IJMTES | International Journal of Modern Trends in Engineering and Science ISSN: 2348-3121

RATING OF TUNGABHADRA LEFT BANK CANAL TUNGABHADRA , Dr S Sampath1, N.P. Khaparde2, B. Suresh Kumar3 1, 2, 3(Central Water and Power Research Station, , , India, [email protected]) ______

Abstract— The management of water resources depends, to a considerable degree, on the availability of hydrological and hydraulic data. The operation and maintenance of irrigation systems requires collecting regular data on water levels and discharges. The calibration of canal sections or structures provides information on canal discharges and hence supports the efficient day-to-day water management and regulation of irrigation systems. The Tungabhadra Dam is constructed across the , a tributary of the . The dam is near the town of in Karnataka. It is a multipurpose dam serving irrigation, electricity generation, flood control, etc. This is a joint project of Karnataka, and after its completion in 1953. The water level profiling was done by CWPRS at the CH 28 in mile 1 during August 2014, March 2015 and August 2015 using Acoustic Doppler Current Profiler (ADCP)[8] and Current Meter[1].The measurements were performed simultaneously with the two methods to present a comparison of discharge measurement made by current meter[14] which is the conventional method[2][3] and latest developed technique, ADCP[13]. Results show that the relative error is very small with the ADCP over the conventional method. Besides the total value of discharge, the ADCP method also offers detailed information about velocity distribution over the cross section.

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1. INTRODUCTION Tungabhadra dam Project (Figure 1) is an interstate, Multipurpose Project between the two states viz. Karnataka and Andhra Pradesh. The Project consists of a High level masonry dam constructed across Tungabhadra River near town in Districts of Karnataka State. The reservoir upstream of Tungabhadra dam has a storage capacity of about 120 TMC. The water from this reservoir is used for generating 126 MW of electricity and irrigating 3, 62,800 Ha of agricultural lands in Karnataka and Andhra Pradesh. Water from the dam is released in to the Left Bank Canal (LBC) and is utilized for power generation and irrigation in the Karnataka state. Three power houses are constructed on the LBC, one at the foot hill of the dam, and other two are at Shivapur and Sanapur. Tail water from the dam power house is carried to Shivapur and Sanapur reservoir through LBC. Tail water of Shivapur power house is released in to LBC. The length of LBC is about 225 km in Karnataka, Operation and maintenance of this canal is under control of Irrigation Department, Government of Karnataka. Estimation of canal discharge at the head at CH 28 in Mile 1, is therefore very Fig 1: Tungabhadra Project significant.

2. TUNGABHADRA LEFT BANK CANAL Tail water of dam power house and irrigation sluices release flow into Tungabhadra left bank canal. The canal is lined and is designed to project carry discharge of 116 m3/s (4100 ft3/s) at head. It has an irrigation potential of 2,43,900 hectares in Karnataka. The left bank canal traverses for a length of 225 km in Karnataka.

Fig 2: Location map of Tungabhadra Dam Left bank canal

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IJMTES | International Journal of Modern Trends in Engineering and Science ISSN: 2348-3121

A. Gauging site at ch. 28 in mile 1. A. Objective The canal in this section is lined and is designed for 116 Studies were conducted in Tungabhadra Left Bank Canal at m3/s (4100 cusec) at the head. A cross regulator is situated ch.28 in mile 1, for different gauge levels to find out on ch.28 in mile 1 which regulate the flow in the corresponding discharges and establish gauge discharge Tungabhadra left bank canal. Fig 2 show the location of map correlation for the above gauging site [15]. of Tungabhadra left bank canal. A permanent gauging site on the canal is located at ch.28 in mile 1. A cross section of the B. Methodology canal at the above site is given in Figure 3. A permanent foot bridge is constructed at one km downstream of the site The discharge in the canal was measured by ‘Area-Velocity’ at ch. 28, which facilitates depth and velocity measurements method as prescribed in BIS 1192: 1981 and ISO 748: 1997 across the width of the canal. A gauge well is constructed on using Current Meter & Echo Sounder [1]. The discharges in the right bank of the canal at the site. The view of the foot the canal were also measured and confirmed by Acoustic bridge of the canal is shown in Figure 4. Doppler Current Profile (ADCP) using River Surveyor instrument for better accuracy [13].

