Hydrology and Water Assessment
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Chapter – 5 Hydrology and Water Assessment 5.0 General The Par-Tapi-Narmada Link Project involves Par, Auranga, Ambica and Purna river basins of South Gujarat and neighboring Maharashtra State. The Hydrological studies of this project comprising Par, Auranga, Ambica and Purna river basins with Jheri, Paikhed, Chasmandva, Chikkar, Dabdar and Kelwan dam sites were carried out by Hydrological Studies Organization, Central Water Commission, New Delhi. The hydrological studies of the Par-Tapi-Narmada link had been compiled in three volumes by Central Water Commission; Volume– I: Water availability studies; Volume– II: Design flood and diversion flood (in two parts); Volume– III: Sedimentation studies and were appended in “Volume– IV: of DPR i.e Appendices – Hydrology and Water Assessment” of the DPR of the link project prepared by NWDA in August, 2015. Brief details of the studies werealso furnished in “Volume-I: Main Report”of the DPR (August-2015) under Chapter-5 - Hydrology and Water Assessment. Since the link canal demands and diversion of surplus yields available for diversion at the above proposed reservoirs are unchanged, no separate Hydrological and Water Assessment studies have been carried out. Brief details of the studies are furnished below. 5.1 General Climate and Hydrology The climate of the Par-Tapi-Narmada link project area is moderate except during the months of April and May. Summer is hot and winter is generally cold. The year may be divided into four seasons, the cold season from Dec to Feb followed by the hot season from March to May and the south-west monsoon season from June to Sept followed by the post- monsoon season from Oct to Nov. As per the Hydrological studies, the Par river at proposed Jheri dam site; Nar river (tributary of Par river) at proposed Paikhed dam site; Tan river (Tributary of Auranga river) at proposed Chasmandva dam; Ambica river at proposed Chikkar dam site; Khapri river (tributary of Ambica river) 147 at proposed Dabdar dam site; and Purna river at proposed Kelwan dam site have been found water surplus at 75% dependability. As such after meeting in-basin requirements (by 2050 AD) of all the above four river basins up to the proposed dam sites and downstream commitments / requirements, surplus water of 1210 MCM has been proposed for diversion to utilize en- route of link canal in the tribal areas lying rightside of link canal,periphery of proposed reservoirs, tribal areas lying right side of Narmada Main Canal (in Chhota Udepur and Panchamahals Districts) by lift;to takeover the command areas of the projects viz., i) Khuntali, ii) Ugta, iii) Sidhumber, iv) Khata Amba and v) Zankhari proposed by Government of Gujarat to supply drinking water to all villages of Dangs District and villages of Kaprada and Dharampur talukas of Valsad District; to fill all possible tanks in the benefitted areas and in water short Saurashtra region of Gujarat by Substitution. The Par-Tapi-Narmada link will also take over the part command area of existing Miyagam Branch Canal of Narmada Canal System and the Narmada waters so saved in Sardar Sarovar dam will be utilized in Chhota Udepur and Panchamahal Districts and Saurashtra region for providing irrigation facilities and drinking water by substitution. The schematic Diagram of the Par-Tapi-NarmLink Project is at Fig. 5.1. 148 5.2 General Information about Regions The Par-Tapi-Narmada link involves Par, Auranga, Ambica and Purna river basins of South Gujarat and neighboring Maharashtra. All these four river basins have the same hydro meteorological characteristics. Most of the 149 rainfall is received during the South-West monsoon period, from June to Sept. The average annual rainfall in the Par, Auranga, Ambica and Purna river basins is 2180 mm, 2055 mm, 1830 mm and 1472 mm respectively. Two meteorological observatories at Surat and Vadodara maintained by India Meteorological Department (IMD) located adjacent to the project area have been used to characterize the climatic conditions of the project area. The average maximum and minimum temperatures recorded are 39.9 °C and 13.2 °C respectively. The monthly mean relative humidity data of the project area indicates the maximum and minimum values of humidity as 94% (August) and 44% (April) during monsoon and summer seasons respectively. The maximum and minimum wind velocities observed are 13.3 km/hr and 2.2 km/hr respectively. The maximum cloud cover is observed during the months of July and August whereas the minimum cloud cover is observed during months of Jan and Feb. There is no pan-evapometer installed in the project area. The mean monthly average evapotranspiration computed for Surat IMD observatory varies from 99.2 (Dec) to 202.0 mm (May), whereas the same at Vadodara IMD observatory varies from 92.9 mm (Dec) to 246.4 mm (May). 