Modelling the impact of sediment management on the trophic state of a tropical reservoir with high water storage variations

Abstract Eutrophication of lakes has affected society in many regions, particularly in water scarce environments where: i) low runoff reduces the self-purification potential of water bodies; ii) water supply relies on surface reservoirs, which are susceptible to nutrient enrichment. This work presents an assessment of the impact of the silted sediment management on the trophic status of a tropical surface reservoir with intense temporal variability of water storage. A complete mixing model describing the total phosphorus budget in the water and sediments was used, based on semi-empirical formulations. The sediment reuse as soil fertilizer has been proposed to increase productivity in small scale agriculture, which should also enhance the water quality by removing the nutrient-enriched sediment from lakes. Model application for a 40-years period indicate that sediment management may improve water quality, changing from poor to acceptable trophic state during roughly 10% of the time when the reservoir is not empty.摘要：湖泊富营养化已对诸多地区的社会造成显著影响，尤其在缺水环境中更为突出：其一，径流量偏低会削弱水体的自净能力；其二，当地供水依赖易受营养物富集威胁的地表水库。本研究针对一座储水量存在强烈时间变异性的热带地表水库，评估了淤积沉积物管理对其营养状态的影响。研究采用基于半经验公式构建的完整混合模型，模拟水体与沉积物中的总磷收支过程。有研究提出将沉积物作为土壤肥料回用，以提升小规模农业的生产效益，同时通过移除湖泊中富集营养物的沉积物来改善水质。基于40年时长的模型应用结果表明，沉积物管理可有效改善水库水质：在水库未干涸的时段中，约10%的时间可将水库的营养状态从较差水平提升至可接受水平。