Pusat Penyelidikan Kejuruteraan Sungai dan Saliran Bandar (REDAC) - Tesis

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    Assessing sustainability index of water resources system for lombok river basin
    (2022-05-01)
    Wit Saputra, Anggara Wiyono
    River basin sustainability is vital for the fulfilment of water demands, but the majority of river basins worldwide, including those in Indonesia, are increasingly being severely degraded, leading to their unsustainability. The Lombok river basin at Nusa Tenggara Barat province, Indonesia, is currently experiencing such problems. Water balance in the Lombok river basin is closely affected by climate conditions, which in turn affects the availability of water. In addition, the basin is experiencing shrinking reservoir storage due to sedimentation, deterioration of river headworks structure, and irrigation efficiency reduction, all of which have a reverse effect on maintaining the sustainability of the water resources system. This study focuses on the Lombok river basin, which experiences unique climate characteristics and conditions in variability which has generally affected water availability and its distribution. Interbasin transfer conveys water from the western area, which has surplus water, to the central and eastern parts of the river basin. This study aims to assess the water resources system sustainability in light of the availability of streamflow and fulfilment of water demand in the Lombok river basin to provide information for the stakeholders and decision-makers. The methodology includes simulation and optimization of the water resources system to assess the water resource system performance indicators (reliability, resilience, and vulnerability) and sustainability index for various system improvement scenarios. The SWAT model was employed to simulate the Lombok streamflow with the corresponding land use and soil map data based on historical data as the required inputs. Calibration and validation processes using SUFI-2 were done to get the appropriate parameters used in SWAT model. By applying simulated streamflow as an input, the MODSIM model was used to simulate and optimize water allocation in the system to predict performance indicators at each headwork for irrigation and domestic demand. The results show that the smallest watershed sustainability index for irrigation was in the Renggung watershed and the Palung watershed was the smallest domestic watershed sustainability. The results show that the smallest watershed sustainability index for irrigation was in the Renggung watershed at 0.188 in 2017-2025, which decreased to 0.177 in the climate change period (2032-2040). Babak watershed was the smallest domestic watershed sustainability index at 0.884 and down to 0.812 in the climate change period. Watershed index with the same weight of 0.50 for domestic and irrigation demand, respectively, showed the highest was Jangkok watershed followed by Dodokan, Meninting-Midang, Renggung, Babak, Palung, Rere Penembem, and Pare Ganti. Results from this study indicated that the operation of the new dams and improvement of irrigation efficiency enhanced the water sustainability index at most simulation scenarios. These results indicate that careful constructing of suitable new dams and improvement of irrigation efficiency is justified in the Lombok river basin as they contribute towards the enhancement of water sustainability in the river basin.
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    Numerical simulation of hydraulic jump using depth-averaged model
    (2022-08-01)
    Ting, Wen Kiat
    The prediction of the location, flow profile and length of hydraulic jump is crucial in the design of hydraulic structure such as stilling basin. For such purposes, numerical model comes in handy and is more cost-efficient as compared to physical modelling. In this study, two governing equations (Saint-Venant (SV) equations and Boussinesq equations) were solved numerically using four numerical algorithms (the Upwind, MUSCL+AB, CIP+SMAC, and CIP/ MM FVM) to simulate the formation of hydraulic jump in a flat rectangular channel. In the model verification process, simulation of dam-break flow problem was carried out. In the model verification process, the CIP+SMAC algorithm showed the best agreement against Ritter solution whilst the CIP/ MM FVM model was well verified against the Stoker’s solution. The numerical models were validated by simulating the one-dimensional hydraulic jump problem. The numerical results were validated against the experimental data. The experiment data were obtained from literature findings and also from the physical experiment conducted at the REDAC Hydraulic Laboratory, USM. Results showed that the Boussinesq equations are better than the SV equations in simulating hydraulic jump. Through qualitative evaluation, the CIP+SMAC algorithm showed the best performance as compared to the Upwind and MUSCL+AB algorithms. Besides, an attempt to simulate the hydraulic jump using the CIP/MM FVM scheme was carried out. Hydraulic jump was successfully simulated using this scheme, with the highest inflow Froude number of 2.3. However, simulation cases with inflow Froude number higher than Fr=2.3 could not be simulated due to numerical instability. Further investigation and model improvement are needed to solve this problem in the future.
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    Simulation Of Flood Inundation Map Associated With Sediment Transport For Sungai Pahang
    (Universiti Sains Malaysia, 2018-07-01)
    Chang, Chun Kiat
    Flood disasters are a major cause of fatalities and economic losses. Several studies indicate that global flood risk is currently increasing. Rapid urbanisation has accelerated impact on the catchment hydrology and geomorphology. When landuse and land cover change as a result of development or human activities, such as logging which takes place in river catchment areas, a dramatic increase in the surface runoff and higher sediment yield are expected. The present study can be divided into four (4) main parts. The first part is to carry out trend analysis using Mann-Kendall test for the annual rainfall time series data. The results demonstrate that increasing trends were detected for eleven (11) rainfall stations while four (4) stations showing decreasing trends in Sungai Pahang river basin. The second part attempts to give an overview of the channel changes and sediment transport phenomena in Sungai Pahang including bed material movement from the upstream of Sungai Pahang to the river mouth at Pekan. River geometry survey associated with the spatial variation in sediment transport has confirmed that changes in river bed profile occurred due to erosion or deposition along Sungai Pahang. The sediment distribution size for Sungai Pahang was found to be made up of very coarse sand and gravel after December 2014 flood. A rainfall-runoff model is developed and implemented for Sungai Pahang river basin. Performance evaluation of the InfoWorks PDM model was moderately successful in reproducing 2003 and 2012 to 2014 hydrographs covering both low and high flow, which have been the emphasis of the third part of this research. The fourth part is intended to deal with flood simulation using InfoWorks RS with the consideration of sediment transport modeling. The flood inundated area has been estimated based on the input design hydrograph of the 100-year annual recurrent interval and storm duration of 8 days. Peak water surface and channel bed changes for Sungai Pahang indicated that the maximum flood level with and without sediment transport modeling has a difference of at least 0.30m. The flooded area was identified to increase by 306.84km² (30.21%) from the simulations results without sediment transport compared to flood simulations with sediment transport. As a result, the current study shows that it is essential to take into account the sediment movement along the river channel for the prediction of flood inundation areas in order to produce digital flood maps.
