Let us remind ourselves at the outset that rivers are not merely channels that carry rain-water runoff to the sea. Perennial rivers are fed by ground water, streams, and occasionally by rain-water runoff during and after storms: perennial streams are fed by ground water, smaller streams, and occasional runoff: the source is a spring or a zone of seepage, and is the highest intersection of the ground surface with the water- table. Common causes of springs are illustrated in Figure 5–1. When there is a depression in the ground that penetrates the water-table, there is a lake: but a lake may also be fed by a stream, and it may overflow as a stream. In these matters we are nearly always concerned with unconfined aquifers, which are recharged by rainfall that percolates downwards through the soil.
Weitere Kapitel dieses Buchs durch Wischen aufrufen
- Aquifers: Springs, Rivers, and Man-Made Drainage
Richard E. Chapman
- Springer Netherlands
Fallstudie Überschwemmungskarten/© Thaut Images | Fotolia