A Spreadsheet Approach for Prediction of Rating Curve Parameters

Streamflow data is required for planning and design of various hydraulic structures and water resource projects such as bridges, culverts, flood plain zoning, flood protection works, flood warning systems, and assessment of water resources potential. A reliable and continuous record of streamflow data is, therefore, of utmost importance. However, it is very difficult to maintain a continuous record of discharge and sometimes even impractical during floods. A continuous record of elevation of water surface in a stream above some arbitrary datum or the stage of river is rather easy and accurate as compared to discharge. A functional relationship between stage and discharge at a site in a river is called the rating curve. The accuracy of discharge estimated from the rating curve depends on the accuracy of stage measurement and development of the rating curve. The conventional method of regression analysis for the development of the rating curve often fails to give stage-discharge relationship accurately. In the present study, a simple and quick Excel solver technique has been used for the development of the rating curve accurately. The results of the solver in Excel are compared with conventional method of regression analysis. The statistical parameters such as root mean square error, correlation coefficient, and Nash criteria were computed for assessment of the performance of these methods for the rating curve development. It has been found that the performance of the Excel solver is better than that of the conventional method.