Lake Management: Lesson Learn from Rawapening Lake

Rawapening was 1 out of 15 national lakes priorities with the main problem of eutrophication, sedimentation and water quality degradation. Eutrophication is the enrichment of aquatic ecosystem with nitrogen and phosphorous which induces uncontrolled aquatic plants, particularly water hyacinth (Euchornia crassipes (Mart.) Solms. As a result about 70% of Rawapening Lake was covered by water hyacinth. This research was conducted in order to evaluate the activities that had been done and to study the growth of water hyacinth with mesocosm in Rawapening Lake. As the smallest lake with huge typical problems of many others Indonesian lakes, the management of water hyacinth had decided as the first super priority program for Save Indonesian Lake, in Indonesia called Gerakan Penyelamatan Danau (Germadan) Rawapening. This was related to its functions for hydroelectricity power, agriculture, fisheries, source for drinking water, social and religious life, and tourism. Every years, there were activities to reduce water hyacinth in Rawapening, but its population still high even higher by times. When harvesting water hyacinth, one thing that do not under consideration is the growth rate of water hyacinth. Therefore, the program of reducing water hyacinth seems unsuccessful. The plastic mesocoms 1×1 m² was developed in 2 sites in Rawapening Lake, each site with 5 replication plots. Based on this research, within 6 days, the number of leaf was doubling. 1 plant of water hyacinth was covered 1 m² within 22 days. This growth rate have to be put into account when develop plan for harvesting water hyacinth.