Use of Ground Water in Canal Command Area

Abstract

Depending upon the purpose, a number of ground water use patterns are possible in the area served by a canal network. The concept and positive and negative factors involved in the use of ground water in canal areas are explained. The scope of ground water use in canal commands includes natural and artificial recharge (monsoon canals), use of shallow or deep tube wells by farmers and by public agency for supplementary irrigation during periods of low canal supplies or canal closures, and managing water supply quality. Augmentation tubewells along the Western Yamuna Canal (Haryana) are an excellent example of planned conjunctive use. A detailed discussion is made of the four possible alternatives for operating ground water facilities, depending upon field conditions. Guidelines for minimum and maximum limits on groundwater extraction, total groundwater extraction, and the quantum of groundwater use for irrigation are discussed. There are certain issues that need to be resolved for efficient operation of ground water facilities. These relate to (i) water prices from canal and tube well sources; (ii) formation of water users association for equitable distribution of canal water and ground water; (iii) control over the development and use of groundwater through private tube-wells; (iv) coordination at field level among activities of various government agencies; and (v) conflict interfaces. A case study on ground water recharge and its withdrawal in Khairana tank irrigation project is disused. The study explains (i) ground water recharge, (ii) canal water budget, (iii) design of wells, and (iv) design of pumping facility.

Appendices

Appendix: Case Study of Khairana Tank Irrigation Project

12.1.1 General

Conjunctive use of ground water in canal commands implies coordinated and harmonious use of surface water and ground water for meeting the water requirements in time and space. Its scope includes (i) recharge of ground water from natural surface water; (ii) artificial and induced recharge from surface water to ground water; (iii) use of shallow or deep wells in canal command areas for supplementary irrigation during periods of low canal supplies or canal closures. It can also take on the form of irrigating pockets exclusively with ground water in a canal command; (iv) use of augmentation tube wells discharging directly into the canal, thereby supplementing the canal supplies, and vertical drainage to lower the ground water level and thus control waterlogging.

Ground water is the main source of water supply for agriculture and drinking purposes in rural areas of India. With the increase in population and the need for more water for irrigation, water demand is on a constantly increasing trend. Several of the existing canal irrigation systems suffer either from inadequate supplies or waterlogging due to excessive irrigation. In fact, even within a command area, there are pockets of water-logged areas and pockets of water deficit areas. Over the years of a continuous canal operation, the water table keeps on rising in the command area, and therefore it becomes necessary to pump put the water.

Chaube (2006) carried out a study on the evaluation of four tank irrigation projects in Sagar District of Madhya Pradesh, India. Subsequently, using the data of this report and other documents, Nissanka (2007) carried out a study on the use of ground water in canal command of Khairana tank irrigation project in Sagar district of Madhya Pradesh state of India. The study covers (i) groundwater recharge in the canal command, (ii) canal water budget in the command area, (iii) design of shallow and deep wells, and (iv) pumping facility for ground water wells. The discussion in what follows is based on these studies.

12.1.2 Ground Water Related Characteristics of Khairana

The characteristics relevant to ground water study in the command area of the four projects (geology, geomorphology, soil type, suitability for artificial recharge etc.) are shown in Table 12.2. The command area of the Khairana project is in Deccan Trap. The characteristic geomorphology is Deccan Plateau and denudational hills.

Table 12.2 Ground water related characteristics of Khairana

12.1.3 Ground Water Recharge

Available ground water data for observation wells in the command area of the tank irrigation project and in the vicinity has been collected from WRD. These data have been analysed to study the impact of tank projects on ground water recharge, as discussed below.

The ground water data of four observation wells in the vicinity of Khairana project command for six years was analyzed. Canal irrigation in the command area is causing a rise in the water table. The average groundwater level in the area has increased by 3.07 m, 1.21 m, and 0.79 m during pre-monsoon (May), post-monsoon (November), and Rabi season (January), respectively, after the project came into existence (Table 12.3). The average ground water fluctuation between pre- and post-monsoon periods is decreased by 1.86 m and pre-monsoon to Rabi season is decreased by 2.7 m.

