Soil acidity/Acid Sulfate Soils - 2005Home | Land | Land Use & Management | Soil Acidity/Acid Sulfate Soils | 2005 What does the Data tell us for 2005Acid Sulphate Soils On June 30, 2004 Shoalhaven City Council and Shoalhaven River Acid Sulfate Soil Working Group (SRADWG) completed the Environmental Trust Acid Sulfate Soil ‘hotspots’ project aimed at implementing on-ground works to reduce acid discharge into streams and other water bodies in the Shoalhaven River-Broughton Creek floodplain and surrounding catchment. At the conclusion of this project, the Catchment Management Authority grant for investigating the possibility of introducing a similar project into the Southern Shoalhaven floodplain was approved and extended SRADWG’s involvement in finding and implementing on-ground solutions for Acid Sulfate Soils in the Shoalhaven for a further 12 months. The grant has been set aside to study the best approach to reducing acid sulfate soil discharge into the Shoalhaven-Crookhaven estuaries. The Shoalhaven River is one of the largest on the south coast of NSW, which is only intermittently open at the Shoalhaven Heads. The majority of time, the river flows through Berry’s canal, a man-made canal that was constructed by Alexander Berry in 1822, and terminates at Crookhaven Heads. The lower-lying land near the Shoalhaven River is made up of a deltaic-estuarine plain, which has now been significantly drained and due to the soils high organic content, is used for pasture grown for cattle (dairy or beef). However with the draining of this land, water quality problems have appeared, which caused a number of fish kills during rain events following drought or low rainfall periods. The main areas are suggested to be associated with former mangroves or shallow marine habitats (Umitsu et al, 2001). Coastal Acid Sulfate Soils (CASS) cause water and soil pollution from the release of toxic levels of elements such as Aluminium and Iron, as a result of a chemical process that produces Acid (H+) and Sulfate (SO42-). The Broughton Creek-Shoalhaven floodplain was identified as an area greatly affected by CASS, and has been researched for many years (Pease 1994; Blunden 2000; Glamore 2003) with numerous management options tested and implemented. However on the Southern side of the Shoalhaven River another floodplain exists where little research has been conducted. As a result this project has aimed to assess the distribution of CASS and the potential of this floodplain to benefit from other management options employed on the Northern Shoalhaven River floodplain and elsewhere in NSW for the purpose of reducing CASS discharge into the Shoalhaven-Crookhaven estuaries.
Figure - Study area and morphology of the Shoalhaven-Crookhaven Flood Plain (Umitsu et al. 2001)
Crookhaven River - Drain - Brundee Swamp Existing data and more recent soil and water sampling has provided a greater understanding of the conditions of the Shoalhaven-Crookhaven Floodplain. Digital elevation data aided in determining the geomorphology and history of the floodplain. As a result, soil sampling was conducted to fill in missing information and provide a greater detailed analysis of the soil profile, giving a good indication of sites suitability for certain management options.
Flood mitigation drain - Terara Swamp
Floodgate - Terara Swamp The project found that the water quality was within the acceptable recommended range (ANZECC, 2000) and not exhibiting past acidic conditions. However, the sampling was limited to a 2-month period due to available resources, and there has been little rainfall to contribute to the acid runoff over the period. The existing data confirmed the presence of acid sulfate soils in the floodplain, and showed they were present to a different extent in each drained area. The data also showed some variation in the elevation of the likely sulfidic layer, making it difficult to predict the amount of acid stored within the soil. To obtain more information about this project contact Shoalhaven City Council’s Environmental Services Section.
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