|Period Covered by the Report:||November 1995 to April 2000|
|Date of Final Report:||May 2000|
|EPA Agreement Number:||R82-4784-010|
|Title:||Scaling up Spatially Distributed Hydrologic Models of Semi-Arid Watersheds|
|Investigators:||David G. Tarboton, C. M. U. Neale, K. Cooley, G. Flerchinger, C. Hanson, M. Seyfried, C. W. Slaughter|
|Institution:||Utah State University|
|Research Category:||Water and Watersheds|
|Project period:||November 1995 to October 1998 (extended to April 2000)|
This spatial variability of snow distribution is environmentally important because snow accumulated in drifts sustains streamflow later into the spring and summer, than would be sustained by a more uniform snowpack. This sustains plant communities and ecosystems that depend upon snowmelt, as well as being important for streamflow and water resources. Through this work our better understanding of snowpack variability allows us to better model these environmental systems.
In the quest to scale up our models and apply them over larger watersheds we explicitly incorporated a parameterization of subgrid variability in snow, through the use of a depletion curve into our snowmelt model [Luce et al., 1999]. A depletion curve quantifies the relationship between snow covered area and snow water equivalent. Snow covered area is an important control on melt and surface water input rates because energy transfers to the snow pack are across the snow covered area. We also developed theoretical relationships between the depletion curve and distribution of snow at peak accumulation [Luce et al., 1999]. To obtain the spatial distribution of snow accumulation over large areas a wind blowing snow model was tested against Reynolds Creek data [Prasad et al., 2001]. This spatial distribution facilitates the derivation of depletion curves for the modeling of surface water inputs over large areas.
In addition to snow, this project, also examined runoff and evapotranspiration processes. To correctly model runoff it is necessary to account for the spatial distribution of snowmelt inputs due to snow drifting. In the past we have accounted for this using a drift factor calibrated based on measurements at each grid element. A drift factor is an index of the snow accumulation accounting for drifting or scour at a particular location relative to an average or gage measurement. For scaling up to large areas it was impractical to apply the grid model at each grid cell so we developed an approach that divides a watershed into three zones based upon drift patterns, soil types and vegetation [Flerchinger et al., 2000; Prasad et al., 2000]. We showed that these zones can be obtained from the distribution of calibrated drift factors at a small watershed. The timing of surface water input on the zone corresponding to deep drifts on the north-facing, leeward slope corresponds closely with the timing of streamflow at the outlet. A lumped hydrologic model was developed which consists of (a) simple parameterization of evapotranspiration, (b) infiltration into the soil zone and recharge to the saturated zone, and (c) subsurface storage-discharge function. This model, applied to each of the three surface water input zones individually was shown to be sufficient to parameterize the volume and timing of runoff from this watershed. To extend this approach to large areas requires a way to estimate drift factors and zones over large areas. Here we again used the wind blowing snow model (SnowTran-3D), in collaboration with Glen Liston the model developer at Colorado State University. Results are reported in Prasad et al. . These results show that although there are discrepancies in pointwise comparisons that require further investigation the wind blowing model provides a reasonable estimate of drift factors.
A ten-year water balance was computed for a 26 ha watershed by dividing the watershed into three zones based upon drift patterns, soil types and vegetation [Flerchinger et al., 2000]. It was shown that approximately 450 mm of precipitation is necessary to generate runoff from the watershed; above this threshold, runoff increases somewhat linearly with precipitation. An estimated 46 mm, or approximately 10% of the annual precipitation was estimated to be lost to deep percolation losses through fractures in the basalt underlying the watershed. Water percolating beyond the root zone as simulated by the Simultaneous Heat and Water (SHAW) model was directly related to measured runoff (R2=0.90). Above a threshold of about 50 mm, 67% of the water percolating beyond the root zone produced runoff. This can have important ramifications in addressing subsurface flow and losses when applying a snowmelt runoff model to simulate runoff and hydrologic processes in the watershed.
In terms of evapotranspiration, the spatial variability of surface vegetation properties is important. The Utah State University airborne videography system was used to acquire high resolution multi-spectral remote sensing imagery. Ground based measurements of leaf area index have been used to relate vegetation parameters such as leaf area index and plant type and height to the remote sensing data [Crosby et al., 2000a]. These relationships facilitate the derivation of hydrologic model inputs [Crosby et al., 2000b]. The remote sensing data, together with a spatially distributed energy balance model for the estimation of evaporation was used to quantify the scale of variability associated with the surface energy balance [Artan et al., 2000]. An innovative aspect of this study was that model testing included comparisons of model surface temperature against spatially distributed thermal imagery from the airborne remote sensing system. This provides a rigorous spatially distributed check of energy balance model performance. The scaling analysis comprising statistical analysis of the spatial fields at different resolutions suggest a grid scale of 10 x 10 m2 for the modeling of surface energy balance processes.
