Interactive web based watershed modeling using Java and GIS

Abstract

Web based hydrologic modeling is a relatively new concept. Very few efforts have been made in this field. So far only a few models like EPIC and SWAT have been put on the web. A Java based interface has been created for both the models. The actual models sit on the webserver and all the parameters are passed to the model using scripts written in CGI and Perl scripting languages, which makes running the models a time consuming process. In this research, a physically based, spatially distributed surface hydrologic modeling environment was developed purely in Java. It is not an interface to some other model. Use has been made of Java RMI (Remote Method Invocation) to access the web-server for writing output files. The way this model operates is that numerous remote clients can access the model residing on the server at the same time. The modeling modules consist of relationships that predict overland flow and channel flow, and other processes of the hydrologic cycle. The ArcView GIS was used to pre-process the input data in the form of DEM and land use grids. To enhance, the use of the hydrologic modeling environment, a graphical user interface (GUI) was constructed by adopting standard paradigm involving windows, icons, menus, and pointers. This GUI, together with the extensive help files, significantly enhanced user navigation of the modeling environment. To test the capability of the modeling environment, the overland flow and channel flow characteristics of Squaw Creek, a predominately agricultural watershed in Iowa was investigated as an example application. This being one of the few attempts at web based distributed hydrologic modeling; a lot of simplifications for routing were carried out in order to develop a basic working model. Various factors like the storage, infiltration and Evapo-transpiration were not accounted for. The runoff from the watershed was calculated using the SCS method for abstractions. A unique aspect of this research was the visualization of the watershed using a virtual watershed. The user can go in, navigate the watershed and actually see the channels and the changes in elevations. At a later stage interaction can be developed between the watershed and the model. This model has not been validated and hypothetical precipitation data has been used for the example application. Extensive model validation tests need to be carried out to ensure the reliability of the model.