Mineralogy, biogeochemistry, hydro-pedology and risks of sediments, salt efflorescences and soils in open drains in the wheatbelt of Western Australia

Document Type

Conference Proceeding

Publication Date

11-2005

Conference Title

Regolith 2005, Ten Years of CRC LEME: Proceedings of the CRC LEME Regional Regolith Symposia, November 2005

Place of Publication

Adelaide

ISBN

ISBN 0-9756895-2-5 (print), ISBN 0-9756895-3-3 (CD-ROM)

Disciplines

Hydrology | Natural Resources and Conservation | Sustainability | Water Resource Management

Abstract

Salinised land in the wheatbelt of Western Australia (WA) is expected to increase to over 3 million hectares if current trends continue and the construction of open drains has increasingly been seen as a major management option (Ali et al. 2004, Dogramaci & Degens 2003). Over 15,000 kilometres of drains have already been constructed in parts of the WA wheatbelt and generally without extensive regional linkages. Unfortunately, most of the drains have been constructed with limited planning, design, and construction guidelines, and usually without an understanding of their effectiveness, stability, or their downstream impacts (Dogramaci & Degens 2003). Initial results in the WA wheatbelt showed that drainage was associated with:

  • Formation of hypersaline soils (drain batters) and sodic soils (edge of drain) (Fitzpatrick et al. 2003);
  • Highly acidic shallow groundwater, which is caused primarily by iron hydrolysis (e.g., Mann (1983)) or ferrolysis (Brinkman 1979) reactions. This situation develops when anoxic water containing dissolved ferrous ions is exposed to air and ferrous ions are oxidised to the ferric ions, which react with water to form reddish-brown precipitates of ferric oxyhydroxides, releasing free hydrogen ions in the process. If the water sample contains a substantial amount of dissolved iron and has a low buffering capacity, the pH of the solution may fall from a value of about 6-7 to 2-3 (George 2002, Rogers & George 2005);
  • Formation of sulfidic and sulfuric materials in drains, especially in waterlogged areas in valley floors through the formation of pyrite in sulfidic materials. Drainage of valley floors causes pyrite to oxidise and release substantial amounts of sulfuric acid to form sulfuric materials (Fitzpatrick et al. 2003); and,
  • High concentrations of metals in the hypersaline groundwater and drain water with low pH ( < 4.5) discharging from drains into streams (Fitzpatrick et al. 2003, George 2002, Rogers & George 2005).

Comments

Published by Cooperative Research Centre for Landscape Environments and Mineral Exploration (CRC LEME)

Link to Full Text

Share

COinS