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Iwan Ridwansyah
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Chemical Engineering, Chemistry & Bioengineering Earth & Planetary Sciences Engineering Environmental Science

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Flood Pulse and Aquatic Habitat Dynamics of The Sentarum Floodplain Lakes Area Hidayat Hidayat; Siti Aisyah; Riky Kurniawan; Iwan Ridwansyah; Octavianto Samir; Gadis Sri Haryani
Indonesian Journal of Limnology Vol. 1 No. 1 (2020): Indonesian Journal of Limnology
Publisher : Indonesian Society of Limnology

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (796.753 KB) | DOI: 10.51264/inajl.v1i1.2

Abstract

The Lake Sentarum is a complex of floodplain lakes in the middle part of the Kapuas River system in West Kalimantan, Indonesia. The area has a great ecological and economic importance, however, the Sentarum lakes complex and its catchment area are generally threatened by deforestation, fire, monoculture agroindustry, and pollution.The objective of this research is to establish the hydrological characteristics of the Sentarum lakes area and to reveal the dynamics of aquatic habitat resulted from changing water levels. Data were collected during our field campaigns of 2013-2017 representing the seasons. The water level was measured using a pressure sensor placed at the Lake Sentarum National Park resort, while rainfall data were obtained from the data portal of the Tropical Rainfall Measuring Mission. Inundation monitoring was carried out using a time-lapse camera. A hydrological model is used to simulate water levels beyond measurement period. Water quality and fish sampling were carried out at the lake area. Vegetation observation was carried out at the selected riparian zone of the lake area using the line transect method. Water level records show that the Sentarum floodplain lakes have two peaks of inundation period following the bimodal pattern of rainfall in the equatorial Kapuas catchment. This water level dynamics induced changes in water quality, nutrient availability, vegetation cover, and fish diversity found in the Sentarum lakes area. Despite its seasonal changes, water quality of Sentarum lakes is generally good and suitable for aquatic biota. Fish diversity of the Sentarum lakes is relatively higher during high water periods.
Dissolved Oxygen Profiles and Its Problems at Lake Maninjau, West Sumatra – Indonesia Luki Subehi; Iwan Ridwansyah; Takehiko Fukushima
Indonesian Journal of Limnology Vol. 1 No. 1 (2020): Indonesian Journal of Limnology
Publisher : Indonesian Society of Limnology

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (439.808 KB) | DOI: 10.51264/inajl.v1i1.3

Abstract

In general, the tropical lake in Indonesia is one of the unique ecosystems which are functioning in both ecological and economic services. This study aims to analyze the dissolved oxygen profile of caldera tropical lake represented by Lake Maninjau at West Sumatera, Indonesia, and its impacts. Lake Maninjau is not only for culture fisheries but also serves as important hydroelectricity power. Surveys at Lake Maninjau were conducted in August 2006, March 2014, September 2017, and April 2018. The results showed that the average depth is 105 m. It covers 13,260 ha of an area with an elevation of 461.5 m above sea level and a maximum depth of 165 m. The lake water comes from rainfall, small rivers, and the surrounding groundwater, with one outflow in the Batang Antokan River. Based on the measurement, it was observed that decreasing dissolved oxygen levels occurred at the surface to the depth of 40 m in 2006, and changed from surface to a depth of 12 m in 2018 indicating the worse condition of water quality compared with the previous years.  Recently, bad water quality with mass mortality of cultured fish often occurs. Next, the percentage of fish cages area at Lake Maninjau in 2017 was 0.43%. Besides human activities, it was suggested that fish cages also contributed pollutant load to this lake. To maintain the sustainability of the lake, basic ecological information is necessary for the next study.
PENDUGAAN POLA ARUS DUA DIMENSI DI DANAU TOBA Hadiid Agita Rustin; Lukman Lukman; Iwan Ridwansyah
LIMNOTEK Perairan Darat Tropis di Indonesia Vol. 21 No. 1 (2014)
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/limnotek.2014.13271

Abstract

Pola arus dari satu badan air seperti danau dapat memberikan pola dinamika massa air secara horizontal dan arah sebaran material yang terbawa di dalamnya. Untuk aspek kebijakan, pola arus merupakan salah satu informasi yang penting dalam sistem pengambilan keputusan terkait penetapan ruang pemanfaatan dan perencanaan tindakan pemulihan badan air. Penelitian ini bertujuan untuk mengetahui pola arus di Danau Toba secara umum untuk menunjang penentuan zonasi badan air. Model numerik yang digunakan adalah RMA2 yang merupakan model rerata kedalaman. Data debit inlet yang menjadi input simulasi diperoleh dari pengukuran pada 10 sungai. Kecepatan angin yang digunakan adalah kecepatan angin yang prevalen di Danau Toba hasil analisis diagram mawar angin. Hasil simulasi menunjukkan bahwa besaran arus di sebagian besar badan danau bernilai kurang dari 0,2 m/detik. Pola arus di bagian utara Danau Toba cenderung bersirkulasi lokal mengindikasikan bahwa polutan yang masuk ke utara danau akan sangat lama dikeluarkan dari danau. Hasil simulasi juga menunjukkan bahwa nilai angin prevalen tidak menunjukkan pengaruh yang siginifikan pada pola arus karena tergolong angin sepoi lemah
POTENSI SUMBERDAYA AIR UNTUK PENGEMBANGAN PLTMH DI DAS CISADANE HULU BERDASARKAN PEMODELAN HIDROLOGI SWAT Iwan Ridwansyah; Hidayat Pawitan; Naik Sinukaban; Yayat Hidayat
LIMNOTEK Perairan Darat Tropis di Indonesia Vol. 22 No. 1 (2015)
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/limnotek.2015.13289

Abstract

Pada saat ini energi listrik merupakan kebutuhan yang penting di Indonesia. Akibat pertumbuhan penduduk yang tinggi, kebutuhan listrik rakyat Indonesia akan bertambah 7 – 9% setiap tahunnya. Pada tahun 2010 rasio elektrifikasi secara nasional adalah 65% sedangkan diJawa Barat mencapai 69,9%. Energi listrik tidak hanya digunakan untuk penerangan tetapi juga untuk menjalankan aktivitas mata pencaharian. Tidak hanya daerah perkotaan, tetapi masyarakat pedesaan yang tinggal di daerah pegunungan juga membutuhkan energi listrik. Wilayah pegunungan biasanya mempunyai kemiringan lereng yang terjal dengan sungaisungai yang mengalir sepanjang waktu. Kondisi tersebut berpotensi untuk dikembangkannya pembangkit listrik mikrohidro (PLTHM). Tujuan penelitian ini adalah mengidentifikasi potensisumberdaya air DAS Cisadane Hulu untuk pengembangan pembangkit listrik tenaga mikro hidro. Penelitian ini mengunakan aplikasi hidrologi model Soil and Water Assesment Tools (SWAT) yang mengkalkulasi hujan sebagai input dan diproses pada sistem DAS yang kemudianoutput model berupa debit, loading sediment dan kualitas air. Dengan model hidrologi yang tervalidasi didapat luaran debit yang kemudian dianalisis untuk mencari debit andalan 80%. Hasil simulasi model dan analisis debit andalan menunjukan DAS Cisadane Hulu mempunyaibanyak potensi energi listrik yang dibangkitkan dengan PLTMH, dua SubDAS klasifikasi PLTA skala kecil, yaitu; SubDAS di Desa Cisarua dengan debit andalan 5,63 m3/detik dan beda tinggi 67 m berpotensi menghasilkan 3.511 kW, kebutuhan volume reservoir sebanyak 22,8 x 106 m3 dan SubDAS di Desa Bantarkaret dengan debit andalan 3,85 m3/detik dan beda tinggi mencapai 39 m berpotensi menghasilkan energi listrik sebesar 1.398,6 kW dengan kebutuhan tampungan air sebesar 9,3 x 106 m3. Sedangkan SubDAS lainnya masuk dalam klasifikasi minihidro (100 kW – 1000 kW).
NERACA AIR SITU CIKARET DAN SITU KABANTENAN DI KABUPATEN BOGOR MENGGUNAKAN PEMODELAN HIDROLOGI SWAT Claudia Tyas Nugraheni; Hidayat Pawitan; Yanuar Jarwadi Purwanto; Iwan Ridwansyah
LIMNOTEK Perairan Darat Tropis di Indonesia Vol. 26 No. 2 (2019)
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/limnotek.2019.13366

Abstract

Bogor regency which is located in the middle of the Ciliwung basin centered in Cibinong city is experiencing rapid urban development. However, with the rapid urban development, most of these small lakes in either disappear or in degraded conditions. In this area presently still maintain 95 urban small lakes or locally known as ‘situ’. Situ has multifunction such as water retention for flood mitigation, irrigation for urban agriculture, fisheries, water sport activities, and ecotourism. The objective of this study was to analyze the water balance of situ. The model was calibrated and validated on the Kampung Kelapa river gauge with manual calibration. The Soil Water Assesment Tool (SWAT) is a hydrological model designed to predict the impact of land use and management on water, sediment and agricultural chemical yields in watersheds, The model was applied to Situ Kabantenan and Cikaret for modeling of the hydrological water balance. The SWAT model simulation was done for the periods of 2008–2015 while it used land use information in 2014. The Calibration was done in 2014 and the validation in 2013, the R2 and Nash Sutcliffe Efficiency (NSE) of the calibration were 0,58 and 0,55 respectively and the validations were 0,54 and 0,49 respectively. The monthly average of volume of Situ Kabantenan and Situ Cikaret from the simulation were 136,955 m3 and 508,907 m3, respectively. The annual inflow of Situ Cikaret was 24,693,822 m3/year and outflow was 25,177,593 m3/year, precipitation was 648,520 m3/year, evaporation was 166,543 m3/year, delta storage 1,794 m3/year, respectively. The average inflow discharge of Situ Cikaret (2008–2015) were 0.78 m3/s and outflow discharge was 0.80 m3/s. The water balance results showed that both sites were in good condition since they have never passed the emergency spillway, but their function needs to be optimized as a flood controller in the Ciliwung Watershed. This study also showed that the SWAT model can be utilized as a potential monitoring tool, especially for small urban lakes as water reservoirs.
Co-Authors Claudia Tyas Nugraheni Gadis Sri Haryani Hadiid Agita Rustin Hidayat Hidayat Hidayat Pawitan Luki Subehi Lukman Lukman Naik Sinukaban Octavianto Samir Riky Kurniawan Siti Aisyah Takehiko Fukushima Yanuar Jarwadi Purwanto Yayat Hidayat