Chapter – 5 Hydrology and Water Assessment

5.0 General The proposed Ponnaiyar (Nedungal) - Palar link project envisages diversion of 86 Mm 3 of flood waters of Ponnaiyar river occurring at Krishnagiri dam for recharging ground water in Palar basin for stabilizing the existing ayacut being irrigated under open wells/bore wells in Vaniyambadi taluka of Vellore district as well as feeding system tanks (Eris) in enroute areas of Krishnagiri and Pochampalli talukas of Krishnagiri district and Tirupattur taluka of Vellore district besides providing drinking water supply to about 1.52 lakh people enroute the link canal. The Ponnaiyar (Nedungal)-Palar link project area has four distinct seasons viz., dry period from January to February, hot period from March to May, south-west monsoon from June to September and north-east monsoon from October to December. The climate is cold from December to February followed by hot season from March to May. In general, the project area has a pleasant climate. The hydrology and water availability studies of the project are based on the Rainfall-Runoff relationship developed at Krishnagiri dam site. However, the divertable quantity is based on the average flood spills during monsoon period from the existing Krishnagiri dam.

5.1 General Information about Regions (a) Ponnaiyar Basin The climate of the basin area is pleasant throughout the year, as per the climatological data observed at Dharmapuri IMD station which is nearer to the project area. The average annual rainfall of the basin is 977 mm. The basin receives about 76% of the annual rainfall during monsoon period i.e. from June to December. The normal daily maximum and minimum temperature found to be 37.1 o C and 17.2 o C in the months of April and January respectively. The normal maximum and minimum relative humidity is found to be 78% and 31% in the months of December and March respectively. The normal maximum and minimum wind velocities are 10.30 km/hr in June and 4.60 km/hr in October. The normal maximum cloud cover is 6.6 oktas during the month of July, where as the normal minimum cloud cover is 1.50 oktas is found during the month of March.

(b) Palar Basin The climate of the Palar basin area is pleasant throughout the year except during summer. The average annual rainfall of the basin is 891 mm. The basin receives most of the rainfall from the south-west and north-east monsoons as such June to December is considered as monsoon period. As per the climatological data of IMD observatory located at Vellore the basin receives about 80% of the annual rainfall during the monsoon period. The normal daily maximum and minimum temperature is 38.9 o C in May and 18.1 o C in January respectively. The normal relative humidity varies from 37% in the month of March to 86% in the month of December. The normal maximum and minimum wind speed is found 10.4 km/hr during June and 5.5 km/hr during October. The normal maximum cloud cover is 6.9 oktas during July and minimum cloud cover 2.0 oktas in May.

5.1.1 Specific Information 5.1.1.1 Drainage Basin (a) Ponnaiyar Basin The Ponnaiyar is a major river amongst the streams between Palar and Cauvery. The Ponnaiyar basin is part of the basin area covered by the streams between Palar and Cauvery. The basin area covered by the streams between Palar and Cauvery comprises four rivers viz., Ongur, Varahanadi, Ponnaiyar including Gadilam and Vellar with each of the four rivers draining independently in to the Bay of Bengal. The Ponnaiyar river originates near Nandidurg in Kolar district of Karnataka State at an elevation of about 900 m above mean sea level. The total length of the river is about 351 km and its average bed slope is 1 in 390. The river basin lies between latitudes 11 o 45’ N and 13 o 30’ N and longitudes 77 o 33’ E and 79 o 47’ E. The total catchment area of Ponnaiyar including Gadilam rivers is 15679 km 2 of which 3545 km 2 lies in Karnataka, 133 km 2 in Andhra Pradesh, 11961 km 2 in Tamil Nadu and 40 km 2 in Union Territory of Puducherry. The entire basin area covered by the streams between Palar and Cauvery has been divided in to three hydrological zones viz., Zone-I: Varahanadi basin (4513 km 2), Zone-II: Ponnaiyar basin including Gadilum river (15679 km 2) and Zone-III: Vellar basin (8086 km 2). The river network in Ponnaiyar and Palar basins showing the above three Zones is depicted in Fig 5.1 .

The Ponnaiyar basin covers Kolar, Chikballapur, Bengaluru urban including Bengaluru city and Bengaluru rural districts of Karnataka; Chittoor district of Andhra Pradesh; Dharmapuri, Krishnagiri, Salem, Vellore Thiruvannamalai, Villupuram and Cuddalore districts of Tamil Nadu; and Union Territory of Puducherry. The Ponnaiyar basin is bounded by

Arkavathi and Chinnar sub-basins of Cauvery basin on the west, Vellar sub-basin on the south, Palar basin on the north and Bay of Bengal on the East. Markanda nadi, Vanniar, Pambar, Kallar and Gadilam are the tributaries of Ponnaiyar river.