5.3 Specific Information 5.3.1 Drainage Basins a) Par Basin The Par River is one of the important west flowing rivers in the region, north of Mumbai and south of the Tapi river. The river originates from the Sahyadri hill ranges near village Gogul of Surgana taluka in Nasik district of Maharashtra at an elevation of about 1100 m above mean sea level. The total length of the river from its origin to its outfall into Arabian Sea is 131 km. The river basin lies between 20°16' – 20°35' N latitudes and 72°54' – 73°44' E longitudes. The total catchment area of the river is 1664 km2, out of which 773 km2 lies in Nasik district of Maharashtra and the remaining 891 km2 in Valsad district of Gujarat. It is bounded by western Ghat ridge separating west flowing rivers and Godavari in east, the ridge separating Kolak and Damanganga rivers in south, Arabian Sea in west and the ridge separating Par and Auranga rivers on north. The important tributaries of Par river are Aroti, Nar, Bhimtas, Vajri and Keng. 150 b) Auranga Basin The Auranga is another important west flowing rivers in the South Gujarat region. The river is known as Auranga after the confluence of its two tributaries the Man and the Tan. Both tributaries originate in the Sahyadri hill ranges in the Nasik district of Maharashtra. The river traverses a distance of about 30 km from confluence of the tributaries before draining into the Arabian Sea. The Auranga river basin lies between 20° 30' to 20° 42' N latitudes, and 72°53' to 73°37' E longitudes. The Auranga basin extends over an area of 787 km2, out of which 150 km2 is in Maharashtra State and 637 km2 is in Gujarat. The effective drainage area of the basin in Gujarat State is 598 km2 since 39 km2 area near the mouth is low-lying, marshy and cannot be beneficially utilized. The basin is bounded by ridge separating Auranga and Par rivers in south and east, Arabian Sea in west and the ridge separating Auranga and Ambica rivers in north. Important tributaries of Auranga River are Man and Tan. c) Ambica Basin The Ambica River is also a west flowing river of South Gujarat region located north of Auranga basin. The catchment area of Ambica basin is lying in Gujarat and Maharashtra. The Ambica River originates in the Sahyadri hill ranges near village Kotambi of Surgana taluka in Nasik district of Maharashtra at an elevation of about 1050 m above mean sea level. The total length of the river from its origin to its outfall into Arabian Sea is 164 km. The river basin lies between 20°31' – 20°57' N latitudes and 72°48' – 73°52' E longitudes. The total catchment area of the basin is 2830 km2, of which 102 km2 lies in Maharashtra and the remaining 2728 km2 in Gujarat. The catchment area of the basin in Gujarat is 2583 km2, since 145 km2 area near mouth is low lying, marshy and cannot be beneficially utilized. Ambica basin is bounded by Western Ghats separating Ambica and Tapi rivers in east, the ridge separating Auranga and Par rivers in south, Arabian Sea in west and the ridge separating Ambica and Purna rivers on north. Important tributaries of Ambica River are Khapri, Olan, Kaveri and Kharera. d) Purna Basin The river Purna, a west flowing river, rises in the Sahyadri hill ranges of the Western Ghats at an elevation of about 1300 m in the Ahwa taluka of 151 Dangs district in Gujarat and after traversing a distance of 180 km, it outfalls into the Arabian sea. The level of the river bed drops steeply from 1300 m at source to about 115 m at the dam site as the river in this reach passes through hilly area covered with dense forest and patches of cultivated land. The Purna basin lies between 20°44' – 21°06' N latitudes and 72°44' – 73°58' E longitudes. The total drainage area of the basin is 2435 km2, out of which 58 km2 lies in Maharashtra and 2377 km2 lies in Gujarat. The effective drainage area of the river is 2193 km2 since 242 km2 near the mouth is low-lying and cannot be beneficially utilized. The Purna basin is bounded by Western Ghats separating Purna and Tapi rivers in east, the ridge separating Purna and Ambica rivers in south, Arabian sea in west and the ridge separating Purna and Mindhola on north. Important tributaries are Girra river, Zankhari river and Damas khadi. 5.3.2 Command Area as per the Revised Irrigation Planning As per the revised planning Par-Tapi-Narmada link project will provide irrigation to 59920 ha new areas in the en-route of main canal; 1270 ha new area in the en-route of Dabdar and Kelwan feeder pipelines; and take over the part command area of existing Miyagam Branch Canal of Narmada Canal System to an extent of 42368 ha.