VARIOUS YIELDS OF RESERVOIR
VARIOUS YIELDS OF RESERVOIR

VARIOUS YIELDS OF RESERVOIR

VARIOUS YIELDS OF RESERVOIR 1. Yield of the Reservoir. It is the amount of water that can be supplied by the reservoir in a specified interval of time. The specified time interval may vary from a day for a small distribution reservoir to a month or year for large conservation reservoirs. If we say that three million cubic metres of water can be supplied from a reservoir in a year then its yield is 3000000 m3/year. The yield of the reservoir is dependent upon the inflow and thus varies from time to time. 2. Safe Yield. It is also known as firm yield. It is the maximum quantity of water that can be supplied from the reservoir with full guarantee during the worst dry period. 3. Design Yield. The critical period for a reservoir is generally considered, when natural flow in the reservoir is minimum. There is possibility that sometimes…

Continue Reading VARIOUS YIELDS OF RESERVOIR
Mass Inflow curve
Flood hydrograph and mass inflow curve

Mass Inflow curve

MASS INFLOW CURVE Mass inflow is a curve which represents the cumulative flow in a reservoir at any particular instance. It is a plot between cumulative inflow in the reservoir with time. It can be prepared with the help of a hydrograph of the river for the dam site for a large number of years. We know hydrograph is a plot or curve between discharge versus time. Figure 9.4 (a) shows a hydrograph of a river for the dam site for a number of years and Fig. 9.4 (b) a corresponding mass curve prepared from the hydrograph of Fig. 9.4 (a). Let starting year of the hydrograph is 1998. The total quantity of water that has flown through the river from 1998 to a time t1 (say 2001) has been represented by the hatched area. In mass curve, the corresponding ordinate at time t1 (ordinate AB) will represent the total…

Continue Reading Mass Inflow curve
Methods of Lifting Water
Water lifting devices

Methods of Lifting Water

METHODS OF LIFTING WATER Water is to be lifted from wells before it is used for irrigation. Sometimes water may have to be lifted from canals, streams, and rain water filled in low lying areas to use it for irrigation. The methods of lifting water vary depending on the source, depth, quantity to be lifted and availability of power. The following are the various methods of lifting water: Rope, pulley and bucket method Dhenkli or lever or let method Mote, charas or leather bag method Nar, Rahat or Persian wheel Basket method Doon method Archimedian screw method Pump method. Each of the above methods have been briefly discussed as follows. 1. Rope-pulley and Bucket Method. This method consists of a pulley over which a rope is passed. A bucket is tied tothe end of the rope hanging in the well and other end of the rope is held by a…

Continue Reading Methods of Lifting Water
Well Troubles
WELL TROUBLES

Well Troubles

WELL TROUBLES Failure of the well or reduction in the yield is not uncommon. Following may be the reason and remedies. Reduction of discharge may be due to a draft greater than the percolation of water. Lowering the pumps may increase the yield for the time being, but permanent remedy is to reduce pumpage. The casing pipe or screen pipe may have collapsed, partially or completely, blocking the flow of water. This trouble necessitates replacement of the casing or screen pipes. If the material in which the well is drilled is unconsolidated it may have to be abandoned. Casing pipe may have corroded or leaked. Due to this, water may escape out into the ground or contaminated ground water may enter the well. The remedy lies in withdrawing and replacing the casing pipe. The life of the casing pipe depends upon the character of water handled by it. If water…

Continue Reading Well Troubles
Methods of drilling tube wells
Driving or Drilling Your Own Well

Methods of drilling tube wells

METHODS OF DRILLING TUBE WELLS Wells for domestic purposes which require small quantity of water are bored with auger turned by hand. Smaller wells in unconsolidated formations may be constructed by cutting action of a jet of water. None of these two methods is however applicable to deep tube wells. Deep and high yield wells are constructed by drilling. There are various techniques of boring the well hole. All the techniques have their own merits and demerits, depending upon the formation in which drilling is to be done. Most commonly used drilling methods have been described as follows. 1. Cable tools method or percussion drilling method. 2. Hydraulic rotary method. 3. Reverse rotary or jetting method. 1. Cable Tool Method or Percussion Drilling Method. This method of drilling of the well hole is based on the use of striking force, (hammering and cutting) of the drilling bit, attached to the…

