IDENTIFICATION OF ACTIVE INFILTRATION ZONES IN GRAND ANICUT CANAL IRRIGATED AREA IN SOUTHERN PART OF THANJAVUR DELTA USING GIS.

In order to understand the active infiltration zone in the study area, thematic layers such as soil, geology, slope, geomorphology and canal density which improve the ground water storages are considered. All the above said layers were overlaid and analysed using ArcGIS software. For each of the above parameters suitable weightage values were assigned based on their ability to store water. As soil is concerned sand, loamy sand was assigned the maximum weightage value followed by sandy loam, Sandy clay loam, clay loam and clay in the decreasing order. Areas with less than 4% slope were assigned higher weightage and progressively lower weightages were assigned to the slope classes of 4-8%, 8-12%, 12-16% and over 16%. Among the various landforms of the study area maximum weightage value was assigned for alluvial plains, flood plain, coastal plain followed by Deltaic plain, Pediment, Lateritic and hill in the decreasing order. After assigning weightage values for various classes of each of these parameters, these thematic layers were integrated and the resultant map was re-classed showing zones of infiltration progressive area. The analysis thus carried out has revealed that the areal extent of zones in the canal irrigated area with poor, moderate, good and excellent infiltration process zones are 30.99 sq.km, 1191.16 sq.km, 2325.87 sq.km and 327.50 sq.km respectively. In general, it is found that in the study area, areas with low, moderate, high and very high infiltration areas are spread towards the southern and north eastern parts, covering about 51.01 per cent and 4.89 per cent of Thanjavur and Pudukkottai District respectively.

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