Reducing evaporation and efficient water harvesting – Demonstration of evaporation control and benchmarking vineyard catchments

Abstract

The wine industry in the Great Southern region of Western Australia relies on irrigation
water harvested from artificial catchments such roaded catchments.

Summary

With a drying environment, the efficient collection, storage and use of water is paramount
for industries dependant on surface water for irrigation in order to sustain productivity and
profitability.

Vineyards in the Great Southern Region of Western Australia collect rainwater using
roaded catchments which are designed to direct the water into a storage dam. Roaded
catchments are constructed with earth moving equipment to form a series of sloping
surfaces of compacted clay to promote rainfall run-off (Stanton, 2005). An effective roaded
catchment harvests about 30% of the annual rainfall which is many times more than the
runoff from a pasture paddock. As a rule approximately one hectare of roaded catchment is
needed for every 2.5 hectares of vineyard assuming an average rainfall of 600mm per year
in this region.

The effectiveness of roaded catchments in the region has been shown to be variable from
property to property (Lantkze, 2005). An effective roaded catchment was shown to shed
water after about 4mm of rain or less while the threshold for an ineffective roaded was up
to 14mm. With an annual rainfall of 600mm, this difference in efficiency equates to
approximately 2.6ML/ha of harvested water. Over an average sized roaded catchment of
say 25ha, this equates to a potential loss of 65ML of harvestable water. This variation in
performance was expected to be typical of the region indicating a huge potential for
efficiency gains.

The Department of Agriculture and Food showed that many roaded catchments in the
region can be improved markedly by rolling/compacting, and the use of a soil sealant
(Lantkze, 2004). Treating the surface of roaded catchments with a spray-on polymer soil
sealant dramatically improved the run-off percentage relative to an untreated “effective”
roaded catchment. This technique was quickly adopted on many vineyards in the region –
at a cost of $2000 per hectare of roaded catchment.