SMALL DAMS PETITS BARRAGES

Fig. 6.1 – Leakage measurement using a vessel and a chronometer.
Fig. 6.2 – Leakage measurement using a triangular weir gauge.
Comparing the turbidity, temperature and water quality of the seepage water with the
reservoir water are potentially useful indicators of potential problems developing. Sediment
traps built in conjunction with manholes and weirs will facilitate visual observations, and can be
used to collect samples for chemical analyses. A large increase in turbidity, for example,
could indicate internal erosion is occurring.
These systems are installed on new dams at the outlet from drainage elements and on
operating dams in areas where leakage is observed. Every effort must be made to ensure that
the point of measurement collects all leakage flows, as well as possible, with no flow around
the measuring point and, if possible, free of any influence of rainfall.
Weirs must be kept clean and the approach channels to weirs must be regularly cleared
of any material deposited or floating one (Fig. 6.3). If granular materials are observed, a
specialized engineering firm should be alerted in order to study whether there is any risk of
internal erosion.
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