the help of irrigation.
There is a drought in 70% of all cultivated land. The reason for water deficiency lies not in the lack of fresh water, but in violation of the chain linking water with soil. Human activity has a noticeable influence on the mode of surface waters. Thus, it resulted in significantly increased consumption of water due to evaporation, development of irrigation and the areas of reservoirs. Reduction of rainfall and river flow by increasing the volatility of internal land areas has reduced their overall hydration. Changes in the exchange of groundwater, their depletion through the creation of artificial reservoirs and reduction as a result of intensive pumping resulted from human activities, too. “Diversions from rivers, pumping from wells and pollutions by farms, cities, and industry all compromise the supply of water.” Every year, about 20 thousand cubic kilometers of groundwater are extracted. Currently, more than 20% of the continental territories are radically transformed under the influence of human activity. It leads to the change of the water regime. With the increase of consumption of water for industrial needs, there will be little freshwater resources in many regions of the world.
These environmental violations have affected the course of the global water consumption. They have already led to the difficulties in water supply in some regions of the Earth. Since the mid-1990s, the Huang He River in China does not fall into the Yellow Sea 260 days a year. It happens due to the fact that along the waterbed, river water is taken for irrigation. Since 1960 the volume of water withdrawn for irrigation increased by more than 60%. There are similar difficulties with water supply in India, Pakistan, North Africa, and other countries of the Mediterranean and the Arabian Peninsula as well as in several countries in Central, South, and North America.
The increase in urbanization has seriously affected the growth of water consumption. In the last century, the scale of water use increased six-fold and more than twice exceeded the population growth. The daily water consumption in a city is 100-400 liters per person. At the same time, in many areas of the globe, this number is equal to 20-30 liters. “Demand is greater during weekends by about 12%, with demand being higher in the summer than in the winter.” Whereas annual water consumption is constantly increasing, nearly a billion of people on the planet are not provided with safe drinking water.
It is known that water is absolutely indispensable for people’s life. The problem is that in the world supplies of clean drinking water are constantly shrinking. It happens due to an increasing volume of water consumption. Freshwater is mainly used in industry, agriculture, and households. However, nowadays, there are areas on the planet with a catastrophic shortage of drinking water. At the present stage, the problem of water supply has become one of the most critical for the life and development of the human society.