The use of reliable stage-discharge curves is one of the most important issues in the management of water resources and river engineering. Discharge measurement in natural rivers is generally difficult and accompanied by errors. The use of new models has an effective role in reducing the time and cost associated with hydrometry. The purpose of the present study is to introduce a new method to estimate discharge in open channels using a novel method that is based on the isovel technique. The significant aspect of the present method is its inherent simplicity, which does not need any calibration. Using the proposed method, it is possible to estimate the stage-discharge curve in the whole section by only using discharge information from just one arbitrary water level. Theoretical discharge can be obtained through a general relationship, which is composed of some parameters with unknown powers. According to the number of parameters as well as the geometric cross-sections, 225 different relations are extracted. The minimization process of error between the observed and estimated data is used to select the most accurate relationship. For validation, data from eight river cross-sections are used. Results indicated that the mean value of error is within 7.2%. Amongst the advantages of the proposed method is that it can be applied to all kinds of hydraulic cross-sections, even those with non-uniform bed roughness distributions.

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