The post Concepts of Watershed Management appeared first on agriinfo.in.
]]>Concepts of Watershed Management
Soil, vegetation and water are most important vital natural resources for the existence of the man and his animals. These three interdependent resources can bee managed collectively, conveniently, simultaneously and efficiently on watershed basis (unit of management.)
Watershed:
Definition:
“Watershed can be defined as a unit of area covers all the land which contributes runoff to a common point or outlet and surrounded by a ridge line”. It is also known as ridge line.
Delineation procedure of watershed:
Watershed delineation is to describe or sketching out the area bounded by ridge line, contributing runoff at common point and dividing or separating it from the adjoining area.
The delineation of priority area can be performed to some extent by reconnaissance survey and study of topo sheets. However, this technique is slow and also not provides very accurate information. Normally, the photographs of 1:15,000 can also be used for the purpose.
The demarcation of priority areas should be accomplished on watershed basis, because a comprehensive watershed management approach is essential for caring out for proper soil conservation measures. It is also necessary that, that the size of watershed to be delineated should be ranges from 10,000 to 20,000 ha, because for small watershed the formulation of soil conservation working plans and their execution over reasonable period is practically possible and easy, too.
The steps for demarcation of small size watershed are described as under:
1. Divide the entire watershed into different subwatersheds following important tributaries.
2. Again, divide each sub watershed into small size, following distinct tributaries and streams passing through respective sub watershed.
3. further, subdivided each small part of watershed [as obtained in step (2) in size ranges from 10,000 to 20,000 ha.]
Causes of watershed Deterioration:
Deterioration of watershed takes place due to faulty and bad management through the activity of man and his animals. These activities are:
Faulty agriculture, forestry and pasture management leading to degradation of land.
Unscientific mining and quarrying.
Faulty road alignment and construction.
Industrialization
Fire.
Apathy of the people.
Results of watershed Deterioration:
Less production from agriculture, forests, grass lands etc.
Erosion increases and decreases biomass production
Rapid siltation of reservoirs, lakes and river beds.
Less storage of water and lowering of water table.
Poverty as a result of less food production.
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]]>Advantages and Limitation of Sprinkler Irrigation
Advantages:
1. Suited to complete range of topographies and field dimensions.
2. High irrigation efficiency due to uniform distribution of water.
3. Accurate and easy measurement of water applied.
4. Land leveling is not essential.
5. Soluble fertilizer, herbicides and fungicides can be applied in the irrigation water economically and with little extra equipment.
6. More land is available for cropping.
7. No interfere with the movement of farm machinery.
8. Can be used to protect to crop against high temp that reduce the quantity and quantity of heaters.
9. Easy to operate, operator may be trained quickly.
10. Sprinklers are also used to irrigation high valued plantation crops like, coffee, cardamom and orchards.
Limitation:
1. It requires high initial investment.
2. Power requirement is usually high since sprinklers operate with more than 0.5 kg/cm2 water pressure.
3. Fine textured soils that have low infiltration rate can not be irrigated efficiently in host windy area.
4. Loss of water due to evaporation from the area during irrigation.
5. The water must be clean and free of sand, debris and large amounts of dissolve salts.
6. Wind distorts sprinkler pattern and cause uneven distribution of water.
7. Ripening of soft fruit must be protected from the spray.
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]]>Object, Use & Principles of Surveying
Objects of surveying:
The primary object of survey is the preparation of plan estate or buildings roads, railways, pipelines, canals, etc. Or to measure area of field, state, nation.
Object of geodetic surveying is to determine precise positions on the surface of the earth of widely distant points.
Uses of Surveying:
To prepare a topographical map this shows the hills, valley, rivers, villages, town, etc, of a country.
To prepare a cadastral map showing the boundaries of fields houses, and other properties.
To prepare an engineering map to show details like roads, railways, canals, etc.
To prepare military map showing roads and railways, communication with different parts of country.
To prepare contour map and to determine capacity of a reservoirs and ton find the best possible route for roads, railways etc.
To prepare archeological map including places where ancient relics exist.
To prepare a geological map showing areas including underground resources.
Principles of surveying:
There are two fundamental principles.
To work from the whole to the part.
Control points: – triangulation of traversing.
Triangulation divided into large triangle.
Triangles subdivided in to small triangles
To control and localize minor errors.
On the other hand –It we work from the part of the whole; small errors are magnified & uncontrollable at the end.
To fix the position of new stations by at least two independent process. The stations are fixed from points already fixed by
Linear measurement or
Angular measurements or B
Both the linear and angular measurements.
E.g. Chain surveying main lines & stations points are checked by means of check or tie lines.
