ABSTRACT
Lakes are best sited where the natural or man-made land formation provides a hollow which makes the lake appear to be the result of natural water seepage and collection. A full hydrological survey is essential if the lake is to remain in a stable and healthy condition, and trial holes or boreholes must be made down to at least 1.5 m below the topsoil and surface layers of subsoil in the deepest part of the proposed lake bed, and deeper if there is any doubt about the lower strata or if the water table cannot be found. Remember that the structure of the ground under the embankment is just as critical as the ground under the lake itself, since the additional loading imposed by the water itself can cause alterations to the ground structure as well as to the lower level aquifers. The minimum basic survey data required for large lakes or ponds is:
• variations in soil texture down to full depth of excavation • vertical permeability • horizontal permeability • soil pH • chemical analysis of soils • soil liability for cracking • infiltration rate of groundwater • soil structure when waterlogged • in mining areas it is probably better to avoid lake construction altogether, since
settlement can continue for many years after mining has ceased.
