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

Volume 16 , Issue 4 , October 2014 , Pages 31-47

Authors

¹ Geology Department, Science College, Basra University

² 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 7424000m3

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.

Statistics