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Purpose
This activity is required to specify the reasons
for which the identification and measurement work is proposed. The
purpose
of an investigation
must be clearly defined from the outset.
Factors to
be considered include:
- Water loss concerns
- Regional environmental concerns
- Local environmental concerns
The reason for an investigation may be due
to recognised problems at a particular location (e.g. visual
evidence of seepage
adjacent to the channel), or it may be to evaluate a reach
of channel
for particular reasons. Usually specific investigation is
in response
to an identified or inferred local problem due to channel
seepage. The scale of this type of predetermined action is
typically
in the order of up to 400m.
Inputs
Costs
and benefits, and community or political reasons for undertaking
an investigation are possible inputs.
If an investigation is not focussed on a particular
length of channel but is really interested in the question
of “Do
I have a seepage problem?”, then the bulk of these guidelines
may not be of particular relevance. Seepage risk,
potential
describes the issues that need to be considered in a regional
investigation (ie, not focussed on particular length of channel)
and presents an outline of three different approaches to regional
assessment, depending on the key drivers behind the investigation.
| Description of activity |
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Seepage data objectives include:
- Is the primary objective to identify high-seepage locations
or to measure the total volume of seepage?
- Is it necessary to
establish either the actual or the relative rate of seepage?
- What
magnitude of seepage loss is considered unacceptable and why?
- What
degree of confidence in the results is required?
- Over what length
of channel is the information required – local
scale or larger?
Operational constraints include:
- What budget might be available?
- When is the information required?
- Is it essential/desirable
to use in-house resources or can it be done by contractors?
- Is
there likely to be any follow-up monitoring after remedial
works?
| Responsibility/decision
makers |
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This is a management function normally
undertaken by the organisation as part of its water management
strategy.
External stakeholders
may also provide input.
| Output |
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A decision concerning the reasons for undertaking
seepage investigations (e.g. asset management);
budget considerations;
scale of the
operation (e.g. whole channel, specific sections,
etc); need for accuracy
and relativity; scope or terms of reference
as a guide to future decision
making; assessment of whether there might
be several iterations of investigations.
Local-scale recommendations
[Up to approximately 400m in length] |
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Considerations in determining the scope of
work for a local-scale project include:
- Has a seepage problem been identified and on what basis?
- Is
the extent of seepage known in the section of interest?
- Is there
a need to map the distribution of highest seepage zones and
if so why?
- Is there scope for further investigation work before
selecting and undertaking measurement?
Intermediate to large-scale recommendations
[Hundreds of metres to tens of kilometres
in length]
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Project objectives for intermediate
to large-scale projects need to
be carefully
defined at
the outset so that costs
incurred provide the most suitable
answers. Implications for channel
rehabilitation
or seepage remediation might need to be considered.
| Related
pages |
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Next: 2 Collate site physical
condition data
General issues in channel seepage identification
and measurement – Issues of
scale |
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