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G.H. Leavesley

Publications and source records attributed to G.H. Leavesley.

15 recordsLinked to original sources
USGS2006

One-way coupling of an atmospheric and a hydrologic model in Colorado

This paper examines the accuracy of high-resolution nested mesoscale model simulations of surface climate. The nesting capabilities of the atmospheric fifth-generation Pennsylvania State University (PSU)-National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5) were used to create high-resolution, 5-yr climate simulations (from 1 October 1994 through 30 September 1999), starting with a coarse nest of 20 km for the western United States. During this 5-yr period, two finer-resolution nests (5 and 1.7 km) were run over the Yampa River basin in northwestern Colorado. Raw and bias-corrected daily precipitation and maximum and minimum temperature time series from the three MM5 nests were used as input to the U.S. Geological Survey's distributed hydrologic model [the Precipitation Runoff Modeling System (PRMS)] and were compared with PRMS results using measured climate station data. The distributed capabilities of PRMS were provided by partitioning the Yampa River basin into hydrologic response units (HRUs). In addition to the classic polygon method of HRU definition, HRUs for PRMS were defined based on the three MM5 nests. This resulted in 16 datasets being tested using PRMS. The input datasets were derived using measured station data and raw and bias-corrected MM5 20-, 5-, and 1.7-km output distributed to 1) polygon HRUs and 2) 20-, 5-, and 1.7-km-gridded HRUs, respectively. Each dataset was calibrated independently, using a multiobjective, stepwise automated procedure. Final results showed a general increase in the accuracy of simulated runoff with an increase in HRU resolution. In all steps of the calibration procedure, the station-based simulations of runoff showed higher accuracy than the MM5-based simulations, although the accuracy of MM5 simulations was close to station data for the high-resolution nests. Further work is warranted in identifying the causes of the biases in MM5 local climate simulations and developing methods to remove them. ?? 2006 American Meteorological Society.

Journal of Hydrometeorology↗
USGS2006

Assimilation of snow covered area information into hydrologic and land-surface models

This paper describes a data assimilation method that uses observations of snow covered area (SCA) to update hydrologic model states in a mountainous catchment in Colorado. The assimilation method uses SCA information as part of an ensemble Kalman filter to alter the sub-basin distribution of snow as well as the basin water balance. This method permits an optimal combination of model simulations and observations, as well as propagation of information across model states. Sensitivity experiments are conducted with a fairly simple snowpack/water-balance model to evaluate effects of the data assimilation scheme on simulations of streamflow. The assimilation of SCA information results in minor improvements in the accuracy of streamflow simulations near the end of the snowmelt season. The small effect from SCA assimilation is initially surprising. It can be explained both because a substantial portion of snowmelts before any bare ground is exposed, and because the transition from 100% to 0% snow coverage occurs fairly quickly. Both of these factors are basin-dependent. Satellite SCA information is expected to be most useful in basins where snow cover is ephemeral. The data assimilation strategy presented in this study improved the accuracy of the streamflow simulation, indicating that SCA is a useful source of independent information that can be used as part of an integrated data assimilation strategy. ?? 2005 Elsevier Ltd. All rights reserved.

Advances in Water Resources↗
USGS2006

Step wise, multiple objective calibration of a hydrologic model for a snowmelt dominated basin

The ability to apply a hydrologic model to large numbers of basins for forecasting purposes requires a quick and effective calibration strategy. This paper presents a step wise, multiple objective, automated procedure for hydrologic model calibration. This procedure includes the sequential calibration of a model's simulation of solar radiation (SR), potential evapotranspiration (PET), water balance, and daily runoff. The procedure uses the Shuffled Complex Evolution global search algorithm to calibrate the U.S. Geological Survey's Precipitation Runoff Modeling System in the Yampa River basin of Colorado. This process assures that intermediate states of the model (SR and PET on a monthly mean basis), as well as the water balance and components of the daily hydrograph are simulated, consistently with measured values.

