Chương I NHỮNG QUY ĐỊNH CHUNG
UNIT 20. WATER USE AND HYDRAULIC
W ater Resources of the Earth, i.e. its hydrosphere, are the totality of the oceans, seas, glaciers, inland seas and lakes, rivers, underground and atmospheric waters. This totality amounts to almost 1,450,000,000 km3, of which over 90% are the world's seas and oceans, the remainder, inland water resources.
O f latest estimates, the world's annual (mean) river runoff is 38,150 km3, o f which 2,950 km3 is drained in Europe and 12,860 km3 in Asia.
The annual river runoff drained from the entire teưitory of the USSR (22,400,000 km3) is 4,350 km3 (4,700 km3, of Voznesensky's estimates), i.e. 11.5% of the world's runoff. The underground water runoff in this country is estimated at 1,020 km3. All in all, the Soviet Union has nearly 90.000 rivers with the total length in excess of 5,000,000 km and almost 250.000 lakes with an overall surface area of 2,300,000 km2.
The major economies utilizing water resources are: (1) electric power generation based on the use of water energy of seas and rivers; (2) water transportation, i.e. ship and timber handling by sea, lake and river; (3) land reclamation (amelioration) which includes: watering of farm lands (irrigation), delivering water to dry land grazing fields and diverting excessive water from waterlagged areas (drainage); (4) water supply for domestic, communal, industrial comforts and wastes disposal (sewerage) inclusive o f treated waters; (5) commercial use of waters, interior, i.e.
fishing, hunting sea animals for sports and fur, extracting salts, and ore deposits, harvesting sea weeds, algae etc.
The governing principle in water management is a comprehensive approach to the utilization of water resources.
It must be noted, however, that water usage for various economic purposes has two important aspects : one is a mere consumptive, i.e. the use of water for, e.g. water supply, irrigation, water delivery where water drawn off from various water sources (rivers, lakes, underground waters)
hardly ever returns thereto, and the other, exclusively exploitative, e.g.
electric power generation, water transportation, fishing.
In view of the comprehensive approach to the utilization of water resources it is not often possible to match up both the consumptive and exploitative uses because of inadequate requirements for water. The consumptive demands may, sometimes, exceed the natural capacity of a given water source thereby giving rise to the problem of a territorial redistribution of water resources, i.e. channeling of the runoff from regions of high rainfall to arid and semi-arid areas.
Hydraulic engineering is an applied science and a branch of mechanical engineering concerned with the utilization of water resources for various economic needs to the benefit of National Economy and the control of wild manifestations of water energy which may take disastrous proportions. Hydraulic engineering tackles a wide range of problems : water sources and their behavior, the structure of the landform of the Earth' crust as the recepticle of waters, the foundation of hydraulic constructions, and the problems related to the design, construction, and operation of water resources developments.
Engineering constructions designed and mechanically fit for managing and utilizing water resources to the best of advantage are known as hydraulic structures, also water works.
The major purpose of hydraulic engineering is to alter the natural behavior of a water source, i.e. river, lake, sea, underground waters, and adapt it to a purposeful use for the benefit of National Economy and to protect the environment.
A n o th e r p u rp o s e o f h y d ra u lic e n g in e e r in g is to p ro v id e artificial watercourses and reservoirs where natural water sources are but few or non-existant, whatever.
Yet another purpose is to provide special installations or water works, such as navigation locks, powerpiant buildings, pumping stations, fish-handling and protecting facilities, etc. to meet the specific requirements of various water-dependent economics
Hydraulic structures designed under the first two objectives are ommon for all interests of the water economy and are termed general lurpose hydraulic structures of water works. Water works which meet (articular requirements (electric power generation, ship-and-timber landling irrigation, water supply, etc.) are known as special hydraulic tructures.
Hydraulic structures designed for river, lake or sea water projects are eferred, respectively, to river, lake and marine water works.
TERMINOLOGIES - Electric power generation - W atering of farm lands - Hydraulic structures - Marine water works - Artificial reservoir QUESTIONS
1) How many rivers and lakes are there in the Russia? What is the ength of these rivers? and surface area of the lakes?
2) What major industries are utilizing the water resources ? 3) What is the governing principle in water management ?
4) What are the purposes of the hydraulic structures or water works ? 5) What are hydraulic structures designed for ?
