EVALUATION OF WATER MANAGEMENT STRATEGIES FOR ACID SULFATE SOILS USING A SIMULATION-MODEL - A CASE-STUDY IN INDONESIA

Reclamation and drainage of potential acid sulphate soils results in p yrite oxidation, acidification and release of toxic elements, hamperin g it's use for agriculture. Moreover, forest reserves and other ecolog ically valuable habitats located downstream of reclamation areas may b e disrupted. Proper water management is essential for a sustainable re clamation of acid sulphate soils. The computer model SMASS (Simulation Model for Acid Sulphate Soils) was developed to predict the effects o f water management on soil and water quality in acid sulphate soil are as. SMASS was applied to evaluate six different water management strat egies for the Barambai area in South Kalimantan, Indonesia. These stra tegies were aimed at oxidation of all pyrite in the topsoil to prevent recurrent acidification during dry periods in the future. Model compu tations showed that all the proposed water management strategies will fail to achieve good soil and water conditions within a few years. Con tinuation of the present water management will result in poor rice yie lds and environmental damage for at least another 10 years. By applica tion of a shallow drainage system to 30-40 cm, soil and water quality will strongly deteriorate during the first 3 years. Thereafter, the so il will be less unfavourable than if the present water management had been continued. The case study presented illustrates how the SMASS mod el can be applied to make a scientifically based evaluation of water m anagement strategies. However, technical, economical and social factor s should be considered as well, when deciding which water management s trategy should be implemented in practice.