The Irrigation Wing (IW) of the Board is in-charge of maintenance of right half of the main dam, whole of the reservoir, Right Bank HLC and Right Bank LLC up to Board’s limit. The Low Level Canal also includes Power Canal and certain common distributories. The total areas localised for irrigation under the project both on right bank and left bank including areas in Karnataka and Andhra Pradesh is 4.899 lakh ha (12.1 lakh acres)(as per project record) excluding the schemes benefited with the assistance of water from Tungabhadra reservoir. The irrigation benefits under each canal/system of the project are given at Annex 2.6
Irrigation Wing is headed by a Chief Engineer,(part-time) who belongs to Irrigation Department of Government of Karnataka Chief Engineer, Irrigation Central Zone (ICZ), stationed at Munirabad is normally deputed by Government of Karnataka to act as Chief Engineer of the Board in addition to his normal duties in ICZ. There is one post of Superintending Engineer, which is filled up by an Officer from I & CAD Department of Andhra Pradesh. There are two Divisions – one at Tungabhadra Dam is filled by an officer from Karnataka and the other at Bellary is headed by officer from Andhra Pradesh. All the other officers and staff are drawn from the Irrigation Departments of Government of Andhra Pradesh and Government of Karnataka on 50:50 basis. Irrigation Wing is given the following responsibilities.
to effect reservoir operation in all seasons for efficient irrigation management in accordance with the approved working table including flood management and dam safety.
to supply quantities of water as per the indents placed by Government of Karnataka and Government of Andhra Pradesh for right bank canal systems, and river assistance as per Krishna Water Disputes Tribunal award
to effect supplies at the distributory heads of the HLC and LLC as per the indents given by Government of Karnataka and Government of Andhra Pradesh up to Board limit
to deliver specific discharges at Board limits of HLC and LLC on the right side
to render the water account of the reservoir and all canal systems including collection of daily drawal data for the systems on the left side from Government of Karnataka; and
to effect supply of water for the hydro electric power generation on the right side through power houses at Tungabhadra dam and at Hampi.
⇒ Krishna Water Dispute Tribunal Award ⇒ Water Regulation ⇒ Negative Inflows into the Reservoir ⇒ Year wise Utilisation of Water ⇒ Drinking Water Demands ⇒ Industrial Water Demands ⇒ Problems in Water Regulation ⇒ Flood Management
KRISHNA WATER DISPUTE TRIBUNAL AWARD
The KWDT award stated that the Board would continue to prepare the working table for utilization of the water of the reservoir and regulate the sharing of water between states of Karnataka and Andhra Pradesh as per the allocations made in the award and in accordance withsuch rules as may be made in this behalf by the Board.
The details of allocations as per KWDT award are given below:
|1.||Right Bank Low Level Canal (RB LLC)||19.00||24.00||43.00|
|2.||Right Bank High Level Canal (RBHLC)||17.50||32.50||50.00|
|3.||Left Bank Low Level Main Canal +Left Bank High Level Canal (LBMC + LBHLC)||93.00||—||93.00|
|4.||Raya and Basavanna Channels (RBC) of the State of Karnataka||7.00||—||7.00|
|5.||Assistance by way of regulated release to Vijayanagar Channels(VNC) other than RBC.||2.00||—||2.00|
|6.||Assistance by way of regulated release to KC Canal (KCC) of the State of AP.||—||10.00||10.00|
|7.||Assistance by way of regulated release to Rajolibanda Diversion Scheme (RDS)||0.49||6.51||7.00|
| Reservoir Evaporation losses (Ratio 12.5 K: 5.5
Irrigation Wing of the Board is responsible for the water regulation of RB HLC and RB LLC and to keep water account of the sluices, transmission and system losses etc. The water regulation of left bank canals, namely, Left Bank Main Canal and High Level Canal (LBMC+ HLC), is entirely with Irrigation Department of Karnataka. Officials of the Board, however, collect the data from these canals to enable them to render water accounts. They also have access to the details of daily drawals of LBMC and HLC for verification of drawals. Utilisation of water in the command area of the project is under the control of respective State Governments and the Board has no jurisdiction on the regulation of water beyond the off take points of the distributories along the two main canals on the right side, except the common distributories
In order to assist the Board in distribution and regulation of water in various canal systems of the project, a Review Committee at the level of Superintending Engineer has been constituted. The committee is headed by Superintending Engineer Irrigation Wing, of the Board and represented by the same level of officers from each of the States of Andhra Pradesh and Karnataka. At the beginning of a water year, the Review Committee assesses, the water availability for the year based on historical data using the criterion of 75% dependable flows. The committee considers the water position as existing, and also considers the indents of the participating states through each of the canal systems and prepares a Draft Working Table, keeping in view the entitlement of water for each canal system as per KWDT award, for operation and regulation of water for the entire water year. The Draft Working Table is approved by the Board and serves as operation schedule to the extent possible. Periodically, the Committee reviews the performance of the reservoir, and re-assesses the availability of water. If necessary, the working table is modified based on re-assessed water availability and also the revised pattern of drawals indicated, if any, by the participating states.The Board considers the recommendations of the committee for according approval.
