この 有効降雨量計算ツール is a helpful tool used to estimate how much rainfall is actually available for plant use, soil storage, or recharge after accounting for losses like runoff, interception, and deep drainage. This is crucial in agriculture, hydrology, irrigation planning, and water resource management.
Instead of just measuring how much rain falls, this calculator focuses on how much rain truly benefits the land. For example, even if it rains a lot, factors like slope, vegetation, and soil type can prevent most of that water from being absorbed. The calculator helps you understand and manage water use better by estimating the effective rainfall.
This tool falls under the category: Hydrology and Agriculture Calculators.
formula of Effective Rainfall Calculator
To calculate the effective rainfall (R_e) that contributes to soil moisture or plant use, the formula is:
R_e = P - (R_s + E_i + D)
どこ：
R_e = Effective rainfall (in mm or inches)
P = Total precipitation over a period (in mm or inches)
R_s = Surface runoff (in mm or inches), calculated as:
R_s = C * P
C = Runoff coefficient (typically from 0 to 1), based on slope, soil type, land cover
E_i = Interception loss (in mm or inches), calculated as:
E_i = min(P, I_c)
I_c = Interception capacity, depending on vegetation canopy and density
D = Deep percolation or drainage loss (in mm or inches), calculated as:
D = max(0, (P - R_s - E_i - S_m))
S_m = Soil moisture storage capacity, based on soil type, depth, and field capacity
This formula includes all major rainfall losses and gives a practical estimation of usable rainfall for irrigation, farming, or groundwater recharge.
General Values Table for Quick Reference
| 契約期間 | 代表的な範囲 | 我が軍の部隊数 | Notes |
|---|---|---|---|
| C (Runoff coeff.) | 0.05 – 0.90 | - | High for paved or steep areas, low for sandy or flat soils |
| I_c | 0.5 – 3.0 | mm | Higher for dense forest, lower for bare ground |
| S_m | 50 – 200 | mm | Varies with soil type and root depth |
| P (Rainfall) | 不定 | mmまたはインチ | Collected from rain gauges or weather data |
| R_s | 計算された | mmまたはインチ | Proportional to precipitation and land characteristics |
| え_i | 計算された | mmまたはインチ | Based on vegetation interception |
| D | 計算された | mmまたはインチ | Occurs only when excess water cannot be stored in the soil |
This table is useful for quick estimation when full input data isn't available.
Example of Effective Rainfall Calculator
Let’s look at an example to understand how this works.
Assume the following conditions for a farmland:
- P = 50 mm (total rainfall)
- C = 0.3 (moderate slope, mixed land cover)
- I_c = 2 mm (moderate vegetation)
- S_m = 100 mm (deep, loamy soil)
Step 1: Surface runoff
R_s = C * P = 0.3 * 50 = 15 mm
Step 2: Interception
E_i = min(P, I_c) = min(50, 2) = 2 mm
Step 3: Deep percolation
D = max(0, (P - R_s - E_i - S_m))
D = max(0, (50 - 15 - 2 - 100)) = max(0, -67) = 0 mm
Step 4: Effective rainfall
R_e = P - (R_s + E_i + D) = 50 - (15 + 2 + 0) = 33 mm
Final Result: Effective Rainfall R_e = 33 mm
This means 33 mm of the 50 mm of rain is available to support plant growth or soil recharge.
最も一般的な FAQ
Effective rainfall is the part of total rainfall that is actually useful for plant growth or soil moisture, after losses like runoff, interception, and drainage are removed.
It helps in planning irrigation and managing water resources efficiently, especially in farming and landscaping.
Yes, using general values from local studies or tables can give a reasonably accurate estimate, especially for planning purposes.