Hydrologic Information SystemsJuly 2005 News
Progress of the CUAHSI Hydrologic Information System
The CUAHSI Hydrologic Information System has four goals: to provide data services for hydrologists, to support the CUAHSI observatories, to advance hydrologic science and to improve hydrologic education. Significant progress has been made towards these goals. Several forms of user surveys have been conducted to establish a basis of facts as to how hydrologic information is presently used by the CUAHSI community, and to define what data sources and which kinds of analysis routines the community would like to employ more effectively. It has been established that direct remote access to national data archives such as the National Water Information System (NWIS) is sufficiently rapid that these archives can effectively be considered as local data sources for the hydrologist.
A set of CUAHSI web data services for NWIS has been constructed which can be incorporated within any application program on any operating system to provide direct access to the national data archive of NWIS streamflow and water quality data, bypassing the need for hydrologists to manually download data from the NWIS web site. The HIS team intends for these web data services to be broadened later to include access to EPA Storet, NCDC, NAWQA, Ameriflux, LTER, and other hydrologic observation data sources. The CUAHSI web data services are being incorporated within a hydrology data portal being constructed at the San Diego Supercomputer Center whose purpose is to provide a comprehensive map view of points of hydrologic measurement across the nation, and automated means of graphing and retrieving data measured at those locations.
A draft data model for Point Hydrologic Observational Data has been proposed whose main purpose is to serve as a standardized data framework for hydrologic data collected at CUAHSI observatory sites. Twenty-two reviews of the proposed model structure have been obtained from individuals in the CUAHSI community, and the data structure is being revised in response to the reviews. A Hydrologic Digital Library has been constructed to archive any kind of digital record of a hydrologic investigation, and a metadata scheme devised to describe the contents of the collections in this library.
NSF has proposed that the next step in the establishment of CUAHSI Observatories is the construction of Digital Watersheds. A Digital Watershed is an assembly and synthesis for a hydrologic region of point hydrologic observation data, GIS data, remote sensing data, and weather and climate gridded data, including Nexrad radar rainfall. The intent is to have a comprehensive digital description of the physical environment and water conditions within a CUAHSI observatory. This description employs a standard geotemporal reference frame for data, specifying a common set of spatial coordinates and time zone, so that data can be defined in (x,y,z,t) using either continuous or discrete domains of space and time.
A prototype Digital Watershed has been constructed for the Neuse basin in North Carolina , which will be examined at a workshop to be held at Duke University on 11-13 July. This workshop will clarify the methods by which Digital Watersheds can be constructed elsewhere, and the means by which hydrologic analysis can be undertaken based on Digital Watersheds using the fundamental components of fluxes, flowpaths, residence times and mass balances identified by the Neuse observatory prototype study. A design effort is being undertaken to establish a core set of HydroObjects and an accompanying library of methods operating on the objects, so as to enable hydrologists to begin exploring new modes of hydrologic behavior on Digital Watersheds. Discussions are being held with the national sources of hydrologic information as to how best to utilize their information for Digital Watershed development. These include stream morphology data and hydraulic models being developed extensively across the nation as part of the FEMA floodplain map modernization program.
Advanced means of hydrologic investigation are being explored including a system called Data to Knowledge developed at the National Center for Supercomputer Applications, which is a means of sequencing the workflow of exploratory data analysis so as to identify patterns in hydrologic data organized in a space-time framework.
The main avenues of progress in the HIS project are that the team now understands the technical means for accomplishing tasks such as “providing better data access for hydrologists”, or “building digital watersheds”, that at the outset of the project were simply abstract goals. Some tangible products, such as the CUAHSI web data services for NWIS, have been developed and are being tested. When these are sufficiently robust, they will be presented for wider evaluation by the CUAHSI community. The status of the HIS project as it stood in March 2005 is summarized in the proceedings of the CUAHSI HIS Symposium held at that time. For further information, feel free to contact the HIS principal investigator, David Maidment, at maidment@mail.utexas.edu..
Hydrologic science spans the interfaces and hydrologic boundaries of the earth (land-surface-atmosphere, land-surface-groundwater, groundwater-surface-water, and land-surface-surface water). Studies at these interfaces have the most potential for advances in understanding. These interfaces are the focus of a Hydrologic Observatory. The main objective of an observatory is to improve the predictive understanding of the flow paths, fluxes, and residence times of water, sediment, nutrients, and other contaminants across a range of spatial and temporal scales. These three characteristics are essential for addressing any hydrologic science hypothesis and so emphasizing these fundamentals will maximize benefit to scientists. Eventually a network of Hydrologic Observatories collecting similar data will be created so that comparisons can be made across climatic and physiographic zones.
