III-3-Development of a GIS Based River Basin Bodel.

Abstract

This study is focused on the development of a GIS based river basin model WSDCM (Water Demand and Supply Calculation Model). WDSCM analyzes water demand and supply at sub-basin level and then, by system water balance, identifies the sub-basin with water deficit and water surplus. The graphical user interface (GUI) and coding of the present version of WDSCM is developed in Microsoft Visual Basic 6. The integration of GIS with WDSCM is done with the help of ESRI Map Object 2.2 to make the model more flexible and user- friendly. The model is applied in the Kangsabati basin, located between latitudes 22° and 23° N and longitudes 86°452 and 88° E of 4217.52 km2, covering Bankum, West Midnapur and East Midnapur districts of West Bengal. The various data Files required to run the model, such as soil data, land use data, groundwater data and population data were prepared at sub-level with the help of Erdas Imagine 8.5 and Arc GIS 9.1. After preparation of all the data required, the model simulations were done over two simulation periods firstly, for the water year 2002-03 (June 2002 to May 2003) and secondly for the Kharif season of the year 2003 (June 2003 to Nov 2003). It is found that for the first simulation period, out of 44 sub-basins, 32 sub-basins are under water deficit condition and the remaining 12 sub-basins are under water surplus condition. The amount of water deficit ranges from 0.24 Mm3 to 20.67 Mm3 and the amount of water surplus ranges from 1.67 Mm3 to 22.06 Mtn'. For the second simulation period out of 44 sub-basins, 41 sub-basins are under water surplus condition and the remaining 3 sub-basins are under water deficit condition. The amount of water deficit ranges from 0.01 Min' to 2.82 Mtn' and the amount of water surplus ranges from 0.63 Mm3 to 57.38 Mm3. However, the results may not be the true representation of the condition in the basin as the data related to water supply through canal were not considered due to non-availability and so was the industrial demand data. Even with this shortcoming, the developed model highlights the uneven distribution of water in the basin.