<![CDATA[Eutrophication triggered by excessive nutrient loading has become a major driver of lake degradation in many parts of the world. Lake Rawapening is one of Indonesia’s national priority lakes for environmental restoration and has experienced eutrophic conditions progressing toward a hypertrophic state due to high phosphorus loads (P-load) and total phosphorus concentrations (TP-C). Despite the implementation of lake rehabilitation programs, their effectiveness in improving trophic status has not been quantitatively evaluated, limiting stakeholders’ understanding of the outcomes. This study evaluates the effectiveness of rehabilitation interventions in controlling the trophic state of Lake Rawapening using a calibrated SWAT hydrological model. Seven scenarios were developed by combining land use changes from seasonal agriculture to agroforestry; fertilizer management in paddy fields; and lake deepening. Model simulations compared TP-C responses across scenarios. The results indicate that conversion of seasonal agricultural land to agroforestry is the most effective intervention, reducing TP-C by 33% (from 0.029 mg/L to 0.020 mg/L) and improving the trophic state from eutrophic to mesotrophic. Conversely, fertilizer management scenarios, even when applied according to recommended dosages, consistently increased TP-C by 14%. Lake deepening scenarios also tended to elevate TP-C by 20.9% due to increased water volume of 90% and phosphorus residence time (P-RS) of 92.4%. The study provides a measurable and replicable approach for simulating spatial dynamics and trophic responses to lake rehabilitation interventions. The findings support the development of multi-scenario management strategies for Lake Rawapening and other lakes in Indonesia.]]>
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