(b) Palar Basin The Palar river originates in Kolar district of Karnataka state near Kaivara village at an altitude of 900 m to the west of Ambojidurga and Rahamankhar peaks. The river basin lies between the latitudes 12 o 15’ N to 13 o 37’ N and longitudes 77 o 53’ E to 80 o 10’ E. The total length of the river is 348 km. The total catchment area of the basin is 17871 km 2 of which 2813 km 2 lies in Karnataka, 5018 km 2 in Andhra Pradesh and 10040 km 2 lies in Tamil Nadu. The tributaries of Palar are Poini, Malattar, Kal Ar, Kaundinya Nadi and Cheyyar. Poini joins Palar from the left side of the river near Ranipet and Cheyyar joins from the right side near Gurumancheri.

The Palar basin covers Bengaluru Rural, Chikballapur and Kolar districts of Karnataka state; Chittoor district of Andhra Pradesh; and Vellore, Thiruvannamalai, Kancheepuram and Thiruvallur districts of Tamil Nadu. The basin is bounded by streams between Palar and Cauvery in the west and south, Pennar basin in the north and streams between Pennar and Palar in the east.

5.1.1.2 Command Area The Ponnaiyar (Nedungal) - Palar link project envisages diversion of 86 Mm 3 of flood waters of Ponnaiyar river from Nedungal Anicut to the water starved Vaniyambadi Taluka of Palar basin along with enroute areas of Krishnagiri and Vellore districts for recharging the Ground water for stabilizing the existing irrigated area to an extent of about 9850 ha annually which is now being irrigated through open wells and bore wells. Out of 9850 ha an area of 7950 ha will be benefitted in Vaniyambadi Taluka of Vellore district by utilising about 57.926 Mm 3 of water and 1900 ha in enroute areas of Krishnagiri and Vellore districts by utilising about 17.215 Mm 3 besides providing drinking water supply to 1.52 lakh people by utilising 3.882 Mm 3.

5.1.1.3 Floods and Drainage (a) Ponnaiyar Basin The gauge and discharge data is being observed by the Public Works Department, Govt. of Tamil Nadu at Krishnagiri dam on Ponnaiyar river which is about 16 km upstream of the existing Nedungal Anicut. The daily inflow data is available for a period of 52 years i.e., from 1958-59 to 2009-10. The maximum observed flood at Krishnagiri dam was 3007 cumec on 11.11.1903. The design flood of Krishnagiri dam was 4234 cumec.

(b) Palar Basin The gauge and discharge data is being recorded by Central Water Commission at Arcot G&D site on Palar river and is available from the year 1972. The maximum observed discharge at this G&D site was 528.2 cumec on 13.09.1981.

The Hydrometeorological, Hydrological stations and Isohyetals in Ponnaiyar and Palar river systems are shown in Fig 5.2 and 5.3 respectively.

5.1.1.4 River Geometry The schematic diagram of Ponnaiyar and Palar river systems is as in Fig. 5.4 gives an overview of the river geometry.

Fig .- 5.4 Schematic diagram of the Ponnaiyar – Palar river system with Major structures and link canal

5.1.1.5 Groundwater Recharge The proposed diversion through link canal recharges the ground water enroute the link canal and in Palar basin, thereby raising ground water table as well as improvement in the quality of water. As per the Central Ground Water Board studies the long term water level fluctuation for the period from 1998 - 2007 indicates rise in water level in Vellore district ranges from 0.0025 to 0.5264 m/year. The fall in water level ranges between 0.568 to 2.3958 m/year.

5.1.1.6 Reservoir Area The Ponnaiyar (Nedungal) - Palar link canal off-takes from the existing Nedungal Anicut across Ponnaiyar river. The Anicut is situated in Krishnagiri Taluka of Krishnagiri District near Nedungal Village at latitude 12 o 22’ N and longitude 78 o 16’ E. The Anicut is located 16 km downstream of the existing Krishnagiri dam. The crest level of the Anicut is 434.71 m. The Anicut is approachable by all weather roads nearby.

The flood water spills from existing Krishnagiri dam will be regulated to link canal through existing Nedungal Anicut. The Krishnagiri dam is located in Krishnagiri District of Tamil Nadu near Krishnagiri Town. The latitude and longitude of the Krishnagiri dam are 12 o 28’ N and 78 o 11’ E respectively. The catchment area of the Ponnaiyar river up to Krishnagiri dam is 5428 km2. Height of the dam is 29.26 m and the length of earth dam and masonry dam is 712.93 m and 277.67 m respectively. The spill way discharge capacity is 4061 cumec with 8 vents of 12.19 x 6.10 m size. The crest level of spillway is 477.01 m. The submergence area of the reservoir at FRL 483.11 m is 10.723 km 2 with gross storage capacity of 47.184 Mm 3.

