Identifying the Favourable Potential Zones in Over Exploited Block Of

IDENTIFICATION OF FAVORABLE POTENTIAL ZONES IN OVER EXPLOITED BLOCK OF THALAIVASAL IN SALEM DISTRICT - VELLAAR BASIN BY USING REMOTE SENSING AND GIS TECHNIQUES

EXECUTIVE SUMMARY In Tamil Nadu there are 385 blocks; of these138 have been declared as over exploited blocks by Central Ground Water Board and State Ground & Surface Water Resources Data Centre, based on the stage of groundwater extraction when it is more than 100% and a significant long term declining trend of groundwater during premonsoon and post monsoon periods. Thalaivasal block of Salem district is one among these 138 blocks which has been assessed as over exploited where the groundwater extraction is more than 100% as per Groundwater Estimation Committee (GEC) – latest norms assessment as on January 2003, vide G.O.Ms.51/PW(R2) Dept. dated 11.02.2004. This causes great concern for the farming communities and they are unable to avail financial assistance from the banks for their agriculture purpose. This assessment has been made on macro level basis where block area is considered as a unit.

But during the course of field investigation it is found that some pockets of villages in this block are favourable where the irrigation wells are sustainable for pumping and further development of groundwater is feasible even though it is estimated as an over exploited block.

In view of this, a project study titled “Identification of favourable potential zones in the over exploited block of Thalaivasal in Salem district-Vellar basin by using Remote Sensing & GIS techniques” was undertaken for reassessing the groundwater potential qualitatively. This project is funded by Tamil Nadu State Land Use Board, State Planning Commission. Vide G.O.Ms. No.96/ Planning Development and special (CSS) dept. dated 01.09.03. An amount of Rs.6.8 lakhs have been sanctioned to conduct the above project study under the new studies.

THE MAIN OBJECTIVES OF THE PROJECT STUDY AREA

Identification of favourable potential areas for further groundwater development using Remote Sensing data with limited field checks in the Thalaivasal block.

Identification of wastelands and suggesting remedial measures for converting them into productive lands.

Identification of the areas affected by salinity and alkalinity.

Identification of suitable areas for construction of artificial recharge structures to improve the ground water potential.

Suggestions for selection of tanks for desilting and modernisaion by using Remote sensing and GIS techniques.

Proper guidance to farmers in construction of suitable groundwater structures (open dug wells, bore wells).

Detection of changes in landuse pattern.

Managing of different methods for optimum utilization of groundwater.

Methodology adopted Generating a Digital Elevation Model (DEM) in order to overlay other thematic maps on DEM by GIS analysis and obtain better results.

Preparation of a satellite image mosaic map by using LISS III and PAN merged data.

Collection of rainfall data for the rainguage stations Virahanur, Kallakurichi and Athur and statistical analysis made for these rainguage stations to ascertain the rainfall for 50% and 75% dependability.

Generation of thematic maps on geology, geomorphology, soil, drainage, fault/lineament zones, rainfall, water level and water quality for pre monsoon and post monsoon periods by using remote sensing and GIS techniques.

2 Groundwater level, rainfall, water quality, geophysical resistivity survey data and soil information were collected for analysis and inference.

Different geomorphic units such as valleyfill, buried pediment moderate, buried pediment shallow, pediment, hills etc., were interpreted using remote sensing techniques and confirmed these units with limited field check.

Geophysical electrical earth resistivity survey was conducted in 97 selected locations including lineament and its intersection points. Topsoil, weathered zone, fractured and jointed zone, depth to bedrock, intensity of lineaments were inferred and correlated with hydrogeological condition.

Intensive fieldwork was carried out, to ascertain the geological, geomorphological features and hydrogeological conditions through inventory of wells in the field.

Water quality theme maps were generated for total dissolved solids, chloride and total hardness of groundwater, based on the geochemical results of water samples collected from the shallow observation wells (dugwells) located in the block.

Tanks located in favourable geomorphological units were examined, to ascertain the need for desilting and enhancement of the storage of surface water. Artificial recharge structures were also suggested in feasible locations of villages to augment the groundwater.

To convert the wastelands into productive lands, this study recommends drilling of bore wells at the intersection points of lineaments, formation of gulley plugs and contour bunding in stony areas.

Based on the ground truth verification, grouping of wells yield with respect to the geological formations, lineaments and different geomorphic units are evolved.

The Principal objectives of the project work carried out and brief descriptions of the methods adopted in the study are presented.

Objectives Achievements 1. Identification of favourable potential 1. Based on satellite data interpretation zones in the over exploited block of hydrogeomorphological zones like Thalaivasal in Salem District – Vellar valley fill, pediments, buried basin by using Remote Sensing and pediments shallow and medium are GIS Techniques. identified. 2. Identification of wastelands and 2. Wastelands are demarcated where - suggestion of methods for converting ever it is available. The various types the wastelands into productive lands of wastelands are categorized. By demarcating lineament and fractured zones both by satellite imageries and by geophysical Vertical Electrical Soundings dug well and borewell points are recommended wherever feasible. 3. Identification of areas affected by 3. These category of lands are identified salinity and alkalinity in the northwestern part and western part of Thalaivasal block. 4. Creation of village resources 4. In the 41 villages micro level study information systems (VRIS) for was conducted in detail. In each sustainable development activities. village details on landuse, geology, geomorphology, structure, water level, water quality, soil, drainage and depth to bedrock details are described. Action plan for sustainable development for each village is furnished.