Continue Reading Methods of drilling tube wells
Types of tube wells
TYPES OF TUBE WELLS

Types of tube wells

TYPES OF TUBE WELLS The tube wells may be further classified into following three types: Strainer wells Cavity well. Slotted wells. All the three types of tube wells have been discussed one by one. 1. Strainer Type Tube Well. It is the most commonly used type of tube well in our country. It is so common that whenever we talk of a tube well, it is automatically understood  referring to strainer type tube well. This tube well consists of blind pipes and strainer pipes or screen pipes. This tube well is generally unsuitable for very fine sandy strata, because in that case screen openings are likely to get choked easily. The boring of the hole is generally carried out by using casing pipe of about 5 to 10 cm larger than the diameter of the well pipe. Thus a 15 cm diameter well, will require a bore hole of 20…

Continue Reading Types of tube wells
Types of strainers
TYPES OF STRAINERS

Types of strainers

TYPES OF STRAINERS The strainer pipe is a perforate pipe which is provid with such an arrangement that only water can be admitted inside the pipe. Various patents types of strainers are available in the market. Some of the strainer are: 1. Cook’s strainer 2. Tej strainer 3. Ashford strainer 4. Leggett strainer 5. Phoenix strainer 6. Layne and Bowler strainer 7. Brownlie strainer 8. Esbee strainer 9. Mesh strainer. 1. Cook’s Strainer. It is made from solid drawn brass tube and is very costly. It consists of wedge shaped slots atits surface. Slots are wider at the inside and finer at the outer surface. The size of the slots depends upon the coarseness of the sand in which it is to be used. It is not used much in India. The size of the slots may vary from 0.1 mm to 0.4 mm. 2. Tej Strainer. It is just…

Continue Reading Types of strainers
Completion of well
Well Completion Design

Completion of well

COMPLETION OF WELL During boring of the well hole by any method it should be ensured that bored hole remains straight and vertical. If well hole is located in consolidate formation, water enters the well hole directly and no casing is required as all the surroundings are quite stable. But if formations are unconsolidated a casing is necessary to support the outside material and also to help in freely admitting the water into the well. The casing should either contain perforations or its lower part may be replaced by a screen or strainer so that water may enter the well. Sometimes in order to increase the effective diameter of the well, the screen or strainer is surrounded by a layer of gravel. Gravel layer keeps fine material out of the well. Such a gravel packed well will have a greater specific capacity than one of the same diameter not surrounded…

Continue Reading Completion of well

Well development

WELL DEVELOPMENT It is a process by which the fine particles are removed from aquifer formation surrounding the strainer pipe of the well. Following favourable effects are obtained from well development: Specific capacity of the well increases. Flow of sand into the well is prevented. Life of the well is increased. The well can be developed by following methods: (i) by pumping, (ii) by surging, (iii) by compressed air, (iv) by back washing, (v) by dry ice. (i) Pumping. In this method, pumping of water is done non-continuous, irregularly and at variable rate. By this fine material surrounding the well gets agitated and carried out of the well. (ii) Surging. A bailer or hollow surge block is moved up and down in the well briskly. By this finer particles are agitated and enter the well from where they are pumped out. Sometimes calgon is also added to well water so…

Continue Reading Well development
Construction of Open wells
CONSTRUCTION OF OPENS WELLS

Construction of Open wells

CONSTRUCTION OF OPENS WELLS Open wells may be constructed in following three ways: Kacha wells or wells having no lining, Wells having pervious lining and Lined wells. 1. Kacha Wells. These wells are of small depths and can be constructed in boulder or hard soils. They can be construct places where water table is very near to the surface of the ground. They can be only temporary source of irrigation water. They may collapse easily and thus sometimes prove very dangerous. 2. Wells having Pervious Lining. In this, the lining of the well is done in dry bricks or stones without using any mortar. The seeping water can enter the well through the open joints of dry masonry. Thus inflow in this case is radial and not axial. Such wells are generally plugged at the bottom by means of concrete. If bottom is not plugged, then water will be entering…

Continue Reading Construction of Open wells