Modelling the irrigation demand profile of Chalakudy river diversion scheme using CROPWAT and GIS tools

Abstract

Irrigation planning for a command area necessitates a proper assessment of irrigation water required by the crops in the area. Net irrigation water demand mainly depends on the cropping pattern and the areal extent. In a vast command area collection of accurate data on cropping pattern and their areal extent is a tedious job. Remote sensing technology and geographic information systems could be utilized effectively for easy and accurate data collection. Rainfall is another important factor in the calculation of irrigation water requirement. Effective rainfall retained in the root zone of crops reduces irrigation requirement. In the present study the average rainfall of the entire command area was calculated using the Thiessen polygon method. The land use map of CRDS command area was prepared using remote sensing and GIS tools. From the prepared land use map, areal coverage of crops in the command area was assessed for the computation of irrigation water requirement. Cultivated crops covered more than 80 per cent of the CRDS command area that comprised paddy 10.51 per cent, mixed crops 37.77 per cent, coconut-dominant mixed crop 31.83 per cent and rubber 12.80 per cent. CROPWAT 8.0 software was used for the computation of irrigation water requirement. The average annual net irrigation demand of CRDS command area was obtained as 46.90 Mm3.