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Tuticorin district, having a total geographical area of 4649.3 sq.km, and a population of 1,565,743 as per 2002 census is a drought prone district, part of the erstwhile composite Tirunelveli district. The district’s population is predominantly rural with about 60% of the total population residing in villages. Paddy, cholam cumbu, green/red grams, cotton and pulses are the major crops grown. Dug wells are the major sources of irrigation in the district and about 28037 wells are in use with independent ayacuts. There are 14351 wells used for domestic purposes and many bore wells and power pumps exist in each habitation. The district receives low rainfall from southwest monsoon varying from 20.8 to 126.7mm and normal northeast monsoon is varying from 397.3 to 522.2mm. The normal annual rainfall (1901-2000) of the district is 661.6mm. Tuticorin district comprises parts of Vaipar, Tambraparni and Karamaniyar sub-basins. Various geomorphic units with fluvial, marine, fluvio-marine, aeolian and erosional landforms have been identified in the district. The district is underlain by geological formations ranging in age from Archaean to Recent. Charnockites, peninsular gneisses and pink granites traversed by quartz veins and pegmatites underlie the major part of the district. Tertiary and Quaternary formations are exposed in the coastal part of the district. A few lineaments have been identified from LANDSAT imagery, the most prominent ones of which are those oriented in NW-SE to NNW-SSE. The thickness of weathering ranges from less than a metre to about 10 m. Central Ground Water Board has constructed 16 Exploratory wells and five observation wells in hard rocks and 4 exploratory wells and one observation well in sedimentary rocks as part of its ground water exploration programme. Also, five exploratory wells varying in depth from 25 to 70m were drilled under brine water studies. In the sediments, the granular zones in the depth range of 18 to 65 mbgl yielded 2.5 to 6.8 lps. The depth of wells drilled in crystalline rocks ranged from 26 to 200 mbgl. Potential fracture zones were encountered in the depth range of 14 to 193 mbgl. The yield of wells ranged from < 1 lps to 16.44 lps. Highly concentrated brine water of 7 to 13.5°Be is encountered in a small pocket near Tuticorin coast. The important aquifers in the district are constituted by (i) Fissured, fractured and weathered crystalline rocks and (ii) porous formations comprising Recent alluvial deposits and Tertiary sediments. Ground water occurs under phreatic to semi-confined conditions in these aquifers. Productive fractures have been encountered down to a maximum depth of 193.0 mbgl in the crystalline rocks. However, the number of fractures is limited to one or two in most of the exploratory sites and production well sites and yield also restricted to less than 2 lps. The absence of potential fractures in more than 80 % of hard rock area is inferred by extrapolating the yield prospects. Ground water occurrence in Teritiary sediments is generally restricted to shallow depths due to its compact nature and lack of thick granular zones. Quaternary alluvial deposits comprising alluvium and colluvium constitute prolific aquifers of limited thickness along the banks of major drainage courses and ‘Teri’ sands are also having limited saturated zones. Pre-monsoon water levels (May 2001) are in the range of 5-10 mbgl with isolated pockets of water level below 10m. and considerable area in the depth to water level range of less than 5 m. The monsoon (November 2001) levels are in the range of 2-5 m in the considerable part of the district. Analysis of water level fluctuation between May 2001 & January 2002 indicated a rise in water levels throughout the district, mostly in the range of 2-4m. The ground water in hard rock areas of the district, in general, is potable and suitable for irrigation and industrial applications except for localised areas. However, ground water in the shallow zone in the sedimentary part of the district is brackish to brine, which is not suitable for irrigation and drinking purposes. However, it is used in salt production and magnesium industries. Preliminary evaluation resources on GEC 1984 norms has indicated that the district still has balance in ground water resources which is of the order of 11432 ha.m/yr and considerable potential remains to be developed in Kayattar, Pudur, Karunkulam, Ottapidaram, Tuticorin, and Alwar Thirunagari blocks and in these blocks, poor hydrogeological conditions exist, which are not favourable for the construction of dugwells/borewells successfully. Owing to the comparatively limited productive zones, ground water development in most of the blocks is low. The wasteland development programme has to be actively implemented. In spite of shallow water levels and lack of major industries causing ground water pollution, the district is highly vulnerable to perils of water scarcity in many pockets for drinking water. A long-term surface and ground water management is needed to overcome the demand-and-supply gap of water resources in this drought-prone district. |