Table 12.3 Groundwater data for Khairana project command

The underground aquifers are supplemented by sources other than rainfall, such as seepage from canals and field canals, ponds, tanks, influent drainage from rivers, deep percolation from irrigated fields etc. In most canal irrigated areas, a substantial component of the water applied to fields percolates below the root zone and contributes to the groundwater potential. A comprehensive and complete assessment of groundwater recharge from canal seepage is possible only through the compilation and analysis of reliable data from systematic scientific studies. Based on annual average rainfall, lengths, and wetted perimeter irrigation canals, area of water bodies, and application efficiency of the irrigation water, the total possible annul recharge in command of Khairana is estimated, as shown in Table 12.4.

Table 12.4 Total annual recharge calculation—Khariana project

As per the preliminary survey conducted by the National Institute of Hydrology, the water table available at a depth of 7–10 m is suitable for shallow tube wells or dug wells.

12.1.4 Estimation of Canal Seepage and Canal Water Budget

Various methods are currently available for the estimation of canal seepage. Estimating canal seepage from lined and unlined canals provides a key input to the economic analysis of canal lining.

Direct Determination of Canal Seepage

Inflow–Outflow Method: The actual inflow entering into one end of the selected reach of the canal and outflow going out of the other end of the reach is measured with the help of existing weir or flumes or by area velocity method with the help of current meter. The difference between inflow and outflow is the seepage. The limitation is that the number of measurements is to be taken to find the average value, and the error could be ±10%.

Ponding Method: It is a more accurate and popular method and is generally used. In this method, a reach of the canal is isolated by making suitable water-tight barriers at both ends. Water is filled in the reach to form a pond. The fall in water level is noted at regular intervals or lost water is replaced to maintain a constant level. It is continued till a steady state is reached. It is corrected for evaporation and precipitation, if any. Thus, the rate of seepage per unit wetted area is evaluated.

Its limitations are.

• 1. Canal operation has to be discontinued for the experiment.

• 2. Deposition of sediment and growth of algae and fungi during the experiment period reduce the seepage rate.

• 3. Changes in the groundwater table due to the stoppage of the canal for the experiment will change the seepage rate.

Empirical Methods

These are only approximate relations and give only a rough estimate. The number of such relations is available, but only the method used in Maharashtra is discussed.

Studies on the main canals in Maharashtra have given the following results. Considering the similarities in geography and other factors, this method is used to calculate seepage loss in irrigation canals in the study area.

Seepage loss in the unlined canal is 8 cfs/Msft of the wetted canal perimeter.

Seepage loss in the lined canal is 2 cfs/Msft of the wetted canal perimeter.

Canal Water Budget for Khairana Project

The canal water budget for the Khairana project is estimated as shown in Table 12.5.

Table 12.5 Canal water budget in Khairana project

Computations are explained below

Line 02—Water losses due to evaporation and percolation from the water body

20% of line 01.

Line 04—20% of line 3 for unlined canals and 15% for lined canal

Line 05—Seepage Losses

Losses (Mm³) − Flow loss rate (ft³/s) (days operation) (seconds/day)*10⁻⁶

Loss rate

Unlined Canal—8 Cfs/Msf

Lined Canal—2 Cfs/Msf

Unlined wetted perimeter—6482 m²

Lined wetted perimeter—5499 m²

Number of days canal operation in Rabi season = 100 days

Seepage loss from the unlined canal

 = 8 × 6482 × 100 × 24 × 60 × 60 × 10⁻¹²/3.28

 = 0.137 Mm³

Seepage losses from the lined canal

 = 2 × 5499 × 100 × 24 × 60 × 60 × 10⁻¹²/3.28

 = 0.029 Mm³

Line 07—Water course losses

10% of line 06.

