Water Requirements of Crops

&

Irrigation Water Quality

Functions of Irrigation Water :

1. It acts as solvent for the nutrients. Water forms thesolution of nutrients, and this solution is absorbed bythe roots.

2. The irrigation water supplies moisture which isessential for the life of bacteria beneficial to the plantgrowth.

3. Irrigation water supplies moisture which is essential for

the chemical action within the plant leading to itsgrowth.

4. Water cools the soil and the atmosphere and thus makes

more favorable environment for healthy plant growth.

5. Irrigation water, with controlled supplies, washes out or

dilutes salts in the soil.

6. It reduce the hazard of soil piping.

7. It softens the tillage pans.

8. Catalyst for food production

Quality of Irrigation Water :

Impurities in irrigation water :

1) Concentration of sediments in water.

2) Total concentration of soluble salts (TDS).

3) Proportion of sodium ions to other cations.

4) Concentration of toxic elements such as boron concentration.

5) Concentration of Bicarbonates viz. Ca & Mg

6) Bacterial concentration.

Classification of Irrigation Water :

Irrigation water may be classified on the following basis:

a) Classification based on total concentration of soluble

salts.

b) Classification based on sodium concentration.

c) Classification based electrical conductivity(EC), (TDS),

sodium concentration, Boron concentration etc.

Classification Based on Total Concentration of

Soluble Salts :

Irrigation water may contain various types of salts such as sodium, calcium, magnesium and potassium

The salts content of irrigation water is usually expressed by one of the following ways:

i. Parts per million(ppm) or milligram per litre (mg/l) both

units being equal.

ii. Milli equivalents per litre (MEQ/L).

iii. Electrical conductivity, expressed in micromhos per

centimeter.

The salinity concentration of soil solution(Cs) can be determined flowing formula :

C= concentration of salt in irrigation water.

Q= total quantity of water applied to the soil.

Cu =consumptive use of water.

Peff = useful rainfall.

Classification of Irrigation Water Based

on Salts Concentration :

S.N. Types of water Suitability for irrigation

1. Low salinity water (C1) conductivity between

100 to 250 micro-mhos/cm at 25 CSuitable for all types of crop and

all kinds of soils. Permissible

under normal irrgation practices

expect in soil of extremely low

permeability.

2. Medium salinity water (C2) conductivity

between 250 to 750 micro mhos/cm at 25 C

Can be used if a moderate amount

leaching occurs .

3. High salinity water (C3) conductivity between

750 to 2250 micro mhos/cm at 25 C

unsuitable for soil with restricted

drainage .

4. Very high salinity (C4) conductivity more then

2250 micro mhos/cm at 25 C

Unsuitable for irrgation.

Classification Based on Sodium

Concentration :

Irrigation water having a higher sodium percentage will, after

some time, give rise to a soil having a large percentage of

replicable sodium in the colloid. Such a soil is often known as

black alkali.

equation:

percentage sodium =

ESP = Exchangeable sodium percentage

If the percentage of sodium is more ,the aggregation ofsoil grains break down, and the soil becomes less

permeable and of proper tilth.

Irrigation water is classified on sodium concentration ,onthe basis of factor called sodium-absorption ratio(SAR).

The Characteristic of the four types of

Irrigation Water Based on SAR :

S.No. Type of water suitability

1. Low sodium water (S1)

SAR: 0 to 10

Suitable for all types of crop and all type of soils

,expect for those crop which are highly sensitive too

sodium.

2. Medium sodium water

(S2)

SAR: 10 to 18

Suitable for coarse textured of organic soil with good

permeability.

3. High sodium water(S3)

SAR: 18 to 26

Harmful for almost all types of soils ,required good

drainage ,high leaching.

4. Very high sodium

water(S4)

SAR above 26

Unsuitable for irrgation

Classification Based on EC, TDS, Sodium

Concentration and Boron Concentration

Based on the following four factor :

i. Electrical conductivity.

ii. Total salt concentration.

iii. % Sodium.

iv. Boron concentration (ppm).

Classification of Soils :

1. Classification according to age of formation.

2. Classification according to geological process of formation.

3. Classification according to content of calcium, aluminium and

iron salts.

4. Classification based on EC, ESP and PH: for saline and alkaline

soils.

5. Soil classification on regional basis.

6. Soil classification on the basis of particle size: textural

classification.

