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| About the IAL seepage management project |
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Introduction
Task force recommendations
In response to concerns about the lack of information available on
seepage from open channel supply systems, in October 1998 the Australian
National Committee on Irrigation and Drainage (IAL) conducted a two-day
workshop. The workshop was held at Moama in New South Wales and had
major support from the Murray-Darling Basin Commission, the Land and
Water Research and Development Corporation, 16 other industry organisations
and the Commonwealth Department of Primary Industries and Energy. The
workshop brought together 90 stakeholders and experts in the field
of channel seepage from throughout Australia.
The key outcome from the workshop was a suite of recommendations seeking
new and extensive investigations aimed at improving the level of knowledge
about channel seepage.
IAL formed an industry task force to advance the investigations.
A three-stage project was designed to implement the recommendations.
- Stage 1 – Investigation of methods for identification
and measurement of channel seepage.
- Stage 2 – Documentation
of procedures and processes for seepage remediation works.
- Stage
3 – Development of decision-support systems,
including this website.
IAL acknowledges the significant support and funding provided
to the project by the Murray-Darling Basin Commission, water
authorities and natural resource management agencies. Without
their valued
support
and interest, the project would not have been possible.
Background
to channel seepage
Water is a crucial resource in Australia, the driest inhabited
continent in the world. Its availability has shaped the pattern
of human settlement,
economic development and options for the future. A critical issue
is balancing the needs of environmental and consumptive uses.
It is within
this context that seepage from unlined earthen channels has become
an important issue in Australia for three reasons (Goss, 1998):
- The loss of an economically valuable resource
- The need to
halt environmental decline within our waterways
- The contribution
to groundwater recharge and associated induced waterlogging
and land salinity.
Objectives of the IAL seepage management project
The Australian National Committee of Irrigation and Drainage
(IAL), in conjunction with the Murray-Darling Basin Commission
(MDBC),
initiated a project to investigate earthen channel seepage
remediation. The main
objectives of the study were to:
- Develop an extensive bibliography of techniques used
in channel remediation
- Develop an understanding of the application
of channel remediation techniques within the Australian
rural water
industry
- Trial the various techniques deemed applicable
to Australia
- Develop a set of guidelines for the application
of remediation techniques.
Aim of guidelines for the application of remediation techniques
Guidelines for the application of remediation techniques
are presented in this website. The guidelines provide:• A
general understanding of the issues affecting channel
remediation.
- Guidance on selecting the most appropriate remediation
options for a particular site.
- Information on specific remediation
techniques and products.
Website audience
The guidelines incorporated in the website are intended for practical
use in undertaking channel seepage investigations
throughout the Australian water industry. Information for engineers,
field technicians
and
water
authorities is presented to enable selection appropriate
remediation techniques appropriate to particular channel systems.
The website provides an online system to identify objectives
for conducting channel remediation. Remediation guidelines
allow procedures
to be
assessed and considered as part of the management
process.
Development of the guidelines
To develop guidelines for application throughout the Australian water
industry, an extensive program evaluated existing knowledge of seepage
remediation issues and techniques from a review of national practices,
international literature and three years of trials assessing a range
of different techniques.
Rural water authority survey
Surveys of 41 rural water authorities throughout Australia provided
a broad understanding of the current state of knowledge and experience
with channel seepage remediation.
Survey response indicated that seepage loss is responsible for approximately
53% of total unaccounted water in irrigation channel systems. The
authorities nominated 22 different remediation methods to meet their
objectives in water savings, asset management and reduction of waterlogging
and salinity.
The principal reason given for selecting a remediation option was
previous success within the authority. Cost-effectiveness and the
ability to reduce seepage were also considered important. Clay lining
was the most widely used technique, followed by pipeline replacement,
which was nominated as the most successful technique, despite being
restricted to small and medium-sized channels.
Literature review
A comprehensive review of the literature was undertaken to identify
issues to consider in channel seepage remediation and techniques
utilised in seepage mitigation (IAL, 2001a). The review sourced
information from Australian practices and research projects, from
libraries including those at the International Commission on Irrigation
and Drainage (ICID) and the United States Bureau of Reclamation (USBR),
and channel remediation experts in the USA.
The study reported on the different remediation techniques, in
terms of:
- Typical applications (where and why they are used)
- Typical
material characteristics
- Installation requirements
- Maintenance requirements
- Effectiveness in managing seepage
- Costs and economics (if
information was available).
Remediation methods were broken down into four main categories
based on their principal method of managing the impacts of
seepage:
- Earth liners
- Hard surface liners
- Flexible membrane liners
- Groundwater intervention.
The IAL trials
Using the information gained in the literature review and expressions
of interest from contractors, a list of potential channel
seepage remediation techniques was compiled.
One objective of the project was to trial various techniques
that were deemed applicable to Australia. Discussion with
water authority
representatives and the results of the IAL survey highlighted
the importance of testing the practices of the water authorities
to enable
comparisons between traditional and newer techniques.
Sinclair Knight Merz, in consultation with Jay Swihart
from the United States Bureau of Reclamation (USBR), assessed
the techniques
and
expressions of interest on their technical merit and generic
installation costs. An emphasis on trialing exposed membranes
was adopted due
to a lack of previous trials of particular exposed membranes
in the Australian setting. However, covered membranes and
traditional methods
such as clay lining and bank remodelling were also incorporated
into the trials. Materials with performance already sufficiently
documented
in other research or reports (as identified in the Literature
Review) were not considered for additional testing as part
of this project.
Thirteen trials were undertaken over a three-year period:
- Murray Irrigation Limited (8 trials)
- Wimmera Mallee
Water (2 trials)
- Goulburn-Murray Water (2 trials)
- Murrumbidgee Irrigation
(1 trial)
The trials were conducted in areas of either existing channel
remediation, or where seepage had been previously identified.
They were based
on the practical scientific and engineering application
of various techniques. |
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