Changes

A river intake always requires a sufficient depth of water in the river. A submerged weir may have to be constructed downstream of the intake to ensure that the necessary depth of water will be available even in dry periods. This type of weir is only a small structure and cannot be expected to provide any storage or flow balancing. Ideally the weir should be founded on rock, to provide the best conditions with regard to bearing capacity, seepage and safety against sliding. Soils with a clay/silt content that reduce permeability and increases cohesion (but with low plasticity) are also acceptable as foundation materials. A key at the upstream toe of the weir will improve stability and an upstream apron will extend the seepage path and thus reduce seepage.

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