To achieve an accurate result for water utilisation rate based on landuse/ land cover, LISS IV image was classified according to level I classification. Based on this, the built-up area (urban), barren rocky /stony waste, crop land and fallow land have been classified. Adoption of higher level of precision water management strategies are needed for these areas. The western portion of Kongu Uplands is covered by forests. This is followed by built-up (rural), scrubland and salt affected lands that have moderate water utilisation level and gullies (ravenous land, sandy area) are categorised as low water utilisation areas.

Figure 2

Therefore, these areas have relatively low priority for adopting soil related water management practices. The built-up area exploits maximum amount of water than any other landuse and hence, there should be a high apprehension on the water resources in these areas. The crop land distributed in Central Tamil Nadu needs to adopt intensive water management practices.

Cropping intensity depicts the feasibility of land for cultivation more than once in a year.The blocks which have high cropping intensity are areas that depend on multiple sources of irrigation methods such as wells, canals, tanks etc. Hence, the water quality assessment and its management are very essential in those areas of exploitations. The blocks of Perundurai, Periyanaickanpalayam, Sulthanpet, Thanthoni, Pollachi North, Pongalur, Puduchatram and Taramangalam have high cropping intensity in the study area. Majority of the blocks in the Upland region have low cropping intensity where the utilisation of water is less. Hence, crops with minimum water requirement are recommended to be cultivated in these regions.

Figure 3

As the population increases the need of water demand also increases and thereby it affects the overall quality and quantity of water resources. The water may be used for several purposes like domestic, agricultural and industrial and thereby increases the pressure on water resources. The density of population is very high in the blocks of Omalur, Salem, Tiruppur and Erode which needs very high management of water due to its high consumption.

Figure 4

Rainfall is one of the most important factors which determine the water availability of a region. In general, rainfall deficient areas have direct relation with groundwater level. Hence areas with low rainfall should be given higher priority for suitable management strategies. Generally, central and southern portion Kongu Uplands receives less amount of rainfall.

Figure 5

The highest rainfall receiving area include Yercaud (1745.55 mm) followed by Avanashi and Topslip. The blocks with moderate rainfall are Ayodhyapattanam, Danispet, Dindigul, Erode, Gobichettipalayam, Mackinaykampatti and Negamam which records between 900mm and 1200mm. Krishnapuram in Karur district, Tholampalayam, and Pallipalayam in Erode have low rainfall. The adoption of dry land farming which is the cultivation of crops which require less amount of water are suggested for arid regions.

The delineation of groundwater potential zones gives an idea about the overall quantity of groundwater the Kongu Uplands. The low potential zones need adequate conservation of quality and quantity by bringing appropriate management measures such as construction of recharge pits, artificial recharge structures and rainwater harvesting measures. The following area needs immediate attention where low groundwater potential area found on central and southern portion of Kongu Uplands especially blocks such as Udumalapettai, Dindigul, Palani, Sanarpatti, Vadamadurai, Ottanachathiram, Thoppampatti, Guziliamparai, Dharapuram, Sulthanpet, Karamadai, Periyanickanpalayam, Elaichipalayam, Salem and Anthiyur.

Figure 6

The water level is determined by the depth at which the water table is located. The depth of water table in terms of shallow or deep is determined by the underlying formation i.e. confined or unconfined aquifer. Besides geology, rainfall, topography, landuse and land cover, evapotranspiration rate also controls the ground water level in a particular region. In general, Kongu Uplands have moderately deep water level of about 15 to 20 mbgl. Over utilisation of groundwater result in water level fluctuation or fall in level of water table. In addition to this, areas where there is over extraction of water have high possibility of salt water intrusion from the adjacent region. A fall in water level is observed in the controls wells located in the blocks like Pollachi, Dindigul, Coimbatore South, Aravakurichi, Sulur, Karur, Kadavur, Krishnarayapuram, Erode, Tiruchengode and Mettupalayam. This indicates water utilisation is high in these area hence more management measures to be implemented to maintain the quantity and quality of groundwater.

