| Abstrakt: |
It has become necessary to calculate the quantities of surface runoff by knowing the amount of rain or precipitation that falls on an area. The SCS-CN method (Soil Conservation Services – Curve Number) has become one of the most accepted methods at the present time by all specialists and hydrological researchers for several reasons, the most important of which are its simplicity, ease of application, stability and efficiency in finding most of the hydrological parameters. It depends largely on soil type, land use/cover, and topography of the area, in addition to other hydrological factors. Recently, CN grid for any watershed could be done by using remote sense image (RS) and geographical information system (GIS used version 10.3) with its hydro tools and Geo-HMS extension (Hydrological Model System). The study area included the Diyala River Basin (DRB), which has an area of 32600 km2 located in the north-east of Iraq. It is very important watershed because of supplying the amount of water to the Diyala river which starts after Hemrin dam and meets to feed Tigris River. So, the goal of this study is to estimate the CN for DRB. It was used the DEM (Digital Elevation Model) Tiff file downloaded from USGS site of NASA with a cell size of 12.5m x 12.5m, land use/cover and soil type data from FAO. After re-classifications, the land use/cover of DRB was found in four classes by about 0.5% water, 76.66% vegetation, 5.15% forest, and 17.69% bare areas. Therefore, the land of DRB is covered for about 82% vegetation cover. The soil type of DRB was for about 87% of loam texture and 13% light clay texture. The estimated CN grid was between 60 to 100, the lowest value refers to low runoff and vice versa but 98 to 100 means the area covered by water. The ratios of estimated CN values were 60-70, 71-80, 81-90, and 91-100 were 52.8%, 10.3%, 6.3%, and 0.6% respectively. [ABSTRACT FROM AUTHOR] |