5.1.1.7 Other Water Usage The flood water spill down the existing Krishnagiri dam will be diverted into link canal through Nedungal Anicut for stabilizing the existing area being irrigated through open wells and bore wells by recharging the Ground water potential in Tirupattur and Vaniyambadi talukas of Vellore District and Krishnagiri and Pochampalli talukas of Krishnagiri District. In addition to irrigation use enroute villages will be supplied with domestic water to the tune of 3.882 Mm 3.

5.1.1.8 Navigation The Ponnaiyar and Palar rivers are not presently used for any navigational purpose. There is no proposal of navigation in the proposed Ponnaiyar (Nedungal) - Palar link canal.

5.1.2 Data Availability (a) Ponnaiyar Basin 5.1.2.1 Hydrological and Meteorological Investigations Rainfall and Snowfall There is no snowfall in Ponnaiyar basin. The precipitation in the basin is in the form of rainfall and the intensity of rainfall varies fairly in time and space as observed from the data. There are 67 raingauge stations in and around the Ponnaiyar basin, out of which 18 stations are in the Ponnaiyar basin upto Krishnagiri dam site. The basin receives almost 80% of the annual rainfall during monsoon period from June to December. The average annual rainfall of the Ponnaiyar basin upto Krishnagiri dam site is 795 mm. The period of availability of rainfall data and average annual rainfall (mm) of each raingauge station of Ponnaiyar basin up to Krishnagiri dam site is given below in Table-5.1. The location of the existing rain gauges in the Ponnaiyar basin is shown in Fig 5.2 .

Table-5.1 Raingauge Stations in Ponnaiyar Basin up to Krishnagiri Dam Site and their Period of Availability

Sl. No. Name of the Rain gauge Period of Record Average Station availability length in Annual From To years Rainfall (mm) 1. Rayakota 1901 2009 109 702 2. Krishnagiri 1901 2009 109 882 3. Hosur 1901 2009 109 757 4. Denkanikota 1901 2009 109 997 5. Anekal 1901 2009 109 915 6. Bengaluru 1901 2009 109 949 7. Hebbal 1901 2009 109 806 8. Devanahalli 1901 2009 109 777 9. Hoskote 1901 2009 109 780 10. Sol Devanahalli 1901 2009 109 711 11. Doddabalapur 1901 2009 109 810 12. Malur 1901 2009 109 725 13. Bangarpet 1901 2009 109 730

Sl. No. Name of the Rain gauge Period of Record Average Station availability length in Annual From To years Rainfall (mm) 14. Chikballapur 1901 2009 109 841 15. Siddalaghatta 1901 2009 109 757 16. Kolar 1901 2009 109 739 17. Chinthamani 1901 2009 109 655 18. Kuppam 1901 2009 109 779 Average 1901 2009 795

Sunshine, Cloud Cover and Visibility The Dharmapuri Meteorological Station is located inside the Ponnaiyar basin and nearer to the link project. As per this IMD observatory, based on the observations during the period 1961-1990, the normal maximum cloud cover of 6.6 Oktas is observed in the month of July and a normal minimum of 1.50 Oktas is observed in the month of March.

Wind Velocity As per the IMD observatory of Dharmapuri, based on the observations during the period 1961-1990, the normal maximum and minimum normal wind speed observed at Dharmapuri IMD observatory is 10.3 kmph and 4.6 kmph during the months of June and October respectively.

Relative Humidity As per the IMD observatory of Dharmapuri, based on the observations during the period 1961-1990, the relative humidity is maximum during monsoon months and minimum during winter and summer months. The monthly normal maximum and minimum relative humidity observed at Dharmapuri IMD observatory is 78% in December and 31% in March, respectively.

Temperature As per the IMD observatory of Dharmapuri, based on the observations during the period 1961-1990, the normal daily maximum and minimum temperature recorded is 37.1 OC in April and 17.2 OC in January.

(b) Palar Basin There are 60 rain gauge stations located in and adjacent of the Palar basin including Poini and Cheyyar basins. There is no snowfall in Palar basin. The data at these stations is available for varying periods from 1901-02 to 2009-10. The location of the

existing rain gauges in the basin is shown in Fig. 5.3. The basin receives almost 80% of the annual rainfall during monsoon period from June to December.

5.1.2.2 Pan Evaporation Though there is a Pan-evaporimeter installed at Krishnagiri dam site, the pan evaporation data observed at this site is not used for calculating the evaporation losses of the reservoir since the link project envisages transfer of flood waters spilling down the existing Krishnagiri dam and as such no simulation study has been carried out.

5.1.2.3 Climatological Parameters like Temperature, Humidity and Wind Speed At Dharmapuri IMD observatory The normal values (1961-1990) of various climatological parameters in the vicinity of Krishnagiri dam (Dharmapuri IMD observatory) are as follows.

