Judul: Water Yield from Several Land Use Changes of The Upper Brantas Watershed
Abstrak: Wilayah Sub DAS Brantas Hulu merupakan daerah yang cukup baik sebagai penyedia air untuk berbagai kebutuhan. Selama kurun waktu 2009-2020 telah terjadi alih guna lahan di Sub DAS Brantas Hulu yang didominasi oleh penurunan luas hutan dan persawahan diikuti oleh perluasan wilayah pemukiman. Penggunaan lahan dan perubahannya akan mempengaruhi hasil air, dimana tutupan lahan berfungsi untuk memodifikasi evapotranspirasi dalam penghitungan nilai hasil air. Penelitian ini bertujuan untuk mengetahui hasil air pada beberapa alih guna lahan di Sub DAS Brantas Hulu dari tahun 2009 hingga 2020. Penelitian ini dilakukan dengan menganalisis data spasial tutupan lahan Sub DAS Brantas Hulu yang digabungkan dengan set data suhu udara dan curah hujan untuk menghitung nilai evapotranspirasi tanaman serta hasil air. Hasil penelitian ini menunjukkan bahwa alih guna lahan memiliki kaitan dengan hasil air, dimana peningkatan penggunaan lahan dengan nilai Kc yang lebih rendah akan meningkatkan nilai hasil air. Hal ini tampak jelas pada tahun 2016, dimana terjadi penambahan lahan pemukiman seluas 202,01 Ha diikuti pengurangan lahan hutan dan pertanian dengan total luasan 205,91 Ha. Alih guna lahan ini berdampak pada penurunan nilai evapotranspirasi diikuti peningkatan nilai hasil air., The Upper Brantas Sub-Watershed area is an area that is quite good as a water provider for various needs. During the period 2009-2020, there has been a land use change in the Upper Brantas sub-watershed which is dominated by a decrease in forest and rice fields followed by the expansion of residential areas. Land use and its changes will affect water yields, where land cover works to modify evapotranspiration in calculating water yield values. This study aims to determine the water yield from several land use changes of the Upper Brantas Sub-Watershed from 2009 to 2020. This study was conducted by analyzing the spatial data of land cover in the Upper Brantas Sub-Watershed which was combined with air temperature and rainfall data to quantify the value of plant evapotranspiration. and water yield. The results of this study indicate that during the 2009-2020 period there has been a change in the proportion for each type of land cover and there has been the addition of two new types of land cover. Land use change has a relationship with water yields, where increasing land use with a lower Kc value will increase the water yield value. This was clearly observable in 2016, where there was an addition of 202.01 Ha of residential land followed by a reduction in forest and agricultural land with a total area of 205.91 Ha. This land use change has an impacton decreasing the value of evapotranspiration followed by an increase in the valueof water yields.
Keyword: crop coefficient, evapotranspiration, land cover, rainfall

Judul: Evaluasi Perubahan Respon Hidrologi pada Kondisi Penutupan Lahan Berbeda di DAS Sanggai Kalimantan Timur
Abstrak: Perubahan penutupan lahan saat ini menjadi salah satu masalah paling mendesak pada daerah aliran sungai (DAS), yang dapat membawa pengaruh pada jasa ekosistem, karakteristik hidrologi tanah, dan pengelolaan air di wilayah DAS. Penelitian ini bertujuan mengevaluasi perubahan respon hidrologi akibat perubahan penutupan lahan di DAS Sanggai Kalimantan Timur tahun 2011 dan 2020 dengan menggunakan model Soil and Water Assessment Tool (SWAT). Respon hidrologi yang dikaji berupa nilai aliran permukaan, aliran lateral, aliran air tanah, hasil air, dan evapotranspirasi. Simulasi model SWAT telah melalui proses kalibrasi (SWAT-CUP SUFI-2) dan validasi pada tahun 2011-2015 dan 2017-2020 menggunakan debit aliran observasi. Kinerja model SWAT telah menunjukkan hasil yang memuaskan berdasarkan uji statistik R2, NSE, PBIAS, KGE, dan RSR. Periode penelitian tahun 2011 dan 2020 menunjukkan perubahan penutupan lahan yang semula didominasi oleh lahan pertanian, transmigrasi dan perkebunan berubah menjadi hutan tanaman, perkebunan dan semak belukar. Respon hidrologi yang terjadi di DAS Sanggai akibat perubahan penutupan lahan yaitu meningkatnya nilai aliran lateral, aliran air tanah, dan evapotranspirasi sebesar 22,2%, 11,2% dan 1,5%. Hal sebaliknya terjadi pada aliran permukaan dan hasil air yang berkurang masing-masing sebesar 26,6% dan 1,3%. Adanya evaluasi dan perubahan nilai ini sangat relevan untuk pengelolaan sumber daya air yang berkelanjutan dalam jangka panjang., Changes in land cover are currently one of the greatest pressing issues facing the watershed, as they can have impacts on ecosystem services, hydrological properties of soil, and water management in watershed areas. In the present study, the Soil and Water Assessment Tool (SWAT) was used to evaluate the hydrological responses to land cover changes in Sanggai Watershed, East Kalimantan during period 2011 and 2020. The hydrological responses examined include surface runoff, lateral flow, groundwater flow, water yield, and evapotranspiration. The SWAT model simulations were calibrated (using SWAT-CUP SUFI-2) and validated for the periods of 2011-2015 and 2017-2020 using observed flow. The performance of the SWAT model showed satisfactory results based on statistical tests such as R2, NSE, PBIAS, KGE, and RSR. During the study period (2011 and 2020), there were changes in land cover where agricultural land-generic, transmigration, and orchard were changed into evergreen forest, orchards and shrublands. The hydrological responses in the Sanggai Watershed due to land cover changes showed an increase in lateral flow, groundwater flow, and evapotranspiration by 22,3%, 11,2% and 1,5%. Conversely, surface runoff and water yield decreased by 26,6% and 1,3%. The evidence of these changes and the evaluation of their effects are particularly relevant for the long-term sustainable management of water resources.
Keyword: debit aliran sungai, hidrologi, neraca air, penggunaan lahan, SWAT

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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