Five graduate students (3 PhD and 2 MS), namely Charlie Luce, Rajiv Prasad, Guleid Artan, Greg Crosby and Kevin Williams worked on this project. Six refereed papers have been published. Three papers are under review. There have been three non refereed conference papers and multiple conference presentations.
Overall this study has led to a better understanding of water balance
processes in western semi-arid rangeland watersheds, and improved modeling
methodology for simulation of hydrologic processes in this region.
Many of the papers and models from this research are available at the web
Many of these publications are available electronically at http://hydrology.usu.edu/dtarb/
Artan, G. A., C. M. U. Neale and D. G. Tarboton, "Characteristic length scale of input data in distributed models: implications for modeling grid size," Journal of Hydrology, 221(1-4): 128-139. 2000. [PDF 506K]
Flerchinger, G. N., K. R. Cooley, C. L. Hanson and M. S. Seyfried, "A Uniform Versus an Aggregated Water Balance of a Semi-Arid Watershed," Hydrological Processes, 12: 331-342. 1998.
Flerchinger, G. N. and K. R. Cooley, "A Ten-Year Water Balance of a Mountainous Semi-Arid Watershed," Journal of Hydrology, (tentatively accepted subject to revisions). 2000.
Luce, C. H., D. G. Tarboton and K. R. Cooley, "The Influence of the Spatial Distribution of Snow on Basin-Averaged Snowmelt," Hydrological Processes, 12(10-11): 1671-1683. 1998. [PDF (414KB), Wiley Reprint]
Luce, C. H., D. G. Tarboton and K. R. Cooley, "Subgrid Parameterization Of Snow Distribution For An Energy And Mass Balance Snow Cover Model," Hydrological Processes, 13: 1921-1933, special issue from International Conference on Snow Hydrology, Brownsville, Vermont, 6-9 October, 1998. 1999. [PDF (388KB), Wiley Reprint]
Prasad, R., D. G. Tarboton, G. E. Liston, C. H. Luce and M. S. Seyfried, (2001) "Testing a Blowing Snow Model Against Distributed Snow Measurements at Upper Sheep Creek," Water Resources Research, 37(5): 1341-1356.. [PDF (10 MB)]
Tarboton, D. G., G. Blöschl, K. Cooley, R. Kirnbauer and C. Luce, (2001), "Spatial Snow Cover Processes at Kühtai and Reynolds Creek," Chapter 7 in Spatial Patterns in Catchment Hydrology: Observations and Modelling, Edited by R. Grayson and G. Blöschl, Cambridge University Press, Cambridge, p.158-186. [PDF (7.4MB)]
Williams, K. S. and D. G. Tarboton, "The ABC's of Snowmelt: A Topographically Factorized Energy Component Snowmelt Model," Hydrological Processes, 13: 1905-1920, special issue from International Conference on Snow Hydrology, Brownsville, Vermont, 6-9 October, 1998. 1999. [Preprint PDF (252KB), Wiley Reprint]
Prasad, R., D. G. Tarboton, G. N. Flerchinger, K. R. Cooley and C. H. Luce, "Understanding the Hydrologic Behavior of a Small Semi-Arid Mountainous Watershed," Submitted to Hydrological Processes. 2000. [PDF (1.6MB)]
Crosby, G. S., C. M. U. Neale and M. Seyfried, "Vegetation Parameter Scaling On A Semi-Arid Watershed," Presented at the "17th Biennial Workshop on Color Photography and Videography in Resource Assessment" - May 5-7, 1999 in Reno, NV. 2000a. [PDF 173K]
Crosby, G. S., C. M. U. Neale, M. Seyfried and D. Tarboton, "Remote Sensing Inputs and a GIS interface for Distributed Hydrologic Modeling," Presented at the "Remote Sensing and Hydrology Days 2000" conference, April 2-7, 2000 in Santa Fe, NM. 2000b. [PDF 257K]
Luce, C. H., D. G. Tarboton and K. R. Cooley, "Spatially Distributed Snowmelt Inputs to a Semi-Arid Mountain Watershed," in Proceedings of the Western Snow Conference, Banff, Canada, May 5-8, 1997. 1997. [PDF (112K)]
Conference Presentations and Abstracts
Flerchinger, G.N. and K.R. Cooley. 1999. A ten-year water balance of a mountainous semi-arid watershed. In: EOS Transactions, Supplement. American Geophysical Union, Washington, D.C.
