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SCS Curve Number Formula:
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The SCS (Soil Conservation Service) Curve Number method is an empirical model developed by the USDA for estimating direct runoff from rainfall events. It's particularly useful for black soils Type I and soils with AMC (Antecedent Moisture Condition) types I, II, and III under Indian conditions.
The calculator uses the SCS Curve Number formula:
Where:
Explanation: The equation estimates the amount of rainfall that becomes direct runoff based on soil characteristics and precipitation amount. The 0.3 factor represents initial abstraction, while 0.7 represents the remaining retention capacity.
Details: Accurate runoff estimation is crucial for water resource management, flood prediction, irrigation planning, and soil conservation efforts, especially in agricultural regions with black soils.
Tips: Enter total precipitation and potential maximum retention values in cubic meters. Both values must be positive numbers. The calculator will compute the direct surface runoff.
Q1: What are AMC types I, II, and III?
A: AMC refers to Antecedent Moisture Condition - Type I (dry), Type II (average), and Type III (wet) conditions that affect the soil's runoff potential.
Q2: Why is this method specific to black soils?
A: Black soils (vertisols) have unique swelling and shrinking properties that affect their infiltration and runoff characteristics differently from other soil types.
Q3: What is the significance of the 0.3 and 0.7 coefficients?
A: These are empirical coefficients representing initial abstraction (0.3) and the remaining retention capacity (0.7) of the soil.
Q4: When is this method most accurate?
A: The method works best for small to medium watersheds and provides reasonable estimates for agricultural and rural areas with black soils.
Q5: Are there limitations to this equation?
A: The method may be less accurate for very large storms, urban areas, or soils with significantly different characteristics from the calibrated conditions.