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    Determination Of Water Quality Depth For Stormwater Facilities In Peninsular Malaysia
    (Universiti Sains Malaysia, 2018-07-01)
    Alang Othman, Mazlina
    Urbanization increases the amount of pollution carried out to downstream waterways. Best Management Practises (BMPs) have been identified as an approach to solve the problems. The effectiveness of BMPs depends on the volume of storm runoff that can be captured and treated by them, which is referred as water quality volume (WQV) and requires a fixed depth of runoff which is referred to as "Water Quality Depth" (WQD). The recommended WQD value for Malaysia stands at 40 mm and generated from limited data. This research aims to determine WQD by using local rainfall data and develop WQD distribution map for Peninsular Malaysia. It shows that 90th percentile is an optimum rainfall depth value for Northern and Central regions of Peninsular Malaysia while 95th percentile for Southern and East Coast regions. At 90th percentile, WQD was found to be in the range of 33 - 57 mm. However, WQD at 95th percentile was much higher which is in the range of 44 - 90 mm. Therefore, WQD of 40 mm was insufficient for Peninsular Malaysia and it is suggested that the WQD be reviewed. Findings of this study can be used for such a purpose. This study also shows that, due to the small number of significant increasing trends in extreme value identified, it was unnecessary to include extreme value in WQD estimation to avoid over design in BMPs facilities. For WQD distribution map, Inverse Distance Weighting (IDW) was chosen as the most reliable method for WQD interpolation at 90th percentile while Ordinary Kriging at 95th percentile. A field study at a constructed wetland was carried out to ascertain the relationship between WQD and BMPs facilities treatment performance. TSS recorded higher performance when rainfall depth was below than WQD value. However, BOD, COD, TN, TP and AN recorded higher performance when rainfall depth exceeded WQD value.
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    Development Of Bio-Ash Supported Nanocomposites For The Photocatalytic Treatment Of Acid Red 88 And Methylene Blue
    (Universiti Sains Malaysia, 2018-11-01)
    Lum, Pei Teng
    To date, the wide scale application of photocatalysis, a new innovative and promising technology for the environmental remediation of textile dye pollutants, is experiencing the technical challenges of particles self-agglomeration and post-separation difficulty. Arising research pertaining to the immobilization of photocatalysts onto different supporting materials have been promoted. Giving insight into the huge generation of agricultural bio-ash and highlighting of their low economical value, the development of a series of bio-ash supported nanocomposites by using simple physical coating and hydrothermal techniques has been attempted. Bio-ash including incense ash (IA), durian shell ash (DSA) and coffee residue ash (CA) was adopted to be the low-cost precursors for the preparation of bio-ash supported SnO2 and ZnO nanocomposites, with different ash impregnation ratio from 1:1 to 1:5. Surface morphology analysis, pore structural measurement, detection of surface functional groups and evaluation of point of zero charge (pHzpc) were carried out. The photocatalytic performance was examined with respect to the batch photocatalytic degradation of Acid Red 88 (AR 88) and Methylene Blue (MB) by varying the operational parameters, catalyst loading, initial dye concentration and irradiation time, and solution pH. Surface morphological studies revealed that the deposition of catalysts onto the surface of different bio-ash was successfully attained. Examination of the porosity development suggested that the capability of bio-ash to improve the overall surface area. Fourier-Transform Infrared Spectroscopy (FT-IR) spectrum ascertained the homogenous deposition of SnO2 and ZnO photocatalysts on the surface of bio-ash. Results illustrated the best photodegradation efficacy was achieved at the optimum catalyst loading of 0.03 g/100 mL for SnO2/CA, 0.04 g/100 mL for SnO2/IA and SnO2/DSA nanocomposites, and 0.40 g/100 mL for ZnO/IA, ZnO/DSA, and ZnO/CA nanocomposites, respectively. Acidic medium favors to the photocatalytic removal of AR 88, while the basic condition prefers to the photodegradation of MB. Increasing initial concentration from 100-500 mg/L for AR 88 and from 50-400 mg/L for MB demonstrated the significant influences on the removal efficacy, and a longer irradiation time was acquired for the complete removal process. Kinetic analysis revealed that the linearity of the photocatalytic plots was well described by the first order model. Reusability test indicated high durability of these newly prepared nanocomposites, with greater than 85% of degradation efficiency even after five regeneration cycles. This study provided a new insight in the preparation of valuable bio-ash supported nanocomposites for the effective purification of textile dye pollutants.