Evaluating the variability of runoff curve number with soil moisture content

الملخص EN

-The curve number (CN) method originally developed by USDA soil conservation services (SCS) is widely used in engineering design water structures, and environmental impact assessment for estimating runoff volume.

Currently the value of curve number is determined from published tables (USDA-SCS,1972) and modified using 5 day antecedent rainfall published in NEH-4 (USDA-SCS, 1985) .

The objective of this study was to investigate the use of antecedent soil rainfall for curve number adjustment .

A dynamic infiltration model (HYDRUS-1D) was used to simulate the temporal variation of soil moisture content.

Curve number values estimated from observed hydrograph were correlated to antecedent soil moisture content.

A strong correlation (r2=0.80) was found between CN values and the natural logarithm of antecedent soil moisture content.

Using Curve number based on antecedent moisture content value improved the estimation of runoff volume greatly compared to the 5-day antecedent rainfall published in NEH-4 (USDA-SCS, 1985).moisture content as an alternative to the 5-day antecedent