Judul: Extreme Rainfall in the Bengawan Solo Watershed
Abstrak: Beberapa dampak curah hujan ekstrem telah terjadi di DAS Bengawan Solo, antara lain banjir besar, korban jiwa dan harta benda, kerusakan infrastruktur, terganggunya pertanian, degradasi lingkungan, serta dampak sosial dan ekonomi. Penelitian ini mengkaji curah hujan ekstrim di DAS Bengawan Solo dengan menganalisis data curah hujan harian periode tahun 1991 sampai 2020 di tiga pos hujan observasi, yaitu Musuk, Tinap, dan Lowayu yang masing-masing terletak di bagian hulu, tengah, dan hilir DAS Bengawan Solo. Teori Nilai Ekstrim (Extreme Value Theoru/EVT) dengan pendekatan Block Maxima yang berdistribusi Generalized Extreme Value (GEV) digunakan untuk menentukan estimasi nilai pengembalian curah hujan maksimum, sedangkan metode Uji Mann-Kendall digunakan untuk mengetahui tren tahunan indeks curah hujan ekstrem sesuai rekomendasi Expert Team on Climate Change Detection and Indices (ETCCDI). Penelitian ini menemukan bahwa perkiraan nilai pengembalian tertinggi curah hujan maksimum tahunan untuk periode 5, 10, 20, 30, dan 50 tahun terdapat di stasiun Musuk dengan nilai yang meningkat seiring dengan lamanya periode pengembalian. Tren signifikan terlihat di wilayah tengah dan hilir dalam hal intensitas curah hujan harian, jumlah hari hujan tahunan dengan curah hujan ≥ 1 mm per hari, jumlah maksimum tahunan lima hari hujan berturut-turut, dan jumlah hari basah berturut-turut setiap tahun dengan curah hujan ≥ 1 mm per hari. Terjadi pula peningkatan jumlah maksimum curah hujan tahunan selama satu hari di stasiun Lowayu yang mengindikasikan semakin tinggi risiko bencana akibat tingginya curah hujan, serta adanya tren peningkatan jumlah curah hujan tahunan di Stasiun Musuk, Tinap, dan Lowayu yang berdampak pada peningkatan potensi ketersediaan air untuk memenuhi kebutuhan air di wilayah tersebut., Several impacts of extreme rainfall have already occurred in the Bengawan Solo watershed, including devastating floods, loss of lives and property, infrastructure damage, disruption of agriculture, environmental degradation, and social and economic impacts. This study examines extreme rainfall in the Bengawan Solo watershed by analyzing daily rainfall data collected from 1991 to 2020 at three surface observation stations namely Musuk, Tinap, and Lowayu, which are respectively located in the upstream, middle, and downstream of the Bengawan Solo watershed. The Extreme Value Theory (EVT) using the Block Maxima approach with a Generalized Extreme Value (GEV) method was used to determine the estimated maximum rainfall return value, while the Mann-Kendall Test method was employed to assess annual trends in extreme rainfall indices recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI). The study found that the highest estimated return value of annual maximum rainfall for 5, 10, 20, 30, and 50-year periods was in Musuk station, which increased with the length of the return period. Significant trends were observed in the middle and downstream areas for daily precipitation intensity, the number of annual rainy days with precipitation ≥ 1 mm per day, the annually maximum amount of five consecutive precipitation days, and the annually number of consecutive wet days with precipitation ≥ 1 mm per day. There is also an increase in the maximum amount of annual rainfall for one day (Rx1day) at Lowayu station, which indicates a higher risk of disaster due to high rainfall, as well as an increase in the trend
Keyword: Bengawan Solo Watershed, Extreme Rainfall Indices, Generalized Extreme Value, Return Level, Trend Analysis

Judul: Analisis Tren Jangka Panjang Curah Hujan dan Debit Daerah Aliran Sungai Bengawan Solo
Abstrak: Bengawan Solo Watershed is classified as one of the most degraded watershed in Indonesia. The Watershed usually was utilized as water resource for irrigation, transportation and industry. The problems in the Bengawan Solo Watershed is deforestation, illegal logging and land conversion. This research aimed to find out trend of rainfall and streamflow in Bengawan Solo Watershed for period of 1980-2010. Twelve rainfall stations in the Watershed were chosen for rainfall trend analysis and calculating rainfall area. The trend analysis was divided into two parts that is before and after reformation era (year at 1998). Trend analysis was performed using Mann-Kendall test at 95% confidence interval (α= 5%). Research result showed that before reformation era we found there were no significantly trend for rainfall and annual streamflow. However, after reformation era we found that there was a significantly negative trend for rainfall at most stations, but significantly positive trend for average annual streamflow. Coefficient of runoff in Bengawan Solo Watershed range 0,4-0,81 and did not occur a significantly trend for this research.
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Judul: Synthesis of Apatite - Chitosan Composite Using Duck Eggshell and Chitosan with Temperature and pH Control
Abstrak: Composite of apatite-chitosan was prepared by using chitosan as polymer matrix. Calcium phosphate was prepared from CaO and (NH4)2HPO4, which the ratio Ca : P had to be 1.67. Chitosan is produced by deacetilase from biopolymer chitin. Duck eggshell (95% CaCO3) as starting material was converted to be calcium oxide (CaO) through calcinations with temperature 1000oC for 5 hours. In-situ and ex-situ methods were prepared from apatite and chitosan (dissolved with acetate acid 2%). Calcium phosphate prepared for bone implantation, but it is too fragile and brittle to be implant into the body. So addition of chitosan can decrease crystalinity and increase mechanic characteristic (tougher). Composite apatite-chitosan was resulted by fast precipitation. Fast precipitation was held in a breaker glass with nitrogen atmosphere, under controlled temperature at 37oC and pH 7, in order to increase amount of hydroxyapatite. Precipitation with CaO which was dropped by (NH4)2HPO4. Hydroxyapatite and chitosan were appearing at samples with in-situ and ex-situ methods which indicating by peak matching of XRD (closed lattice parameter, crystal size), overlapping at FTIR spectra and supporting by SEM picture (homogenous and agglomerated particle). However, it still needs further research to examine biocompatibility osteoconductive degree of sample by in-vivo and in-vitro test.
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