Antecedent Moisture Conditions (AMC) Definition
Antecedent Moisture Conditions (AMC) are crucial in hydrology and soil science. They describe the level of moisture in the soil before a rainfall event occurs. This level significantly impacts how the soil will respond to future precipitation, affecting runoff and infiltration.
Determining AMC Period
AMC is typically evaluated based on the total rainfall received over a specific preceding period. This allows engineers and hydrologists to categorize the soil's moisture state (e.g., dry, average, wet).
AMC Rainfall Calculation Period
The standard definition for calculating AMC relies on the total rainfall recorded during the previous $5$ days. This period is considered representative of the recent moisture status of the soil.
Conclusion on AMC Days
Therefore, Antecedent Moisture Conditions (AMC) for a soil are defined based on the total rainfall that occurred during the previous $5$ days.
Important Questions from Runoff Estimation
- A $0.80\text{ km}^2$ agricultural watershed has a slope of $0.30\%$ and the maximum length of travel of water is $1\text{ km}$. The 10-year maximum depth of rainfall is tabulated below:
Duration (minutes) 5 10 20 30 40 60 Maximum depth of rainfall (mm) 16 24 39 50 60 65
Half of the watershed has row crops (runoff coefficient = $0.40$), whilst the other half of the watershed has pasture (runoff coefficient = $0.35$). The peak flow rate for the watershed (in $\text{m}^3\text{.s}^{-1}$) for the 10-year return period is ________. (Rounded off to two decimal places) - The mass curve of a rainfall event of 100 min duration over a catchment is given in the table.
If the initial loss is 0.6 cm and $\phi$-index is 0.6 cm/hour, the total surface runoff from the catchment is ______ cm (rounded off to one decimal place).Time from start of rainfall (min) 0 20 40 60 80 100 Cumulative rainfall (cm) 0 0.5 1.2 2.6 3.3 3.5 - The Rational method is used to estimate
- A $100 \text{ ha}$ watershed received rainfall at a rate of $5 \text{ cm h}^{-1}$ for $2 \text{ hours}$. If the runoff generated by the storm was at the rate of $1 \text{ m}^3 \text{ s}^{-1}$ for $10 \text{ hours}$, the runoff coefficient for the watershed would be
The Curve Number (CN) of a watershed of $40$ ha area under given hydrologic soil group, land use and management practices, and Antecedent Moisture Condition (AMC)-II is $80$. The initial abstraction is $20$% of maximum retention. For the rainfall event of $40$ mm, the direct runoff in mm (round off to $2$ decimal places) is _____________
