(1) Coupling of surface-water and ground-water models- The watershed model PRMS, the 1-D channel hydraulics model DAFLOW, and the ground-water model MODFLOW have been coupled for fully integrated applications.

(2) Objective parameter estimation- The USGS is participating in the Model Parameter Estimation Experiment (MOPEX) program to investigate a priori parameter estimation methodologies for a variety of hydrologic process conceptualizations. MOPEX is also a component of the Prediction of Ungauged Basins (PUBS) program of the IAHS.

(3) Water management decision-support systems- Work is continuing under the joint USGS-Bureau of Reclamation Watershed and River System Management Program. The focus remains the research and development of decision support systems and their application to achieve an equitable balance among water resource issues.

(4) Incorporation of remotely sensed data- The USGS is a collaborator with the University of Arizona, University of Colorado, and Lawrence Berkeley Laboratory in the NASA Southwest Regional Earth Science Research Center. The purpose is to investigate the integration of remotely sensed data into resource-management applications. The first work is to explore the use of remotely sensed snow-covered area and snowpack water equivalent data in river basin management.

(5) Forecast methodologies- The coupling of atmospheric and hydrologic models is being investigated at several spatial scales. Downscaling from the MRF weather forecast model is being used to make 15-day hydrological forecasts on the upper Colorado River basin. Dynamical downscaling from the MM5 local scale atmospheric model is being investigated on the Yampa River basin.

(6) Improved hydrologic and ecosystem process simulation- The Water, Energy, and Biogeochemical Budgets (WEBB) program of the USGS is investigating these processes and their interactions to better define and model the flow paths and residence times of water in a basin. The use of isotopes as tracers is one aspect of the WEBB program to help identify flow paths and residence times. Interest in this approach and the use of a modular modeling framework has facilitated the development of new research activities with the International Atomic Energy Agency to explore the use of isotopes in river basin management.

(7) Integrated analysis and support tools- The USGS is collaboratively working with the U.S. Agricultural Research Service, U.S. Natural Resources Conservation Service, and the Friedrich Schiller University in Germany to integrate the Modular Modeling System (MMS) with the fully object-oriented Object Modeling System (OMS). A larger integrated program has also been initiated among eight U.S. government agencies to facilitate the development and sharing of models, analysis tools, and databases. These participating agencies are the USGS, Nuclear Regulatory Commission, Department of Energy, Environmental Protection Agency, Army Corps of Engineers, National Oceanic and Atmospheric Administration, Agricultural Research Service, and Natural Resources Conservation Service.

Kazuhiko Fukami overviewed the objective of this topic, i.e. the improvement of accuracy and reliability of hydrologic analysis and forecasting even under the change of climatic/hydrologic environments.    Then he explained the PWRI’s activities on this topic as follows:

1. Application of efficient monitoring of basin environment using remote sensing from satellites and/or aircrafts

1.1 Snow water equivalent (SWE) mapping with Synthetic Aperture Radar (SAR) aboard satellite

In order to estimate water resources due to snow in a river or dam watershed, PWRI made a study on snowcover-extent & SWE monitoring with RADARSAT-SAR (active remote sensor in the microwave region).  The study area was the Chuetsu district of the Niigata Prefecture of Japan.   An algorithm to retrieve the spatial distribution of SWE from SAR images was developed.  On the basis of ground-based snow surveys, it was verified that the algorithm was applicable to classifying SWE into four ranks irrespective of the variation of the snowpack’s physical condition in plains of wet-snow region.

1.2  Monitoring basin-wide hydrologic / hydraulic conditions using remote sensing

 PWRI investigated the applicability of high-res. remote sensing data to river channel & its physical environment.  The IKONOS image was effective monitoring the temporal change of stream channels, although the 1m-resolution was not still enough to monitor the conditions of river structures.  The applicability of three-line-sensor (TLS) aboard a helicopter was also investigated.  The TLS was applicable to 1) topographic mapping including riverbed beneath clear water, 2) the detection of targets in river area, 3) monitoring river-bed materials (size distribution of river-bed sands & gravels), etc.

PWRI is now conducting a research also on the estimation of water budget of the Tonle Sap Lake in Cambodia with remote sensing, sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT).  

2. Development of GIS-based distributed-parameter models

Two types of GIS-based distributed-parameter model were developed.  One is a conceptual distributed-parameter hydrologic model, “Modified PWRI-Distributed Model,” developed for long-term precipitation-runoff simulations.  The model utilizes a physically-based scheme for land-atmosphere interactions (evapotranspiration & infiltration) the parameters of which are correlated to the physical properties of soil and vegetation.  The other parts are conceptual and based on the former PWRI-distributed model.  The other  is fully physically-based distributed-parameter hydrologic model, “Watershed Environmental Hydrology (WEHY) Model,” which was developed by the cooperative research with Prof. M.L.Kavvas of the University of California at Davis, as a flood analyzing and forecasting tool.  The latter model is based on areally-averaged conservation equations.  Both the models was applied and verified at two mountainous forested watersheds.  These two models are expected to be useful to evaluate the effect of the change of climate and watershed environment (forest, land-use, urbanization, etc.) on hydrologic regime.  

3. Relations Between Flow Regime and Regional Climatic and Geophysical Conditions

 The DAD characteristics of the Tokai Storm (Year 2000) was investigated and clarified quantitatively.  As a result,  the effectiveness of DAD analyses was confirmed to understand and compare the storm characteristics among various rainfall events in Japan and to improve a geographic zoning in terms of DAD characteristics to estimate the largest-level storms and floods.

Lastly, he supplemented a study on the development of low-flow management system at the Yasu River in Japan.

Both organizations share common interests in hydrologic modeling and analysis for the purpose of water resources management.

Through discussions conducted during the meeting, the following research topics were identified as areas of possible collaboration over the next 12-24 months.

1) Establish basin-wide hydrologic modeling tools and methodologies utilizing GIS analyses. A major need is to avoid being dependent on existing hydrologic databases, in order to be able to predict and/or evaluate the effects of changes in land use and climate on water resources. (PWRI - development of GIS-based hydrologic model such as PWRI distributed model; USGS - development of the OMS-MMS-GIS Weasel system and the multi-media environmental model, and MOPEX)

2) Promote technical support for basins facing water conflicts caused by water shortage. (PWRI -Yasugawa-river project; USGS - Water2025)

3) To propose suitable methodologies for the investigation, analysis, and solution of problems related to the water resources of international rivers. (PWRI - Mekong-river study; USGS - tracer applications to international rivers)

Fukami and Leavesley agreed that both organizations would promote cooperative activities in common areas of interest, particularly on the above three items. Cooperation will be accomplished through information and personnel exchanges. For example, the PWRI plans to incorporate the OMS-MMS-GIS Weasel system into the PWRI distributed model.