| Water is becoming an increasingly
valuable commodity and the source of much debate. With losses due to
evaporation accounting for one third to a half of the water lost on
Queensland farms, Queensland Department of Natural Resources and Mines
has funded a project to evaluate the effectiveness and viability of
commercially available products for reducing evaporation from rural
water storages.
The Rural Water Use Efficiency Initiative — Evaporation Control
Project aims to evaluate various products which claim to reduce water
losses due to evaporation as well as assess the effect on water quality,
the economic benefits and mechanical integrity of the products.
The National Centre for Engineering in Agriculture was awarded the contract
to conduct the trials and expressions of interest were sought earlier
this year from individuals or businesses with products and ideas for
controlling evaporation. A technical panel selected products from five
companies for evaluation. The products selected were:
EvapCaps/Darling Downs Tarpaulins
A lightweight, impervious, black and white, polyeythylene ‘bubble
wrap’ style of floating plastic cover.
Netpro
A 300 gram per square metre, black, monofilament shade cloth that is
suspended from a high tensile, webbed cable structure secured with screw
anchors around the perimeter of the storage.
Fabtech SA
A lightweight, floating plastic cover that forms a complete seal over
the surface of the storage and is ballasted to keep the cover taught
and aid in the collection of rainwater.
Ondeo Nalco (Water$aver)
A chemical solution that is self spreading and forms a thin mono-layer
of a fatty alcohol across the water surface. The product has been designated
as environmentally sound technology by the United Nations international
environment program.
Ciba Specialty Chemicals
A smaller scale trial will be undertaken to evaluate the effectiveness
of polyacrylamide (PAM) in reducing evaporation
The project has trials at a range of sites situated in various climatic
areas on storages varying from 10 metre diameter ring tanks to storages
of well over 100 hectares. The opportunity to test these products on
such a large scale is a direct result of Queensland Department of Natural
Resources funding and significant contributions from product suppliers
and landholders.
One of the difficulties in evaluating the various evaporation control
techniques is obtaining an accurate figure on evaporation losses with
and without the products installed. As part of the project, a method
for measuring evaporation and seepage losses from water storages is
being developed.
This technique involves the accurate measurement of water height in
the storage and allows the user to delineate between evaporation and
seepage (Figure 1). This allows daily calculations of seepage and evaporation
losses and, when coupled with a detailed land or hydrographic survey,
enables the landholder to determine the actual volume of water ‘lost’
through evaporation and seepage.
Testing and evaluation of the evaporation control products will occur
over the next 12 months and will allow for analysis under a variety
of weather conditions and evaporation rates. It is anticipated that
the final report (due in December 2004) will provide guidance on the
viability of evaporation control technologies.
Suppliers of evaporation control products will also receive constructive
feedback to improve and develop their products to suit varying situations
and raise the awareness of evaporation losses and the economic benefits
of evaporation control.
Landholders and interested parties should also gain a useful aid in
assessing the benefits of installing various evaporation control products
and their applicability and suitability to a variety of farming and
municipal enterprises.
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