Monday, March 15, 2010
Tuesday, March 9, 2010
Specific yield
Specific yield, also known as the drainable porosity, is a ratio, less than or equal to the effective porosity, indicating the volumetric fraction of the bulk aquifer volume that a given aquifer will yield when all the water is allowed to drain out of it under the forces of gravity:
where
- Vwd is the volume of water drained, and
- VT is the total rock or material volume
|
| Specific Yield (%) | ||
| Material | Maximum | Minimum | Average |
| coarse gravel | 26 | 12 | 22 |
| medium gravel | 26 | 13 | 23 |
| fine gravel | 35 | 21 | 25 |
| gravelly sand | 35 | 20 | 25 |
| coarse sand | 35 | 20 | 27 |
| medium sand | 32 | 15 | 26 |
| fine sand | 28 | 10 | 21 |
| silt | 19 | 3 | 18 |
| sandy clay | 12 | 3 | 7 |
| clay | 5 | 0 | 2 |
| (Johnson (1967) as quoted by C.W. Fetter) | |||
Tuesday, March 2, 2010
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