Lesson 11 Water Resources
1、Ancient civilizations developed along rivers that supplied water for farming. As early as 5000 B.C., the Egyptians cultivated land made fertile by the floodwaters of the Nile River. By about 3000 B.C., they had built an elaborate canal system that carried water from the Nile to their fields. Large irrigation systems also had been constructed by then in China, India, and southwest Asia. Indians in Mexico and Peru used water from streams to grow corn as early as 800 B.C. When the Spaniards arrived in those countries during the A.D. 1500s, they found great civilizations based on irrigated agriculture.Archaeologists have discovered evidence of early irrigation ditches in the southwestern United States, and it is believed that these ditches date from before the 600s.Scientists estimate that Indians of that period irrigated thousands of acres or hectares of land in what became central Arizona.
2、The 20th century has witnessed unprecedented rises in human populations, from 2.8 billion in 1955 to 5.3 billion in 1990 and is expected to reach between 7.9 and 9.1billion by 2025 (Engelman and LeRoy, 1993). Consequently, human demands for water,for domestic, industrial and agricultural purposes, are also increasing rapidly. The amount of water that people use varies, but tends to rise with living standards. In the United States, each individual typically uses 700 liters per day for domestic tasks, while in Senegal, the average use is 29 liters per day. In general, 100 liters per person per day is considered a minimum threshold for personal use. However, when agricultural and industrial uses are included, countries with less than 1,700m3 per person per year (about 4,600 liters per day) are considered to experience water stress, those with less than 1,000m3, water scarcity. Because of the spatial mismatch between water resources and people, twelve African countries, with a total population of approximately 250 million have already been suffering from severe water stress. A further ten African countries will be similarly stressed by the year 2025 containing some 1.1 billion people, or two thirds of Africa’s population, while four (Kenya, Rwanda, Burundi and Malawi) will be facing an extreme water crisis.
3、With such a water crisis facing many countries, it seems an immense task just to manage water so that there is enough for people to drink, let alone enough for agricultural,environmental, and industrial uses. The situation is often presented as a conflict of competing demand, as though it was a matter of choice between water for people,or for wildlife, or for the environment. While people need access to water directly to drink, providing water to the environment means using water indirectly for people.More attention needs to be given to the role of natural ecosystems in managing the hydrological cycle and their potential as alternatives to major engineering works. As an example, well managed headwater grasslands and forests reduce runoff during wet periods, increase infiltration to the soil and aquifers and reduce erosion, such as sustaining flows during drought periods and reducing runoff during floods. Conserving wetlands in particular, by ensuring that they have adequate supplies of water to maintain their functioning, can be a positive benefit to humanity. Many wetlands provide important fisheries, arable and pasture land, fuel wood and medicines as well as habitats for wildlife. Some wetlands also perform many important natural hydrological functions including flooding reduction, water quality improvement (by removing pollutants) and groundwater recharge. Thus for the millions of people worldwide who depend directly on wetland resources or benefit from wetland functions, water provided for the environment is growing at seven percent per year. In some areas, providing water for the environment and for people are one and the same.
4、When water resources are used at a rate greater than they are being replenished,the resource will decline and the usage becomes unsustainable. In many areas of the world, for example, groundwater is being extracted from the underlying aquifer more rapidly than it is being replenished. Around Quetta in Pakistan, where the abstraction rate is 2.5 cubic meters per second (cumecs), while the recharge rate is 2.0 cumecs, the groundwater level is falling at around one meter per year. Furthermore, the problem is likely to worsen as the population is growing at seven percent per year. In some areas of Libya, no recharge currently occurs, the sustainable use rate is zero and thus the water is effectively being mined. Part of the problem is that planning has often taken place by deciding first how much water is needed and then trying to find a source. In contrast,the opposite process is likely to lead to more sustainable water use, by first assessing the available water resource and then deciding how best it can be used.
5、There is a need to develop a broad-based approach to water management, with greater emphasis on integrated regional planning and conservation of critical habitats.The environment is composed of a set of physical, chemical and biological components,including water, oxygen, plants, animals, soils and minerals. Each plays an important role either in providing structure, such as rocks, or through interaction with other components, maintains crucial processes, such as energy flow or nutrient cycling.Superimposed on this natural environment is the effect of human beings. There is no place on earth unaffected by human beings, who have had large scale impacts on the earth’s environment ever since agriculture began thousands of years ago. The ecosystem management approach aims to integrate all the important physical, chemical and biological components and processes which interact with social, economic and institutional factors. This requires integrated management of mountains, dry lands, forests,agriculture, housing, industry, transport, waste disposal, aquifers, rivers, lakes, wetlands and anything which has an effect on the environment. Once the scientific basis for management options had been defined by professional staff, the participation of local communities, farmers, industry and conservation organizations is needed to satisfy the needs of different interest groups.
6、Institutions at various levels are essential for equitable allocation of water. Whatever the level, institutions need well-informed members who have an appreciation of the wide range of issues facing water resource allocation. Training is an essential element, but training needs vary with the type of institution. Professional technical advisors require formal training courses, for example, on water resource planning and wetland management, while local community representatives may be best trained with involvement in local activities, such as participatory rural appraisal or through visits to demonstration projects.
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Exercises
Ⅰ. How well did you read?
1. [Note the details] Irrigation systems appeared in the following countries except______ in ancient times.
A. Egypt B. China C. Japan
2. [Note the reason] Twelve African countries are suffering from water stress because of ______.
A. people’s bad habit of overusing water
B. the spatial mismatch between water and people
C. the lack of awareness in environmental protection
3. [See the point] The writer seems to believe that ______.
A. we need to cut down on drinking too much water
B. protecting wetland holds the key to the world’s water stress
C. providing water to human and the environment should be the same
4. [See the point] The writer advocates the following except ______.
A. a broad-based water management
B. human beings stop taking underground water
C. institutions working together at allocation of water
Ⅱ. Read for words.
Look back at the paragraphs and find the words that mean the following:
1. to prepare land and grow plants on it (Para. 1)
2. to make an approximate judgment or calculation of something (Para. 1)
3. the level or point at which you start to experience something (Para. 2)
4. being extremely large or great (Para. 3)
5. to continue or maintain something for a long time (Para. 3)
6. to make something full or complete again (Para. 4)
7. the parts that make up something (Para. 5)
8. the decision that something should be given to a particular person or used for a particular purpose (Para. 6)