Textural Classification Chart :

Preparation of Land for Irrigation :

This can be done as follows:

i. Removal of thick jungle, bushes etc. from the raw land.

The roots of the trees should be extracted and burnt. The

land should thereafter be properly cleaned.

ii. The land should be made level. High patches should be

scraped and depression filled.

iii. The land should be provided with regular slope in the

direction of falling gradient .

iv. The land should be divided into suitable plots by small levees

according to the method of irrigation to be practiced.

v. Permanent supply ditches and water courses should be

excavated at regular spacings which facilitate proper distribution

of water to the entire field.

vi. A drain ditch which carries the waste water should also be

excavated.

vii. Proper drainage measures should be adopted where the danger

of water logging may become eminent after the introduction of

canal irrigation.

Suitability of Soil for Irrigation :

The soil should be carefully studied with regard to the following :

a) Size of soil particles.

b) Compactness.

c) Depth.

d) Organic matter content.

e) Position of water table.

Classification of Soil Water :

Some of the definitions related to the water held in the

soil pores are as follows:

1. Gravitational water: A soil sample saturated with

water and left to drain the excess out by gravity holds on

to a certain amount of water. The volume of water that

could easily drain off is termed as the gravitational water.

This water is not available for plants use as it drains off

rapidly from the root zone.

2. Capillary water: The water content retained in the soil

after the gravitational water has drained off from the soil is

known as the capillary water. This water is held in the soil by

surface tension. Plant roots gradually absorb the capillary

water and thus constitute the principle source of water for

plant growth.

3. Hygroscopic water: The water that an oven dry sample of

soil absorbs when exposed to moist air is termed as

hygroscopic water. It is held as a very thin film over the

surface of the soil particles and is under tremendous negative

(gauge) pressure. This water is not available to plants.

Soil Water Classes :

Soil Water Constants :

Saturation capacity : This is the total water content of the soil whenall the pores of the soil are filled with water. It is also termed as the

maximum water holding capacity of the soil. At saturation capacity,

the soil moisture tension is almost equal to zero.

Field capacity (Fc) : This is the water retained by an initiallysaturated soil against the force of gravity. Hence, as the gravitational

water gets drained off from the soil, it is said to reach the field

capacity. At field capacity, the macro-pores of the soil are drained off,

but water is retained in the micro-pores. Though the soil moisture

tension at field capacity varies from soil to soil, it is normally between

1/10 (for clayey soils) to 1/3 (for sandy soils) atmospheres.

Permanent Wilting Point: Plant roots are able to extract water from asoil matrix, which is saturated up to field capacity. However, as the waterextraction proceeds, the moisture content diminishes and the negative(gauge) pressure increases. At one point, the plant cannot extract any furtherwater and thus wilts.

The soil moisture tension may range between 7 to 40 atm.

For most of the soils, wilting coefficient is about 150% of the hygroscopic water andis estimated by dividing the Fc by a factor varying from 2 to 2.4.

Two stages of wilting points are recognized and they are:

1. Temporary wilting point: This denotes the soil water content at which theplant wilts at day time, but recovers during right or when water is added tothe soil.

2. Ultimate wilting point (hygroscopic coeff.): At such a soil water content,the plant wilts and fails to regain life even after addition of water to soil.(Hygroscopic coeff. is about 2/3 of permanent wilting point).

Available Moisture : The difference in water content of the soilbetween field capacity and permanent wilting point is known as

available water or available moisture.

Soil moisture deficiency = Fc actual moisture content

Readily Available Moisture : It is that portion of the availablemoisture that is most easily extracted by plants, and is approximately

75% of the available moisture.

Depth of Water Stored in Root Zone and

Available to Plants :

In order to estimate the depth of water stored in the root zone of soil containing water upto field capacity:

Let,

Root zone depth = d(m)

Dry unit weight of soil = d(kg/m3)

Unit weight of water = w (kg/m3)

Area of plot considered = 1m x 1m

Fc = =

Weight of water retained in unit area =

Depth of water stored (in depth d) = m

A part of this depth of water will be available for evapo-transpiration.

Available moisture depth (dw ) is given by :

Sg = Specific gravity

Limiting Soil Moisture Condition :

Note :

The plant growth may be retarded if the soil-moisture iseither deficient or excessive.

If the soil moisture is only slightly more than the wiltingcoefficient, the plant must expend extra energy obtain it

and the plant growth healthy.

