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All Journal Indonesian Journal of Limnology
Iwan Ridwansyah
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Chemical Engineering, Chemistry & Bioengineering Earth & Planetary Sciences 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.
Co-Authors Gadis Sri Haryani Hidayat Hidayat Luki Subehi Octavianto Samir Riky Kurniawan Siti Aisyah Takehiko Fukushima