Enter the reading on the ruler/gauge after the time interval.
Calculated Infiltration Rate
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function updateLabels() {
var unit = document.getElementById('unitSystem').value;
var startLabel = document.getElementById('startLabel');
var endLabel = document.getElementById('endLabel');
if (unit === 'mm') {
startLabel.innerHTML = 'Initial Water Level (mm)';
endLabel.innerHTML = 'Final Water Level (mm)';
} else {
startLabel.innerHTML = 'Initial Water Level (inches)';
endLabel.innerHTML = 'Final Water Level (inches)';
}
}
function calculateInfiltration() {
// Get Inputs
var unit = document.getElementById('unitSystem').value;
var start = parseFloat(document.getElementById('startLevel').value);
var end = parseFloat(document.getElementById('endLevel').value);
var time = parseFloat(document.getElementById('timeElapsed').value);
var resultBox = document.getElementById('resultBox');
var rateResult = document.getElementById('rateResult');
var classResult = document.getElementById('classificationResult');
// Validation
if (isNaN(start) || isNaN(end) || isNaN(time)) {
alert("Please enter valid numerical values for all fields.");
return;
}
if (time <= 0) {
alert("Time interval must be greater than zero.");
return;
}
// Calculate Drop (Difference)
// Assuming measurement from bottom up or top down, we need absolute difference
var drop = Math.abs(start – end);
if (drop === 0) {
resultBox.style.display = "block";
rateResult.innerHTML = "0 " + (unit === 'mm' ? 'mm/hr' : 'in/hr');
classResult.innerHTML = "Impermeable: No infiltration detected.";
return;
}
// Calculate Rate per Minute then per Hour
var ratePerMin = drop / time;
var ratePerHour = ratePerMin * 60;
// Display Result
resultBox.style.display = "block";
var unitText = (unit === 'mm') ? 'mm/hr' : 'in/hr';
rateResult.innerHTML = ratePerHour.toFixed(2) + " " + unitText;
// Soil Classification Logic
// Normalize to mm/hr for classification
var rateInMM = (unit === 'mm') ? ratePerHour : (ratePerHour * 25.4);
var soilType = "";
var desc = "";
if (rateInMM >= 30) {
soilType = "Rapid (Sandy / Gravelly)";
desc = "Water drains very quickly. Low water retention.";
} else if (rateInMM >= 15 && rateInMM = 5 && rateInMM = 1 && rateInMM < 5) {
soilType = "Moderately Slow (Clay Loam)";
desc = "Risk of surface runoff during heavy rain.";
} else {
soilType = "Slow to Very Slow (Clay)";
desc = "High runoff potential. Poor drainage.";
}
classResult.innerHTML = "Soil Permeability Class: " + soilType + "" + desc + "";
}
Understanding Soil Infiltration Rate
The soil infiltration rate is a critical measure in hydrology, agriculture, and civil engineering. It defines how fast water enters the soil surface. Knowing this rate is essential for designing efficient irrigation systems, preventing soil erosion, and managing stormwater runoff.
How to Use This Calculator
This calculator is designed to interpret data from a standard field infiltration test (such as a Single Ring or Double Ring Infiltrometer). Follow these steps:
Select Unit: Choose between Millimeters (Metric) or Inches (Imperial).
Initial Water Level: Record the water height in your testing ring at the start of your timer.
Final Water Level: Record the water height after a specific time interval.
Time Interval: Input how many minutes elapsed between the two measurements.
The calculator determines the rate per hour, which is the standard unit for comparing soil permeability.
Infiltration Rate Formula
The basic logic for determining the infiltration rate from field measurements is:
Infiltration Rate = (Water Drop / Time Interval) × 60
Where:
Water Drop: The absolute difference between the start and end water levels.
Time Interval: The duration of the test in minutes.
60: Conversion factor to normalize the rate to "per hour".
Soil Type Classification Table
Different soil textures allow water to pass through at different speeds. Below is a general guide used to classify soils based on their infiltration rates (Basic Intake Rate):
Soil Texture
Infiltration Rate (mm/hr)
Infiltration Rate (in/hr)
Description
Sand
> 30
> 1.2
Rapid absorption, low runoff risk.
Sandy Loam
20 – 30
0.8 – 1.2
Moderately rapid.
Loam
10 – 20
0.4 – 0.8
Moderate. Balanced drainage.
Clay Loam
5 – 10
0.2 – 0.4
Moderately slow.
Clay
< 5
< 0.2
Slow. High runoff risk.
Why Infiltration Matters
Irrigation Scheduling: If you apply water faster than the infiltration rate, it results in runoff and waste. Farmers use this rate to select the correct sprinkler nozzles.
Septic System Design: Drain fields require soil that infiltrates well enough to treat effluent but not so fast that it contaminates groundwater.
Flood Prevention: Soils with low infiltration rates (like compacted clay or urban soils) contribute significantly to flash flooding.