UN IT 21. E A R T H AND R O C K F IL L DAMS
Earth and rockfill dams are water impounding structures composed of Fragmental materials. These materials are made up of discrete particles tvhich maintain their individual identities, and which have spaces or voids between them. They derive their strength from position, internal friction, ind mutual attraction of their particles. Unlike materials which are rigidly :emented together, they form a somewhat flexible structure which can
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deform slightly to conform to the deflection of the foundation without failure.
There is no standardized terminology for these structures. They arc most commonly known as eorth dams or dikes (sometimes spelt as dykes). They are also occasionally referred to as embankment dams or simply embankments or banks. Earth dams that follow nvers and are used to confine flood waters are called levees or guide banks. They are also termed as parallel dikes. Rockfill dams are essentially no different from earthfill dams except that the particles of which these embankments constructed are larger than a man can easily lift.
Use of Earth and Rockfill Dams-
Earth and rockfill dams have been in existence for countless centuries.
The earliest forms of these were not made by man. Landslides and rock-falls in mountainous areas frequently cut off streams and form natural dams, some of which are very large and have a surprisingly long life. Most of these, however, are temporary and remain only until the lakes which they create cause them to burst or wash out. An example is a landslide which occurred in 1840 on the upper reaches of the Indus River (1). The failure took place at the foot of Nanga Parbat (altitude 26,660 ft.
or 8,000m) just south of Gilgit. A dam 1,000 ft. (300m) high was formed which soon impounded a lake over 900 ft. deep. Six months later, the dam burst, flooding the valley below and causing great loss of life and property. Similar failures have occurred in the Alps and in the Rocky Mountains of North America.
Glacial action has also formed numerous earth dams. During the periods when formations of ice are advancing, they thrust up large ridges of materials, including both soil and broken rock, like giant bulldozers.
When the climatic changes cause the glaciers to retreat, the melting water from the ice is trapped between the earth ridges (or terminal moraines).
Many of the natural lakes in North America and Northern Europe were fo rm e d in th is w ay . It IS r e m a rk a b le h o w w e ll s o m e o f th e s e glacial moraine dcims have stood up for the ensuing thousands of ycETS
Animals other than men have also been builders of earth dams. The beavers o f North America (large animals of the rodent family weighing about 40 lb. and equipped with flat tail for swimming and long incisor teeth for gnawing) construct large dams of wood, leaves, and earth. These animals cut trees as much as 4 inches in diameter, haul them or float them to a stream, and lodge them together to form a crude framework.
Small sticks, leaves, and mud are worked into this frame to create a dam.
Some of these have been several hundred feet long and three or four feet high. W hile they leak badly, they are fairly durable, and last for many years if given constant repair. The beaver creates these lakes to submerge entrances to his grass and stick huts which dot the lake like small stacks of hay, and thereby to preserve his winter supply of food which consists of tree bark submerged by the rising water.
Man has built dikes of earth to impound water since pre-historic times.
Reservoirs to hold water for irrigation have been found in Iraq, Jordan, and Israel which were built by tribes whose other works have since disappeared. Numerous "tanks" or reservoirs are found in South India and Ceylon, many o f which are over 2,000 years old. One such tank in Ceylon is said to be 30 miles long. The Moti Talab tank in Mysore, India, which is over 1,000 years old, is an earth embankment 80 ft. high at places. Dumped earth and rock baưages have been used in many parts of the world to divert rivers and create deep ponds on otherwise shallow streams. Dikes or levees were built to protect land from flooding by rivers in ancient China, and for centuries the Dutch have increased their land area by walling off the sea by earth dikes.
Earth and rockfill dams are being constructed nowadays at an increasing rate throughout the world. Many such structures over 300 ft.
high are successfully impounding water. In fact several earth dams have also been constructed even over 500 ft. in height. The largest structure ever built by man is an earth dam. The Fort Peck Dam in Montana has a volume of 130,000,000 cu.yd. (100,000,000 cu. meter). It can, therefore, be said that the use and safety of earth and rockfill dams have been established by long experience of structures both small and large.
TERMINOLOGIES Earth dam Rockfill dam
Đập đất Đập đá đổ Discrete particles
Internal friction Mutual attraction Glacial action
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