Peak Discharge in Jemelak Subwatershed, Sintang District

Jemelak Sub Watershed is close to the junction of two big rivers, i.e., Kapuas and Melawi. Therefore, this location faces environmental issues such as a flood. To avoid its possible damages, information on peak discharge becomes critical, particularly in calculating the drainage structure. This study was aimed to predict the peak discharge in this area using a rational method. The maximum daily rainfall data from 1998 to 2017 were divided into two periods of 10 years and analyzed. In the first period,  maximum rainfall rangesfrom98.6 to 176.3 mm, while the second period fluctuates from67.6 to 190 mm. Analysis of land cover described that 43.97% of secondary swamp forests turned into shrubs and swamp shrubs in the first period. Furthermore, about 800.71 ha of secondary swamp forest tuned into 582.80 ha of bare land, 181.04 ha of a plantation, and 36.88 ha of swamp shrubs in the second period. About 95.15% of shrubs were also turned into agricultural land mixed with shrubs in the second period. The result showed that the changes in the maximum daily rainfall and land cover simultaneously affected the improvement of the peak discharge by about 2.53% in the first period and 28.30% in the second period. If the peak discharge exceeds the river capacity, then the local flooding will occur along the river border. Keywords: land cover, peak discharge, rainfall, Jemela

Temporal Distribution of Sediment Yield From Catchments Covered by Different Pine Plantation Areas

Soil erosion and sedimentation are environmental problems faced by tropical countries. Many researches on soil erosion-sedimentation have been conducted with various results. Quantifying soil erosion-sedimentation and its temporal distribution are important for watershed management. Therefore, a study with the objective to quantify the amount of suspended sediment from catchments under various pine plantation areas was conducted. The research was undertaken during 2010 to 2017 in seven catchments with various percentage of pine coverage in Kebumen Regency, Central Java Province. The rainfall data were collected from two rainfall stations. A tide gauge was installed at the outlet of each catchment to monitor stream water level. The water samples for every stream water level increment were analyzed to obtain sediment concentration. The results showed that monthly suspended sediment of the catchments was high in January to April and October to December, and low in May to September. The annual suspended sediment fluctuated during the study period. Non-linear correlations were observed between suspended sediment and rainfall as well as suspended sediment and percentage pine areas. The line trend between suspended sediment and percentage of pine areas showed that the increase in pine areas decreased suspended sediment, with the slope of the graph is sharp at the percentage of pine areas from 8% to 40%, then is gentle for pine plantation areas more than 40%

Baseflow and lowflow of catchments covered by various old teak forest areas

Drought has become a severe disaster faced by several regions in Java, Indonesia due to land cover changes including forest conversion and the increase in air temperature. In this regards, the availability of forests related to lowflow has been a controversial debate. Forest in Java is dominated by teak; however, the hydrological teak forest has not been well known. Therefore, a research has been undertaken to know the baseflow and low-flow of teak catchments covered by various old teak forest areas. The research areas were in Blora District, Central Java, Indonesia. Data of2008-2015 from five catchments with areas of 3.38, 13.47, 20.14, 27.79, 64.80, and 69.20 ha and covered by old teak forests of 82, 82, 74, 70, and 53% of the catchment were analyzed. In this study, baseflow is the delayed flow from bank storage, and low-flow is stream flow in the dry season. The results showed that baseflow is affected by the percentage of old teak plantation areas, rainfall and antecedent soil moisture condition. Areas of the old teak plantation and the baseflow show negative and non-linear correlation. High low-flow occurs in the catchments with the percentage of old teak plantation about 74 to 70%

Model Dinamika Stok Karbon Berdasarkan Laju Perubahan Tutupan Hutan dan Lahan di Provinsi Jawa Tengah

The enhancement of carbon emission from deforestration and forest degradation has leaded to the increase of global climate change. Hence, this research was conducted to make a dynamic model of landuse and carbon stock and to estimate the carbon stock in Central Java. The change of carbon stock was being evaluated to identify its relation to forest change and landuse rate in Central Java using a system dynamic model. The result shows that there was a reduction of carbon stock caused by deforestation and forest degradation. The research also found that in 2004 the total carbon stock was 182.3 mega tons and in 2050 is predicted to decrease by 49.1 mega tons to 133.2 mega tons. The application of forest and land rehabilitation, law enforcement, evaluation of forest plantation management, and conservation provinc