Estimation Runoff by Using SCS-CN Model at Upper Yom Watershed

Abstract

The aim of this research was to apply geoinformatics data and SCS-CN model for estimation runoff and compare with measurement data. The study procedure were collect data from the various source such as topographic data, soil data, and land use data. All spatial data were analyzed the physiographic and hydrological characteristic of upper yom watershed for determination curve number (CN) and concern with rainfall amount for estimation runoff. The results were indicated watershed status in term of hydrology and potential runoff of upper yom watershed.

The results showed that annual runoff from SCS-CN model was 625.71 MCM. while direct measurement was 828.23 MCM. Moreover, the relationship between rainfall and runoff was moderately (r² = 0.6). During the wet period, the runoff was 633.06 MCM. while measurement was 916.22 MCM., in dry period runoff was 7.35 MCM. The relationship between rainfall and runoff was highest in the wet period as an r² = 0.99 contrast with the dry period with r² = 0.58. Watershed hydrological characteristic was used for explained watershed hydrological potential as the percentage of rainfall and runoff, the ratio between wet flow and dry flow and timing portion between wet and dry period. The results were indicated that the percentage of rainfall and runoff was 67.9 percent. The runoff ratio between wet and dry period was 99:1 and timing portion between the wet and dry period from the model was 7:5 month. The model application selected two scenarios with watershed classification condition and slope condition. The results showed that runoff data from watershed classification and slope condition was 695.89 and 559.13 MCM.