4. DISCHARGE MEASUREMENT USING AREA VELOCITY METHOD A. Gauge Observations For confirmation of stable flow condition at the gauging site, gauge observations were made at a regular interval from two to three hours prior to commencement of discharge measurements and also during the period of discharge measurements. It was observed that zero at the average bed level of the canal i.e. depth measurements and gauge readings were same. A gauge plate graduated in feet was mounted on the inside wall of the gauge well. Figure 5 depicts the view of the gauge well at Fig 3: Cross section of canal at ch. 28 in mile 1 site. The gauge data, as observed during these studies, is given in Table-1.

B. Depth measurements using Echo Sounder The canal section of base width 25.46 m (83.53 ft) at ch. 28, was divided into 7 equal segments to cover the flow having uniform depth. Two segments were marked on either sides for lower water level and four segments were marked for higher water level to cover the flow in the sloping bank canal portion. Depths were measured at the center of each of the vertical using Echo sounder, where sufficient depth was available. Sounding rod was used to measure the small depths in the end segments. Details of verticals are shown in Figure 6. Depths were measured at the start and end of the measurements and average value was taken as the depth for computation of area of the segment.

C. Velocity measurements using Current Meter Velocity measurements were subsequently taken at the Figure 4: Gauging site at km 2.842 verticals located at the center of each of segment. Velocities were measured at 0.2, 0.6 and 0.8 depth from the surface. 3. FIELD MEASUREMENTS Velocity measurements were carried out using self-recording The field studies were carried out at the canal site for propeller type current meter average velocity on each vertical gauge and corresponding discharge at the gauging site. The of a segment was worked out as: observations were confined to the discharge range as indicated below. Discharges from 72.62 m3/s (2564 ft3/s) to 124.37 m3/sec. (4392 ft3/s). During the field measurements, the discharge in the canal was gradually increased from lower to higher water depths. Discharges were computed using values of areas of the Different sets of observations were carried out for different segments and average velocity of the segment as per the mid- water levels in the canal [14]. section method given in IS 1192:1981

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IJMTES | International Journal of Modern Trends in Engineering and Science ISSN: 2348-3121

Fig 7: Discharge measurements using ADCP at ch 28 in mile 1 Figure 5: Gauge well on LBC at ch. 28 in mile 1 5. OPERATIONAL PRINCIPLES: Various observations were carried out for different gauge The ADCP measures velocity magnitude and direction using levels in canal ranging from 10.1 ft to 12.5 ft at the above the Doppler shift of acoustic energy reflected by material site in August 2014, March 2015 and August 2015. Details suspended in the water column. The ADCP transmits pairs of of these observations are given in Table 1. short acoustic pulses along a narrow beam from each of the four transducers. As the pulses travel through the water column, they strike suspended sediment and organic particles (referred to as “scatterers”) that reflect some of the acoustic energy back to the ADCP. The ADCP receives and records the reflected pulses. The reflected pulses are separated by time differences into successive, uniformly spaced volumes called “depth cells”. The frequency shift (known as the “Doppler effect”) and the time-lag change between successive reflected pulses are proportional to the velocity of the scatterers relative to the ADCP. The ADCP computes a velocity component along each beam; because the beams are positioned orthogonally to one another and at a known angle Fig 6: Depth / Velocity verticals across LBC at ch. 28 in mile 1 from the vertical (usually 20 or 30 degrees), trigonometric D. Computation of Discharge using Current Meter and Echo relations are used to compute three-dimensional water- Sounder velocity vectors for each depth cell. Thus, the ADCP The average of the three velocities observed on a vertical produces vertical velocity profiles composed of water speeds was taken as the mean velocity of flow through the segment. and directions at regularly spaced intervals. By knowing the width, depth and mean velocity of the flow, ADCP discharge measurements are made from moving the discharge passing through each segment was worked out boats; therefore, the boat velocities must be subtracted from using mid section method as explained in BIS 1192: 1981 the ADCP measured water velocities. ADCP’s can compute and ISO 748: 1997. Total discharge in the canal was then the boat speed and direction using “bottom tracking” (RD obtained by adding all the segment discharges. The discharge Instruments, 1989). The channel bottom is tracked by data, as observed on different days, is given in Table - 1. measuring the Doppler shift of acoustic pulses reflected from E. ACOUSTIC DOPPLER CURRENT PROFILER the bottom to measure boat speed; direction is determined The main external components of an ADCP are a transducer with the ADCP on-board compass. If the channel bottom is assembly and a pressure case. The transducer assembly stationary, this technique accurately measures the velocity consists of nine transducers that operate at a fixed, ultrasonic and direction of the boat. The bottom-track echoes also are frequency, typically Dual 4-beam 3.0 MHz/1.0 MHz, Janus used to estimate the depth of the river (Oberg, 1994). 25° Slant Angle, 0.5 MHz Vertical Beam Echo sounder. The ADCP discharge measurements are made by moving the pressure case is attached to the transducer assembly and ADCP across the channel while it collects vertical- velocity contains most of the instrument electronics. profile and channel-depth data. The ADCP transmits acoustic When an ADCP is deployed from a moving boat, it is pulses into the water column. The groups of pulses include connected by Bluetooth to a portable laptop. The computer is water-profiling pulses and bottom-tracking pulses. A group used to program the instrument, monitor its operation, and of pulses containing an operator- set number of water- collect and store the data. profiling pulses (or water pings) interspersed with an operator-set number of bottom- tracking pulses (or bottom pings) is an “ensemble”; a single ensemble may be compared to a single vertical from a conventional discharge measurement (Oberg, 1994). A single crossing of the stream

