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Specific Retention Formula:
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Specific Retention (in %) tells how much water remains in the rock after it is drained by gravity. It represents the water content that a soil or rock can retain against the force of gravity.
The calculator uses the Specific Retention formula:
Where:
Explanation: The formula calculates the percentage of water that remains in the soil or rock sample after gravitational drainage, indicating the material's water retention capacity.
Details: Specific Retention is crucial in hydrogeology for understanding aquifer properties, groundwater storage, and the behavior of water in different geological materials. It helps in assessing the water-holding capacity of soils and rocks.
Tips: Enter the volume of water retained and the total volume of the soil or rock sample in cubic meters. Both values must be positive, with the total volume greater than zero.
Q1: What is the difference between Specific Retention and Specific Yield?
A: Specific Retention is the water retained against gravity, while Specific Yield is the water that drains out by gravity. They are complementary properties that sum to the total porosity.
Q2: What are typical Specific Retention values for different materials?
A: Clay has high specific retention (25-50%), sand has moderate values (5-15%), while gravel has low specific retention (1-5%).
Q3: How is Specific Retention measured in laboratory settings?
A: Typically measured using drainage tests where a saturated sample is allowed to drain, and the retained water volume is measured after drainage ceases.
Q4: Why is Specific Retention important in groundwater studies?
A: It helps determine how much water an aquifer can store and release, which is essential for water resource management and well yield calculations.
Q5: Can Specific Retention change over time?
A: Yes, it can be affected by factors such as compaction, mineral composition changes, and biological activity in the soil.