Max. Min. Air temperature ( oC) 37.1 (April) 17.2 (Jan.) Humidity (Percentage) 78.0 (Dec.) 31.0 (March) Wind speed (km/hr) 10.3(June) 4.6 (Oct.) Cloud cover (oktas) 6.6 (July) 1.5 (March)

At Vellore IMD observatory The normal values (1961 – 1990) of various climatological parameters for the command area (IMD observatory at Vellore) of the link project are as follows.

Max. Min. Air temperature ( oC) 38.9 (May) 18.1(Jan.) Humidity (Percentage) 86.0 (Dec.) 37.0 (Mar.) Wind speed (km/hr) 10.4 (June) 5.5 (Oct.) Cloud cover (oktas) 6.9 (July) 2.0 (March)

5.1.2.4 River Gauge and Discharge Gauge and Discharge data is being observed by Public Works Department, Govt. of Tamil Nadu at 5 G&D sites across Ponnaiyar river. The Central Water Commission is also maintaining 3 G&D sites on Ponnaiyar river. The details of these G&D sites are given in Table 5.2.

Table 5.2 Details of G&D Sites Sl. Name of Gauge & Maintained River / Catchment Year from No. discharge site by Tributary area which data (Km 2) is available 1. Krishnagiri Reservoir PWD Ponnaiyar 5428 19 58 2. Nedungal Anicut PWD -do - 5694 1960 3. Sat hanur Reservoir PWD -do - 10826 1960 4. Tirukkoilur Anicut PWD -do - 12318 1960 5. Ellis Choultry Anicut PWD -do - 12477 1960 6. Gummanur CWC -do - 4620 1978 7. Valavachchanur CWC -do - 10780 1978 8. Villupuram CWC -do - 12900 1973

Out of the above 8 G&D sites the G&D site at Krishnagiri reservoir located on Ponnaiyar river for which the monthly inflow data is available for a period of 52 years from 1958-59 to 2009-10 has been used for correlating rainfall-runoff relationship by regression analysis at Krishnagiri dam site.

5.1.2.5 Sediment (Suspended and Bed Load) Inflow Sediment analysis is being carried out by Central Water Commission (CWC) at Gummanur G&D site (C.A:4620 km 2) and at Valavachchanur G&D site (C.A:10780 km 2). Since the existing Krishnagiri dam (C.A:5428 km 2) is proposed as controlling structure to divert the flood water of Ponnaiyar river the data on sediment inflow at Gummanur G&D site which is located u/s of Krishnagiri dam for the period from 1982-83 to 2012-13 is furnished in Table 5.3.

Table 5.3 Annual Sediment Load at Gummanur G&D Site on Ponnaiyar River C.A: 4620 km 2 Year Monsoon Non -Monsoon Annual Load Annual (M.T.) (M.T.) (M.T.) Run-off (MCM) 1982 -1983 33482 271 33753 64 1983 -1984 43348 213 43561 83 1984 -1985 138032 1152 139184 130 1985 -1986 58559 19182 77741 62

Year Monsoon Non -Monsoon Annual Load Annual (M.T.) (M.T.) (M.T.) Run-off (MCM) 1986 -1987 123427 48 123475 198 1987 -1988 285900 173 286073 220 1988 -1989 194828 27 194855 243 1989 -1990 89420 10965 100385 173 1990 -1991 24680 83 24763 26 1991 -1992 305967 3210 309177 532 1992 -1993 29938 20 29958 70 1993 -1994 12321 174 12495 170 1994 -1995 3446 70 3516 78 1995 -1996 13163 8 13171 141 1996 -1997 18541 91 18632 234 1997 -1998 118661 2153 120814 314 1998 -1999 31774 176 31950 301 1999 -2000 46108 132 46240 245 2000 -2001 23572 21 23593 309 2001 -2002 38780 90 38870 309 2002 -2003 436 4 440 46 2003 -2004 1597 80 1677 51 2004 -2005 15692 1102 16794 197 2005 -2006 207415 5653 213068 795 2006 -2007 Sediment observation not done 2007 -2008 Sediment observation not done 2008 -2009 12834 1393 14227 311 2009 -2010 7264 1391 8655 216 2010 -2011 4497 2662 7159 205 2011 -2012 6785 2079 8864 218 2012 -2013 4491 1859 6350 99

Source: Office of the Executive Engineer, SR Division, CWC, Coimbatore, Tamil Nadu.

From the above data the average annual sediment inflow at Gummanur site works out to 67222 M.T.

5.1.2.6 Water Quality Public Works Department (PWD), Govt. of Tamil Nadu collected the Water samples of Krishnagiri Dam during all the months from different points such as reservoir, seepage water from drainage galleries, toe-drain of earthen section for analysis at Soil Mechanics and Research Division, WRO, PWD, Chennai for both chemical and physio- chemical analysis for ascertaining the water quality status. The latest data for the period from 2009 to 2013 on laboratory test results of the water samples of Krishnagiri reservoir has been collected. Details on results of the water samples are given in Chapter-4 ‘Surveys & Investigations’ under para 4.6.7 .

