How does storativity affect the amount of water that can be obtained from each type of aquifer? I learned that storativity is much smaller for confined aquifer, but does that not go hand-in-hand with the fact that the water from confined aquifer comes from pressure reduction?
I'm not sure if i got your point. But the greater the storativity, the greater will be fractional change in volume per unit head drop, which means the aquifer are expected to provide less water. To be a confined aquifer, the unit need to be saturared with the head above its upper interface. Hence, the pressure of water is higher in confined aquifers. In other words, if a confined and unconfined aquifer have the same transmissivity, the confined are expected to produce more water because it has a higher water pressure and hence, a lower fractional change per unit head drop.
When you mention the pressure change and drop how will the aquifer material contract, isn’t higher pressure the one related with compressing material into a smaller place or is the contraction here because water is being drained so pores are left empty ?
Changes in pressure affect storage of water in a confined aquifer by compression or expansion. Increasing pressure expands the pore space and increases the water density. These factors increase the volume of water that can be stored. If the water table is close to the injection point, then you can also increase the storage of water by raising the water table. This causes pores that were partially empty to become filled with water, increasing the water storage. The compression effect also occurs at the water table, but it is much smaller than pore drainage or filling.
When it’s mentioned per unit area so the depth of the material is anything we want right But when it’s unit volume the calculation itself is giving a final product with respect to a depth of 1 right ?
Storativity is per unit area because it applies to the entire thickness of the aquifer. It is a property of the layer that forms the aquifer. Specific storage is per unit volume. It is a property of the aquifer material. Neither of them depend on the depth. This is similar to transmissivity, which is a property of the aquifer layer, and hydraulic conductivity, which is a property of the aquifer material.
Also, when you mention how after you pump water out, some of the water in the area where the table dropped drains out Isn’t that water already pumped out or does pumping only take some of that out whilst some still stays in the pores even after pumping out of the well ?
Some water drains from the pores by gravity when a water table drops. Some water is retained. These quantities are determined by the specific yield and the specific retention. The water that remains in the pores under gravity drainage is held there by capillary forces.
You can drop the pressure in a confined aquifer using a pump in a well. The pressure drop causes the water to expand and the pore space to shrink. This is why you can recover water from a confined aquifer.
How does storativity affect the amount of water that can be obtained from each type of aquifer? I learned that storativity is much smaller for confined aquifer, but does that not go hand-in-hand with the fact that the water from confined aquifer comes from pressure reduction?
I'm not sure if i got your point. But the greater the storativity, the greater will be fractional change in volume per unit head drop, which means the aquifer are expected to provide less water.
To be a confined aquifer, the unit need to be saturared with the head above its upper interface. Hence, the pressure of water is higher in confined aquifers. In other words, if a confined and unconfined aquifer have the same transmissivity, the confined are expected to produce more water because it has a higher water pressure and hence, a lower fractional change per unit head drop.
Excellent
Very well explained, thanks so much!
This is very helpful, thank you very much!
When you mention the pressure change and drop how will the aquifer material contract, isn’t higher pressure the one related with compressing material into a smaller place or is the contraction here because water is being drained so pores are left empty ?
Changes in pressure affect storage of water in a confined aquifer by compression or expansion. Increasing pressure expands the pore space and increases the water density. These factors increase the volume of water that can be stored. If the water table is close to the injection point, then you can also increase the storage of water by raising the water table. This causes pores that were partially empty to become filled with water, increasing the water storage. The compression effect also occurs at the water table, but it is much smaller than pore drainage or filling.
When it’s mentioned per unit area so the depth of the material is anything we want right
But when it’s unit volume the calculation itself is giving a final product with respect to a depth of 1 right ?
Storativity is per unit area because it applies to the entire thickness of the aquifer. It is a property of the layer that forms the aquifer. Specific storage is per unit volume. It is a property of the aquifer material. Neither of them depend on the depth. This is similar to transmissivity, which is a property of the aquifer layer, and hydraulic conductivity, which is a property of the aquifer material.
Also, when you mention how after you pump water out, some of the water in the area where the table dropped drains out
Isn’t that water already pumped out or does pumping only take some of that out whilst some still stays in the pores even after pumping out of the well ?
Some water drains from the pores by gravity when a water table drops. Some water is retained. These quantities are determined by the specific yield and the specific retention. The water that remains in the pores under gravity drainage is held there by capillary forces.
A good lecture
what do you mean when you say drop the pressure in a confined aquifer?
You can drop the pressure in a confined aquifer using a pump in a well. The pressure drop causes the water to expand and the pore space to shrink. This is why you can recover water from a confined aquifer.
helpful, v. good
thank you
Nice sir
Thank U
Thank U
Hi