The optimum moisture percentage is thus the moisturecorresponding to which optimum growth of plant take

place.

Depth and Frequency of Irrigation :

At any time, the moisture content in the soil should be between the field capacity and the lower limit (mo), of

the readily available moisture.

mo is the maximum level upto which the soil moisture may be allowed to be depleted in the root zone without

fall in the yield.

The depth of water dw to be given during each watering is found from the following expression :

where is the dry unit weight of soil.

And is unit weight of water.

Both F0 and m0 are moisture contents to be expressed as ratio.

If Cu is the daily consumptive use rate, frequency of watering fw is given by :

fw =

Time Required to Irrigate a Certain Area :

Let t be the time required to apply the desired water depth dw to bring the water level in the soil form mo to

the field capacity Fc ,over an irrigation field of area A.

if q is discharge in the field channel in cumecs, then :

PRINCIPAL CROPS AND CROP SEASONS

Crops can be classified in the following ways:

1. Agricultural classification : Field crops, Commercial crops, Oil seed crops, Horticulture crops, Plantation crops, Forage crop.

2. Classification based On crop seasons: Rabi crops or WinterCrops, Kharif crops or monsoon crops, Perennial crops, Eightmonths crops

3. Classification based on irrigation requirement: Dry crops,wet crops, garden crops

Crop Ratio:-It is the ratio of the area irrigated in Rabi season tothe area irrigated in Kharif season.

Overlap allowance :- It may happen sometimes that the crop of someseason may overlap some period of the next crop season. When suchoverlapping takes place, the crops of both the seasons require watersimultaneously. Thus the overlap allowance is the extra discharge forthis purpose.

PRINCIPAL CROPS OF INDIA

Duty of Water :

The term duty means the area of land that can be irrigated

with unit volume of irrigation water. Quantitatively, duty is

defined as the area of land expressed in hectares that can be

irrigated with unit discharge, that is, 1 cumec flowing

throughout the base period, expressed in days.

For eg : If 4 cumecs of water supply is required for a crop

sown in an area of 4800 hectares, the duty of irrigation

water will be 4800/4 = 1200 hectares/cumec, i.e. a discharge

of 4 cumecs will be required throughout the base period.

Crop period : It is the time in days that a crop takes fromthe instant of its sowing to that of harvesting.

Base period : It refers to the whole period of cultivationfrom the time when irrigation water is first issued for

preparation of the ground for planting the crop, to its last

watering before harvesting.

Ways of Reckoning DUTY :

4 ways :

1. By the number of hectares that 1 cumec of water canirrigate during the base period.

2. By total depth of water.

3. By number of hectares that can be irrigated by a millioncubic metre of stored water.

4. By the number of hectare metres expended per hectareirrigated.

Factors Affecting DUTY :

1. Methods and system of irrigation.

2. Mode of applying water to the crops.

3. Method of cultivation.

4. Time and frequency of tilling.

5. Type of the crop.

6. Base period of the crop.

7. Climatic conditions of the area.

8. Quality of water.

9. Method of assessment of irrigation water.

10. Canal conditions.

11. Characteristics of soil and sub-soil of the canal.

12. Characteristics of irrigation fields.

Methods of Improving DUTY :

1) Suitable method of applying water to the crop should be used.

2) The land should be properly ploughed and leveled before sowing the crop.It should be given good tilth.

3) The alignment of canal either in sandy soil or in fissured rock should beavoided.

4) The idle length of canal should be reduced.

5) The rotation of crop must be practiced.

6) Volumetric method of assessment should be used .

7) The source of supply should be such that it gives good quality of water.

8. The land should be cultivated frequently, since frequent cultivation

reduces loss of moisture specially when the ground water is within

capillary reach of the ground surface.

9. The canals should be lined. This reduces seepage and percolation losses.

Also, water can be conveyed quickly, thus reducing , thus reducing

evaporation losses.

10. Parallel canals should be constructed. If there are two canals running

side by side, the F.S.L will be lowered, and the losses will be reduced.

11. The canal should be so aligned that the areas to be cultivated are

concentrated along it.

12. The farmers must be trained in the proper use of water, so that they

apply correct quantity of water at correct timing.

Variation of DUTY with the Place of its

Measurement :

The measurement of duty are taken at four point noted below :

i. At the head of main canal known as gross quantity.

ii. At the head of branch canal-known as lateral quantity

iii. At the outlet of canal-known as outlet factor.

iv. At the head of land to be irrigated known as net quantity.