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]]>The post BinaryFractions appeared first on agriinfo.in.
]]>Binary Fractions
Just as we use decimal point for representing fractional decimal numbers, binary point is used to represent a fraction in binary numbers. The positional values in this case are 2^1,2^2,2^3,….. for successive positions starting from binary point to its right.
For example,
(0.111)2 = 1 x 2^1 + 1 x 2^2 + 1 x 2^3
= 1 x 0.5 + 1 x 0.25 + 1 x 0.125
= (0.875)10
To convert decimal fraction to binary fraction, following rules are used:
Multiply decimal fraction repeatedly by 2. The whole number part of the result gives the first bit of the binary fraction. The above procedure is repeated with fractional part of the result and so on.
Example: Convert (0.375)10 to binary fraction
0.375 x 2 = 0.750 ——– 0
0.750 x 2 = 1.50 ——– 1
0.50 x 2 = 1.00 ——— 1
Hence (0.375) 10 = (0.011)2
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]]>The post Data Communication appeared first on agriinfo.in.
]]>Data Communication
Communication is to transfer information from one place to another. Communication from a source to destination requires a proper methodology and technique. It requires a medium, source, message formation, storage and input for transmission etc. A reverse procedure at destination is repeated to get the exact message. This, in turn, requires a complete system for communication. Most popular media types used for communication between two computer systems, are twisted pair of wires, coaxial cable, fiber, optic cable, microwave and satellite. Communication between two systems can be established using the facility of media provided by telecommunication network (Telephone Lines) through modems, fax machines etc.
Modem is a modulating demodulating device. It encodes the data while sending and decodes it at the receiving end. Modem to modem communication is through telephone lines. Modem can be directly connected to a computer through a serial port.
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]]>Models Design of Drip Irrigation System
Crop = Mango ( 5m X 5m)
Area= 1 ha ( Assume square plot)
Pan evaporation = 8 mm/day
Pan coefficient = 0.7
Crop factor= 0.75
% wetted area= 60
Soil type= medium
Water source is well at the corner of the field ( well depth) = 10m
Assume pump efficiency 70% and motor efficiency = 80%
Solution:
i) Determination of Water Requirement ( WR):
WR= Crop area X PE X PC X KC X % wetted area
= 5m X 5m X 8 X0.7X 0.75 X 0.6
= 63 lit /day/ plant
ii) Selection of Dripper:
Selection 2 dripper of 8 lph capacity per plant
Total no of plants = Total area
__________
Plant area
= 10,000/ 5 X 5 = 400
No of drippers = 400 X 2 = 800
iii) Selection and Design of Lateral:
Flow rate of lateral = No of dripper on lateral X Discharge of drippers per plant.
No of dripper on lateral = Length of Lateral
____________________________
Spacing between two drippers
= 50/5
= 10
Q of lateral = 10X 2 X8 = 160 lit/hr
Give the submain at the centre of the point
Length of lateral = 50 m
Diameter of lateral= 12 mm = 1.2 cm
Head loss in lateral ∆H= 1.526 X 104 X (Q/C) 1.852 X D 4.871 X LX F
Where, Q= Flow rate of lateral in m3 /hr
C= Hazen and William constant
D= Diameter of pipe in cm
L= Length of pipe in m
F= Outlet factor
∆H= 1.526 X 104 X (0.16/150) 1.852 X (1.2) 4.871 X 50 X 0.39
∆H= 0.38
∆ Head loss is less than 2 m , hence design is acceptable.
iv) Selection and Design of Submain: Select 40 mm Sub main.
Select 40 mm mainline
Flow rate of mainline= Flow rate of Submain
Q= 6.4 m3 /hr
Diameter of mainline = 4cm
Diameter of mainline= 40mm=4cm.
Head loss in Mainline,
H= 1.526 X 104 X ( Q/C) 1.852 X D 4.871 X L X F
= 1.526 X 104 X ( 6.4/150) 1.852 X (4) 4.871 X 100
So, H= 2.58m
Selection Pump:
Total discharge,
Q=6.4 m3 /hr
Q= 6400 lph
Q = 6400 lps
________ 1.77lps
60 X 60
Total head of pump = ( Suction head+ delivery head) + operating pressure of drip irrigation system+ filter loss + fitting loss + mainline loss + ventury loss + elevation difference
Suction head + delivery head = 10
Operating pressure= 1 kg /cm2 or 10m
Filter loss = 2m for sand filter + 2m for screen filter
= 4m
Ventury loss = 5m
Fitting loss= 2m
Main line loss= 2.58
Elevation difference = 2m
So, Total head of pump = 10+10+4 + 2 +2.58 +5+2
= 35.5 m
H.P of pump = Q ( lps) X H (m)
_______________
75 X 0.7 X 0.8
So, Pump efficiency and motor efficiency is given as 70% and 80% respectively.