Right Bank High Level Canal.
The Right Bank High Level Canal (RB HLC) is designed for carrying a discharge of 113.27 cumecs (4000 cusecs) at head. This is a lined and seasonal canal envisaged to cater to the supplemental irrigation needs from 15th July to the middle of December. The sill level of HLC sluices is 483.10 m ( + 1585 ft.) which is higher than sill levels of all other canal systems. The total length of the canal is 196.43 Km and jurisdiction of the Board is restricted upto 105.487Km i.e., Karnataka State border. Within the Board’s limit, in the Karnataka area, there are 26 direct off take sluices in HLC to cater to the needs of 80,939 ha (1, 99,920 acres) of ayacut in state if Karnataka. The canal further serves an area of 76,927 ha (1, 90,035 acres) in State if Andhra Pradesh. 4.5.4 As per KWDT Award 1415.84 Mm3 (50 TMCft) of water is allocated to HLC out of an allocation of 6003.17 Mm3 (212 TMCft) to Tungabhadra Project. Further distribution of HLC water between State of Karnataka and Andhra Pradesh is in the ration of 35:65. Thus the allocation of water under HLC for State of Karnataka is 17.5 TMCft and for State of Andhra Pradesh 32.5 TMCft. However, due to lesser utilization of water under the project in last ten years, average availability of water for HLC has reduced. The actual average drawals including diversion from other systems to HLC during the last ten years have been 16.744TMCft for State of Karnataka and 29.282 TMCft for State of Andhra Pradesh respectively
Right Bank Low Level Canal.
The Right Bank Low Level Canal is designed for carrying a discharge of 50.97 cumecs(1,800 cusecs) at head and 20.53 cumecs (725 cusecs) at Board’s limit. The total length of RB LLC is 348.2 km out of which the Board is incharge of 250.58 km. Before finally entering in the State of Andhra Pradesh the RBLLC is meandering both in State of Karnataka and Andhra Pradesh in short length as detailed below.
Canal Reach in Karnataka Canal Reach Andhra Pradesh
territory (Km) territory(Km).
0.000 to 131.500 131.500 to 135.700
135.700 to 147.800 147.800 to 148.000
148.000 to 156.000 156.000 to 188.000
188.000 to 190.800 190.800 to 250.580
RBLLC usually runs for ten months in a year and is generally closed in May and June months for maintenance works. This was an unlined canal to begin with in entire length. Subsequently, lining of the canal was taken up in a phased manner in identified vulnerable reaches in order to improve the efficiency of the canal. It has 92 direct off-take points upto the Boards limit. Further, there are 11 common distributaries (Annex4.1) running about 91 km and serving ayacuts of both the States. RBLLC serves an ayacut of 37,518 ha (92,670 acres) in the state of Karnataka and 63,588 ha (1,57,062 acres) in Andhra Pradesh.
As per KWDT award the water allocated for RBLLC for the states of Karnataka and Andhra Pradesh is19.0 TMCft and 24.0 TMCft respectively, which is exclusive of prorata reservoir evaporation losses of 3.5 TMCft and 5.5 TMCft respectively. Due to lesser utilization of the water from the project, water availability during the last ten years has reduced. Accordingly, the actual drawals in the canal have been 17.19 TMCft for Karnataka and 18.90 TMCft to Andhra Pradesh respectively.
Whenever pipings or breaches occur in the canals a certain quantum of water is allowed to flow through the escapes to deplete the water level at the piping/breach site quickly, to take up repairs. Certain amount of water also flows through the breaches whenever they occur. Board in its 130th meeting held on 29-01-1988 being aware of the water losses due to certain unauthorised drawals by various means and noting that the law enforcing authorities are not able to effectively prevent/control these unauthorised drawals, permitted to make provision for these losses, termed as system losses. This is in addition to the usual provision of transmission losses. In respect of RBLLC the Board permitted to account a maximum of 120 cusecs as system losses from the water year 1987-88. Similarly during the 165th meeting the Board permitted to account for a maximum of 120 cusecs as system losses in RBHLC also with effect from 1998-99.
The daily reports indicating the performance of reservoir, 10 day drawal account, and the details of drawals under each canal system by both the states are sent by the Board officials and to all concerned authorities of Government of Karnataka, Government of Andhra Pradesh and Government of India regularly.