DELTA :

Delta is the total depth of water required-by a crop during the entire period of crop in the field, and is denoted by a

symbol .

For Example, if a crop requires, about 11 waterings at an interval of 10 days and a water depth of 10 cm is applied

in every watering, then the delta for that crop will be 11 x

10 = 110cm = 1.1 metres.

Relation between Duty and Delta

Let, D = Duty in hectares/cumec.

= Total depth of water (in meters), and

B = Base period in days.

(a) If we take a field of area D hectares; water supplied to the

field corresponding to the water depth meters will be

= D hectare-metres = D l04 cubic metres ...(1)

= 8.64 B/D meters

(b) Again for the same field of D hectares, one cumec of

water is required to flow during the entire base

period. Hence, water supplied to this field

= 1 x (B x 24 x 60 x 60) m3 .(2)

Equating Eqtns. (1) and (2) we get,

High and low duty: Duty being referred to as being high or lowaccording to the number of hectares/cumec irrigated is large or small.

GROSS commanded area(G.C.A.): The gross command area lyingbetween drainage boundaries which can be commanded or irrigated bycanal system.

Culturable commanded area(C.C.A.):The area on which crops can begrown satisfactory is known as Culturable commanded area.

Thus;

G.C.A. = C.C.A + unculturable area.

The culturable commanded area can further divided into :

1. Culturable cultivated area: It is the area in which crop is grown atparticular time or crop season.

2. Culturable uncultivated area: It is that area in which crop is not sownin a particular season.

Intensity of Irrigation

It is defined as the % of C.C.A proposed to be irrigatedduring either a crop season or during a year.

For eg: If C.C.A of an irrigation field is 120 hectares, out ofwhich 90 ha of the land is cultivated during kharif season and 60 ha

of the land is cultivated during rabi season, the intensity of

irrigation during kharif season will be = (90/120)x 100 = 75% and

the intensity of irrigation during rabi season will be = (60/120)x100

= 50%.

However, yearly intensity of irrigation will be equal to

75 + 50 = 125%. (yearly intensity of irrigation can be more than

100%)

Some Definitions :

1) kor period and kor depth: During the subsequent watering thequantity of water needed by crops gradually decreases and is least

when crop gains maturity. The first watering is known as kor

watering ,and the depth applied is known a kor depth. The portion of

the base period in which kor watering is needed is known as kor

period.

2) Outlet factor : It is defined as the duty at the outlet.

3) Cumec day : The quantity of water flowing for one day at the rateof 1 cumec is known as a cumec day. It is equal to 8.64 hactares-

metres.

4) Time factor: The time factor of a canal is ratio of the numberof days the canal has actually run to the number of days of

irrigation period.

5) Capacity factor: This is the ratio of the mean supply(discharge) to the full supply of canal.

6) Nominal duty: Nominal duty is the ratio of the area of whichthe permit has been granted for the period divided by the mean

supply for the base period.

7) Root zone depth : Root zone depth is the maximum depth ofsoil strata in which the crop spreads its root system and derives

water from the soil.

8) Paleo : It is the first watering before sowing the crop. Thisenhances moisture to the unsaturated zone and is required for the

initial growth of the crop.

9) Full supply coefficient : It is defined as the area estimated to beirrigated during the base period divided by the design full supply

discharge of the channel at its head during maximum demand. Also

known as duty on capacity.

10) Open discharge : It is the ratio of the number of cumec-days tothe number of days the canal has actually been used for irrigation.

Consumptive Use of Water

(Evapotranspiration) :

It is the depth of water consumed by evaporation and transpirationduring crop growth, including water consumed by accompanyingweed growth.

Consumptive use of water for a crop is the water required for itsmetabolism.

The value of consumptive use is different for different crops.

Even for same crop its value may be changed with place and itsstages.

Its value changes throughout the day, month, year.

Potential Evapotranspiration (PET) and Actual

Evapotranspiration (AET)

Potential Evapotranspiration(PET)- If sufficient moisture isalways available to completely meet the needs of the plants, the

resulting evapotranspiration is called potential evapo-transpiration

Actual evapotranspiration (AET)- The real evapotranspirationoccurring in a specific situation is called actual evapo-

transpiration

At the moisture content in the soil corresponding to field capacity(Fc), the water supply to the plant is adequate and hence AET will

be equal to PET, or in other words, the ratio AET/PET will be

equal to 1.

