There are serveral API available to access the data. The CUAHSI hydrodesktop accesses the services using SOAP API called WaterOneFlow. This returns WaterML 1.x documents. A REST endpoint that matches the .Net webservice over httpGet has been added to this version of te services. 
  • WaterOneFlow SOAP
    • Version 1.0
    • Version 1.1
  • WaterOneFlow REST
    • Version 1.0
    • Version 1.1
In the future that access will be done using OpenGeospatial Consortium Standards, and the SOS specifically. The WaterML 2 REST endpoint transforms WaterML 1.1 into WaterML 2. And SOS endpoint is in development.
  • WaterML 2
    • REST
    • version 1.1
  • SOS
    • IN Development