Dynamic modelling of a shallow freshwater lake for ecological and economic sustainability

Abstract This research deals with the dynamic simulation modelling of a shallow freshwater lake ecosystem and analysis of potential sustainable management policies. The study region consists of a shallow freshwater lake and its surroundings, where fishing is a major commercial activity. The lake is under high nutrient loads, hence eutrophic with macrophyte dominance. The goal of this research is to find a balance between the ecosystem and economic activities in the region. To this end, a system dynamics model of the wetland is constructed. The results obtained from model simulations show that there is no threat of a shift to algal dominance in the near future. The major problem seems to be a potential decline in the welfare of the inhabitants, mainly due to unsustainable population increase. Different scenario runs reveal that the lake would have become eutrophic with algal dominance, if the crayfish population did not collapse due to a fungus disease in 1986. One particular scenario analysis (the recovery of crayfish sometime in the future within the model time frame) results in increase in crayfish harvest; hence in income from fishing, leading to betterment in social conditions. As for the alternative policies tested, ‘improved agricultural techniques’ is the only policy that leads to better social conditions, through increased yield per hectare. It is hoped that the dynamic simulation model will serve as a laboratory to study the different features of the eutrophication problem in shallow freshwater lakes and to analyse different policy alternatives with an integrated, systemic approach.

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