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: Water Yield Analysis using Water Balance Approach in The Lower Citarum Watershed
Abstrak: Perubahan lahan skala besar dan curah hujan mampu mengubah jumlah aliran daerah aliran sungai (DAS) yang berpengaruh besar pada besar kecilnya hasil air, sehingga penelitian ini bertujuan untuk mengevaluasi pengaruh perubahan lahan dan curah hujan terhadap hasil air. Proses dilakukan dengan menganalisis perubahan lahan dalam kategori vegetasi non-vegetasi berdasarkan jenis tutupan lahan. Selanjutnya, dilakukan analisis hasil air melalui perbandingan hasil air antara tahun 2011 dan 2020. Sebelumnya, dilakukan simulasi perhitungan hasil air dengan salah satu variabelnya merupakan variabel bebas sebagai uji adanya pengaruh perubahan lahan dan curah hujan terhadap hasil air. Hasil air dihitung dengan mengurangi curah hujan dengan nilai evapotranspirasi tanaman (ETc) yang didapatkan melalui perkalian nilai evapotranspirasi standar (ET0) dengan koefisiensi tanaman (Kc). Analisis korelasi dilakukan pada setiap nilai perubahan Kc, ET0, curah hujan, dan hasil air untuk mengevaluasi seberapa besar variabel tersebut berpengaruh pada hasil air. Hasil menunjukkan bahwa vegetasi berkurang sebesar 14953 ha atau 5.7% dan hasil air rata-rata bertambah 605 mm/tahun. Uji korelasi menunjukkan nilai yang tinggi antara variabel Kc dan curah hujan dengan hasil air, yaitu sebesar –0.797 dan 0.997. Dapat disimpulkan bahwa perubahan curah hujan menjadi faktor alami, sedangkan tutupan lahan menjadi faktor antropogenik yang mampu memengaruhi hasil air., Large-scale land changes and rainfall can alter the streamflow of a watershed, significantly impacting water yield. This study aims to evaluate the influence of land changes and rainfall on water yield. The process involved analyzing land changes categorized into vegetation and non-vegetation based on land cover types. Subsequently, water yield was analyzed by comparing the water yield between 2011 and 2020. A simulation of water yield calculations was conducted, using a variable as a free variable to test the influence of land changes and rainfall on water yield. Water yield was calculated by subtracting rainfall with the crop evapotranspiration (ETc) value, obtained by multiplying the reference evapotranspiration (ET0) with the crop coefficient (Kc). Correlation analysis was conducted for each value of Kc, ET0, rainfall, and water yield to evaluate the extent to which these variables influence water yield. The results show that vegetation decreased by 14953 ha or 5.7%, and the average water yield increased by 605 mm/year. Correlation tests showed high values between the variables Kc and rainfall with water yield, which were -0.797 and 0.997, respectively. It can be concluded that changes in rainfall are a natural factor, while land cover is an anthropogenic factor that can influence water yield.
Keyword: penggunaan lahan, vegetasi, non-vegetasi, DAS Citarum Hilir

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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