5.2 Surface Water Balance of Ponnaiyar Basin upto Krishnagiri Dam Site 5.2.1 Hydrological Data Requirement For development of rainfall-runoff relationship monthly rainfall and concurrent stream flow data is required. The inflows to the reservoir are affected by water utilization in the upstream. Hence the utilization data of the upstream projects is also required to compute the reservoir inflows. The periodic water demands, releases from the reservoir and evaporation rates in the reservoir area are also required.

5.2.2 Time Unit for Simulation Studies The project envisages diversion of flood waters spilled down the existing Krishnagiri dam as such no simulation studies are carried out. However, monthly monsoon spill data at Krishnagiri reservoir for the period from 1958 to 2009 is considered to estimate flood water spills down the Krishnagiri reservoir.

5.2.3 Compilation and Processing of Basic Hydrological Data 5.2.3.1 Hydrological Investigation As indicated above, the observed monthly inflow data at Krishnagiri reservoir is available for the period from 1958-59 to 2008-09 and the same is used for development of rainfall-runoff relationship by regression analysis at Krishnagiri dam site. The catchment area of Ponnaiyar basin upto Krishnagiri dam site is 5428 km 2. The State-wise/District-wise break up of catchment area upto Krishnagiri dam is furnished in Table 5.4.

Table 5.4 District wise break-up of catchment area up to Krishnagiri Dam Site Sl. State / District Catchment area Percentage to the total No. in km 2 Catchment area 1. Karnataka a) Kolar 1143 21.06 b) Chikballapur 498 9.18 c) Bengaluru urban 797 14.68 Incl. Bengaluru City (241+556) d) Bengaluru rural 1107 20.39 Sub -total: 3545 65.31 2. Andhra Pradesh a) Chittoor 94 1.73 3. Tamil Nadu a) Krishnagiri 1789 32.96 Total 5428 100.00

5.2.3.2 Data from other Sources Most of the data used in this study was collected from other Central and State Govt. Agencies. Rainfall data was collected from IMD and Department of Economics and statistics, Govt. of Karnataka and Tamil Nadu. The inflows, spills and upstream project utilizations were collected from Water Resources Department, Govt. of Tamil Nadu.

5.2.4 Processing of Data The following hydrological variables were processed in this study: (i) rainfall data (ii) reservoir inflow data (iii) upstream project utilisation data (iv) export from the basin and import to the basin upto Krishnagiri dam site and (v) monthly spill discharges from Krishnagiri reservoir.

5.2.4.1 Quality of Data There are some missing records in daily rainfall data. The missing data have been estimated using standard statistical methods. Further, analysis of the rainfall-runoff correlation is carried out at Krishnagiri dam site. The intercepting catchment area between the existing Krishnagiri dam and Nedungal Anicut is 266 km 2 and the contribution of yield from this area is computed on proportionate area basis using the yield series developed at the Krishnagiri dam site.

5.2.4.2 Filling of Short Data Gaps The rainfall data up to Krishnagiri dam site is mostly available for all the 18 stations from 1901-02 to 2009-10 and the same has been considered in this study. The gaps in the rainfall data have been filled using standard procedure. The missing records in rainfall data have been estimated using standard statistical methods. These gaps are filled by the normal ratio formula as given below:

Px = Nx/m [ P 1/N 1+ P 2/N 2+ ……… P m/N m] Where,

Px = estimated rainfall of a station

Nx = normal rainfall of a station

P1, P2…… P m = observed rainfall values of neighbouring stations

N1 N2 …….N m = normal rainfall values of neighbouring stations

5.2.4.3 Adjustment of Records The observed inflow data of Krishnagiri reservoir is available for the period from 1970-71 to 2009-10. To compute the monsoon virgin yield series at Krishnagiri reservoir actual upstream utilizations under the existing projects and regeneration on import from Bengaluru water supply schemes are considered based on the proportionate area of Bengaluru city lying in Ponnaiyar basin from the date of stage-wise commissioning of the water supply schemes. The gross monsoon virgin yield series at Krishnagiri reservoir are arrived by adding the inflow at Krishnagiri dam to the net upstream utilizations by the irrigation projects and subtracting regeneration from the Bengaluru water supply scheme (import) for each year from 1970-71 to 2009-10.

5.3 Water Balance upto Krishnagiri Dam Site The 75% and 50% dependable annual yields as well as estimated utilisations for various uses by 2050 AD are computed as per various approved guidelines of TAC of NWDA. The details of Water Availability analysis and projected utilisations are furnished as Appendix 5.1 . The water balance taking into account the availability, import, export, regeneration and water needs for the basin area up to Krishnagiri dam site is given in Table 5.5.

