Harshal M Galgale, Mukund G Shinde
Research Scholar, Water, Engineering and Development Centre (WEDC),
Loughborough University, LE11 3TU, UK
Ian Smout
Director, Water, Engineering and Development Centre (WEDC)
Loughborough University, LE11 3TU, UK
Abstract
Morphological characteristics like stream order, drainage density, aerial extent, watershed length and width, channel length, channel slope and relief aspects of watershed are important in understanding the hydrology of the watershed. Runoff response of the watershed is different for different slopes, shapes, lengths, widths and areas of watershed. Response is also affected by the factors like drainage density, length of overland flow, stream frequency, relative relief and relief ratios. Computation of watershed morphological characteristics is prerequisite to further detailed hydrological analysis of the watershed. Hydrologists have attempted to relate the hydrologic response of watersheds to watershed morphologic characteristics. Presently these characteristics are determined manually from the topographic and stream network map of the watershed. Manual computation in order to generate these characteristics is not only tedious and error prone but also time consuming. Computers can be used to compute these characteristics with greater efficiency and accuracy.
Technologies like Geographic Information systems (GIS), have gained significant importance over the last decade in their applications pertaining to distributed hydrologic modelling. GIS is suitable for analysis of spatially referenced data. GIS can handle both spatial and aspatial data effectively and efficiently. Nowadays GIS is widely used for resources planning in watershed. GIS can be used for the computation of these morphological characteristics of the watershed. Using the presently available GIS one has to go through tedious steps for generating these characteristics. Moreover the user must be fully acquainted with both the type of GIS being used for the generation of the morphologic characteristics as well as the morphologic characteristics of interest. Thus a suitable model should be developed with the help of GIS to generate these watershed morphologic characteristics.
The paper describes one such model developed with Arc/Info GIS to compute the important morphological characteristics of the watershed. It is window based, user friendly and can be used by the non-specialist for determining the morphological characteristics of the watershed. Important watershed characteristics included in the model are: area of watershed, perimeter, elongation ratio, circulatory ratio, form factor, stream order, drainage density, average slope of watershed, main stream channel slope etc. The model uses watershed boundary map, drainage network map and contour map for computation of the morphological characteristics. The paper includes an example application of the watershed where these characteristics are computed with the developed GIS model. The paper also describes in brief the significance of these morphological characteristics in the hydrological analysis of the watershed.