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IJMTES | International Journal of Modern Trends in Engineering and Science ISSN: 2348-3121 from one side to the other is referred to as a “transect.” Each the same is plotted in Figure 9. This plot indicates that transect normally contains many ensembles. When depth and relationship between gauge and data is non-linear. A water velocities are known for each ensemble, an ADCP can statistical analysis of this data using method of least square, compute the discharge for each ensemble. The discharge revealed following relationship between depth of flow and from all transect ensembles are summed, yielding a discharge. computation of river discharge for the entire transect. ADCP Q=7.483 G2.524 Where Q = Discharge in ft3/sec and operational parameters (such as depth-cell length, number of G=Gauge / Flow depth in feet. water and bottom pings per ensemble, and time between The above relationship has a correlation coefficient (R2) = pings) are set by the instrument user. The settings for these 0.9969. It would be seen that the correlation coefficient is parameters are governed by canal/river conditions (such as very high and the standard error (0.0031) is well within the depth and water speed) and also by the frequency and reasonable limit i.e., 5%. The results of the statistical physical configuration of the ADCP unit (RD Instruments, analysis thus indicate that the quality of field data is very 1989). accurate and the error in estimation of discharge will, F. Measurement Procedure using ADCP therefore, be very small. A rating curve and a chart, prepared The Hydro boat carrying the ADCP is traversed from one on the basis of above relationship, are given in Figure – 9 end to the other end of the canal across the section. The and Table – 2 respectively. It may, however, be mentioned measurement of discharge using the river surveyor system that the above rating curve and chart should be used within comprises of three components viz., Start Edge, Transect and the observed range of data. Any extrapolation of the rating End Edge. ADCP calculates the total discharge by summing curve / chart may likely to cause additional error. It is also the Start Edge, Top Estimate, Measured Area, Bottom mentioned that the rating curve / chart is valid as long as the Estimate and End Edge. Only the Measured Area is site conditions under which the field measurements were calculated by ADCP and all other areas are calculated by a carried out are not changed i.e., no silting or no scouring of technique known as Velocity Profile canal bed canal lining not disturbed or removed no weed growth in the canal, the downstream cross regulator gates kept fully opened and location of gauge well and zero of the gauge not changed. TABLE – 1: GAUGE DISCHARGE DATA OF TUNGABHADRA LEFT BANK CANAL AT CH 28 IN MILE 1

S Discharge Time of Gauge . measured by Date Gauging in Hrs. reading N ADCP in Feet o From To ft3/s m3/s 1 03.08.2014 11.30 12.50 10.01 2564 72.62 2 03.08.2014 14.45 15.40 10.4 2761 78.18 3 04.08.2014 16.30 17.15 11.0 3181 90.07 4 04.08.2014 18.00 19.00 11.1 3254 92.15 5 17.03.2015 09.45 10.30 12.0 3962 112.20 6 17.03.2015 11.30 12.10 12.2 4131 116.98

7 06.08.2015 13.40 14.20 12.3 4217 119.41 Fig 8: Pixel data collection across the canal using ADCP 8 07.08.2015 15.00 16.00 12.5 4392 124.37 Extrapolation using power law velocity profile, which is inbuilt in the software. At least four cycles of measurements are taken by ADCP for each gauge observation and the average of four measurements are computed during data processing. Likewise for different gauges the procedure is repeated and the observations are tabulated, the measurement observation using ADCP at the gauging site is shown in Figure 7. An insight of the pixel data across the canal is shown in Figure 8.

6. ANALYSIS OF FIELD DATA The technical features/specifications as described above clearly show that accuracy of ADCP is higher than the current meter used for measurements in the canal. Hence, data collected by the ADCP and Current Meter is compared and better results are incorporated in Table 1. Fig 9: Gauge-discharge curve of Tungabhadra LBC at ch. 28 in mile 1

The gauge and discharge data as observed on Tungabhadra Left Bank Canal at ch 28 in mile 1 is given in Table – 1 and

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IJMTES | International Journal of Modern Trends in Engineering and Science ISSN: 2348-3121

TABLE – 2: RATING CHART OF TUNGABHADRA ii)Rating curve and rating chart based on above statistical LEFT BANK CANAL AT CH 28 IN MILE 1 relationship are given in Figure 9 and Table 2 respectively.

REFERENCES Gauge(G) Discharge(Q) in 3 Discharge (Q) in m /s in ft ft3/s 10.1 2564 72.62 [1] BIS 1192: 1981, “Velocity area methods for measurement of flow in open channels”. 10.2 2629 74.44 [2] Herschy RW (1985), “Stream flow measurement”, Elsevier Applied Science Publishers 10.3 2694 76.30 [3] ISO 748: 1997, ”Measurement of liquid flow in open channels – Velocity are methods” 10.4 2761 78.18 [4] Chen YC, Chiu CL (2002) “An efficient method of discharge measurement in tidal streams”. J Hydrol 265(1– 4):212–224 10.5 2829 80.09 [5] Chiu CL, Chen YC (2003) “An efficient method of discharge estimation based on probability concept”. J Hydraul Res 41(6):589– 10.6 2897 82.03 596 10.7 2966 84.00 [6] Lemon, D. D., D. Billenness and J. Lampa, 2002. “Recent advances in estimating uncertainties in discharge measurements with the 10.8 3037 86.00 ASFM”. Proc. Hydro 2002, Kiris, Turkey. [7] Maidment, D.R., 1992. “Handbook of Hydrology”, McGraw-Hill, 10.9 3108 88.02 New York. [8] Nihei, Y., Irokawa, Y., Ide, K., and Takamura, T. (2008) “Study on 11.0 3181 90.07 River-Discharge Measurements using Accoustic Doppler Current Profilers”, Journal of Hydraulic, Coastal and Environmental 11.1 3254 92.15 Engineering, vol.64, No.2, pp.99-114. [9] Oberg, K.A., and Schmidt, A.R., 1994, “Measurements of leakage 11.2 3329 94.26 from Lake Michigan through three control structures near Chicago, 11.3 3404 96.40 Illinois”, April–October 1993: U.S. Geological Survey Water- Resources Investigations Report 94-4112, 48 p. 11.4 3481 98.57 [10] Operational Hydrology Report No. 13; WMO - No. 519, World Meteorological rganization,Geneva. 11.5 3559 100.77 [11] Rantz, S. E., “Measurement and computation of streamflow”, Volume 1, Measurement of stage and discharge, 11.6 3637 102.99 [12] Sauer, V. B. and R. W. Meyer, “Determination of error individual discharge measurements”, U.S. Geol. Survey. 11.7 3717 105.25 [13] Teledyne RD Instruments (2006) “Acoustic Doppler Current Profiler Principles of Operation a Practical Primer”. 11.8 3798 107.54 [14] WMO 1980 Manual on Stream Gauging. Vol I, Fieldwork. Vol II, 11.9 3879 109.85 Computation of Discharge. [15] Technical Report No 5348, January 2016, CWPRS, Pune 12.0 3962 112.20

12.1 4046 114.57

12.2 4131 116.98

12.3 4217 119.41

12.4 4304 121.88

12.5 4392 124.37

7. RECOMMENDATIONS Based on the field studies for rating of Tungabhadra Left Bank canal at ch 28 in mile 1. carried out by CWPRS, Pune following recommendations are made: i) The gauge and discharge data is given in Table 2 and plot of gauge vs. discharge is given in Figure 9. A statistical analysis of the above field data revealed following relationship between gauge and discharge of the best fit curve.

Q = 7.483 G 2.524

Where Q = Discharge in ft3/s and

G = Gauge / depth in feet.

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