Assessment of the empirical methods for the development of the synthetic unit hydrograph: a case study of a semi-arid river basin

Abstract

This study aims to assess various empirical synthetic unit hydrograph (SUH) methods and find the best method. Ideally, each river should have a definite rain gauge station (RGS) to get sufficient rainfall data that is available for carrying out meaningful analysis. The provisions of Indian Standard (IS) 4987:1994 determined the optimum number of RGS. In the absence of RGS, the SUH is recommended. SUHs have been developed using various methods such as Snyder's, Taylor and Schwarz, Soil Conservation Service, Mitchell's and Central Water Commission (CWC). In the present study, the Rel River Basin (RRB) is considered as the study area which has two existing RGS. IS 4987:1994 suggested that four RGS are required for more reliable rainfall data. Various efficiency criteria such as Correlation Coefficient, Pearson Coefficient, Nash Sutcliffe Efficiency, Index of Agreement, Normalized Root Mean Square Error, Mean Absolute Error, Root Mean Square Error and Kling-Gupta Efficiency have been used to compare SUH methods. The ranking of SUH methods was reported based on the compound factor (CF) through efficiency criteria. The 1.125 CF was observed as the minimum for the CWC method and recommended for determining peak discharge and timing for the study area. HIGHLIGHTS An optimum number of RGS has been examined at the initial level of the study.; Various empirical methods of SUH have been evaluated.; Numerous efficiency criteria have been used to compare different SUH methods.; The compound factor (as an MCDM technique) has been used to find the best SUH method, which is a new concept in SUH.;

Keywords

• compound factor
• multiple criteria decisions making
• optimum number of rain gauge stations
• synthetic unit hydrograph
• ungauged basin