Table 5.5 Surface Water Balance of Ponnaiyar Basin up to Krishnagiri Dam Site Unit : Mm 3

1. Surface Water Availability (a) Gross annual yield i) At 75% dependability 200 ii) At 50% dependability 315

(b) Surface water import 293 (as regeneration from Cauvery basin) (c) Surface water export Nil (d) Overall availability i) At 75% dependability 493 ii) At 50% dependability 608 2. Surface Water Requirement i) Irrigation 30 1 ii) Domestic 76 iii) Industrial use 113 iv ) Hydropower needs Nil 490 490 3. Regeneration i) Irrigation 2 ii) Domestic 61 iii) Industrial use 90 153 153 4. Surface Water Balance i) At 75% dependability 156 ii) At 50% dependability 271

Thus, the annual surface water balance of 156 Mm 3 and 271 Mm 3 at 75% and 50% dependabilities respectively have been computed at Krishnagiri dam site.

5.4 Water Balance upto Nedungal Anicut

Projected Domestic Water Needs of Basin Area up to Nedungal Anicut Nature of Estimated Per capita Water Requirement Population Population by Need (Litres) by 2050 AD 2050 AD (in ‘000) (in Mm 3) Urban 1282 135 63 Rural 1267 70 32 Live stock 1257 50 23 Total: 118

The entire urban water requirement excluding Bengaluru city and 50% of rural water requirement for human population are proposed to be met from surface water resources. This works out to 79 Mm 3. 80% of surface water to be utilized for domestic purpose is considered to be available as return flow, which work out to 63 Mm 3.

Industrial Water Requirement In absence of relevant data, the industrial water needs by 2050 AD have been assumed to be of the same order as that of domestic water requirement. Accordingly, the industrial water requirement would be 118 Mm 3. This requirement is proposed to be met from surface water resources. 80% of this use is considered to be available as regeneration, which works out to 94 Mm 3.

The water balance taking into account the availability, import, export, regeneration and water needs for the basin area upto Nedungal Anicut is given in Table 5.6.

Table 5.6 Surface Water Balance of Ponnaiyar Basin upto Nedungal Anicut Unit : Mm 3

1. Surface Water Availability (a) Gross annual yield i) At 75% dependability 210 ii) At 50% dependability 330 (b) Surface water import 293 (c) Surface water export Nil (d) Overall availability i) At 75% dependability 503 ii) At 50% dependability 623 2. Surface Water Requirement

i) Irrigation 30 1 ii) Domestic 79 iii) Industrial use 118 iv) Hydropower needs Nil 498 498 3. Regeneration i) Irrigation 7 (Kalavarapalli : 2 Mm 3) (Krishnagiri : 5 Mm 3) ii) Domestic 63 iii) Industrial use 94 164 164 4. Surface Water Balance i) At 75% dependability 169 ii) At 50% dependability 289

Thus, the annual surface water balance of 169 Mm 3 and 289 Mm 3 at 75% and 50% dependabilities respectively have been computed at Nedungal Anicut.

In the assessment of overall availability of water at diversion point, the requirement of downstream projects are also to be considered. There are 3 existing medium projects viz., Inchampadi anicut, Tirukkoilur anicut and Sathanur anicut located on Ponnaiyar river downstream of Krishnagiri dam. The utilizations and the availability of yields at these projects are furnished below.

5.5 Downstream Projects 5.5.1 Computation of Yield at Inchampadi Anicut The Inchampadi Anicut which is an existing medium project located at downstream of confluence of Pulapatti Ar, a tributary of river Ponnaiyar. The catchment area of this tributary is 908 km 2 and the yield @ 75% dependability from this catchment works out to 33 Mm 3 (908/5428*200), on proportionate area basis of the yield computed at Krishnagiri dam. The utilization under this project is 21 Mm 3. Hence, the contribution from this independent stream can cater to the needs of this project.

5.5.2 Computation of Yield at Tirukoilur Anicut The intercepting catchment area between Krishnagiri dam and Tirukoilur Anicut is 6890 km 2 and this area lies in a rainfall zone of 800 - 1100 mm, where as the catchment area above Krishnagiri dam site lies in a rainfall zone of less than 800 mm.

Hence, the yield computed at 75% dependability for the intercepting catchment area of 6890 km 2 is on the conservative side which works out to 254 Mm 3 on proportionate area basis of yield worked out at Krishnagiri dam site by regression analysis. The yield available at Tirukoilur Anicut at 75% dependability and its committed requirement for irrigation and requirement for domestic and industrial needs and regeneration are furnished below.

