Environmental Engineering Reference
In-Depth Information
FSL
(a)
FSL
(b)
FSL
(c)
FSL
(d)
FSL
(e)
Water table, prior to storage
Water table after filling of storage
Zone where water from the storage has filled voids
Direction of possible water flow
Figure 2.45.
Storages formed by non-soluble rocks - watertightness models.
potential for leakage. The storage should be essentially watertight, and will be fed partly
by groundwater. As the storage fills, a very small amount of water will fill the voids in the
adjacent rock mass (shaded). When the storage is full, the water table beneath the valley
side will have risen slightly and will meet it at the FSL (see dotted line).
There are many storages fitting this model in non-soluble rock areas with high rainfall.
Model (b).
The topographic and geological situations are similar to those for Model (a),
but the water table lies below the proposed FSL. There may be some bodies of perched
water, above this true water table. The reasons for the water table being so much lower than
for Model (a), may include any or all of the following:
1. The climate is drier;
2. The surface runoff is greater;
3. The rock is more permeable and drains more rapidly towards the valleys.
