Chapter – 5 Hydrology and Water Assessment
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Chapter 5 Hydrology and water assessment 5.0 General The proposed Godavari (Janampet) - Cauvery (Grand Anicut) link system envisages diversion of 7000 Mm3 from the proposed Janampet barrage on Godavari for extending irrigation, domestic and industrial water supply benefits in the States of Telangana, Andhra Pradesh and Tamil Nadu before out falling into Grand Anicut on Cauvery river. This DPR consists of following three link projects for which feasibility reports have already been prepared and circulated by NWDA to the concerned States. a) Godavari (Janampet) - Krishna (Nagarjunasagar) link project-340 km (Reach-I) b) Krishna (Nagarjunasagar) - Pennar (Somasila) link project-393 km (Reach-II) c) Pennar (Somasila) - Palar - Cauvery (Grand Anicut) link project-529 km (Reach-III) In the above first link proposal (Reach-I), the link was proposed to off take from Inchampalli dam, on Godavari basin at feasibility stage. Due to large area coming under submergence, it is decided that an alternative site is to be located in order to get less area under submergence. Accordingly, a barrage site is finally selected about 85 km d/s of Inchampalli dam i.e. Janampet barrage. In view of this modified proposal, the alignment of this link has been slightly changed from the original, whereas the link alignments of other two reaches are the same. Seasonal climate prevails in the link project area. Generally, four distinct seasons are noticeable in the year viz., Monsoon from June to October, Post- monsoon from October to December, Winter from January to February and Summer from March to May. The climate is normally cold from January to February which is followed by hot season from March to May. The hydrology and water availability studies of the project are based on the Water balance studies of Indravati (TS No. 42, December-2015) and Lower Godavari (TS No. 83, February-2016) sub-basins of Godavari basin prepared by NWDA. 126 Detailed Project Report of Godavari (Inchampalli/ Janampet) –Cauvery (Grand Anicut) link project 5.1 General Information about Regions The salient features/general information of the four major basins concerning the link system viz. Godavari, Krishna, Pennar and Cauvery is described as under: (i) Godavari basin The river Godavari is the second largest in the country and the largest in Southern India. It rises in the Sahyadri hills at an altitude of about 1067 m near Triambakeswar in the Nashik district of Maharashtra State and flows for about 1465 km in a general southeastern direction through the States of Maharashtra, Telangana and Andhra Pradesh before joining the Bay of Bengal at about 97 km south of Rajahmundry in Andhra Pradesh. The basin extends over an area of 312813 km2 covering the States of Maharashtra, Karnataka, Madhya Pradesh, Chhattisgarh, Odisha, Telanganga and Andhra Pradesh which is nearly 10% of the total geographical area of the country. The major tributaries joining the Godavari are the Pravara, the Purna, the Manjra, the Maner, the Pranhita, the Penganga, the Wardha, the Indravati and the Sabari. The Godavari basin receives major part of its rainfall during the Southwest monsoon period. The other rainy seasons are not so well defined and well spread as the South-West monsoon season. The annual rainfall of the basin varies from 3000 mm to 600 mm. The Godavari basin has a tropical climate. The mean annual surface temperature in the Western Ghat area is about 24oC, and it increases gradually towards the east and attains a maximum of 29.4oC on the East Coast. During January the mean daily minimum temperature increases from West to East from 15oC on the Western Ghats to about 18oC on the East Coast. The mean maximum daily temperature generally exceeds 30o C in the western part of the Godavari basin and it is only slightly less than 300 C in the Eastern part. The newly proposed Janampet barrage, identified as the diversion point for the link system, is located on main Godavari river in Telangana. 127 Chapter 5: Hydrology and Water Assessment (ii) Krishna basin The Krishna is the second largest river in the Peninsular India flowing east and draining into the Bay of Bengal. The river rises in the Mahadev range of the Western ghats near Mahabaleshwar at an altitude of about 1337 m above mean sea level and flows through the States of Maharashtra, Karnataka, Telangana and Andhra Pradesh. The total length of the river from source to its outfall into Bay of Bengal is about 1400 km of which 305 km is in Maharashtra, 483 km in Karnataka and 612 km in Telangana and Andhra Pradesh. The basin extends over an area of 258948 km2 spread in the States of Maharashtra, Karnataka, Telanganga and Andhra Pradesh which is nearly 8% of the total geographical area of the