ANALISIS KEKERINGAN DI KABUPATEN SRAGEN DENGAN METODE PALMER, THORNTHWAITE, DAN STANDARDIZED PRECIPITATION INDEX

El Nino and La Nina in Indonesia are one of the reasons that caused climate changes, which has possibility of drought and flood disasters. Sragen Regency wherethe dry season occurs, drought happened meanwhile other areas experience floods and landslides. A study on drought needs to be carried out so as to reduce the risk of losses due to the drought hazard. This study is to determine the drought index in Sragen Regency based on several methods and the correlation of each methods and its suitability to the Southern Oscillation Index (SOI) and rainfall. Drought was analyzed using several methods such as Palmer Drought Severity Index (PDSI), Thornthwaite-Matter, and Standardized Precipitation Index (SPI) then correlated with SOI to determine the most suitable method for SOI. The variables are applied in this method are rainfall, temperature, and evapotranspiration. The results showed that the drought potential of the Palmer method is only in Near Normal conditions, which is 1%, Severe drought conditions are 29% for the Thornthwaite-Matter method, and Extreme Dry conditions only reach 1,11% for the SPI method. The PDSI and SPI methods are inversely proportional to the Thornthwaite-Matter method and the most suitable method for SOI values or rainfall is the SPI method. These three methods can be identified the potential for drought with only a few variables so that they could be applied if they only have those data.Keywords: Drought, PDSI, Thornthwaite-Matter, SPI, SOI

MODEL ESTIMASI BIOKINETIKA UNTUK PROSES POST-DENITRIFIKASI AIR LIMBAH DOMESTIK PADA UNIT ANAEROBIC BAFFLED REACTOR

This study developed a combination of Continuous Stirred Tank Reactor (CSTR) for the acid fermentation and the Anaerobic Baffled Reactor (ABR) post-denitrification through high nitrite injection. Volatile Fatty Acids (VFAs) as a substrate for the post-denitrification process were optimally produced in the acid fermentation process. The aim of this study was to obtain the estimation of biokinetic values to predict the effluent wastewater quality in ABR post-denitrification process under unsteady state. The reactor was operated for HRT 7 days at temperature 25-28 ˚C and pH 6-7,2. The influent and effluent substrate concentration were monitored continuously for 160 days. Post-denitrification biokinetic from the Contois equation resulted in the value of hydrolysis rate (Kh) of 0.077 day-1, the substrate transport rate (k) of 4.364×10-6 Lmg-1day-1, maximum specific growth rate (μmax) of 0.559 day-1, half saturation constant (KS) of 0.209 mgL-1, microbial decay coefficient (b) of 0.0145 days-1; yield coefficient (Y) of 0.084 g-VSSg-COD-1. The validation of biokinetic parameters based on statistical analysis showed fairly precise results following the trend of experimental data to determine the substrate concentration in the effluent unit. Therefore, the biokinetic values can be applied in the design of ABR post-denitrification using primary sludge incorporation with high strength nitrate.Keywords: Anaerobic baffled reactor, biokinetics, Contois, hydrolysis, post-denitrification.

TINJAUAN POTENSI TEKNIS DAN KELAYAKAN EKONOMI PLTA PADA PROYEK KERJA SAMA PEMERINTAH DENGAN BADAN USAHA BENDUNGAN MERANGIN

One of the utilizations of a multipurpose dam that has socio-economic value during its operation iselectricity generation. The addition of a hydropower component to a PPP project is quite a challenge due to substantial uncertainty related to hydrological aspects that will impact electricity production and revenue, as well as high initial investment costs for generating units. This study aims to map the technical potential of hydropower and evaluate the economic feasibility of hydropower in the Merangin Dam PPP Project. The potential for power and energy generation is obtained through simulations of the hydropower operation for 19 years using hydrological data, HEC-HMS model generated-data, and dam engineering design. According to the results, the technical potential of hydropower can produce, on average, power of Pp = 103.8 MW during peak load, Pb = 98.53 MW during base load, and total energy of 636.66 GWh/year. The economic potential is evaluated through social cost-benefits analysis (SCBA) by estimating the additional benefits obtained from the hydropower compared to the PPP structure of the Merangin Dam without hydropower. Through SCBA, the addition of hydropower to the Merangin Dam PPP structure has an EIRR value of 35.24%, NPV of Rp. 2.104.212.122.723,- and BCR = 3.06. Based on these indicators, the provision of hydropower plants is considered economically feasible because the benefits that will be generated and obtained by the community are higher than the economic costs incurred.Keywords: Technical potential, economic feasibility, hydropower plant, multipurpose dam, PPP

