Central Ground Water Board  North Central Chhattisgarh Region  Raipur
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Chhattisgarh is a newly created state, which was carved out of Madhya Pradesh in November 2000. The state is located between the North latitudes 17o 52’ and 240 00’ & East longitudes 780 58’ and 840 28’. The state has been divided into 16 districts and 146 blocks.It is spread over a total area of 136030 sq.km.

Physiographically the state can be divided into 3 distinct zones:

• Bastar Plateau This region covering the districts of Kanker, Bastar and Dantewara is mostly covered by forests. The average elevation is in between 700 and 800 m amsl.

• Chhattisgarh Plains Spread over the central part of the state, the Chhattisgarh plains has an average elevation of 400m amsl. The western fringe area is distinguished by high mounds or hillocks of average elevation of 700 m amsl which forms part of the Maikhal Hill Ranges

• Northern Hill Region It covers parts of Surguja, Koriya, Korba, Bilaspur, Jashpur and Raigarh Districts. It forms part of Sonpar hill ranges and Ramgarh hills of Central India. The main rivers flowing in the state are Mahanadi and its tributaries like Seonath, Hasdeo, Mand, Arpa etc, which drain the central part of the state. The river Indravati, a tributary of Godavari drains the southern part. Tributaries of the Ganges like Son, Gopad, Rihand etc. drain the northern part and river Sankh, a tributary of the river Bramhani drain a small portion along the northeastern part of the state.

Based on the drainage the state can be divided into five basins/ subbasins

• Ganga Basin The northern part forms a part of the Ganga Basin and is designated as lower Ganges sub-basin. This covers parts of Koriya, Surguja and Jashpur districts

• Mahanadi Basin The Central part forms part of the Mahanadi Basin covering parts of Raigarh, Surguja, Jashpur, Durg,Rajnandgaon, Kawardha, Bilaspur, Raipur, Mahasamund, Dhamtari etc.

• Godavari Basin The southern part forms part of the Godavari Basin and the main river draining the area is Indravati.Parts of Kanker, Bastar and Dantewara districts fall within Godavari basin.

• Narmada Basin A narrow strip of area in the western part of Rajnandgaon forms part of Narmada Basin.

• Sankh sub-basin A small portion along the north eastern part of Jashpur district is drained by Sankh river, which is a tributary to the Brahmani river and this part is designated as Sankh sub- basin. The state has a sub-tropical humid climate and experiences rainfall caused by SW Monsoon. The monsoon period lasts from mid June to mid September. Normal annual rainfall (IMD) in the districts varies from 1112 mm in Rajnandgaon to 1487 mm in Jashpurnagar. Normal non-monsoon rainfall in the districts varies from a minimum of 117mm in Bilaspur to a maximum of 210mm in Bastar district. On an average, normal non-monsoon rainfall accounts for 11.5% of the total normal annual rainfall.

The area is underlain by diverse rock types of different geological ages from Pre-Cambrian to Recent.Each unit has its particular hydrological characteristics (Mishra and Mohapatra, 2002), which control ground water occurrences, movement and availability.Map showing the generalised geology of the state is give below followed by the stratigraphic succession (modified after Das et al,1992)

The Archaean crystallines comprising granites, gneisses and charnockites form the major litho units of the state. They form discontinuous, unconfined and semi-confined to confined aquifers. All the districts are covered partly or wholly with these crystalline formations. Weathered mantle and fractures form the main repository of ground water in these rock formations.

Next major litho units in the area are the Proterozoic, arenaceous, argillaceous and calcareous rocks of Chhattisgarh, Indravati, Nawagarh and Sukma Groups. Ground water potential zone is restricted to weathered mantle, caverns, fracture and formation contacts. The karstified -calcareous rocks are more productive than compact –sillicfied arenaceous rocks. The gypsiferous Maniari shales are highly porous and form potential aquifers. The karstification in the Indravati basin is more intense and has high ground water potential. These rocks are seen in all districts except Koriya, Surguja and Jashpur.

Rocks belonging to Gondwana Super Group consisting of Sandstone, Shale with or without coal are the third major litho unit of this state. The sandstones have primary and occasional secondary porosity. They form potential and extensive unconfined to confined aquifers down to 450 mbgl. Free flowing artesian conditions are reported from localized pockets.Ground water with temperatures up to 50° Centigrade has been recorded from Tamnar of Raigarh districts. These formations are seen in Korba, Koriya, Surguja and Raigarh district. The unconsolidated formation of Quaternary age comprising alluvium, clay, silt, laterite etc. form thin and extensive unconfined aquifers in several isolated patches and near major river courses with thickness up to 30 mbgl.

By and large, ground water is potable and also meets the quality requirement for irrigation. Ground water is moderately alkaline to near natural in nature. The pH ranges from 6.5 to 8.5. The electrical conductivity is below 1000m S/cm in 90 percent of the wells, which is indicative of fresh water.

In a few places such as northern part of Durg, part of Bilaspur and Raigarh districts ground water is high in sulphate content. Excess amount of arsenic (>0.05 ppm) in ground water has also been reported from Kaudikasa village of Rajnandgaon district. Excess fluoride has been reported from Bhopalpatnam area of Bastar district. Similarly excess amount of iron (>0.3 ppm) in ground water has been encountered in parts of Bastar district. Occasional high TDS values have been recorded in ground water in parts of Raigarh and Bilaspur districts.