Kajian dampak dinamika penggunaan lahan di DAS Wanggu terhadap sedimentasi di Teluk Kendari Sulawesi Tenggara

Abstract

The dynamic of land use in Wanggu Watershed had been causing land degradation disruption of hydrological function of the watershed and sedimentation in Kendari Bay. These degradations were indicated by the increasing of river fluctuation and erosion was higher than the local tolerable soil losts. The impact of erosion had further decreased land productivity, farmer’s income, and also increasing sedimentation in Kendari Bay as well. The objectives of this research were 1) to identify the biophysical characteristics of Wanggu watershed. 2) to study the impact of land use dynamic on erosion, run off, river flow fluctuation and sedimentation in Kendari Bay, 3) to develope land use models and agrotechnologies that can increase soil infiltration capacity, decrease run off coefficient, river flow fluctuation, rate of erosion and sedimentation in Kendari Bay, 4) to formulate land use planning and agrotechnology model in Wanggu watershed to guarantee sustainable land management. This research was carried out in September 2009 to August 2010. The result of this research showed that forested land characteristics were much better than those with other land uses particularly the characteristics that related to hydrological function of watershed. There were a continuous decrease forest land (1.1% per year) and bushes land (0.8% per year) but on the other hand a continuous increase of mixed plantation land (1.1% per year), dry land use (0.4% per year) and settlement area (0.4% per year). These dynamic giving the impact to increase erosion rate (12.7 tons/ha), surface run off (262.7 mm), run off coeficient (0.13) since 1992-2010, and in turn increase sedimentation rate in Kendari Bay. The source of those sediment come from land erosion 104.000 m3 per year (9,3%), from waste 21.310 m3 per year (2%), and river bank erosion-infrastructure-landslide 954.000 m3 per year (88,7%), to make total sedimentation in Kendari Bay was 1.071.000 m3 per year. The existing land use of Wanggu watershed in 2010 could not guarantee sustainable land management. The alternative land use planning for sustainable Wanggu watershed management is 33 % forest, 44 % mixed plantation,9% dry field, 1% bush and 13% settlement. The land use management in mixced plantation should be under Agrosilvopastoral with perennial crops (cacao, pepper, citrut fruit, banana, teak, elephant grass+3 cows), and in dry field should be under multiple cropping system(corn + cassava + peanut) - (green beans + legume + tomato). To increase productivity of both systems, the using of chemical fertilizers, manure, and compost should be applied as necessary.