Your Dam Your Responsibility (PDF~1.2MB)

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7 Operation and Maintenance of Dams
The term ‘operation’ when applied to a dam may at first be regarded as applicable only
to larger dams. Typically, such dams have a variety of control equipment in use as part of
the structure (such as valves, flood gates and electrical control panels). However, when
we define it as any activity or practice which allows the owner to keep inflows and
outflows under control, or which safeguards the integrity of the dam, even small dams
without elaborate equipment can be, and should be, operated.
This is because the nature of the responsibility carried by a dam owner is the same for a
small dam as for a large one. The only difference is in the scale of the responsibility – and
that is then reflected in the smaller scale and sophistication of activities which usually
applies for a small dam compared with a large one.
The definition of operation given above also implies that monitoring of performance, and
maintenance, are inherently part of the duty of care attached to ownership of a dam,
regardless of its size.
The following sections deal only with some very basic aspects of operation and
maintenance.
7.1 Control of Flows
Operation of a dam includes the control of flow of water from or around a dam via bypass
channels, outlet works or spillway structures. ‘Control’ refers to activities or design
features aimed at ensuring that :
• inflows do not overtop or endanger the dam structure;
• outflows achieve the required environmental (compensation) flow rate where this is
applicable; and
• outflows are delivered in such a way as not to endanger the dam or to cause damage
downstream (in larger dams this may include flood regulation; in small dams it will
include avoiding erosion of the toe of the dam, the spillway channel or the area
downstream).
7.2 Routine Surveillance
Routine surveillance or inspections can also be called operation activities because they are
not specifically maintenance. Surveillance/inspections involve observing the behaviour of
the dam and recording flows into or out of the dam or water level gauges. It is geared
towards securing both safety of the dam (see Section 6) and satisfactory technical
performance.
7.3 Filling and Emptying
Be aware that the rate of filling or emptying a dam should be controlled. If done too
quickly problems can occur in an earth embankment.
If filled too fast, especially for the first time or after a long dry period, the material
within the bank does not have enough time to get sufficiently wet, expand and seal.
Therefore leakage may occur. In the case of embankments constructed from dispersive
clayey soils, this problem is more severe and can lead to rapid and complete failure of the
embankment.
Even in dams not constructed from dispersive clayey soils, emptying too quickly prevents
the moisture in the embankment from draining fast enough, and with the water load