With the reduction in the available moisture in the soil, the ratioAET/PET decreases and finally AET will be zero at wilting point.

For the same AET/PET ratio, sandy soil has more availablemoisture than clayey soil.

AET/PET will be less for sandy soil than for clayey soil.

Factor Affecting the Consumptive Use :

1. Evaporation.

2. Mean monthly temperature.

3. Growing season of crop and cropping pattern.

4. Monthly precipitation.

5. Irrigation depth.

6. Wind velocity.

7. Soil and topography.

8. Irrigation practices.

9. Stage of growth.

10. Intensity of sunlight.

11. Amount of foliage.

12. Depth of water applied in one watering.

Measurement Methods for Consumptive Use :

Direct measurement

Soil moisture studies

Lysimeter method

Experimental plot method

Integration method

Inflow and outflow studies

Empirical method

Blaney- criddle method

Hargreaves pan evaporation

method

Penman method

Thornthwaite method

Lowry Johnson method

DIRECT MEASUREMENT OF CONSUMPTIVE USE

1. Tank and Lysimeter Method

Tanks are containers set flush with the ground level having an area of10 sq. m and 3 m deep.

The tank is filled with soil of the field and crop is grown in it.Consumptive use is determined by measuring the quantity of water

required to maintain constant moisture conditions within the tank for

satisfactory proper growth of the crop.

In Lysimeter, bottom is pervious and draining water collected in a pan.

2. Field Experimental Plots

In this method, irrigation water is applied to the selected fieldexperimental plots in such a way that there is neither runoff nor deep

percolation.

Yield obtained from different fields are plotted against the total waterused, and, as basis for arriving at the consumptive use, those yields

are selected which appear to be most profitable.

It is seen from observations that for every type of crop, the yieldincreases rapidly with an increase of water used to a certain point,

and then decreases with further increase in water.

3. Soil Moisture Studies

This method is specially suited to those areas where soil is fairlyUniform and ground water is deep enough so that it does not affect

the fluctuations in soil moisture within the root zone of the soil.

Soil moisture measurements are done before and after each irrigation.The quantity of water extracted per day from soil is computed for

each period. A curve is drawn by plotting the rate of use against time

arid from this curve, seasonal use can be determined.

4. Integration Method

In this method, it is necessary to know the division of total area underirrigation crops, natural vegetation, water surface area & bare land area.The integration method is summation of the products of

(i) Unit consumptive use for each crop times its area

(ii) Unit consumptive use of native vegetation times its area

(iii) Water surface evaporation times the water surface are

(iv) Evaporation from bare land times its area

5. InfIow-outflow Studies for Large Areas

In this method annual consumptive use is found for large areas. If U is thevalley consumptive use, its value is given by-

U = Valley consumptive use (in hectare-metre) ; R= yearly outflow

I = Total inflow during 12-months year

P = Yearly precipitation on valley floor

Gs= Ground storage at the beginnjng of the year

Ge = Ground storage at the end of the year

Empirical methods

Where, = monthly consumptive use in cm.

= monthly crop coefficient to be determined from

experimental data.

= monthly consumptive use factor given by

= mean monthly temperature in

= monthly percentage of hours of bright sunshine in the

year.

Total consumptive use or seasonal consumptive use is given by :

1. Blaney-Criddle Method

However, if the crop coefficient (or crop factor) also varies frommonth to month, the total consumptive use or seasonal consumptive

use is given by-

2. Penman Method :

= Evapotranspiration, mm/day

= psychromatic constant = 0.49 mm Hg/ c

= Slope of the curve

= Drying power of air which includes wind velocity and saturation deficit

= Daily net radiation in mm

Penman developed a theoretical formula based on principles of both

energy budget and mass-transfer approaches to compute potential

evapo-transpiration in the following form-

3. Hargreaves Class A Pan Evaporation Method :

This method is very much used in India, According to this method,the consumptive use (Cu) or Evapo-transpiration (Et) is given by

= Consumptive use coefficient

= Class A pan evaporation

The value of K depends upon

(i ) Type of crop

(ii) Place or location of irrigation field

(iii)Stage of the growth of the crop or % of crop growing season

Irrigation Efficiencies :

Irrigation efficiency

Water application efficiency

Water conveyance efficiency

Water use efficiency

Water storage efficiency

Water distribution efficiency

Water Application Efficiency :

Application efficiency relates to the actual storage of

water in the root zone to meet the crop water needs in

relation to the water applied to the field.