Journal of the American Water Resources Associatio↗
USGS2005

The watershed and river systems management program

The Watershed and River System Management Program (WaRSMP), a joint effort between the U.S. Geological Survey (USGS) and the U.S. Bureau of Reclamation (Reclamation), is focused on research and development of decision support systems and their application to achieve an equitable balance among diverse water resource management demands. Considerations include: (1) legal and political constraints; (2) stake holder and consensus-building; (3) sound technical knowledge; (4) flood control, consumptive use, and hydropower; (5) water transfers; (6) irrigation return flows and water quality; (7) recreation; (8) habitat for endangered species; (9) water supply and proration; (10) near-surface groundwater; and (11) water ownership, accounting, and rights. To address the interdisciplinary and multi-stake holder needs of real-time watershed management, WaRSMP has developed a decision support system toolbox. The USGS Object User Interface facilitates the coupling of Reclamation's RiverWare reservoir operations model with the USGS Modular Modeling and Precipitation Runoff Modeling Systems through a central database. This integration is accomplished through the use of Model and Data Management Interfaces. WaRSMP applications include Colorado River Main stem and Gunnison Basin, the Yakima Basin, the Middle Rio Grande Basin, the Truckee-Carson Basin, and the Umatilla Basin.

Conference Paper↗
USGS2005

The GIS weasel - An interface for the development of spatial information in modeling

The GIS Weasel is a map and Graphical User Interface (GUI) driven tool that has been developed as an aid to modelers in the delineation, characterization of geographic features, and their parameterization for use in distributed or lumped parameter physical process models. The interface does not require user expertise in geographic information systems (GIS). The user does need knowledge of how the model will use the output from the GIS Weasel. The GIS Weasel uses Workstation ArcInfo and its the Grid extension. The GIS Weasel will run on all platforms that Workstation ArcInfo runs (i.e. numerous flavors of Unix and Microsoft Windows).The GIS Weasel requires an input ArcInfo grid of some topographical description of the Area of Interest (AOI). This is normally a digital elevation model, but can be the surface of a ground water table or any other data that flow direction can be resolved from. The user may define the AOI as a custom drainage area based on an interactively specified watershed outlet point, or use a previously created map. The user is then able to use any combination of the GIS Weasel's tool set to create one or more maps for depicting different kinds of geographic features. Once the spatial feature maps have been prepared, then the GIS Weasel s many parameterization routines can be used to create descriptions of each element in each of the user s created maps. Over 200 parameterization routines currently exist, generating information about shape, area, and topological association with other features of the same or different maps, as well many types of information based on ancillary data layers such as soil and vegetation properties. These tools easily integrate other similarly formatted data sets.

Conference Paper↗
USGS2002

A modular approach to addressing model design, scale, and parameter estimation issues in distributed hydrological modelling

A modular approach to model design and construction provides a flexible framework in which to focus the multidisciplinary research and operational efforts needed to facilitate the development, selection, and application of the most robust distributed modelling methods. A variety of modular approaches have been developed, but with little consideration for compatibility among systems and concepts. Several systems are proprietary, limiting any user interaction. The US Geological Survey modular modelling system (MMS) is a modular modelling framework that uses an open source software approach to enable all members of the scientific community to address collaboratively the many complex issues associated with the design, development, and application of distributed hydrological and environmental models. Implementation of a common modular concept is not a trivial task. However, it brings the resources of a larger community to bear on the problems of distributed modelling, provides a framework in which to compare alternative modelling approaches objectively, and provides a means of sharing the latest modelling advances. The concepts and components of the MMS are described and an example application of the MMS, in a decision-support system context, is presented to demonstrate current system capabilities. Copyright ?? 2002 John Wiley and Sons, Ltd.

Hydrological Processes↗
USGS2001

Evaluation of flash-flood discharge forecasts in complex terrain using precipitation

