Estimation of Surface Runoff In Northeastern Missan Governorate by Using (Nrcs-Cn) Technique And Gis

1 Alaa M. Atiaa, 2 Mukdad H. Aljabbari, 3 Ayser M.Al-Shamma’a
1 Geology Department, Science College, Basra University, 2,3 Geology Department, Science College, Baghdad University,

In this study, an attempted was made to estimate average of annual total surface runoff in the
northeastern Missan Governorate, south of Iraq by using Natural Resources Conservation Services
Curve Number (NRCS – CN) empirical technique in GIS platform. Thematic layers of soil
hydrological groups and LULC were created using ArcGIS 9.3 software. Intersection of these two
thematic layers generated a map with new polygons representing the merged hydrological soil group
and LULC. The appropriated CN values adapted from different sources and technical release of
United State of Department of Agriculture (USDA) were assigned manually for each new merged
polygon. The curve numbers for different antecedent moisture content (AMC) were calculated as 38,
59, 77 for dry, normal, and wet soil conditions. The associated maximum potential retention for each
AMC were calculated as 75,87, 176.51, and 414.42 for dry, normal, and wet soil moisture conditions.
Application of the method showed that the average annual runoff depth is 0.36 mm. This figure was
multiplied by the area of the study area (1856) km2 to get the total average of runoff volume 7424000m
which represents 0.0003 from the total annual average of rainfall. The applied method is robust
and easy to implement and could be used to roughly estimate the surface runoff with minimal data.

Key words: Surface runoff, NRCS-CN technique, GIS, Missan Governorate, Iraq

[1] Al-Jabari, S. J. Estimation of runoff for agricultural watershed using SCS curve number and
GIS, Master thesis, Birzeit University, Palestine, 91p, 2007.
[2] Anderson, M. G., McDonnell, J.J. Encyclopedia of Hydrological Sciences, John Wiley and
Sons, Inc., 5 volume set, 3456 p, 2005.
[3] Chow, V. T., Maidment, D. K., and Mays, L. W. Applied Hydrology, McGrow-Hill Book
Company, New York, USA. 588p, 2002.
[4] Dutta S., A. Mishra, S. Kar, S. Panigraphy.. Estimating spatial curve number for
hydrological response analysis of a small watershed. 6(2): 57-67,2006.
[5] Mabboubeh, E., S. Lai, H. Mohd, A. Ismail.. Application of natural resources conservation
service – curve number method for runoff estimation with GIS in the Kardeh watershed,
Iraq. European J. of Scientific Research. 34(4): 575-590,2009.
[6] Manoharam, A. and Murugappan, A. Estimation of runoff in an ungagged rural watershed,
Tamilandu State, India. International J. of Engineering Sciences and Technology. 4(2): 449
– 456,2012.
[7] Melesse, A. M. and Shih, S. F. Spatially distributed storm runoff depth estimation using
Landsat images and GIS, Computes and Electronic in Agriculture, 37: 173-183,2002.
[8] Patil, J. P., A. Saragi, O. P., Singh, A. K. Singh, T. Ahmed,. Development of a GIS –
interface for estimation of runoff from watersheds, Water Resource Management, 22(9):
1221 – 1239, 2008.
[9] Patil, J., A. Sarangi, A. K. Singh, T. Ahmed.. Evaluation of modified CN methods for
watershed runoff estimation using a GIS – based interface. Biosystem Engineering. 100(1):
137-146, 2008.
[10] SCS, Hydrology National Engineering Handbook, Supplement A, Section 4 Chapter 10,
Soil Conservation Service, USDA, Washington, DC, 1956.
[11] U. S. Department of Agriculture (USDA). Urban hydrology for small watersheds, Technical
Release No. 55, Washington DC, 1986.
[12] U. S. Department of Agriculture, Soil Conservation Service (USDA-SCS). National
Engineering Handbook, Section 4, Washington, DC,1975.
[13] Zahraa, GM., A. Hachum . Estimating runoff coefficient for water harvesting at Tal – Abata
area, Nineveh governorate. 31(5): 41-52, 2013.