Expert systems for unit hydrograph analysis - A research report by National Institute of Hydrology

The report deals with expert systems for unit hydrograph analysis, an emerging technology, which may in years to come, revolutionize professional activities in the field of surface water analysis and modeling. The literature review on the topic revealed the potential of application of expert system for unit hydrograph analysis. A prototype expert system has been developed for the selection of the most appropriate model for unit hydrograph derivation of a given catchment.

The system has been developed on an experimental basis and its domain is limited to seven models for gauged catchments and two models for ungauged catchments. The system first identifies the most appropriate unit hydrograph model for the given catchment depending upon the availability of data, importance of the project and location of the catchment.

The system then guides the user to prepare the input data for the selected model and then runs it to derive the unit hydrograph for the given catchment. The expert system has been implemented through an expert system development shell, EXSYS and runs on personal computers.

The present work involved the following:

• Extensive literature survey was carried on expert systems in surface water analysis and modeling
• Based upon literature review and experience of some experts in this field, rules have been formulated for the selection of most appropriate unit hydrograph derivation model.
• The knowledge about the domain has been divided into modules, one for gauged catchments and the other for ungauged catchments.
• In module 1, model selection for gauged catchments is done. The models incorporated in this module are conventional method (with and without baseflow options), Collin’s method, conventional Nash model, integer Nash model and Clark model. Depending upon the user’s response about availability for the catchment and importance of project, the system selects the most suitable model, guides the user for preparation of an input data file and with the prepared input data file, runs the selected model to derive the unit hydrograph.
• In module 2, model selection for ungauged catchments is done. In this module, the Synder’s method and the regional relationships developed by the CWC have been incorporated. Depending upon the user’s response regarding location of the catchment, the system picks up the regional relationships of that particular region and derives the unit hydrograph.
• The knowledge base has been implemented through the expert system shell, EXSYS and is in the form of production rules and there are some FORTRAN programs in each module. The interfacing between the rules and the FORTRAN programs has been done through the shell, EXSYS.
• The expert system has been provided with knowledge acquisition facility through the shell. This facility would help in updating the knowledge base periodically as one gains experience with practical problems and proven solutions.

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