YEARWISE UTILISTION OF WATER
The Krishna water Disputes Tribunal (KWDT) has allocated 212 TM cft of water for Tungabhadra Project for irrigation utilization excluding reservoir evaporation losses. The year wise actual irrigation utilization for the last 23 years is given in Annex 4.2 The utilization of water was maximum during the year 1992-93, at 139.269 TMCft by Karnataka and 72.717 TMCft by Andhra Pradesh, totaling to 211.986 TMCft. This was due to unprecedented floods which occurred in the month of November1992, thereby replenishing the reservoir to its full capacity. Drawals of water from the reservoir by the States of Karnataka and Andhra Pradesh the Annex 4.2 rough different canal systemsfor the water year 1993-94 to 1998-99 as against allocations made in KWDT are given at It is observed that utilization in the project is far below the water allocated to the project. Main reasons for lesser utilization are
Reduction in the storage capacity of reservoir due to progressive siltation
Realisation of lesser inflows than estimated during the period from December to April, and
Late arrivals of inflows at the beginning of the water year resulting in delay in the opening of canals and thereby lesser utilization in Khariff season in the Pre-surplussing and surplussing period upto November.
The utilization of water is directly proportional to the inflows realised in the reservoir with their time distribution and the climatological conditions during the water year.The problem of shortage of water for the authorised ayacutdars has aggravated as some farmers are also violating the cropping pattern and drawing more water than permitted by forcibly operating the sluices
The unauthorised tapping of water in the command is generally by one of the following methods
- by damaging the regulating mechanism
- by syphoning through pipes to feed the areas out side the localised ayacut and lying close to and along the canal
- by laying pipes hidden under the embankments
- by damaging the escape shutters and taking water to further patches of land all along natural drainage courses;
- by cutting the canals and
- by perforating holes in the bed of canal and cross drainage structures
DRINKING WATER DEMANDS
While extending irrigation benefits to the command area of the project through a net work of canal systems,the demand for drinking water is being met with. Year after year such demand is increasing due to population growth for the towns such as Raichur in Karnataka on the left bank, and Bellary in Karnataka, Adoni, Alur, Kurnool and Anatapur towns in Andhra Pradesh on the right bank situated nearer to the canal systems. Demands are coming in for drinking water supplies for other towns and groups of villages through the respective Governments, for consideration of the Board. Board permits these drawals out of the respective irrigation water quota of the two states.
INDUSTRIAL WATER DEMANDS
Due to overall economic development of the area on account of benefits accrued from the project, many industries are coming up in the command areas and in the areas near the dam. Demand for water from the project for industrial purposes too is increasing. These demands are met out of the allocations by the respective states, by adjustments of irrigation requirements within a State. A list of industries drawing water for industrial use from various systems of the Project as approved by the Board from time to time are given in.
PROBLEMS IN THE WATER REGULATION
Sometimes, the field staffs on patrolling duty are facing problems of man handling from the miscreants when mobs of ryots resort to illegal actions such as forcible excess drawals through sluices by damaging the structures or tap water by various illegal means. Staff members resenting against such man handling are resorted to strikes on certain occasions. Police complaints are promptly being lodged on all such offences. The Board has to depend upon the local police only for all security arrangement, whenever water regulation problems arise.
The flood management of the reservoir is one of the main functions of Irrigation Wing. As planned, the live storage capacity of the reservoir has no provision for flood absorption. The entire flood impinging on the reservoir has to be either stored in it to the extent possible allowing discharge into power houses for maximum power generation or passed over the spillway. For this purpose the spillway with 33 gates is designed to allow a maximum discharge of 18,406 cumecs (6,50,000 cusces) at Full Reservoir Level of 1633ft. The operation of spillway gates is carried out in accordance with approved schedules duly ensuring the dam safety.
Central Water Commission provides daily information about the flood inflows and rainfall occurrence at
- Thirthahalli on the Tunga river,
- Harlahalli on the Tungabhadra river and
- Marol on the Varada river.
Based on the flood observed on these upstream stations, and the incidence of rainfall, the probable flood expected at the dam is assessed by the CWC authorities and communicated to the project authorities over wireless sets to enable the operation of spillway gates. Inflow forecasts provided by CWC are fairly accurate and useful but in certain cases, due to contribution from the un-gauged lower catchment the project authorities are caught unaware.However, based on these inflow forecasts efforts are made to moderate the inflow peaks by judicially creating storage in the reservoir through advance depleting. The concerned Irrigation, Revenue and Police authorities are alerted in advance about the flood releases to be made from the reservoir to enable them to make necessary advance arrangements all along the river, downstream of the dam, to ensure safety of the public and properties. The information about release of discharges is also passed onto All India Radio and Door Darsan for wide publicity.
The peak flood received in the reservoir and discharged over the spillway during the last six years is given in the table below.