PREDIKSI TINGKAT KEKERUHAN (TURBIDITAS) MENGGUNAKAN CITRA SATELIT SENTINEL-2A DI WADUK JATILUHUR, JAWA BARAT

Turbidity is one of the remote sensing indicators on the reservoir physical characteristics that can reduce its brightness level. Measuring reservoir physical characteristics traditionally are expensive and time consuming as well. Therefore, remote sensing is used as an alternative for turbidity measurement because it can provide data and products spatially, temporally as well as synoptically with low cost. This study aims to obtain an algorithm using a combination of in-situ turbidity data measurement and Sentinel-2A satellite imagery data. The resulting algorithm can be used to predict and map turbidity in Jatiluhur Reservoir. Based on the multiregression between B3 (green band) and B4 (red band) with in-situ turbidity data measurement, it is obtainted that the regression coefficients are a = 76.77, b = 63.22 and c = -34.31 respectively, with the equation of Y = 76, 77+63.22 X1-34.31X2 (Y=predicted turbidity, X1=lnB3, X2=lnB4). The correlation value between in situ and turbidity prediction is quite strong with a coefficient of determination (R2) of 0.60, and Root Mean Square Error (RMSE) of 1.95 NTU. Based on Mean Absolute Percentage Error (MAPE) analysis, the deviation is 31.1%. High levels of turbidity can reduce the main productivity of water and its organisms, especially in respiratory and visual problems. Sedimentation caused by high turbidity levels can make siltation which results in reservoir capacity loss.Keywords: Turbidity, remote sensing, Sentinel-2A satellite imagery data, Jatiluhur Reservoir, siltation

ANALISIS KEBUTUHAN KAPASITAS TAMPUNGAN EMBUNG DANAU ASAM KABUPATEN KOTAWARINGIN BARAT

This study aims to analyze the requirement for the storage capacity of Danau Asam Reservoir as one of the solutions in increasing the availability of water to meet the needs of raw water due to population growth and climate change which is quite extreme. The study was conducted in the Danau Asam Reservoir with source of water from two watersheds that flow into the reservoir, namely the Lopo River Basin with a catchment area of 11.81 Km2 and Kamat Bay with a catchment area of 12.42 Km2 in Kotawaringin Lama District in the West Kotawaringin Regency. The method used is a quantitative approach based on a simulation of the water balance between the inflow and outflow. The inflow parameter is calculated based on 90% probability reliable discharge using the FJ Mock method in two watersheds and the outflow parameter is based on the raw water demand discharge which is calculated based on the population growth rate. The result of the research indicate that the capacity of the Danau Asam Reservoir is 391,842.72 m3 to meet the raw water needs in Kotawaringin Lama District with a population of 35397 people.Keywords: Drought, Raw Water, Storage, Kotawaringin Barat

Hydrostratigraphy And Aquifer Geometry In Palu Groundwater Basin, Central Sulawesi Province After Earthquake

Palu Groundwater Basin can be assumed to have a post-earthquake deformation in 2018. To identify current state of Palu Groundwater Basin, modeling approach was conducted using GMS 10.4 (Groundwater Modeling System) with IDW (Inverse Distance Weighting), with the data used for the model was obtained from 41 boreholes. The results show that Palu Groundwater Basin aquifer geometry can be divided into 4 types. The unconfined aquifer consisting of Alluvium and Coastal Deposits (Qa) have an area 412,69 km², with 17,77 - 72.48 m thickness top layer have elevation 341 MSL (mean sea level) and bottom layer have elevation -2,29 MSL. Top aquitard consisting of Celebes Mollase of Sarasin and Sarasin (QTms) have an area 391,1 km² with 0.1 - 20,61 mm thickness top layer have elevation 268,52 MSL and the bottom of layer have elevation -20,06 MSL. Confined aquifer consisting of Celebes Mollase of Sarasin and Sarasin (QTms) have an area 351,98 km² with 20,58 - 86,51 m thickness top layer have elevation 268,42 MSL and bottom layer have elevation -40,67 msl. Bottom aquitard consisting of Granite and Granodiorite (Tmpi), Tinombo Formation (Tts), Metamorphic Complex (Km), Latimojong Formation (Kls) have an area 78,24 km² with 20,58 - 86,51 m thickness 3,01 - 4,1 m top layer have elevation 181,91 MSL and bottom layer have elevation -29,09 MSLKeywords: Groundwater, basin, modeling, geometry, aquifer