Operational prediction of flash floods produced by thunderstorm (convective) precipitation in mountainous areas requires accurate estimates or predictions of the precipitation distribution in space and time. The details of the spatial distribution are especially critical in complex terrain because the watersheds are generally small in size, and small position errors in the forecast or observed placement of the precipitation can distribute the rain over the wrong watershed. In addition to the need for good precipitation estimates and predictions, accurate flood prediction requires a surface-hydrologic model that is capable of predicting stream or river discharge based on the precipitation-rate input data. Different techniques for the estimation and prediction of convective precipitation will be applied to the Buffalo Creek, Colorado flash flood of July 1996, where over 75 mm of rain from a thunderstorm fell on the watershed in less than 1 h. The hydrologic impact of the precipitation was exacerbated by the fact that a significant fraction of the watershed experienced a wildfire approximately two months prior to the rain event. Precipitation estimates from the National Weather Service's operational Weather Surveillance Radar-Doppler 1988 and the National Center for Atmospheric Research S-band, research, dual-polarization radar, colocated to the east of Denver, are compared. In addition, very short range forecasts from a convection-resolving dynamic model, which is initialized variationally using the radar reflectivity and Doppler winds, are compared with forecasts from an automated-algorithmic forecast system that also employs the radar data. The radar estimates of rain rate, and the two forecasting systems that employ the radar data, have degraded accuracy by virtue of the fact that they are applied in complex terrain. Nevertheless, the radar data and forecasts from the dynamic model and the automated algorithm could be operationally useful for input to surface-hydrologic models employed for flood warning. Precipitation data provided by these various techniques at short time scales and at fine spatial resolutions are employed as detailed input to a distributed-parameter hydrologic model for flash-flood prediction and analysis. With the radar-based precipitation estimates employed as input, the simulated flood discharge was similar to that observed. The dynamic-model precipitation forecast showed the most promise in providing a significant discharge-forecast lead time. The algorithmic system's precipitation forecast did not demonstrate as much skill, but the associated discharge forecast would still have been sufficient to have provided an alert of impending flood danger.

Journal of Hydrologic Engineering↗
USGS2000

Hydrological responses to dynamically and statistically downscaled climate model output

Daily rainfall and surface temperature series were simulated for the Animas River basin, Colorado using dynamically and statistically downscaled output from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis. A distributed hydrological model was then applied to the downscaled data. Relative to raw NCEP output, downscaled climate variables provided more realistic stimulations of basin scale hydrology. However, the results highlight the sensitivity of modeled processes to the choice of downscaling technique, and point to the need for caution when interpreting future hydrological scenarios.

Geophysical Research Letters↗
USGS1997

Assessment of climate change and freshwater ecosystems of the Rocky Mountains, USA and Canada

The Rocky Mountains in the USA and Canada encompass the interior cordillera of western North America, from the southern Yukon to northern New Mexico. Annual weather patterns are cold in winter and mild in summer. Precipitation has high seasonal and interannual variation and may differ by an order of magnitude between geographically close locales, depending on slope, aspect and local climatic and orographic conditions. The region's hydrology is characterized by the accumulation of winter snow, spring snowmelt and autumnal baseflows. During the 2–3-month ‘spring runoff’ period, rivers frequently discharge > 70% of their annual water budget and have instantaneous discharges 10–100 times mean low flow.

Hydrological Processes↗
USGS1996

The Modular Modeling System (MMS): User's Manual

The Modular Modeling System (MMS) is an integrated system of computer software that has been developed to provide the research and operational framework needed to support development, testing, and evaluation of physical-process algorithms and to facilitate integration of user-selected sets of algorithms into operational physical-process models. MMS uses a module library that contains modules for simulating a variety of water, energy, and biogeochemical processes. A model is created by selectively coupling the most appropriate modules from the library to create a 'suitable' model for the desired application. Where existing modules do not provide appropriate process algorithms, new modules can be developed. The MMS user's manual provides installation instructions and a detailed discussion of system concepts, module development, and model development and application using the MMS graphical user interface.

Open-File Report↗
USGS1995

Biotic and abiotic processes controlling water chemistry during snowmelt at rabbit ears pass, Rocky Mountains, Colorado, U.S.A.

