Abstract
Water resource is required for agricultural, industrial, and domestic activities and for environmental preservation. However, with the increase in population and growth of urbanization, industrialization, and commercial activities, planning and management of water resources have become a challenging task to meet various water demands globally. Information and data on streamflow hydrology are, thus, crucial for this purpose. However, availability of measured flow data in many cases is either inadequate or not available at all. When there is no gauging station available at the site of interest, various empirical methods are generally used to estimate the flow there and the best estimation is chosen. This study is focused on the estimation of monthly average flows by such methods popular in Nepal and assessment of how they compare with the results of hydrological simulation. Performance evaluation of those methods was made with a newly introduced index, Global Performance Index (GPI) utilizing six commonly used goodness-of-fit parameters viz. coefficient of determination, mean absolute error, root mean square error, percentage of volume bias, Nash Sutcliff Efficiency and Kling-Gupta Efficiency. This study showed that hydrological modeling is the best among the considered methods of flow estimation for ungauged catchments.
Highlights
IntroductionRazavi and Coulibaly [6] reviewed regional methods and highlighted that those methods making use of different combinations of physiographic information and meteorological attributes, among others, were found to predict streamflows in ungagged basins/sites better
This study showed that hydrological modeling is the best among the considered methods of flow estimation for ungauged catchments
The Digital Elevation Model (DEM) and soil map were downloaded from Shuttle Radar Topography Mission (SRTM) and SOTER soil map site respectively while Land Use and Land Cover (LULC) Map was obtained from International Center for Integrated Mountain Development (ICIMOD), Nepal, Department of Water Resources and Irrigation (DoWRI) and district soil map of Nepal Agriculture Research Council (NARC)
Summary
Razavi and Coulibaly [6] reviewed regional methods and highlighted that those methods making use of different combinations of physiographic information and meteorological attributes, among others, were found to predict streamflows in ungagged basins/sites better They listed catchment area, elevation, slope of basin, rainfall and temperature as the main parameters used in those methods. Another popular method is transposition of gauged streamflow data to ungauged sites. SWAT (Soil and Water Assessment Tool), a public domain hydrological model and capable for hydrological modeling in Nepalese catchments [23] [26] [27] [33] was used to estimate the flow at ungauged sites in this study and compared with other commonly used methods viz.WECS/DHM1990, NEA1997, DHM2004, DAR and its variant GT methods. It was found that hydrological simulation ranked the best among the considered methods
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