Yield:- Water balance available at Krishnagiri dam site at 75% dependability 156 Mm 3

Yield at 75% dependability from the intercepting catchment below Krishnagiri dam site and upto Tirukkoilur Anicut including Pulapatti Ar 254 Mm 3 tributary - (6890/5428*200 = 254)

Total 410 Mm 3

Requirement:-

1) Domestic (Mm 3) 143 2) Industrial (Mm 3) 273 416 (+) 416 3) Irrigation (Mm 3) i) Inchampadi Anicut 21 ii) Sathanur project 170 iii) Tirukkoilur project 122 313 (+) 313 Regeneration (Mm 3) 1) Domestic and industrial use (-) 332

However, keeping in view the committed water utilizations from the existing projects, it is proposed to divert the flood flows during monsoon period. The details are given in para 5.7 .

The 75% dependable yield available from the intercepting catchment area between Krishnagiri dam and Tirukoilur Anicut and the surplus water balance at Krishnagiri dam works out to 410 Mm 3 against the committed irrigation requirement for the projects downstream of Krishnagiri dam and domestic and industrial requirement of 313 Mm 3, 416 Mm 3 respectively. After considering regeneration of 332 Mm 3 from the domestic and industrial use, 397 Mm 3 will be the net requirement. The contribution from this intermittent catchment can cater the needs of this requirement.

The quantum of diversion (99 Mm 3) proposed through Ponnaiyar (Sathanur) - Palar (Cheyyar) link by Govt. of Tamil Nadu has not been considered in arriving the

availability of yield @ 75% dependability, since the proposal is framed for diversion of flood flows of Ponnaiyar at Sathanur dam.

Ponnaiyar (Nedungal) – Palar Link Canal Even though there is surplus water available at Krishnagiri dam and Nedungal Anicut, only spills during flood season are proposed for diversion. Hence the hydrological regime of the Ponnaiyar basin is not likely to be affected significantly. The diversion of water is proposed during the months of October, November and December only.

5.6 Presentation of Hydrologic Inputs 5.6.1 Water Inflows Water inflows observed at Krishnagiri G&D site on Ponnaiyar river were used for Hydrological purpose. However, monthly spill data of Krishnagiri reservoir based on regulated releases of flood/spills are used to assess the quantum of flood water for proposed diversion.

5.6.2 Data Generation The observed in-flow data at Krishnagiri reservoir is available for a continuous period of about 52 years from 1958-59 to 2009-10. Therefore, the process of data generation is not required.

5.6.3 Sedimentation Studies 5.6.3.1 Rate of Sedimentation Sediment analysis was done by the Central Water Commission (CWC), at Gummanur G&D site which is located upstream of Krishnagiri dam site. As per the sediment data available at the site during the period from 1982-83 to 2012-13 the rate of average annual sediment inflow to the reservoir works out to 67222 M.T, out of which 65343 M.T is during the monsoon period.

5.6.3.2 Area Capacity Curves The existing Krishnagiri dam on Ponnaiyar river with a catchment area of 5428 Km 2 is proposed as a controlling structure for transfer of water through the link canal. The Elevation - Area - Capacity curves of Krishnagiri reservoir are presented in Fig. 5.5.

2 RESERVOIR LEVEL in 'm' Fig-5.5 483.1 482.5 481.9 481.3 480.7 480.1 479.5 478.8 478.2 477.6 477.0 476.4 475.8 475.2 474.6 474.0 473.4 472.7 472.1 471.5 470.9 470.3 467.3 AREA AREA km 0 1 2 3 AREA 4 5 3 6 CAPACITY Mm 7 8 9 10 CAPACITY AREA -AREA CAPACITY CURVE OF KRISHNAGIRI RESERVOIR 0 5 10 15 20 25 30 35 40 45 50 11 483.1 482.5 481.9 481.3 480.7 480.1 479.5 478.8 478.2 477.6 477.0 476.4 475.8 475.2 474.6 474.0 473.4 472.7 472.1 471.5 470.9 470.3 467.3 RESERVOIR LEVEL in 'm'

5.6.4 Potential Evapotranspiration and Rainfall Normal potential evapo-transpiration data of Vellore IMD observatory is used for computation of crop water requirement in the command area. The command area proposed for stabilisation through this link project is being irrigated by waters from local tanks and bore wells. The link canal feeds the tanks and recharges the ground water.

5.6.5 Flood Inputs Flood water available at the Krishnagiri dam is proposed for diversion through Ponnaiyar (Nedungal) – Palar link project. The monthly spill discharges for all the months based on the daily data of Krishnagiri reservoir are collected from the Project authorities for the period from 1958-59 to 2009-10 and used to estimate the quantum of flood water spilling down the existing Krishnagiri dam which can be available for diversion.

5.6.6 Inputs for Water Quality Different chemical and physio-chemical parameters of water quality of Ponnaiyar river at Krishnagiri dam are observed by PWD, WRD, Govt. of Tamil Nadu regularly and are being tested at water quality testing laboratory of Soil Mechanics and Research Division, PWD, WRD, Chennai. From the test results of the water samples of Ponnaiyar river collected at Krishnagiri dam from reservoir water, seepage water from Earthen dam toe-drain and Drainage galleries it is seen that in general the water is fit for domestic, industrial and agricultural purposes.