HP= 1.49 hp
So, HP of Pump is 1.49 hp say 2 HP
vi) Irrigation Time:
Irrigation Time = Peak water requirement per plant
____________________________
Discharge of dripper per plant
= 63
_____= 3.9 ( say 4 hours)
2 X 8
So, Irrigation time required is 4 hrs.
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Plane Table Surveying
Plane table is a graphical method of surveying in which the field works and the plotting is done simultaneously. It is particularly adopting in small mapping. Plane table surveying is used for locating the field computation of area of field.
Merits:
It is most suitable for preparing small scale map or surveying small area.
It is most rapid method.
Field book is not necessary.
No great skill is required for satisfactory map.
It is particularly suitable for magnetic area where prismatic compass is not reliable.
Contour and irregular object may be represented accurately.
It is less costly.
Demerits:
Plane Table Essentially a tropical instruments.
It is not suitable to work in wet climate.
There are several accessories to be carried out and therefore they are likely to be lost.
It is not suitable for accurate work.
Parts of plane Table:
Plane table essentially consist of
Drawing board mounted on tripod.
Alidade.
1. Drawing board mounted on tripod
A sheet of drawing paper, called plane table sheet is fastened to the board. Board is made up of well seasoned wood such as teak of size 40×30 to 75x60cm. it had plane and smooth top. It is mounted on a tripod in manner that it can be leveled. Leveling up of the table is done by shifting the legs of tripod. Some tripod provided with leveling screw or by ball and socket head for accurate leveling.
2. Alidade:
Alidade consists of two vertical sight vane fitted at end the end of straightedge. The straight edge ruler usually made of brass or teak wood graduated beloved edge. One of the sight veins is provided with narrow slit and the other with a central vertical wire or hair. Beveled working edge alidade is called fiducial edge.
Accessories:
A through campus for marking the direction magnetic meridian on paper.
Sprit level for leveling the table.
Forked plumb for centering the table.
Water proof cover to protect the sheet from rain.
Centering:
It is the process of keeping the table over the station that the point on the paper representing the station being occupied is vertically over the point on the ground. It is done by forked plumb bob.
Orientation:
When the table has to be set up at more than one station it is necessary that it is be oriented so that the lines on the paper remain parallel to the lie which they represent on the ground. So orientation is “the process of keeping the table to the position which is occupied at the first station”.
Orientation is done by two methods:
By use of the magnetic needle.
Orientation by back sighting.
Orientation by the magnetic needle:
To orient the table at any subsequent station, the through compass(or circular box compass) is placed along the line representing the magnetic meridian which has been drawn on the paper at the first station, and the board is then turned until the ends of the needle oare opposite the zeros of the scale. The board is then clamped in position. It is suitable for rough small scale mapping.
Orientation by back sighting:
This is the most accurate method of orientation and is always be preferred. Suppose a table is set up over station Q on the line PQ which ahs been previously drowned as PQ from station p. The alidade is placed along the line QP and board then turned until the line of sight bisects the ranging rod at P. Board is then properly clamped.
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]]>Soil –Plant – Water – Relationships
Soil –Plant –Water relation relates to the physical properties of soil and plants that effect the movement, retention and use of water. These relations must be considered in designing and operation systems.
Soil is a store house of plant nutrients, a habitat for bacteria , an anchorage for plant and a reservoir that hold the water needed for plant growth. The amount of water a soil can hold in available from for plant use is determined by its physical properties. This amount determines the length of time a plant can survive without water being added. It determines both the frequency of irrigation and the capacity of irrigation system needed to ensure continuous crop growth.
Soil is a three phase system comprising of the soil phase made of mineral and organic matter and various chemical compounds, the liquid phase called soil moisture and the gaseous phase called the soil air. They also contain variety of living an organism. Two important physical properties of soil, which differ the supply of water and air in soil, are texture and structure.
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]]>Hydraulics of Drip Irrigation Lines
Flow in the drip irrigation lines is hydraulically steady, spatially varied pipe flow with lateral out flows. The total discharge in the drip irrigation lines ( lateral, submain or main) decreases with respect to the length of line. The lateral and submain can be considered as having the same hydraulic characteristics and area designed to maintain the smallest pressure, the required pressure and the slope of the energy gradient line, which will give the total energy higher than that required at any submain for irrigation.