Line 09—Application Losses

20% of line 08.

Line 10—Available for Crop

Line8–line9.

Line 11—Overall efficiency

Line 10/Line 3 × 100.

Line 12—Existing canal irrigation cropping intensity 54% (Table 4.1).

Irrigation cropping intensity after concrete lining

54/49.3*59.4 = 65.06%.

Water Withdrawal Using Shallow Wells

12.2.1 Calculation of Head of Pumping

• 1. Static Head = Depth of water table average 9.0 m.

• 2. Delivery Head = 1.25 m.

• 3. Drawdown calculation from the formula

  $$ Q_{p} = \frac{2\pi TS}{{2.3\log \left( { \frac{{R_{e} }}{{R_{w} }} } \right)}} $$

where Q_p = the discharge of pumping in m³/sec;

T = the coefficient of transmissivity in m²/s = 0.0069 m²/s;

S = the drawdown in well in m;

R_e = the radius of the depression cone, taken 150 m; and

R_w = the radius of pumping well = taken 3 m.

$$ S = \frac{{2.3*Q_{p} *\log \left( { \frac{{R_{e} }}{{R_{w} }} } \right)}}{2\pi *T} $$

Taking Q = 15 lits/s (small farmer) = 0.015 m³/s

$$ \begin{aligned} S & = \frac{{2.3*0.015*\log \left( \frac{150}{3} \right)}}{2*3.14*0.0069} \\ & = { 1}.{35}\;{\text{m}} \\ \end{aligned} $$

• 4. Velocity head: limiting the velocity at the delivery side to 2.0 m/s

  $$ \begin{aligned} & = \frac{{v^{2} }}{2g} \\ & = { 2}^{{2}} /{2 } \times { 9}.{81} \\ & = \, 0.{2}0{4}\;{\text{m}} \\ \end{aligned} $$

• 5. Friction head:

  $$ {{Head}}\,{{ loss}}\,{{ due}}\,{{ to}} \,{{friction}}\,{{ in}}\, {{the}} \,{{pipe}} = \frac{{4flv^{2} }}{2gd} $$

where l = total length of pipeline in meter;

V = the velocity of flow in the pipe in m/s, taken as 2 m/s;

D = the diameter of the pipe line in meter, taken as 0.125 m; and

F = the coefficient of friction, generally assumed as 0.006.

$$ h_{f} = \frac{{4*0.006*11.6*2^{2} }}{2*9.81*0.125} $$

h_f = 0.45 m

L losses at entry and bends taken as 25% of friction losses in the pipe line h_b = 0.11 m

$$ \begin{aligned} \therefore {{Total head of lifting}} & = { 9}.0 \, + { 1}.{25 } + { 1}.{35 } + \, 0.{2}0{4 } + \, 0.{45 } + \, 0.{11 }\,{\text{m}} \\ & = { 12}.{364 }\,{\text{m}}\,\,{\text{ Say}}\,{ 12}.{4}0\,{\text{m}} \\ \end{aligned} $$

12.2.2 Calculation of Pumping Unit

$$ {{Horse}}\,{{ power}}\,{{ of}}\,{{ a}}\,{{ motor}} = \frac{W*Q*H}{{75*\eta }} $$

where

W = the unit weight of water in kg/m³;

η = the efficiency of the set, which is generally taken as 60%;

Q = the discharge to be delivered in cumec; and

H = the total head in meters against which the motor has to operate.

$$ HP = \frac{1000*0.015*12.4}{{75*0.60}} $$

Considering an extra cover of 20% for the seasonal variation of load on motor

${{HP of motor }} = { 4}.{13 } \times { 1}.{2 } = { 4}.{956} = {{ Say 5 HP}}$.