5.6.7 Low Flow Inputs The monthly inflow details of Krishnagiri reservoir were collected for the period from 1958-59 to 2009-10. From the inflow data it is seen that the average flow during non-monsoon (January to May) i.e., lean flow season is about 20 Mm 3 only which works out to about 6.5% of average annual inflow.

5.6.8 Surface to Ground Water Recharge The Ground water Division, Public Works Department, WRO, Vellore, Govt. of Tamil Nadu has studied the possible ground water recharge zones and identified the areas having possibilities of ground water recharge enroute the link canal as well as on either side of the rivers Kal Ar and Palar in Vaniyambadi and Tirupattur talukas of Vellore district. The details are discussed in Chapter-8: Irrigation Planning and Command Area .

5.7 Study of Spill Waters from Krishnagiri Dam and Quantum of diversion and Link Canal Capacity The monthly spill discharges for all the months at Krishnagiri reservoir are collected for the years from 1958-59 to 2009-10 from project authorities, from which the quantum of average monsoon flood spills at Krishnagiri dam site has been assessed to be 157 Mm 3. Out of 157 Mm 3, 86 Mm 3 is proposed for diversion through the link canal. Details are furnished in Annexure-5.1 . The summary of daily spill data for the months of October, November and December for the period from 1979-80 to 2009-10 is furnished at Annexures-5.2.1 to 5.2.3 . The canal has been designed for 68 cumec capacity to flow for a period of 18 days annually.

5.8 Design Flood and Diversion Flood Since the diversion is proposed from the existing Nedungal Anicut, the aspects of design flood and diversion flood etc. are not discussed in the present study.

5.9 Studies for Design of Drainage in the Command Area No new command area is proposed to be brought under irrigation from the project except stabilisation of existing command area through ground water recharge. As such no studies are carried for design of drainage in the command area.

5.10 Determination of Levels for Locating Structures on Outlets The crest level of the Nedungal anicut is 434.710 m. In order to divert required water the pond level in the front of the proposed head regulator for link diversion is considered as 435.01 m keeping in view the raise in water level during the floods. The sill level of the Head Regulator is kept at 433.0 m with the FSL of the link canal at start as 434.450 m. The sill level of existing Barur channel sluice is 433.16 m, which is located just 60 m d/s of the proposed head regulator.

5.10.1 Location of Structures The link project envisages construction of following components: 1. Canal Head Regulator at off-take point at Nedungal Anicut 2. A link canal of 54.15 km length with off-take at FSL 434.450 m from Nedungal anicut. 3. Enroute Cross drainage and Cross masonry Structures.

5.10.2 Location of Outlets There is no direct canal irrigation proposed enroute the link canal. However, suitable outlets are proposed to be provided to feed the enroute existing system tanks. The hydraulic particulars of these tanks are discussed in the Chapter – 6: Design Aspects .

5.11 Model Studies Since the existing structures viz., Krishnagiri dam and Nedungal anicut are proposed for regulation and diversion of flood flows, no model studies are required.

5.12 Minimum Flow for Environmental Consideration Since, only flood water are proposed for diversion and also several small streams are joining the Ponnaiyar river d/s of the diversion point viz., Nedungal anicut, no adverse effect is anticipated on minimum flows in the river.

5.13 Effect of Project on Hydrologic Regime During the flood period, the spillway operation of the Krishnagiri reservoir is so controlled as to pass the design flood without adverse affects on the downstream side due the floods. While the crest level of the spillway is at 477.01 m, the FRL and MWL are at 483.11 m and 484.63 m respectively. As per the flood rules of Krishnagiri Reservoir Project, all the spillway gates shall be opened uniformly and the height of opening shall be increased according to the intensity of flood. Whenever flood flows are received over 10000 cusecs (280 cumec), the reservoir level will be gradually reduced to 482.50 m during the rising floods. During the receding floods, the reservoir will be gradually filled upto FRL 483.11 m. Since only the part of spills during the flood is contemplated for diversion through the link canal, no adverse effect on d/s hydrologic regime is anticipated.

5.13.1 Effect on Low Flows Since as already discussed, only flood flows during period of spill occurrence are proposed for diversion during monsoon period, there will be no adverse effect on low flows because of proposed diversion.

5.13.2 Effect on Peak Flood It is expected that peak flood will be smoothened because of diversion of spill flows during times of flood.

5.14 Water Allocation and Inter-state Aspects Both Ponnaiyar and Palar basins are not covered under any tribunal awards. Though the proposed project is an Intra-state link project of Govt. of Tamil Nadu, the Ponnaiyar originates in Karnataka State. This aspect is already discussed in Chapter 3: Interstate Aspects.