Mahi

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Hydrological Observation Stations Map

The Mahi basin extends over states of Madhya Pradesh, Rajasthan and Gujarat having total area of 34,842 Sq.km with a maximum length and width of about 330 km and 250 km. It lies between 72°21’ to 75°19’ east longitudes and 21°46’ to 24°30’ north latitudes. It is bounded by Aravalli hills on the north and the north-west, by Malwa Plateau on the east, by the Vindhyas on the south and by the Gulf of Khambhat on the west. Mahi is one of the major interstate west flowing rivers of India. It originates from the northern slopes of Vindhyas at an altitude of 500 m near village Bhopawar, Sardarpur tehsil in Dhar district of Madhya Pradesh. The total length of Mahi is 583 km. The Som is its principal tributary which joins from right, and the Anas and the Panam joins the river from left. It drains into the Arabian Sea through the Gulf of Khambhat. The major part of basin is covered with agricultural land accounting to 63.63% of the total area and 4.34% of the basin is covered by water bodies. The basin spreads over 11 parliamentary constituencies (2009) comprising 6 of Gujarat, 3 of Rajasthan, and 2 of Madhya Pradesh.

The state wise distribution of the drainage area is shown in the following Table.

Initially the river flows Northwards through Dhar and Jhabua districts of M.P. and then turns left and passes through the Ratlam district of M.P., then turning to North - West, it enters the Banswara district of Rajasthan and flows in South - West directions and thereafter enters the Panchmahal district of Gujarat state. Then the river continuously flows in the same direction through Kheda district of Gujarat and finally falls into the Gulf of Khambhat in Arabian Sea.

This river receives several tributaries on both the banks, out of which the main tributaries are Som, Anas and Panam.

This is a right bank tributary of Mahi.Som river rises near Som on the Eastern slopes of the Aravalli hills in the Udaipur district of Rajasthan at an elevation of 600 m above m.s.l. and flows in the Eastern direction to join the main river Mahi on the right bank 6.3 km upstream of Paderdibadi site in Dungarpur district of Rajasthan. Its total length is about 155 km. The total drainage area of Som is 8707 sq.km. Gomti & Jakham are the major right bank sub tributaries of Som.

This is a Left bank tributary of Mahi. Anas River rises near Kalmora on the Northern slopes of Vindhyas in Jhabua district in Madhya Pradesh at an elevation of 450 m above m.s.l. and flows in the North - West direction and joins the main river Mahi on left bank in the Dungarpur district in Rajasthan. It has a total length of about 156 km and the total drainage area of 5604 sq.km.

This is a Left bank tributary of Mahi. Panam river rises near Bhadra on Northern slopes of the Vindhyas near Jhabua district in Madhya Pradesh at an elevation of about 300 m above m.s.l. and flows in the North - West direction and joins the main river on the left bank in the Panchmahal district of Gujarat. It has a total length of about 127 km and drainage area of about 2470 sq.km.

The Mahi basin experiences 3 marked seasons – summer (Mar-May), Monsoon (June-Sep) & winter (Oct-Feb). From the available data & record, the basin contains two climatic regions, the northern part of the basin comprises sub tropical wet climate (generally basin area occupied by Rajasthan). The major part of basin comprises tropical wet climate, caused mainly due to existence of Vindhyas & the Western Ghats. Due to relatively high elevation in forest land, the area of the basin near the origin of the river experiences relatively cooler & moderate rainfall climate which gradually changes to warm & dry climate as the river flows northwards entering into & flowing through Rajasthan. After the river bends south westwards and enters Gujarat the climate gradually changes towards tropical wet climate again.

TEMPERATURE IN (°C ) CWC SITES Year 2008-09

The average rainfall in the Mahi basin is 785 mm. The South - West monsoon sets in by the middle of June and withdraws by the first week of October. About 90 percent of total rainfall is received during the monsoon months of which 50 percent is received during July and August. The rainfall is mainly influenced by the southwest monsoon. The effect is most pronounced in Vadodara lying on the windward side of the Western Ghats. Ratlam also receives similar rainfall, lying between the Arravalli and hill ranges north of Western-Ghats. Monsoon contributes nearly 91-94% of annual precipitation in Vadodara & Ratlam respectively.

Mean Annual Rainfall in mm Mahi Basin CWC Sites

Average wind speed is the lowest in Udaipur & the highest in Dahod. In general, wind speed is the lowest in post monsoon period (Oct-Nov) & the highest in June. The predominant wind direction is from west in Ratlam & Dahod from Northwest in Udaipur and Southwest in Vadodara. The wind direction remains uniform from post monsoon till early winter i.e. Oct – Feb. Change of direction takes place in March/April. In Ratlam, Vadodara & Dahod the dominant wind direction is from North east and east respectively during post monsoon and in winter changes to Westerly and South westerly. In Udaipur, the post monsoon and winter wind direction is from North & North West which changes to South-westerly & westerly during the remaining part of the year.

Hydro geologically the river basin is categorised by two distinct units:

• Consolidated formation: This hydro geological unit is mainly dominated by basaltic lava flows associated with inter trappean, infratrappean and Archean rock formation represented by phyllites, gneisses, quartzite & granites. The MP, Rajasthan & North eastern parts of Gujarat are mainly underlain by consolidated rocks.

• Unconsolidated formation: Ground water occurs under water table and inconfined condition in the bed of sand, kankar & gravel that constitutes the alluvial aquifers occurred as discontinuous beds of varying thickness in hard rocks- terrain in the north & northeastern part of basin.

The valley-fills that are having good ground water potential are quite prominent and significant in the hard rock areas in the District of Jhabua, Chittorgarh, Udaipur, Banswara & Panchmahal. The southern part of the basin is occupied by quaternary, post Miocene and tertiary sediment deposited over a sinking basement between two major structurally controlled lineaments.

Jaisamund tank in Udaipur district of Rajasthan is the oldest irrigation project in the basin constructed in the pre-plan period. The important projects in the basin constructed during plan period are Mahi Bajaj Sagar, Jakham, Panam, Mahi Phase - I & II comprising of Wankbori weir and Kadana dam and Mahi (M.P.) projects.

At present Hydro Power stations are located in Mahi Bajaj Sagar dam and at Kadana Dam. The Power house located at Kadana is a pump storage scheme.

Vadodara is the only important urban centre in the basin. There are not many industries in the basin. Some of the industries are cotton textile, paper, newsprint, drugs and pharmaceuticals. Most of these industries are located at Tatlam.

Hydrological observation, in the basin are carried out by the Central and State Governments. The Central Water Commission maintains 12 gauge-discharge sites in the basin. Sediment observations are also taken at 3 of the above sites. In addition, gauge-discharge data are available at 13 sites established by the State Governments. The Central Water Commission operates two flood forecasting stations in the basin.

Mahi Bajaj Sagar is an important interstate project of Gujarat and Rajasthan. Mahi Control Board was set up by the Government of India in 1971 in consultation with the State Governments to ensure early execution of Mahi Bajaj Sagar Dam Project. The organisation is closed as the project is completed.

1. Agreement dated 10th January, 1966 between Government of Rajasthan and Gujarat regarding exploitation of Mahi river
2. Supplemental to the agreement of 1966, dated 29th August 1975
3. Supplemental to agreement of 1966 & 1975, dated 2nd September 1976
4. Supplemental to the agreement of 1966, 1975 & 1976, dated 5th April 1978