DEMs Resolution Effect on SCS Curve Number Derived through WI_CN Method Based on Saturation Excess Concept.

Document Type : Research Paper


1 Postgraduate Student in water structures, Tehran University, Karaj, Iran

2 Associate Professor, Water Engineering Dept., Faculty of Engineering and Technology, Imam Khomeini International University, Qazvin, Iran

3 Associate Professor, Irrigation and Reclamation Dept., Faculty of Agriculture and Technology, Tehran University, Karaj, Iran


The effects of DEM resolution on the curve number values as. Based on WI_CN method is addressed in the present research. This method, due to a use of TOPMODEL’s excesses saturation concept, is considerably dependent on the topographic index and subsequently on DEM cell sizes. The results of WI_CN method application in the Kasilian watershed for different DEM cell sizes indicated that the watershed averaged curve number in DEMs with resolutions of 50 and 300 meters   amount to 59.8 and 71.8, respectively, which means when DEM resolution gets coarser the difference between WI_CN method and common methods (derived CN using GIS and RS techniques) increases. For instance the maximum differences observed between the two methods (in 50 and 300 meter cell sizes) are 8.3% and 29.9%, respectively. Therefore, when making use of the saturation excess based methods for deriving curve number raster maps, especially in ungauged watersheds, DEM resolution effects should be defined with respect to data resolution.


Main Subjects

Arnold, J. G., Williams, J. R., Srinivasan, R., and King, K. W. (1996). ″SWAT: Soil and Water Assessment Tool″, USDA-ARS. Soil and Water Research Laboratory. Temple. TX.
Azizian, A., Amiri, E., and Shokoohi, A. R. (2013). ″Effect of DEM Resolution on Topographic Index and Runoff Simulation in Semi Distributed Model: Topmodel″, Water Research Journal, 1(1), 17-26. (In Farsi)
Azizian, A. and Shokoohi, A. R. (2014). ″Development of a new method for estimation of curve number based on Saturation Excess Concept″, Iran-Water Resources Research, 11(1), 20-43. (In Farsi)
Beven, K. J. (1997). ″TOPMODEL: a critique″, Hydrological Processes, 11, 1069-1085.
Beven, K. J. and Kirkby, M. J. (1979). ″A physically based, variable contributing area model of basin hydrology″, Hydrological Sciences Bulletin, 24, 43-69.
Cosby, B. J., Hornberger, G. M., Clapp, R. B., and Ginn, T. R. (1984). ″A statistical exploration of the relationships of soil mixture characteristics to the physical properties of soils″, Water Resources. Research, 20, 682-690.
Hjelmfelt, A. T. (1980). ″Curve number procedure as infiltration method″, Journal of Hydrology, 106, 1107-1111.
Kansas, L. (1993). ″Simulating the Variable Source Area Concept of Stream flow Generation with the Watershed Model TOPMODEL, U.S. Geological Survey, Water Resources Investigations Report, 36.
Mishra, K. S. and Singh, P. V. (1999). ″Another look at SCS-CN Method″, Journal of Hydrologic Engineering, ASCE,4(3), 257-264.
Pradahan, N. R., Ogden, F. R., Tachikawa, Y., and Takara, K. (2008). ″Scaling of slope, upslope area, and soil water deficit: Implications for transferability and regionalization in topographic index modeling″, Water Resources Research, 44, 12-21.
Quinn, P. F., Beven, K. J., and Lamb, R. (1995). ″The ln[a/tan β] index :How to calculate it and how to use it within the TOPMODEL framework″, Hydrological Processes, 9, 161-182.
Rawls, W. J., Ahuja, L. R., Brakensiek, D. L., and Shirmohammadi, A. (1993). Infiltration and soil water movement. Handbook of Hydrology. (ed. by D. R. Maidment). New York: McGraw-Hill.
Soil Conservation Service (SCS). (1986). ″Urban hydrology for small watersheds″, Technical Release55, Springfield, USDA.
Steenhuis, T. S., Winchell, M., Rossing, J., Zollweg, J. A., and Walter, M. F. (1995). ″SCS Runoff Equation Revisited for Variable-Source Runoff Areas″, ASCE Journal of Irrigation and Drainage. Engineering, 121(3), 234-238.
Steve, W., Lyon, M., Todd, W., Pierre, G. M., and Tammo, S. S. (2004). ″Using a Topographic Index to Distribute Variable Source Area Runoff Predicted with the SCS Curve-number Equation″, Hydrological Processes, 18 (15), 2757-2771.
Tarboton, D. G. (1991). ″On the extraction of channel networks from digital elevation data″, Hydrological Processes, 5(1), 81-100.
Williams, J. R. (1995). ″The EPIC model. In: Singh, V.P. (Ed.), Computer Models of Watershed Hydrology″, Water Resources Publications (909-1000).
Wolock, D. M. and Price, C. V. (1994). ″Effects of digital Elevation model map scale and data resolution on a topography-based watershed model″, Water Resources Research, 30, 3041-3052.
Woodward, D. E., Hawkins, R. H., Jiang, R., Hjelmfelt, A. T., Mullem, J. A., and Quan, Q. D. (2003). ″Runoff Curve Number Method: Examination of the Initial Abstraction ratio″, In: Proc of the World Water & Environmental Resources Congress and Related Symposia. American Society of Civil Engineering, Washington DC.
Yaghobzade, M. (2008). ″Determination of SCS curve number using GIS and RS techniques, Msc.  thesis, Bahonar University, Kerman. (In Farsi)
Young, R. A., Onstad, C. A., Bosch, D. D., and Anderson, W. P. (1987). ″AGNPS, Agricultural Non-Point Source Pollution Model: A Watershed Analysis Tool″, USDA Conservation Report 35.USDA-ARS, Washington DC.
Zhan, X. and Huang, M. (2004). ″ArcCN-Runoff: an ArcGIS tool for generating curve number and runoff maps″, Environmental Modelling & Software, 19(10), 875-879.