Model Dinamika Nitrogen dan Fosfor sebagai Upaya Pengendalian Eutrofikasi Danau Laut Tawar Aceh Tengah

Abstract

Lake Laut Tawar (freshwater lake) is located in a mountainous area at the height of 1,230 above sea water, on the east side of Takengon, Aceh Tengah regency. The increase in activities around the catchment area and waters causes changes in the tropical state of lake water. This research aims to construct the model of a dynamic system to predict the level and time of eutrophication of Lake Laut Tawar. This research is conducted.from October 2016 to September 2017. The research area is 24,750 Ha which includes I8,877.23 Ha of the catchment area, 5,862 Ha of lake water, and 10.77 Ha of the lake water outlet. Based on the area use. the activities around the catchment area include jungle, bushes, plantation, rice.field, and settlement. The number of population living in the settlement area is 74,475 people. Floating net cages (keffong) are used in 2.79 Ha of lake water. The amount of nutrients loaded to Lake Laut Tawar is 365.80 ton N/year and 85.59 ton Plyear, while 195.65 ton N/year and 7.76 ton Plyear are from the Catchment area. The activities using floating net cages produce 170. I6 ton N/year and 77.83 ton Plyear. In addition, Lake Laut Tawar also receives suspended sediment from the catchment area in the amount of I9, I 44 ton/year. The fake water indicates the concentration of TN at 7I 5 µg/L, TP at 34 µg/L, TSS at 66 mg/L Chlorophyll-a at I I µg/L, and in secchi disk depth at 2.32 meter. The tropic status of Lake Laut Tawar waters in 20 I 7 indicates a mild eutrophication level with the tropic index value at 52.20. The tropic: status of Lake Laut Tawar is predicted to be remained at the mild eutrophication level until 2027 with the tropic index value increasing up to 53.59. Lake Laut Tawar eutrophication control can be carried out by limiting the amount offish food and P concentration in the fish food inside the floating net cage.