JURNAL SUMBER DAYA AIR
Latest articles in this journal
JURNAL SUMBER DAYA AIR, Volume 16, pp 35-50; doi:10.32679/jsda.v16i1.606
Saguling reservoir is one of the three largest reservoirs in the Citarum River Basin. The water source of its reservoir originates from Upper Citarum river basin, with gauging station located in Citarum-Nanjung and local discharge from tributaries around the reservoir. The problem is there is no observation of local discharge from the tributaries, thus its potential is estimated. The purpose of this study is to analyze the potential of local discharge with the Hydrology Engineering Center-Hydrologic Modeling System (HEC-HMS) model. The HEC-HMS Rainfall-runoff method is used for calculating the potential of the local discharge that flows into Saguling resevrvoir. The parameters used in the model are deficit constant (loss parameter), linear reservoir (baseflow parameter), dan lag time (transform parameter). Rainfall-runoff model produced good calibration values for Citarum-Nanjung Gauging Station with R2 of 0.8 and the Nash-Sutcliffe efficiency (NSE) value of 0.788. The verification result carried out in Saguling reservoir gives NSE of 0.8343 and R2 value of 0.83. The simulation shows that the potential discharge from local river contributes about 21.64% of the total discharge that enters into the reservoir with monthly dependable flow for power plants, Q80 and Q85 values at 8,23 m3/s and 5,69 m3/s, respectively. The average discharge of local rivers can generate electricity of 3.89 MW - 162 MW.Keywords: Local discharge, rainfall runoff, potential discharge, Saguling reservoir
JURNAL SUMBER DAYA AIR, Volume 16, pp 23-34; doi:10.32679/jsda.v16i1.616
The debris flow that happen on the of Mount Merapi is really hard to be seen, therefore, it is necessary to conduct laboratory-scale simulations to know when debris flows will happen as regard to rainfall intensity and the slope of Mount of Merapi. This research examines the correlation between the slope and the potential for debris flow at 25 mm/h rainfall intensity. This will be a reference for early warning of landslides on Mount of Merapi. This research uses a tool such as flume that sized 3 x 5 x 0,15 m as a model of slope of Mount of Merapi, and artificial rainfall apparatus as the rain simulator. The simulation is conducted using five years rainfall intensity of 25 mm/h in combination of slope i.e. 15, 20, 25, 30 and 35 degrees whereas the material used to represent the sediment is in form of sand taken from Gendol River upstream with 4,75 mm passing mesh sieves. The result of this simulation is the steeper the slope is, the faster the duration for the rain to cause debris flow. This research can be continued with change variation of rainfall intensity to understand the debris flows behavior. Keywords: Debris flow, Mount of Merapi, laboratory test, rainfall intensity, flume model
JURNAL SUMBER DAYA AIR, Volume 16, pp 11-22; doi:10.32679/jsda.v16i1.487
The estimation of baseflow is a crucial task for water resources management. This research aimed to calibrate, validate, and evaluate the performance of the digital graphical method to separate baseflow. Two outlets of Brantas watersheds located at Kertosono (±6414,2 km2) and Ploso (± 8844,2 km2) were used for this study. This study used three digital graphics filters known as a local-minimum, fixed-interval and sliding-interval. The methodology consists of (1) data inventory, (2) data processing, (3) calibration, (4) validation, and (5) evaluating of models performance. Daily discharge data were separated into two periods, from 1996 to 2005 for the calibration and from 2006 to 2015 for the validation. Firstly, each method was tested annually by entering parameter values through trial and error. The period from July to September is considered as the peak of dry seasons and used to calibrate. The optimal values of parameters for calibration obtained by Averaging yearly values. Secondly, the optimal values from calibration are then used to test the model during the validation. Furthermore, statistical analysis was used to compare model performance during calibration and validation. Results show that the three methods could be used and perform well; however, the best performance is a local-minimum method.Keywords: Baseflow, separation, graphical-method, digital-filter, Brantas
JURNAL SUMBER DAYA AIR, Volume 16, pp 51-62; doi:10.32679/jsda.v16i1.646
