Judul: The development of sustainable water resources of way betung watershed, Bandar Lampung city
Abstrak: Way Betung watershed is one of the most potential watersheds as water supplier in Lampung Province and the most potential water resources for Bandar Lampung City particularly for potable water provided by regional water supplier company (PDAM). The ever increasing population and economic activities in Bandar Lampung City resulted in the increasing need of clean water. However, over time, the conditions of Way Betung watershed as water resources supplier have been declined. Therefore, to improve or to restore the conditions of Way Betung watershed, the forest and land rehabilitations programs are necessary. Thus research was aimed: (a) to study the impact of land use change in Way Betung watershed on its potential as water resources supplier of Bandar Lampung City, (b) to study the economic value of Way Betung water resources (c) to formulate sustainable water resources development plan of Way Betung watershed. The impact of land use change on the Way Betung water resources was analyzed by a regression method, and the annual economic value of water resources was analyzed by Willingness to Pay (WTP) method. The development plan of sustainable water resources of Way Betung watershed was arranged in five scenarios. To determine the best scenario, the simulations of the erosion level by the USLE method and the runoff volume by the SCS method were performed. The results showed that the land use change of Way Betung watershed (1991-2006) resulted in the increasing of the annual run off coefficient, the maximum daily discharge (Q max), and the decreasing of the daily minimum discharge (Q min), as well as the increasing of the river discharge fluctuation. The total annual economic value of water resources of Way Betung watershed was Rp101.1 billion/year and the total willingness to pay value for the rehabilitation of Way Betung watershed was Rp1.5 billion/year, which were derived from PDAM sector, tourism, water mineral companies, households and paddy field farmers in the upstream watershed. The best development of sustainable water resources of Way Betung watershed was the scenario-4 (the forest as much as 30% of watershed areas + alley cropping on mixed farms). Scenario-4 will reduce the erosion to lower than the tolerable soil loss (TSL), will decrease the fluctuation of monthly run off from 64.7 to 30.9, and the forest rehabilitation will be achieved in the best time (10 years with a scheme-B). Therefore, economically the water users community are willing to pay the rehabilitation costs (WTP) and socially it is accepted by the society.
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Judul: An Approach to Water Resource Management through Land Use Planning in the Way Besai Watershed in Lampung Province
Abstrak: Land use changes may have an impact on the decrease in water supply. In the meantime, water demand keeps increasing along with the increase in population and economic activities. The Way Besai Watershed, covering an area of 44 720 ha, plays an important role in providing water resources. Therefore, to ensure the sustainability of the water resources, there should be a good land use planning, particularly in relation with the efforts to protect the forest areas. This research, which was conducted in the Way Besai Watershed in 2013, aimed: (1) to find out the water supply and demand, (2) to assess water balance in terms of the supply and demand, (3) to formulate recommendations for the best land use planning, and (4) to study the economic value of the water resources. The total water demand by households, livestock activities, rice fields, and hydropower (PLTA) was calculated. Similarly, the water supply was calculated based on surface runoff using various mathematical equations. Next, SCS Model was used in the formulation of different scenarios of land use planning. Scenario 1 described the existing biophysical condition of the Way Besai Watershed. Scenario 2 was related to the land management by accommodating community activities in the forest through HKm by applying an agroforestry planting pattern. Scenario 3 was the combination Scenario 2 and the forest rehabilitation outside HKm area. Scenario 4 was the combination of scenario 3 and the efforts to change the pattern of coffee cropping monoculture. The best recommendation scenario for land use planning was selected based on hydrological as well as economic aspects using benefit and cost ratio (BCR). The water need of the Way Besai Watershed in 2011 was 441 450 909 m3/year, and it could still be fulfilled by the water supply amounting to 460 452 600 m3/year. In terms of the distribution, however, based on the analysis of water balance, there was a shortage of water supply during the dry season, particularly in July, August, September and October, that is, 7 861 736; 16 246 136; 17 800 951 and 21 384 649 m3, respectively. The simulation results of land use planning showed that the surface runoff of scenario1 was 1 073.48, scenario 2 was 1 061.25, scenario 3 was 1 056.09, and scenario 4 was 1 055.79 mm/year. The total runoff coefficient of Scenario 1, Scenario 2, Scenario 3 and Scenario 4 were 39.27, 38.72, 38.54 and 38.52 %, respectively. The surface runoff volume ratio of Scenario 1, Scenario 2, Scenario 3 and Scenario 4 were 6.08, 5.88, 5.47 and 5.47 %, respectively. Meanwhile, water storage variances of Scenario 2, Scenario 3 and Scenario 4 were 5 468 276; 7 774 304; and 7 911 617 m3/year, respectively. The simulations formulated showed that hydrologically scenario 4 was the best as indicated by the decreased in surface runoff, total runoff coefficient, and surface runoff volume ratio, and the increase in water supply during the dry season (July-October). The total economic value of water utilization in the Way Besai Watershed was Rp 108 936 635 040 per year. The highest water utilization
Keyword: curve number, landuse simulation, water demand, water economic value, water supply.

Judul: Grup dan Homomorfisma Grup pada Rubik Revenge
Abstrak: Rubik cube is a kind of puzzle game. A player must arrange rubik sides, which have been disordered, back to the position where every side has the same colour. This paper does not focus on the settlement solution, but instead on proving the existence of a group homomorphism between rubik movement group and S96 symmetric permutation group in rubik revenge. Firstly, it has been proved that rubik movement set is a group. Then, it also has been proved that the M set, which contains numeric labels of 1 until 96 in cubinos sides, is S96 symmetric permutation group.
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