IS 15823 : 2009 Hydrometry - Computing Stream Flow Using an Unsteady Flow Model

1 SCOPE

This standard lays down a method for computingcontinuous records of stream flow in an open channelthrough the numerical solution of the one-dimensionalunsteady flow equations. Such an approach is typically identified as an unsteadyflow model and generally involves the use of computersfor solution of the flow equations.

The method described in this standard is applicableto steady and unsteady flows and to tidal flows inwhich there are no significant longitudinal andvertical density gradients. The method is consideredequivalent to, or better than, the commonly usedstage-fall-discharge technique [see 7.2 and Annex Cof IS 15119 (Part 1)] because the method usesinformation on the physical characteristics of thechannel, including the cross-sectional geometry,channel rugosity and channel slope, and the methodis based on a mathematical description of the physicsof fluid flow.

This standard also describes the theoretical basisand fundamental assumptions of the technique, andprovides a summary of selected numerical methodsused to solve the unsteady flow equations. Thedetails on the application of an unsteady flow model,including data requirements, procedures for modelcalibration, testing, and applications, andidentification of uncertainties associated with themethod have also been included.

This standard, however does not provide sufficientinformation for the development of a computerprogramme for solving the unsteady flow equations,but rather it is based on the assumption that anadequately documented computer programme isavailable.

2 References

The following standards contain provisions whichthrough reference in this text, constitute provisionsof this standard. At the time of publication, theeditions indicated were valid. All standards aresubject to revision and parties to agreements basedon this standard are encouraged to investigate thepossibility of applying the most recent editions ofthe standards indicated below: