Reservoir sedimentation regime analysis: case study of Kedungombo reservoir and Sermo reservoir

The Kedungombo and the Sermo Reservoirs have problems in fulfilling basic services because of sedimentation. Sedimentation that occurs in each of the reservoirs would form a specific reservoir sedimentation pattern that is supposed to be similar because the hydrology and physiography conditions of the reservoir's catchment area are similar. This study aims to determine the dynamics of sedimentation patterns that occur in the dead storage for reviewing the characteristics/sedimentation regime of the two reservoirs. The analysis was carried out by processing bathymetrical data which were processed into a digital terrain model (DTM) using ArcGIS. Furthermore, the storage volume, sedimentation volume, storage percentage, and specific reservoir sedimentation rate are calculated. The results showed that the two reservoirs showed an increase in sedimentation volume each year so that the reservoir characteristic curve shifted from the plan graph. The dead storage capacity of Kedungombo Reservoir is 100% in 1989 to 43% in 2016 and 100% of Sermo Reservoir in 1997 to 58% in 2011. The specific reservoir sedimentation rate, i.e. 0.0031 and 0.0042 million m3/year/km2 for the Kedungombo Reservoir (between 1989 and 2016) and the Sermo Reservoir (between 1997 and 2011) respectively, indicating that the two reservoirs are in the same regime

Analysis of Floating Net Cages on The Carrying Capacity of The Darma Reservoir

Darma Reservoir functions as a reservoir for irrigation, fisheries, and recreational and sports facilities. Currently, it only functions for irrigation and fish farming by floating net ponds. The development of floating net frameworks was so rapid that it conflicted with reservoir management. This study aims to determine the density of the floating net framework of the sedimentation conditions of the Darma Reservoir and to determine the development of the sedimentation rate of the Darma Reservoir in relation to the service life of the reservoir characterized by reduced dead storage. The first step was carried out by surveying the presence of the number of floating net cages, the distribution of the feed, the percentage of feed demand, the carrying capacity of the reservoir, then a topographic survey of the depth of the Darma reservoir to determine the capacity, rate and volume of sediment deposits. This study used quantitative approach, it began with distributing questionnaire forms and measuring the depth of the reservoir. The current condition of floating net cages is 4916 occupying 5.819% of the inundation area of 312.15 ha with an elevation of 712.50 m, while floating net cages are allowed according to the carrying capacity of Darma Reservoir waters amounting to 1,021. tons / harvest while the spawning pond is 3.483 tons/harvest. The volume of normal active storage for elevation 712.50 in 2020 is 28.086 million m3, while the volume of sediment deposits is 9.262 million m3 32.98%, the average sediment rate in the reservoir from 1988 to 2020 is 0.2894 million m3/year, while the sediment rate in catchment area Dam Dharma with an area of 23.5 km2 of 71.873 mm/year. Sedimentation in the Darma Reservoir has exceeded the limit of the base elevation of the reservoir, the elevation of the dead reservoir and the lowest elevation, but the reservoir is still functional. The planning life of the darma reservoir is up to 50 years, the suitability of the initial planning of operations in 1970 with operations until 2020.

PENGARUH PELAKSANAAN FLUSHING TERHADAP PENGURANGAN VOLUME AIR DAN SEDIMEN DI WADUK MRICA

Waduk Mrica merupakan salah satu waduk di Indonesia yang terus mengalami problematik terkait peningkatan sedimentasi. Sampai dengan tahun 2017, total sedimen yang masuk ke waduk telah mencapai 114 juta m3. Angka ini di satu sisi sudah mencapai kapasitas dead storage dari waduk tersebut dan dianggap telah mengganggu kinerja operasional waduk. Berbagai upaya terus dilakukan oleh manajemen waduk utnuk mengurangi peningkatan sedimentasi. Upaya yang sering dilakukan adalah dengan melakukan flushing untuk membuang sedimen yang masuk dan mengurangi rsiko terhadap operasional PLTMH di waduk tersebut. Paper ini dimaksudkan untuk menganalisis pengaruh upaya flushing di waduk Mrica terhadap resiko pengurangan volume air terbuang dibandingkan dengan volume sedimen yang terbuang. Metode yang diterapkan dalam analisis ini menggunakan analisis statistika untu melihat hubungan dalam upaya pengurangan sedimen dan volume air yang terbuang dalam kurun waktu tertentu. Hasil penelitian ini menunjukkan bahwa jumlah volume air yang terbuang jauh lebih besar dibandingkan volume sedimen yang ikut terbuang pada saat pelaksanaan flushing. Total volume sedimen yang terbuang kurun waktu 2009-2018 dan prediksi tahun 2018-2028 hanya mencapai 29,986 juta m3, sedangkan volume air yang ikut terbuang di kurun waktu tersebut mencapai 971,817 juta m3

How the Dead Storage of Consumer Electronics Creates Consumer Value

Consumers across the globe tend to store their small electronic devices when they reach their end of life instead of disposing of them. This is a problem because if end-of-life devices are not recovered from consumers’ homes, the devices cannot be re-used or recycled, leading to increased production. We study what motivates consumers to store their end-of-life devices by looking at how storage creates consumer value. Applying a practice-based understanding of value, we find that storage is a social practice that generates value by protecting consumers from four different kinds of risk: practical risks, existential risks, environmental risks, and moral risks. Storage gives consumers a sense of security in their everyday lives and thus generates what we call ‘security value’. This notion implies that even though end-of-life devices sit idle in consumers’ homes, their value generating capacity remains active. The findings have implications for the role of consumers in reverse logistics strategies for sustainable systems.

CATCHMENT AREA EROSION STUDY IN ESTIMATION OF RESERVOIR CAPACITY AT THE END OF LIFE EXPECTANCY (CASE STUDY : GONDANG RESERVOIR, KARANGANYAR)

Gondang Reservoir is one of The National Strategic Projects. Located in Karanganyar Regency, Central Java Province, Gondang Reservoir has 2.08 Mm3 flood storage, 5.03 Mm3 effective storage, 2.03 Mm3 dead storage and 30 years lifetime. In the dam management, one of the problems that often occurs is sedimentation. To overcome this problem, we need to know the sedimentation rate and distribution pattern of Gondang Reservoir for optimalizing the reservoir management. To predict the distribution pattern of the reservoir we use Empirical Area Reduction Methods. The findings of the study show that the sediment volume of the reservoir throughout its effective life is 2,79 Mm3, the new zero elevation is +496 m, there is no remaining dead storage and the remaining effective storage is 2.2 Mm3. This indicates that theoretically the reservoir will work well up to its life expectancy. Dam sedimentation management with structural or non structural must be planned especially at effective storage. Dam sedimentation management at effective storage is very important in order to maintain Gondang Reservoir benefits.

PENGARUH SEDIMEN TERHADAP UMUR LAYANAN PADA TAMPUNGAN MATI (DEAD STORAGE) WADUK KRISAK DI WONOGIRI DENGAN METODE USLE (UNIVERSAL SOIL LOSSES EQUATION)

<p>Salah satu masalah dalam pengelolaan waduk adalah sedimentasi. Sedimen diakibatkan dari erosi, angkutan sedimen bertambah maka sedimen akan mengendap di dalam waduk dan kapasitas tampungan mati waduk akan berkurang. Kemudian umur waduk tersebut akan mengalami percepatan pengurangan layanannya. Daerah Aliran Sungai (DAS) Bengawan Solo merupakan salah satu DAS di Indonesia yang segera memerlukan penanganan (Joko Sutrisno, 2011). Kondisi daerah aliran sungainya Bengawan Solo sudah memprihatinkan, terutama besarnya laju erosi yang cukup tinggi serta produktivitas lahan yang dinilai semakin menurun. SUB-DAS Jlantah yang berlokasi di muara Sungai Krisak berada di dekat tempat pengambilan air Waduk Krisak, dinilai menyumbang sedimentasi terbesar yang akan sangat mengganggu operasional waduk. Selain menyebabkan sedimentasi, erosi juga akan menyebabkan berkurangnya ketebalan tanah dan berkurangnya tingkat kesuburan tanah di wilayah hulu. Tujuan dari penelitian ini adalah mendapatkan pengaruh sedimen terhadap umur waduk pada tampungan mati menggunakan metode USLE. Metode penelitian ini menggunakan metode deskriptif kuantitatif dan secara garis besar dibagi menjadi 3 tahapan pelaksanaan sebagai berikut : pengumpulan data, analisa data, kesimpulan dan saran. Data yang digunakan berupa data curah hujan jangka waktu 10 tahun antara tahun 2009 sampai 2018. Peta yang digunakan adalah Peta Tanah, Peta Topografi dan Peta Tata Guna Lahan. Pengumpulan data dilakukan melalui studi literatur serta menggunakan data yang dimiliki Balai Penelitian Teknologi Kehutanan Pengelolaan Daerah Aliran Sungai Surakarta, Balai Besar Wilayah Sungai Begawan Solo dan Jasa Tirta Wonogiri. Hasil analisis berdasarkan prediksi erosi USLE diperoleh 2.437.833,4990 ton/tahun dengan volume yang masuk pada tampungan sedimen Waduk Krisak yaitu 816.147,8068 m3/tahun dengan umur layanan 4,6 tahun.</p>