Where,

= Water application efficiency.

= Water stored in the root zone during irrigation.

= Water delivered to the farm.

Water Conveyance Efficiency :

Where,

= Water conveyance efficiency.

= Water delivered to the farm.

= Water supplied from the river or reservoir.

Water Use Efficiency :

Where,

= Water use efficiency.

= Water used beneficially or consumptively.

= Water delivered.

Water Storage Efficiency :

Where,

= Water storage efficiency.

= Water stored in the root zone.

= Water needed in the root zone.

= (Field capacity Available moisture)

Water Distribution Efficiency :

Where,

= Water distribution efficiency.

= avg. numerical deviation in depth of water stored

avg. depth stored during irrigation.

= avg. depth of water stored during irrigation.

Consumptive Use Efficiency :

Where,

= Normal consumptive use of water.

= Net amount of water depleted from root zone of soil.

Determination of Irrigation Requirements of Crops :

1) Effective rainfall (Re) : It is that part of the precipitation fallingduring the growing period of a crop that is available to meet theevapo-transpiration needs of the crop.

2) Consumptive irrigation requirement (CIR) : It is defined as theamount of irrigation water that is required to meet the evapo-transpiration needs of the crop during its full growth.

CIR = Cu Re ; Cu is the consumptive use of water.

3) Net irrigation requirement (NIR) : It is defined as the amountof irrigation water required at the plot to meet the evapo-transpiration needs of water as well as other needs such asleaching.

NIR = Cu Re + water lost in deep percolation for the purposeof leaching.

4) Field irrigation requirement (FIR) : It is the amount of water

required to meet net irrigation requirements plus the water lost

in percolation in the field water courses, field channels and in

field applications of water.

If is water application efficiency, we have..

5) Gross irrigation requirement (GIR) : It is the sum of water

required to satisfy the field irrigation requirement and the water

lost as conveyance losses in distributaries unto the field.

if is the water conveyance efficiency, we have..

Soil Fertility :

A soil is fertile when it contains :

1. Ample supplies of organic materials.

2. The source of nitrogen.

3. Sufficient soluble compounds of the mineral elements needed

for the growth of food plants.

Maintenance of soil fertility

1. By use of proper cultivation methods.

2. By spreading all farmyard manure.

3. Planting of different crops in rotation on different areas.

4. Application of carefully selected commercial fertilizers.

5. Ploughing under or disking-in of crop, plants etc.

6. Stubble mulch farming.

7. Suitable procedures for reducing erosions may improve soil fertility.

8. Irrigation with silty water.

9. Soils of acidic nature may show improvement with the application of calcium oxide to the extent of 1000kg per hectare.

Crop rotation : It implies that nature of the crop sown in aparticular field is changed year after year.

Necessity for rotation : The necessity for rotation arises fromthe fact that soil gradually losses its fertility if the same crop is

sown every year and the field has to be allowed to lie fallow in

order to regain its fertility.

Crop diseases and insect pests harmful for the crops can be reduced

using crop rotation technique.

Assessment of Irrigation Water :

The water which has been supplied for irrigation to the farmers isat the government expenses. Some nominal charges must be levied

on the farmers for using this water. The fixation of such charges is

known as assessment of irrigation water.

The charges must be levied on the farmers for following reasons :

1. To recover the cost of construction of the project.

2. To recover the maintenance cost of various works and staff.

3. To collect some revenue for the nation.

4. To check the cultivators against uneconomical and careless use of

water

Methods of Assessment :

5 Methods :

1. Assessment on area basis or crop rate basis: In this system, areasowing crops is recorded by a patrol both at the time of sowing

and maturity.

2. Volumetric assessment: This method involves levying charges onactual volume of water supplied. It is an ideal system for which an

irrigator has an incentive for economic use of water.

3. Assessment on seasonal basis: In this method, the rate of

assessment is based on the type of crop grown in a particular

tract during certain crop season.

4. Composite rate basis: It is a combination of both water

charges and land revenue.

5. Permanent assessment: It is carried out on a wara bandi

system fixed by the Divisional Canal Officer. Under this

system each shareholder is given his turn in hours according

to the area, out of seven days in a week.

Thank You !!