A drip irrigation system is made by a combination of different size of plastic pipes which are usually considered as smooth pipe. One empirically equation frequently used is the Hazen and Williams formula. Also, because of the possibility of laminar, turbulent or fully turbulent flow in trickle the Darcy Weisbach equation can be used to compute the head loss due to pipe friction.
Darcy Weisbach equation
Hf= 2fl v2
______
g.d
In which,
Hf= head loss in pipe, m
f= coefficient of friction for pipe
l= length of pipe, m
v= velocity of water in pipe, m/sec
g= acceleration due to gravity m/sec2
d= diameter of pipe, m
The Darcy Weisbach friction factor, f for small diameter trickle irrigation tubing is related to the Reynolds number, (N.R). The Reynolds number, NR is computed with following equation.
NR= S D.V/ K.M
Where,
NR= Reynolds number
S= density of water, gm/cm3
D= diameter of pipe, cm,
V= Average velocity, cm/s
u = viscosity of fluid, n s/m2
K= unit constant (K =10 for S in gm/cm3, d in cm, v in cm/s)
The equation used to computer f depends on the magnitude of NR.
When Reynolds number is less than 2000 then flow is laminar, when NR is between 2000 to 10,000 flow is turbulent and when NR is greater than 10,000 flow is fully turbulent.
In general, the friction drop equation for pipe flow can be shown in simplified form as,
∆H= a. Qm. ∆L
Where,
∆H = is the total energy drop of pipe section, m
a = is constant for given pipe size
Q = is total discharge rate, lps
∆L= is length of pipe, m
m = 1 for laminar flow
m = 1.75 for turbulent flow in smooth pipe
m = 1.852 for turbulent flow using the Hazen and William formula
m= 2 for a fully turbulent flow
Where friction coefficient is constant,
Among all the equations, the Hazen and Williams formula is commonly and most frequently used.
The Hazen and William equation for smooth pipe is,
∆H= 1.526X 104 X (Q/C) 1.852 X D4.871 X L
Where,
∆H= head loss in pipe, m
Q= total discharge in pipe, cum/hr
C= is Hazen and William constant (for smooth pipe C=150
D= is the diameter of pipe, cm
L= is the length of pipe, m
Since, the discharge in the cub –main and lateral, decreases with respect to length , the total energy drop will be less than, the one given by equation. Therefore, for lateral and submain head loss is calculated by introducing a Fvalues i.e called as outlet factor ( F).
∆H= 1.526 X 104 X (Q/C) 1.852 X D4.871 X (L + le) X F
Where,
le = is the equivalent length of pipe or lateral , m
F= is outlet factor, and is depends on No of outlets.
Table: Values of Outlet Factor ( F) for Lateral or Pipe:
No of Outlet 
FValue 
No of Outlet 
FValue 
1 
1.00 
1215 
0.40 
2 
0.65 
1620 
0.39 
3 
0.55 
2130 
0.38 
4 
0.50 
3136 
0.37 
5 
0.47 
3740 
0.36 
6 
0.45 
More than 40 
0.35 
7 
0.44 


89 
0.42 


1011 
0.41 


Hydraulically, the pressure variation along a submain will cause a lateral flow variation along a Submain and pressure variation along a lateral will cause an emitter flow variation along the lateral through each emitter.
The pressure variation and emitter flow variation are related and can be expressed as ,
Q var= 1(1H var) 0.5
Where,
The emitter flow variation, q var is defined as;
Q var= q max 1 min / q max
In which,
q max= is the maximum emitter flow along the line, and
q min= is the minimum flow along the line, and
q var= should be less than 10% ( desirable)
The pressure variation, Hvar is defined as
H var = h max – h min / h max
In which,
h max and h min = are the maximum and minimum pressure variation respectively along the line and H var should be less than 20 percent.
In drip irrigation systems design, the design criterion is generally based on an emitter flow variation of less than 20 percent and pressure variation less than 10 percent i.e. acceptable limits.
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]]>The post Orifices appeared first on agriinfo.in.
]]>Orifices
Orifices in open channels are usually circular or rectangular opening in vertically bulkhead through water flows. The edge of opening is sharp and often constructed of metal.
Free flow orifices:
It can be used to measure comparatively small stream like the flow into border strips, or check basin. They consist of sheet of iron, steel, or aluminum plate that contains accurately machined circular opening ranging from 2.5 cm to 7.5 cm. A plastic scale may be fixed directly on upstream flow of orifices with zero coinciding with the center of orifice.
Submerged Orifices:
Submerged orifices may be divided in to two types:
1) Those having orifices of fixed dimension.
2) Those in which the height of opening may be varied.
The discharge through standard submerged orifices may be obtained using above equation.
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