Figure 7

The above mentioned parameters have been assigned weight and rank through weighted overlay analysis and classified the Uplands into Priority Classes I, II, III, and IV based on the water utilisation. The output of the analysis shows the water utilisation pattern of whole Kongu Uplands. Areas with high utilisation of water need immediate attention to properly manage and conserve it for a long period.

Figure 8

Around 2,492 sq.km of the Kongu Uplands is classified under priority class I, where the water utilisation is very high and further due to over exploitation it affects the water quality too. The geology under this area is marked with granite, pink migmatite and quartzite rocks. The areas which need high management isSultanpet Block in Coimbatore District which covers an area of 203.97 sq.km. This is followed by Sulur (185.74 sq.km), Pongalur (161.26 sq.km), Udumalapet (142.2 sq.km) and Periyanaickanpalayam (114.64 sq.km). Besides this Thanthoni, Pollachi North, Karamadai, Reddiarchattiram, Kodumudi, Palani, Salem, Krishnarayapuram, Sanarpatti, Perundurai, Vadamadurai, Senthamangalam, Tiruppur, Puduchatram, Pallipalayam and Namakkal needs more management as the water utilisation rate is very high. The dominant LU/LC is fallow land, crop land, built up area and barren lands. The fallow land covers an area of 4,980 sq.km. This area considered as fallow land need to be efficiently managed in terms of its quality otherwise which may expand to nearby regions. The crop land distribution of the Upland region covers an area of 11,335.8 sq.km. The crop land needs more water, so the water utilisation is high here and leads to deterioration of water quality. Built-up areas (urban) utilises more water as population is very high and most of the people depends on groundwater as the only source for drinking and other purposes. There is a close relationship between cropping intensity and water level. The area where cropping intensity is high consumes more water and hence there is a fall in water level. The study on Kongu Uplands also reveals that areas where rainfall is scarce and cropping intensity is high depends on other irrigation sources mainly underground water. This dependence on other irrigation sources increases the groundwater extraction further results in groundwater depletion and leads to unavailability of water. These areas require immediate attention and hence falls under Priority class I in terms of adoption of management practices to slow down the runoff rate and maintain the water level by construction of recharge structures like check dams, storage bunds etc.

Almost 10,792.83 sq.km i.e. 42 percentage of the geographical area of Kongu Uplands is classified under Priority class II. This area also needs management for the problems occurred in this region. The geology of the area is marked up with ultramafic, pyroxene granulite, gneiss, gabbro, laterite and dunite. Boulders and valley fill were also dominant in this region. The main LU/LC of this region is scrub, salt affected land, industrial and built-up area (rural) which utilises more water. In this category the areas needs more management is Anthiyur in Dindigul District which covers an area of 520.39 sq.km followed by Karur Paramathi (400 sq.km), Guziliamparai (332 sq.km), Palani (292 sq.km), Thanthoni (262 sq.km), Kinathukadavu (260 sq.km), Palladam (258 sq.km), Ottanachathiram (236sq.km), Krishnarayapuram (229sq.km), Reddiarchattiram (225sq.km), Sanarpatti (220 sq.km) andKaramadai (218 sq.km). Since water utilisation is high in these blocks, these area falls under Priority Class II.

Thoppampatti (420 sq.km), Avinashi (306 sq.km), Karamadai (289 sq.km) and Udumalapet (279 sq.km)are the blocks that comes under this category. These areas are categorised as Priority Class III, since the water utilisation pattern is moderate in these blocks. The geology of this area is marked with charnockites and hornblende biotite gneiss. The major landuse type of this region is clad area and gullied/ravenous land. Small stretches of sandy area is also seen along the industrial areas.

This class generally covers the blocks of Kadayampatti (81 sq.km), Kolathur (176 sq.km), Thoockanaickenpalayam (96 sq.km), Aravakurichi (278 sq.km), Mulanur (227.78 sq.km), Dharapuram (196 sq.km) and Kundadam (272 sq.km), Anthiyur (452 sq.km), Thoppampatti (420 sq.km), Udumalapet (279 sq.km), Madukkarai (220 sq.km).Approximately, 2,650 sq.km falls under this category which 10% of the Kongu Uplands.