CHPS - an NWS development to enter the interoperability era

The NOAA National Weather Service (NWS) is the designated federal agency to provide hydrological forecast information to the wider public. Until now, this task has been conducted using the NWS River Forecast System (NWSRFS). While the NWSRFS has served the NWS’s needs for a long time, its architecture and code base limits the NWS ability to embrace and incorporate new techniques developed in the research arena. Therefore, the NWS Office of Hydrologic Development (OHD) is modernizing the software infrastructure so it can more easily accommodate advances in hydrologic science developed in the public and private community. The Community Hydrologic Prediction System (CHPS) program has been initiated for this purpose. After several studies and assessments, DelftFEWS, developed by Deltares, was selected as the future software infrastructure for CHPS. With flow forecasting applications around the world, DelftFEWS has shown its capability to deploy a wide variety of hydrological models from multiple suppliers in a forecasting context. Nowadays, nearly 40 different numerical software models in the river, coastal and water quality domain can be deployed within DelftFEWS. Model states, parameters, run-time settings and forcings, either lumped or gridded, are exchanged with models using the so-called Published Interface (PI), a standardized set of XML-files. Model adapters typically transfer this data into native formats, but may also use Application Programming Interface (API) calls to feed the data to a model. In those cases where process interaction is needed between software models, a model composition may be deployed as one execution receiving their states, run-time settings and forcings via e.g. a FEWS-to-OpenMI adapter. Since the NWS manually interacts with its models during the forecasting process, DelftFEWS has been extended with capabilities to modify time series, model parameters and states during the forecasting process. In addition, an API is being offered to develop dedicated display functionality. CHPS is the NWS-specific application of DelftFEWS. The hydrological basis will be software models extracted from NWSRFS and wrapped in a shared OHDFewsModel adapter. Each River Forecast Centre (RFC) will have its own client-server system with an RFC-specific configuration using a live feed of observation and model forcings data. With the introduction of CHPS, the NWS anticipates a shift from lumped forcings (by basin) to gridded forcings. CHPS can also be run in stand-alone mode which offers many opportunities to conduct research, run hindcasts and calibrate models in the same software environment. The capabilities of CHPS allow the NWS to build a community for hydrological prediction purposes where it can co-operate with the academic arena on issues such as expanding its model base, model interoperability and data assimilation using the actual forecasting environment. CHPS is currently being rolled out nation wide and will go live in 2010-2011. Once CHPS is in place, the next challenge will be system interoperability between different water management agencies.