A Novel Buffer Tank to Attenuate the Peak Flow of Runoff

Impermeable pavements and roofs in urban areas convert most rainfall to runoff, which is commonly discharged to local sewers pipes and finally to the nearby streams and rivers. In case of heavy rain, the peak flow of runoff usually exceeds the carrying capacity of the local sewer pipes, leading to urban flooding. Traditional facilities, such as green roofs, permeable pavements, soakaways, rainwater tanks, rain barrels, and others reduce the runoff volume in case of a small rain but fail in case of a heavy rain. Here we propose a novel rainwater buffer tank to detain runoff from the nearby sealed surfaces in case of heavy rain and then to discharge rainwater from an orifice at the tank’s bottom. We found that considering a 100m2 rooftop with 0.80 runoff coefficient and a 10cm rainfall depth for an hour, a cubic tank with internal edge side of a square of 2 m attenuates the peak flow about 45%. To reduce a desirable peak flow, the outlet orifice of the buffer tank must be optimized according to site-specific conditions. The orifice can be set at an elevation from the tank’s bottom to create a dead storage for harvesting rainwater.

Flood Mitigation Using an Innovative Flood Control Scheme in a Large Lake: Dongting Lake, China

A large lake plays an important role in mitigating flood disasters in its nearby regions during the flooding period; however, the effect is limited, because most of its storage capacity becomes dead storage prior to the arrival of the flood wave. In the current study, an innovative flood control scheme (IFCS) is applied to Dongting Lake (the second largest freshwater lake in China) to alleviate flood disasters. MIKE 21 FM was used to examine its feasibility to mitigate flood disasters. One of the largest floods in the 20th century, the 1998-type flood, was modelled and the maximum water levels with/without IFCS were compared. The result shows that the effective flood control storage could be at least doubled when compared with the natural condition once IFCS was applied. The peak flood level in the Dongting Lake could be lowered by at least 0.32 m at the Chenglingji station in the same flood passage of Dongting Lake. The case study reveals that, after applying IFCS, the hydraulic gates play a very important role in floodwater regulation and further study should be conducted to find the optimized operation for each gate in the flood control scheme system.

Reservoir Sedimentation Volume Changing Analysis of Pangsar Soedirman Dam Through USLE Based Rainfall Characteristics

Penelitian ini dimaksudkan untuk menganalisis pengaruh karakteristik curah hujan di daerah tangkapan air Waduk Pangsar Sudirman terhadap peningkatan sedimentasi Waduk. Penelitian dilakukan menggunakan formula USLE dengan faktor curah hujan (erosivitas) di DTA Waduk Pangsar Soedirman sebagai penentu. Data laju sedimentasi waduk tahun 1989-2010 digunakan sebagai verifikasi hasil analisis. Hasil penelitian menunjukkan DTA Waduk Pangsar Soedirman memiliki curah hujan tahunan rata-rata sebesar 3.900 mm/tahun. Karakteristik curah hujan ini menyebabkan potensi kejadian erosi dan sedimentasi cukup besar. Volume sedimen di Waduk Pangsar Soedirman sejak tahun 1989 hingga 2010, mencapai 92,77 juta m3 atau sekitar 60 % dari volume dead storage dengan volume inflow rata-rata sedimen mencapai 4,2 juta m3/tahun.

Erosion index formulation with respect to reservoir life in the upper Citarum watershed

This study aimed to formulate erosion index in the upper Citarum watershed with respect to the Saguling reservoir life. Soil and Water Assessment Tool model was incorporated to simulate hydrological processes in the catchment. From the calibration and validation results, the model is considerably of good performance. The simulated sediment inflow at Nanjung outlet was then extrapolated to determine the sediment inflow into the reservoir. The study revealed that the average value of sediment inflow into the reservoir is 29.24 tonnes/ha/year just below the tolerable erosion limit of 30 tonnes/ha/year assumed by Hammer (1981). It was also found that the relationship between sediment yield and sediment inflow is non linear. Erosion index is formulated as the ratio between the mean annual sediment yield generated in the watershed and the mean annual sediment yield that leads dead storage to be full in the designated life of the reservoir. Erosion index equals to 1.0 indicates that the dead storage will be full in the designated life of the reservoir. A classification of erosion index can be subsequently be made based on erosion index and reservoir life relationship.