12.2.3 Calculation of Number of Shallow Wells Required

Assuming 1000 hours working in a year,

Annual yield per well in a year = 0.015 × 60 × 60 × 1000/1000,000 Mcm = 0.054 Mcm

Current water duty at farm outlet level = 0.0043 Mcm/ha

Area in ha proposed to irrigate under GW = 76 ha

Groundwater requirement = 0.33 Mcm

Number of wells required = 6.11

(with extra a well to facilitate sharing excess with neighboring farmers) = Say 8 Nos.

12.2.4 Water Withdrawal Using Tubewells

Tube well supplies differ from canal supplies in several aspects. Tube wells usually provide a steady water supply for irrigation. It is easy to provide irrigation at optimum times with reference to the stage of growth of crops, thus maximizing production. Canal supplies fluctuation, and canals often remain closed for long periods. In the case of canals, the annual working expenses remain the same in spite of the variations in the volume of water supplied. On the other hand, in tube wells, the cost of power consumed in pumping and, to some extent, the maintenance cost is related to the volume of water pumped. In tube wells, it is also possible to conveniently measure the discharge rate with a simple V- notch and relate the volumetric discharge with the power consumed. This facility and the high cost of tube wells and pumps make it desirable that the tube well water is charged based on water supplied to individual farmers.

12.2.5 Calculation of Pumping Rate

Present water supply factor = 75.33%

Proposed water supply factor with conjunctive use = 100%

CCA = 308 ha.

Irrigation duty at farm out let = 0.43 m.

Extra quantity of water required = 0.2467 × 308 ×  0.43 × 10⁴/10⁶ = 0.3267 Mm³

Conveyance losses (20%) = 0.0653 Mm³

Total pumping quantity = 0.3920 Mm³

Assuming Number of pumping hours as 1000 h.

Required pumping rate = 0.3920 × 10⁶/1000 × 60 × 60  = 0.1089 Cumec.

12.2.6 Well Design

Coarse sand strata (assumed) = 40–70 m.

Thickness of confined aquifer = 70–40 m = 30 m.

Discharge required = 6534 Lit/min.

• i. Casing and well screen diameter

Casing diameter = 45 cm (Table 14.1 Varshney-1997).

Optimum diameter of well screen = 30 cm (Fig. 14.12 Varshney-1997).

• ii. Length of strainer and slot size

  • 70–80% of aquifer depth may be screened for confined well

  • Assume 75% length of screen = 30 × 75/100 = 22.5 m

  • Slot size = 2.0 mm.

• iii. Discharge of well

The maximum depression head permitted is between 9 and 40 m

$$ q = \frac{{2\pi kb\left( {H - h_{w} } \right)}}{{2.3{\text{log}}\left( \frac{R}{rw} \right)}} $$

where K = 0.09 cm/s = 9 × 10^–4 m/s

b = 22.5 m.

H − h_w = 31 m.

R = 400 m (assumed).

R_w = 0.15 m.

Q = 2 × π × 9 × 10^–4 × 22.5 × 31/(2.3 × log₁₀ (400/0.15)) = 0.5005 cumec  = 30,003 Lit/min.

The well is capable of discharging much higher discharge than required.

• iv. Screen entrance velocity

Assume 20% of slot area, the screen entrance velocity when discharging 0.11 cumec is given by

π × 30 × 20/100 × 22.5 × 100 × V = 110 × 1000

V = 2.59 m/s.

Since screen entrance velocity is within the admissible limit (i.e. <3 m/s), the assembly is O.K.

12.2.6.1 H.P. of Motor

$$ {{Horse}}\,{{ power}}\,{{ of}}\,{{ a}}\,{{ motor}}\,{{ is}}\,{{ given}}\,{{ by}} = H.P. = \frac{W*Q*H}{{75*\eta }} $$

Velocity through casing pipe = 0.11 × 4/(π  ×  0.30²) = 1.56 m/s.