Luce, C., D. G. Tarboton and K. Cooley, "Sub-grid Parameterization for Modeling Snow Properties and Melt," Invited Presentation at AGU Fall Meeting, San Francisco, December 6 to 10. 1998.
Luce, C. H., D. G. Tarboton and K. R. Cooley, "Spatially Integrated Snowmelt Modeling of a Semi-arid Mountain Watershed," in Presentation at American Geophysical Union Fall Meeting, San Francisco, December 8-12. 1997.
Neale, C., M. Seyfried and G. Crosby, "High resolution Multispectral Imagery for Hydrologic Model Input Variable Determination and Model Verification in Heterogeneous Semi-Arid Mountain Watersheds," in , Presentation at 17th Annual AGU Hydrology days, April 14-18, Fort Collins, Colorado. 1997.
Prasad, R., D. G. Tarboton, G. N. Flerchinger, K. R. Cooley and C. H. Luce, "Understanding the Hydrologic Behavior of a Snowmelt Driven Small Semi-Arid Mountainous Watershed," Presentation at AGU Fall Meeting, San Francisco, December 13-17. 1999a. [PDF of poster]
Prasad, R., D. G. Tarboton, G. E. Liston, C. H. Luce and M. S. Seyfried, "Testing a Blowing Snow Model Against Distributed Snow Measurements at Upper Sheep Creek," Invited Presentation at AGU Fall Meeting, San Francisco, December 13-17. 1999b. [Powerpoint presentation]
Seyfried, M.S., Harris, R., Crosby, G., Neale, C., Clark, P. Upscaling leaf area measurements for evapotranspiration simulation in heterogeneous semiarid environments. EOS Trans. AGU, 80(4): AGU Fall Meeting Suppl. F324. 1999.
Seyfried, M., D. G. Tarboton, K. Cooley, C. M. U. Neale, C. Luce, G. Flerchinger and R. Prasad, "Scaling Up Spatially Distributed Hydrologic Models of Semi-Arid Watersheds," Presentation at AGU Spring Meeting, Boston, May 26 to 29. 1998.
Tarboton, D. G., "Spatial Analysis of the Hydrologic Properties of the Landscape," Presentation at GIS Hydro 99, ESRI Users Conference Pre-Conference Seminar, July 25, Published on ESRI GIS Hydro 99 CDROM. 1999.
Tarboton, D. G., C. M. U. Neale, K. R. Cooley, G. A. Artan and T. H. Jackson, "Distributed Hydrologic Modeling: Combining Models, Measurements and Remote Sensing at Reynolds Creek Experimental Watershed," in Remote Sensing Applications, Conference and Workshop with specific examples for Precision Agriculture, Utah State University, May 29-30. 1997.
Tarboton, D. G., C. M. U. Neale, R. Prasad, G. Artan, C. Luce, M. Seyfreid, G. Flerchinger and K. Cooley, "Distributed Hydrologic Modeling: Combining Models and Measurements at Reynolds Creek Experimental Watershed," Eos Trans. AGU, 77(46): AGU Fall Meeting Suppl., F226, Presentation at American Geophysical Union Fall Meeting. 1996.
Tarboton, D. G., C. M. U. Neale, R. Prasad, C. Luce, K. Williams, K. Cooley, G. Flerchinger, C. Hanson, M. Seyfreid and C. W. Slaughter, "Scaling Up Spatially Distributed Hydrologic Models of Semi-Arid Watersheds," Preprint Volume, Second Annual Scientific Conference on the Global Energy and Water Cycle, 17-21 June 1996, Washington, DC. 1996.
Tarboton, D. G., C. M. U. Neale, R. Prasad, C. Luce, K. Williams, K. Cooley, G. Flerchinger, C. Hanson, M. Seyfreid and C. W. Slaughter, "Scaling Up Spatially Distributed Hydrologic Models of Semi-Arid Watersheds," Eos Trans. AGU, 77(22): Western Pacific Geophysics Meeting Suppl., W34, Invited presentation at Western Pacific Geophysics Meeting. 1996.
Tarboton, D. G., K. Williams and C. Luce, "Development and Testing of a Parsimonious Energy Balance Snowmelt Model," Eos Trans. AGU, 77(46): AGU Fall Meeting Suppl., F219, Invited presentation at American Geophysical Union Fall Meeting. 1996.
Watersheds, scaling, hydrology, modeling, remote sensing, western, Utah, UT, Idaho, ID.
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