country.The important tributaries of the Krishna are the Bhima, Ghataprabha, the Malaprabha and the Tungabhadra u/s of the Nagarjunasagar project and the Musi, the Palleru and the Muneru d/s of the project. The Krishna basin receives the major portion of its rainfall during Southwest monsoon period. During this period, the basin receives about 80% of its total annual rainfall. The annual rainfall in the Krishna basin varies from 3048 mm to 600 mm. The Krishna basin has a tropical climate. The mean annual surface temperature in the Western Ghats is about 24oC. It increases gradually towards the East and attains a maximum of 29.4oC on the East Coast. During January, the mean daily minimum temperature increases from West to East from 15oC in the Western Ghats to about 18oC in the East Coast; the mean daily maximum temperature generally exceeds 30o C in the Western part of the Krishna basin and is only slightly less than 30o C in the Eastern part. The Nagarjunasagar project on Krishna river is identified as the balancing reservoir in the proposed link system for diversion of water from Krishna to Pennar. (iii) Pennar basin Pennar river is one of the major rivers of the Indian Peninsula flowing eastwards and draining into the Bay of Bengal. The Pennar river rises in Chennakesava hill of the Nandidurg range in Kolar district of Karnataka State. The total length of the river from the source to its out fall into the sea is 597 km, Detailed Project Report of Godavari (Inchampalli/ Janampet) –Cauvery (Grand Anicut) link project of which about 61 km is in Karnataka and the remaining 536 km in Andhra Pradesh. The total catchment area of the basin is 55213 km2 located in the States of Karnataka and Andhra Pradesh. The principal tributaries of the river are the Jayamangali, the Kunderu and the Sagileru from the left and the Chitravati, the Papagni and the Cheyyeru from the right. The Pennar basin receives rainfall both during the south-west and north- east monsoons. The rainfall during the non-monsoon period is not significant. The north-east monsoon (October through January) provides a little precipitation but the predominant rain falls when the south-west monsoon (June through September) occurs. Post monsoon cyclonic activity in the Bay of Bengal during September and October produces increased rainfall in the coastal region. The mean annual rainfall within the drainage basin varies from about 550 mm near Anantapur area to 900 mm in the vicinity of Nellore. The mean maximum daily temperature varies from 40.3oC observed at Cuddapah to 34.7oC observed at Arogyavaram and the mean minimum daily temperature varies from 20°C observed at Nellore to 15.3°C observed at Arogyavaram. In general, humidity is high during the monsoon period and moderate during non-monsoon period. The relative humidity in the catchment of Pennar basin ranges from 21 to 84 percent. The Somasila project on Pennar river is identified as the balancing reservoir in the proposed link system for diversion of water from Pennar to Cauvery. (iv) Cauvery basin The Cauvery river rises in the Western Ghats in Kodagu district of Karnataka at an altitude of about 1341 m above mean sea level and flows through the States of Kerala, Karnataka, Tamil Nadu and the Union Territory of Puducherry. The total length of the river from the source to its outfall in Bay of Bengal is about 800 km of which 320 km is in Karnataka, 416 km in Tamil Nadu and 64 km in the common boundaries between Karnataka and Tamil Nadu. The basin extends over an area of 81155 km2 in the States of Karnataka, Kerala, Tamil Nadu and Puducherry (UT). The principal tributaries of the 129 Chapter 5: Hydrology and Water Assessment Cauvery are Lakshmanthirtha, Hemavathi, Harangi, Shimsha, Kabini, Arkavati, Suvarnavathi, Palar, Bhavani, Amaravathi, Noyil and Ponnanaiar. The Cauvery basin experiences tropical climate. Here, the main climatic feature is the monsoon rain. The north-east monsoon provides the greater portion of the annual precipitation. The far north-western part of the drainage basin has a pre-humid climate which passes eastwards into humid, moist sub- humid, dry sub-humid and semi-arid zones. The recorded maximum and minimum temperatures are 44°C and 18°C respectively. The highest rainfall in the basin is received along the western border of the basin during the south-west monsoon. The eastern side of the basin gets most of the rain during the north-east monsoon. Depressions in the Bay of Bengal affect the basin in the monsoon, causing cyclones and widespread heavy rains. The Grand Anicut across Cauvery is identified as the terminal reservoir for the link system. The drainage areas of various basins/sub-basins concerning the project area are tabulated in Table 5.1 below. Table 5.1 Drainage areas of basins/sub-basins concerning the project area Sl.