PEMANFAATAN DTM HASIL FOTOGRAMETRI UAV UNTUK ESTIMASI KETINGGIAN GENANGAN AIR BANJIR HASIL DETEKSI CITRA SAR

Utilization of The Unmanned Aerial Vehicle (UAV) or Drone has brought revolution in digital photogrammetry. The feature matching on surface reconstruction or Digital Surface Model (DSM) are quickly finished. However, DSM doesn’t represent itself as a part of topography, that is why DSM should be converted into Digital Terrain Model (DTM). This research is to investigate the accuracy of UAV photogrammetry’s DTM for hydraulic modeling purpose. This study has produced 4 sets of DTMs; 2 sets of DTMs with different grid resolution which are 2 cm & 40 cm, also the 2 other sets of DTM with extra fine nature algorithm and set of filtering parameters adjustment; bulge, offset, spike and standard deviation. Every DTM are validated by Ground Control Point (GCP) from Real Time Kinematic-Different Global Positioning System (RTK-DGPS) measurement. According to the validation, the adjustment of filtering parameters is the most accurate method with Root Mean Square Error (RMSE) of 6,17 cm for 2 cm resolution; and 5,22 cm for 40 cm resolution. Next, DTM UAV is used to estimate the flood water level from Synthetic Aperture Radar (SAR) Image detection with 46 flood images on Glane and Losser area, east part of Overijssel, The Netherlands, since October 2014 to December 2017, then validated with the insitu water level measurement and resulted RMSE 6,72 cm for set of UAV DTM’s 40 cm resolution with the filtering parameters adjustment. Therefore, this DTM UAV can be used as a topography parameter in hydraulic modeling, especially at the similar flat-surface terrain where this research have been conducted. Keywords: UAV photogrammetry, SAR detection, DTM production

PENGURANGAN POTENSI LAJU SEDIMENTASI RAWAPENING MELALUI PENERAPAN TEKNOSABO

Rawapening has an area of 2,667 acres, which now ceases to exist. This natural reservoir serves to preserve water, control flood, generate electric turbine, and raw water resource. The depth of this lake decreases 42 cm annually, with the shallowing could cause flooding of the lakeside and and reducing the water supply. This study finds the additional amount of structure and dimension of sabo dam to prevent hazards at each river: at Panjang 2 (B=20m H=2m, and B=25m H=2,5 m), at Galeh 2 (each of B=8m H=2,4m), at Legi 2 (B=10m H=2m, and B=25m and H=2,5m), at Parat 1 (B=13m H=2,7m), at upstream Sraten 1 (B=15m H=2,7m), at downstream Sraten 1 (B=15m H=2,7m), and at Kedungringgis 1 (B=12m H=1,8m). Existing materials are fine and rough sand. Using WaTEM/SEDEM, saboplan guideline by processing the designed capacity, it is estimated that each river’s potential annual yield (in tonnes): Panjang 86.221,8, Galeh/Torong 45.138,24, Legi 42.404,04, Parat 28.579,32, Sraten 25.988,76, and Kedung Ringis 6.955,2. Overall, sabo dam is designed to be a closed type dam located in inlet rivers of Rawapening. Sabo dam construction holds 25% of potential sediment. Collectively, it adds a control volume of 2.885 m3, from 11.539 m3 to become approximately to become 14.424 m3. To cope with sedimentation in Rawapening, the structural approachment (sabodam) should be combined with non structural approachment such as restoring land use in the upstream area for more optimal sedimentation control.Keywords: Sedimentation, rawapening, erosion, WaTEM/SEDEM

Analisis Keberlanjutan Pengendalian Pencemaran Air Limbah Domestik Menggunakan Constructed Wetlands Teknik Surface Flow (SF)

Along with the significant increase of population in Bandung City at the moment, domestic wastewater management process must be considered to avoid river contamination, which one of the causes is domestic wastewater disposal without any prior management process. This study is located in Bandung City, which the research was performed in Research Center for Water Resources Office (PUSAIR) Bandung by involving residents of RW 09 Kelurahan Dago as respondents. The method used in this research is a combination of qualitative and quantitative methods. This study aims to analyze the sustainability of the domestic wastewater management process which is carried out using constructed wetlands by considering the economic, environmental, social, and technological aspects. The result shows that the sustainability value of the domestic wastewater management process conducted in the PUSAIR office is approximately 65.2% with the status of moderate sustainability. The detail result of each aspects is economic dimension 62.5%; ecological dimension 75%; social dimension 33.3%; and technological dimension 90%.Keywords: Domestic wastewater, Constructed wetlands, Surface flow techniques, Sustainability analysis

KAJIAN PENANGANAN BANJIR DENGAN SISTEM POMPA DI SUNGAI BENDUNG PALEMBANG

Floods around the Bendung River in Palembang City have caused material and non-material losses. One of the reasons was the decreasing river capacity and backwater during the Musi River flood season, which is the Bendung River's outlet. This paper discusses the impact of adding a pump system to reduce flood impact. 1-dimensional and 2-dimensional numerical model using MIKE 11 and MIKE FLOOD were made to analyze the best measures. Various alternative scenarios were implemented in the model. Based on the modeling results, using the most optimal alternative, alternative 4 with 6 pumps of 36 m3/s and normalization of the Bendung River channel by 1 meter. The inundation area was reduced by 0.74 km2. Also, the maximum inundation height for the flood decreased by 0.6 meters, and the inundation duration was reduced by 8.5 hours. These modeling results can be a reference for managers and policymakers in managing flood events.Keywords: River channel normalization, pump system, numerical model, flood control, Bendung river