The construction of the Temef Dam in Oenino Village, Oenino District, and Konbaki Village, Polen District, South Central Timor Regency requires long and reliable rainfall data. To overcome the minimum data or the unavailability of automatic rainfall (ARR) and discharge data in the past decades, the use of Tropical Rainfall Measuring Mission (TRMM) satellite data is foreseen. The accuracy of TRMM data is obtained when the parameters of suitability and compatibility of TRMM are in a good agreement with the ARR. For the Temef watershed, there are six rainfall stations that were reviewed, namely Fatumnasi, Oeoh, Noelnoni, Polen, Nifukani, and Batinifukoko rainfall stations. Direct comparisons of rainfall data were conducted for 20 years (1998-2018) with temporal resolution on a monthly and daily basis. The results of the study show that the rainfall patterns in the TRMM data product (version 3B42V7) tend to be consistent with 3 rainfall stations in the Temef watershed namely Noelnoni, Fatumnasi, and Batinifukoko. A correlation coefficient of 0.505 – 0.813 was obtained from TRMM data calibration at monthly basis while a correction factor level of 0.0056 - 0.0129 was obtained for daily. The calibration on the annual maximum daily rainfall data resulted in a correction factor of 0.0298 - 0.2516. Monthly and daily TRMM data fit well with the data of 3 rainfall stations. However, the Noelnoni rainfall station showed poor results on the annual maximum daily rainfall.Keywords: TRMM data, ARR data, correction factor, correlation coefficient
JURNAL SUMBER DAYA AIR, Volume 16, pp 1-10; doi:10.32679/jsda.v16i1.483
The mayority of landslide occur due to high rainfall in certain time in areas that have geological potential landslides. Therefore, it is necessary to conduct a research on rainfall characteristics that trigger landslides. So that, it can be used to establish the relationship between rainfall and predicted landslides. This research is aimed to analyze and determine the daily and 3 days rainfall thresholds used for landslides early warning system (LEWS). The case study is placed in both very high risks and high area landslide areas, based on the ground motion maps of the Geological Agency. The analysis was done based on landslide event data from BNPB, as well as TRMM (Tropical Rainfall Measuring Mission) and ECMWF (The European Center for Medium-Range Weather Forecasts) rainfall data. Identification of the rain trigger values from the TRMM rain data was done after collecting landslide incidents at various locations.. The results show that the rainfall threshold values are 61 mm per day and 91 mm per 3 days Keywords: Rainfall treshold,landslide prediction, TRMM, ECMWF
JURNAL SUMBER DAYA AIR, Volume 15, pp 81-94; doi:10.32679/jsda.v15i2.587
Mangroves in Indonesia have a large enough area, but in the last 3 decades the area has been reduced to 40%. Besides having a function as a coastal protector, mangroves are also able to maintain the quality of the waters around it. Currently, the construction of a reclamation island in Jakarta Bay is being carried out which will have an impact on the surrounding mangrove forests. Therefore, the purpose of this study was to identify the impact of island reclamation in Jakarta Bay on sedimentation and mangrove growth in surrounding area. This research was conducted with literature studies, vegetation analysis, water quality analysis and also spatial analysis with WorldView-2 satellite imagery. The results showed that the mangrove forests on the coast of North Jakarta, especially in the Muara Angke area tend to increase, especially in the reclaimed island area. The mangrove stands increase by approximately 1.32 ha / year. The density and stem diameters vary in 5 locations. Oxygen levels at the study site are very low but the existing mangrove forests can absorb dissolved heavy metals. The results of the study also show that the area that has the potential to be planted with mangroves is 30 ha. Overall, the sedimentation process helps expand mangrove forests naturally while the bad quality of water does not significantly affect the development of mangroves. On the contrary, the existing mangrove is able to keep the stability of the water quality in surrounding area.
JURNAL SUMBER DAYA AIR, Volume 15, pp 107-120; doi:10.32679/jsda.v15i2.503
The increasing demand of raw water in DKI Jakarta has caused excessive groundwater abstraction. It causes the groundwater level drop to certain level and has emerged cone of depression in some areas. Groundwater management as an effort to recover the groundwater level, requires an integrated groundwater monitoring system. Recently, there are approximately 161 groundwater monitoring wells in Jakarta groundwater basin. Those wells are generally categorized as secondary network, since determined by groundwater abstraction activity. Meanwhile, a representative primary network to monitor the natural condition of groundwater in each aquifer layer is not yet available completely. The method of Inverse Distance Weighting (IDW) spatial estimation is applied to determine the number and distribution of primary monitoring wells based on aquifer geometry using Groundwater Modeling System (GMS) software. Based on the aquifer geometry, it can be arranged monitoring zones and the number of monitoring wells in each zone. There are 9 monitoring zones in Jakarta groundwater basin consist of 1 zone with 1 monitoring well, 2 zones with 2 monitoring wells, 3 zones with 3 monitoring wells, and 3 zones with 4 monitoring wells, so that the total of primary monitoring wells for groundwater monitoring in Jakarta groundwater basin is 26 monitoring wells. This research is expected to be useful for stakeholders to optimize the representative monitoring wells network based on aquifer geometry in sustainable groundwater management.
