Web services are computer applications that interact with and exchange information with other applications over the internet. The CUAHSI web services, named WaterOneFlow, have been developed to be a standard mechanism for flow of hydrologic data between hydrologic data servers (databases) and users. Web services streamline the often time consuming tasks of extracting data from a data source, transforming it into a usable format and loading it in to an analysis environment. The figure (right) illustrates the service oriented architecture that underlies CUAHSI web services. WaterOneFlow web services are designed to access information from:

1. third party servers for national databases, such as the USGS National Streamflow Information Program and National Climate Data Center (NCDC);
2. Observatory servers holding data from hydrologic or environmental observatories;
3. CUAHSI Servers holding general collections of CUAHSI data.

Information is served to users via:

1. The Hydrologic Data Access System (HDAS) Website Portal and Map Viewer accessed in the conventional way using an internet browser;
2. Web services that make the capability of the CUAHSI HIS available from within the analysis or applications programming environment of a user's choice, thus minimizing the additional learning required for a user to access web services. Web services provide cross platform capability for users with varying levels of programming sophistication.

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