The chemical composition of snowmelt, groundwater, and streamwater was monitored during the spring of 1991 and 1992 in a 200-ha subalpine catchment on the western flank of the Rocky Mountains near Steamboat Springs, Colorado. Most of the snowmelt occurred during a one-month period annually that began in mid-May 1991 and mid-April 1992. The average water quality characteristics of individual sampling sites (meltwater, streamwater, and groundwater) were similar in 1991 and 1992. The major ions in meltwater were differentially eluted from the snowpack, and meltwater was dominated by Ca2+, SO4/2-, and NO3/-. Groundwater and streamwater were dominated by weathering products, including Ca2+, HCO3/- (measured as alkalinity), and SiO2, and their concentrations decreased as snowmelt progressed. One well had extremely high NO3/- concentrations, which were balanced by Ca2+ concentrations. For this well, hydrogen ion was hypothesized to be generated from nitrification in overlying soils, and subsequently exchanged with other cations, particularly Ca2+. Solute concentrations in streamwater also decreased as snowmelt progressed. Variations in groundwater levels and solute concentrations indicate thai most of the meltwater traveled through the surficial materials. A mass balance for 1992 indicated that the watershed retained H+, NH4/+, NO3/-, SO4/2- and Cl- and was the primary source of base cations and other weathering products. Proportionally more SO4/2- was deposited with the unusually high summer rainfall in 1992 compared to that released from snowmelt, whereas NO3/- was higher in snowmelt and Cl- was the same. The sum of snowmelt and rainfall could account for greater than 90% of the H+ and NH4/+ retained by the watershed and greater than 50% of the NO3/-.The chemical composition of snowmelt, groundwater, and streamwater was monitored during the spring of 1991 and 1992 in a 200-ha subalpine catchment on the western flank of the Rocky Mountains near Steamboat Springs, Colorado. The major ions in meltwater were differentially eluted from the snowpack, and meltwater was dominated by Ca2+, SO42-, and NO3-. Groundwater and streamwater were dominated by weathering products and their concentrations decreased as snowmelt progressed. Solute concentrations in streamwater also decreased as snowmelt progressed. A mass balance for 1992 showed that the watershed retained H+, NH4+, NO3-, SO42- and Cl- and was the primary source of base cations and other weathering products.

Conference Paper↗
USGS1989

Problems of snowmelt runoff modelling for a variety of physiographic and climatic conditions

Problems include: a) definition of the spatial and temporal distribution of model input; b) measurement or estimation of snow accumulation, snowmelt, and runoff process parameters for a range of applications and scales; and c) development of accurate short term and long term snowmelt runoff forecasts. Procedures being investigated to solve these problems include: a) integrating conventional and remote-sensing data to improve estimates of input data; b) developing snowmelt process algorithms which have parameters that are closely related to measurable basin and climatic characteristics; and c) updating model paramters and components using measured data or knowledge of past uncertainty. -from Author

Hydrological Sciences Journal↗
USGS1989

Assessment of the potential effects of climate change on water resources of the Delaware River basin; work plan for 1988-90

The current consensus is that some global atmospheric warming will occur as a result of increasing ' greenhouse ' gases. Water resources scientists, planners, and managers are concerned about the uncertainty associated with climatic-change effects on water supplies and what planning might be necessary to mitigate the effects. Collaborative studies between climatologists, hydrologists, biologists, and others are needed to gain this understanding. The Delaware River basin study is an interdisciplinary effort on the part of the U.S. Geological Survey that was initiated to improve understanding of the sensitivity of the basin 's water resources to the potential effects of climate change. The Delaware River basin is 12,765 sq mi in area, crosses five physiographic provinces, and supplies water for an estimated 20 million people within and outside the basin. Climate change presumably will result in changes in precipitation and temperature and could have significant effects on evapotranspiration, streamflow, and groundwater recharge. A rise in sea level is likely to accompany global warming and, depending on changes in freshwater inflows, could alter the salinity of the Estuary and increase saline-water intrusion into adjacent aquifer systems. Because the potential effects are not well understood, this report discusses how the effects of climate change on the basin 's water resources might be defined and evaluated. The study objective is to investigate the basin 's hydrologic response, under existing water management policy and infrastructure, to various scenarios of climate change. Specific objectives include defining the temporal and spatial variability of basin hydrology under existing climate conditions , developing climate-change scenarios, and evaluating the potential effects and sensitivities of basin water availability to these scenarios. The objectives will be accomplished through intensive modeling analysis of the basin 's climate, watershed, estuary, and aquifer systems. (USGS)

Open-File Report↗
USGS1983

Precipitation-runoff modeling system; user's manual

The concepts, structure, theoretical development, and data requirements of the precipitation-runoff modeling system (PRMS) are described. The precipitation-runoff modeling system is a modular-design, deterministic, distributed-parameter modeling system developed to evaluate the impacts of various combinations of precipitation, climate, and land use on streamflow, sediment yields, and general basin hydrology. Basin response to normal and extreme rainfall and snowmelt can be simulated to evaluate changes in water balance relationships, flow regimes, flood peaks and volumes, soil-water relationships, sediment yields, and groundwater recharge. Parameter-optimization and sensitivity analysis capabilites are provided to fit selected model parameters and evaluate their individual and joint effects on model output. The modular design provides a flexible framework for continued model system enhancement and hydrologic modeling research and development. (Author 's abstract)

Water-Resources Investigations Report↗