JURNAL SUMBER DAYA AIR, Volume 15, pp 69-80; doi:10.32679/jsda.v15i2.416
North Coast of Java Island continues to experience coastal dynamics which resulted significant coastline erosion problems. According to the Ministry of Marine and Fisheries data (KKP), from 100 locations of coastline erosion in 17 provinces of Indonesia, North Coast of Java Island suffered the worst erosion, reaching 745 km or 44 percent of total coastline length. The shoreline retreat can be caused by three factors: sea level rise, erosion and land subsidence. The aim of this research was to determine the correlation between sediment equilibrium in coastal cells and the initial hypothesis of land subsidence which caused a coastline retreat. The method to calculate sediment equilibrium uses hypothetical sediment budget model. Modeling itself is done along the North Coast of Java. LITDRIFT model of Longshore Sediment Drift is employed to assess the coastline profile. The result of the research shows that there is anomalous model that is the condition of sediment is surplus but the condition of the field is backward. Several locations experienced a sediment surplus but experienced a coastline retreat, and after comparison with field observations and secondary data there was evidence of land subsidence: Pondok Bali Beach, Randusongo Beach, Muara Reja Beach, Depok Beach, Slamaran Beach, Jeruksari-Mulyorejo Beach and Sriwulan Beach. Furthermore this result can be used as an initial indicator of the land subsidence causing the coastline to retreat. In order to solve the erosion and sedimentation problem, the detail study with more comprehensive parameter needs to be conducted.
JURNAL SUMBER DAYA AIR, Volume 15, pp 95-106; doi:10.32679/jsda.v15i2.480
The Tilong Reservoir located in Kupang District, has 154.97 ha surface area with an average depth of 12.5 m, water volume is 19 million m3 and water discharge around 86.4-106.3 m3/day. The main function of this reservoir is for irrigation. Capture fisheries activity has not been optimally developed. The development of capture fisheries can be done through culture-based fisheries (CBF), namely milkfish (Channos channos) or tilapia (Oreochromis niloticus) stocking. The aims of this study is to determine the potential of fisheries production and the seed needs for CBF development in the Tilong reservoir. The study was conducted in March and September 2016 at three observation stations. Water sample was taken at 0.5 and 2.0 m from the surface which is the euphotic depth. The results showed that CBF activities in the Tilong Reservoir could successful because supported by the limnology conditions was suitable for fish life, the availability of seeds produced from hatchery was sufficient for stocking and support of local communities through local wisdom. Fish seeds are produced by 13 hatchery which are capable of producing milkfish and tilapia seeds of 7,040,770 and 7,023,400 per year. Based on these aspects, capture fisheries through CBF are feasible to be developed in the Tilong Reservoir. The fisheries production potential in the Tilong Reservoir ranges from 75.9 to 77.5 kg/ha/year or 11.9-12.0 tons/year. The optimal number of milkfish and tilapia seeds that can be stocked ranges from 71,000-73,500 individuals/year and 72,000-75,000 individuals/year respectively. The fish production estimated from stocking was about 40% of the potential production with economic value of Rp 20,500,000 and Rp 21,500,000.
JURNAL SUMBER DAYA AIR, Volume 15, pp 121-136; doi:10.32679/jsda.v15i2.600
Uji validasi data merupakan langkah pemeriksaan untuk memastikan data hidrologi yang disajikan telah sesuai dengan kriteria yang ditetapkan, merupakan salah satu bagian dari proses kendali mutu. Teknik validasi dirancang untuk mendeteksi kesalahan umum yang mungkin terjadi dan hasil validasi didesain untuk menunjukkan alasan mengapa suatu nilai data ditandai. Tujuannya adalah menganalisis data dengan metode uji validasi homogenitas dan trend, mendeteksi penyimpangan data, dan memberikan informasi kondisi kualitas data dengan jenis kategori. Uji validasi data debit dengan studi kasus DAS Citarum Hulu dilakukan pada 4 pos duga air terpilih menggunakan metode Pettitt dan T untuk uji homogenitas, metode Mann-Kendall dan Spearman untuk uji trend pada tingkat signifikansi 5%. Hasil kajian menunjukkan bahwa uji homogenitas dengan metode Pettitt lebih baik diterapkan pada kajian ini karena memiliki populasi data debit yang tidak berdistribusi normal. Kelebihan dari metode Pettitt adalah dapat menguji data tanpa adanya asumsi harus berdistribusi normal. Hasil uji trend dengan metode Mann-Kendall dan Spearman menunjukkan hasil signifikansi yang relatif sama, karena kedua uji tersebut memiliki metode statistik non parametrik. Kekuatan kedua uji ini tergantung pada tingkat signifikansi, ukuran sampel data, dan jenis distribusi. Hasil uji menunjukkan kondisi data di pos Citarum-Nanjung, Cigulung-Maribaya, Cikapundung-Maribaya dan Cikapundung-Gandok, masing-masing berkategori Baik, Tidak Realistis, Meragukan dan Meragukan. Homogenitas dan trend data debit di DAS Citarum Hulu tidak merata. Trend data debit di sub DAS Cikapundung mengalami kenaikan secara signifikan mulai tahun 1980an dan mengalami penurunan trend BFI di pos Cikapundung-Maribaya pada tahun 1990-2013. Hal ini mengindikasikan adanya pengaruh perubahan fungsi lahan pada sub DAS Cikapundung.Kata Kunci: Validasi data, data debi, Mann Kendall, Pettitt, Base flow Index (BFI)