Studi Perencanaan Pengelolaan DAS dengan Model Optimasi Penggunaan Lahan di Bagian Hulu DAS Mahakam
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Land use which is not in accordance with the land capability, will cause land degradation. In Indonesia, there is progressive increase of critical land area size, every year, and this exerts an impact toward watershed damage. Objectives which are sought in the planning of watershed management often negate each other because from one point of view, there is a desire to maintain natural resources sustainability, and from other (economic) point of view, there is a desire to increase farmer's income. In order to obtain a model for planning sustainable watershed management, land use optiminazation was conducted and designed using the analysis of Linear Goals Programming (L GP) The study area had the size of 29 686 ha, comprising 3 subdistricts (namely Damai, Barong Tongkok and Melak) that were situated in the district of Kutai Barat, the province of East Kalimantan. The formulation of model for land use optimization was designed to achieve four targets, namely peak discharge. reduced rate of erosion (so that it is equal with or smaller than the targeted discharge and tolerable soil loss), ability of each farmer family to fulfill the need for food and rice, and ability of on farm income to create appropriate level of welfare. Research unit was homogeneous land unit. Data source for model input came from improvement of cropping pattern and alternative agrotechnology which was conducted by using simulation of CP factor. Data processing and analysis used the method of SCS, USLE and farm analysis. On the other hand, the completion of model used software General Algebraic Modeling System (GAMS) and Arcview 3,2. Land use with existing cropping pattern gave peak discharge of 116.39 m3/seconcj, erosion between 157-876 tonlha, production of upland rice 1.52 ton GKPlhalyear, and income Rp 3 268 636,-halyear. On the other hand, optimum land use pattern from the six scenarios model, showed better results as compared with the existing condition because ecologically, the land use could maintain the stability of peak discharge, and reduce erosion to the level below the targeted value. Although scenario model la and llla (with land use composition in the form of non irrigated rice field and dry land crop field) gave better result than those of existing conditions, but the occurring erosion were still higher than those in scenario model I, 11, Ill, and IV (with land use composition in the form of non irrigated rice field, dry land crop field, and estate field). This was because the priority for achieving erosion target in scenario la and llla was only up to the tolerable rate of soil erosion. Testing of scenario model I, 11, Ill, and IV showed that there was a tendency for increasing proportion of dry land crop field area size, but on the other hand, decreasing proportion of non irrigated rice field and estate field area size, if the target of achieving living standard is continuously increased. Spatially, recommendation that could be given for /and units of non irrigated rice field, dry land crop field and estate field is in the form of cropping pattern and agrotechnology LI *, L3b* , T5, T6, and KMZb*. Meanwhile, land use of other land units, are directed in accordance with land capability assessment. The best optimum land use pattern was obtained in scenario model IV because it produced on farm income and average production of upland rice, higher than those of other scenario models. Comparing with the existing condition, the scenario model IV could increase rice production and income, namely 9.87% and 136. 1 % respectively, but could reduce peak discharge and erosion up to 87% and 14% respectively.
- MT - Agriculture