Increasing runoff from roaded catchments by chemical application

Abstract

In the Great Southern region of Western Australia, harvesting irrigation water from roaded catchments is a common practice and local grape growers wished to investigate the merits of various soil sealants. It was found that some polymer sealants could vastly reduce infiltration and increase the amount of water collected.

Summary

This work was prompted by a high regional priority being given to improving water harvesting efficiency following lower than average falls of rain in recent years.

With solid sealants like bitumen being considered too expensive, attention turned to eight relatively cheap spray-on chemicals used by the mining industry for controlling dust and stabilising gravel roads. It was thought that these could provide run-off from short rainfall events that would normally not result in run-off from unsealed catchments, and this proved to be the case for most of the products and three in particular. Importantly, laboratory tests and field trials have enabled the compilation of a report which compares performance of commercially available products on clays and loams. In the process, experience has been gained in application techniques and grape growers have been able to assess existing roaded catchments and treatments like rolling and steeper batter construction.

The result for grape growers has been a choice of options that will be economical and effective. Only about 7% of rainfall is collected by paddock dams in the region, compared with 85% using a bitumen catchment, while a normal roaded catchment collects around 30% and up to double this amount if sealed.