Velocity head = 1.56²/(2 × 9.81) = 0.12 m

$$ {{Loss\; of \;head \;due \;to \;friction \;in \;pipe}} = \frac{{4flv^{2} }}{2gd} $$

where f = the coefficient of friction assumed as 0.006

l = the length of pipe including horizontal length = 75 m.

d = the diameter of pipe in m = 0.30 m.

h_f = 4 × 0.006 × 75 × 1.56²/(2 × 9.81 × 0.3) = 0.74 m.

Assuming entry losses in the strainer and bend as 25% of friction loss = 0.19 m.

Total head loss = 9 + 31 + 012 + 0.74 + 0.19 = 41.0 m.

H.P. required = 1000 × 0.11 × 41/(75 × 0.7) = 85.9 Say 90 Hp.

12.2.6.2 Financial Performance

Results of the financial performance pertaining to possible future investment and their implications are discussed as follows.

The financial performance of the Khairana project in connection with concrete lining and conjunctive use of surface and groundwater was also analyzed by Chaube (2000) as part of the sponsored research project. Results are given in the table below.

Source	PWC	PWB	NPV	B/C	IRR
Surface irrigation	124.66	79.65	−45.01	0.64	10.34
Concrete lining	19.28	15.981	3.299	0.83	12.18
Shallow well	35.735	44.078	8.36	1.23	19.05
Tube well	33.725	44.078	10.355	1.31	21.60
Combination of concrete lining and tube well	47.509	49.689	2.179	1.05	15.8

1. PWC present worth of cost; PWB present worth of benefit; NPV net present worth; BC benefit–cost ratio; IRR internal rate of return

Financial parameters, such as B/C ratio and IRR for concrete lining, at 15% discount rate are 0.83 and 12.18, respectively. Therefore, concrete lining in the entire canal length is infeasible. Limited concrete lining where seepage losses are high along with some management improvements such as rotational water issues can further improve financial parameters.

The conjunctive use of surface and ground water in shallow wells, Public Tube wells, and a combination of concrete lining and tube wells has become economically feasible. The B/C ratio and IRR at a discount rate 15% corresponding to the above three cases are 1.23, 1.31, 1.05, and 19.05%, 21.6%, 15.8%, respectively.

Inequity, unreliability, and untimeliness are the major issues in surface irrigation projects. The conjunctive use of surface water and groundwater can improve efficiencies in lower reaches where surface water is used to irrigate land close to the canal and groundwater to irrigate land which is further away.

The reduced uncertainty of poor or irregular supply from surface water allows farmers to risk investment in water-intensive and higher-value crops, HYV seeds, and associated inputs like fertilizer and pesticides.

Questions

• 1. Explain the following terms:

  Surface water—groundwater interaction, natural recharge, artificial recharge, water charge, augmentation tube well, and unplanned conjunctive use.

• 2. Explain various advantages of an irrigation project planned on the basis of conjunctive use of surface water and groundwater.

• 3. Explain alternative strategies of conjunctive use of surface water and groundwater.

• 4. Write a note on artificial recharge and its use for irrigation.

• 5. Explain why the charges for the supply of canal water and groundwater for irrigation are different?

• 6. Why the irrigation charges are different for different crops?

• 7. What is the basis for the rationalization of irrigation charges?

• 8. From your experience what could be the interface problems between (i) farmers and electricity departments; and (ii) farmers and canal irrigation department.

• 9. Identify various government agencies involved in the conjunctive use of surface water and groundwater.

• 10. Explain the role of water user association in conjunctive use management.

• 11. Explain the need for a comprehensive Groundwater Act.

• 12. Referring to appendix Sect. “Water Withdrawal Using Shallow Wells”.@@

  Calculate the total head of lifting and HP of the pump if static head = 8 m, delivery head = 1.4 m; other data being same.

  If working hours are 1100 in a year, how many shallow wells are required.

• 13. Referring to Appendix “Water Withdrawal Using Tubewells” calculate the required pumping rate if the water supply factor is 78% and the number of pumping hours in a year are 1100; other data are the same.