Development of analytical probabilistic model parameters for urban stormwater management

Analytical probabilistic models (APM) are closed form mathematical expressions for long term system’s output performance derived from the probability distribution of the system’s input variables. In order to apply the APM for urban stormwater control systems’ design, APM parameters have to be made known. These input parameters include APM parameters which are derived from the meteorological rainfall characteristics; storm depth, duration, intensity and inter-event time. This study is aimed to develop meteorological APM parameters that can be used for detention pond design in Peninsular Malaysia. Hourly rainfall data covering 10 to 40 years period were analyzed from 13 different locations spread across the Peninsular. The data were analyzed to obtain the APM parameters at different values of minimum storm separation time (MSST). The APM parameter of rainfall duration (λ) was found to range from a mean value of 0.260 h-1 for 2 h MSST to 0.04 h-1 for 24 h MSST. The APM parameter of rainfall volume (ζ) ranges from a mean value of 0.091 mm-1 for 2 h MSST to 0.038 mm-1 for 24 h MSST. Similarly, the APM parameter of rainfall intensity (β) ranges from a mean value of 0.355 h/mm for 2 h MSST to 0.504 h/mm for 24 h MSST. Finally, the APM parameter of inter-event time (ψ) ranges from a mean value of 0.025 h-1 for 2 h MSST to 0.012 h-1 for 24 h MSST. Once the APM parameters are determined for a particular area, the long term stormwater control systems’ performance can easily be determined

Water quality: a comprehensive review of element in water quality improvement

The paper presents a comprehensive review of elements in water quality improvements especially on the technology to be used. The current technology applied in the activity of water quality is one of the most important information for the relevant agencies of water. Water resources in Malaysia come in the forms of rivers, lakes, ponds and groundwater. Lakes and ponds are important water resources naturally or constructed in Malaysia. Rapid pace of the development surrounding many of the water catchment area had significant effects on the quality of water bodies. Management of water resources is becoming increasingly comprehensive demanded and complicated due to large concentrations of population, commercial activities and industries around the cities and towns, increasing water consumption, increasing water pollution, increasing land use conflicts and climate changes. Urban storm water pollution can be a large contributor to the water quality problems of many receiving waters, as runoff transports a wide spectrum of pollutants to local receiving waters and their cumulative magnitude is large. The study has reviewed the improvement elements of water quality from two different functions of materials – Titanium (IV) Oxide and Zeolite that was categorized from natural and synthesised

An overview of geopolymer materials based zeolite as an antifouling layer in improving water quality

The paper presents an overview of the geopolymer concrete based fly ash as well as zeolite and titanium dioxide powder as an admixtures to create a nitrogen removal in polluted water. This geopolymeration process occurred from the fly ash or zeolite powder and fine aggregate are mixed together with the alkaline solution to form geopolymer concrete. The sodium silicate solution and the sodium hydroxide are chosen and mixed together to produce the alkaline solution. The geopolymer concrete acts as the rough film, contaminants removal in polluted water body and consequently acts as antifouling. The surface of foulant layer created from the contaminant itself that need to mitigate time to time. Meanwhile, the water sample was collected from the selected stations, i.e.; Sungai Gombak, Sungai Klang and Sungai Batu. The existing data quality of water at Sungai Gombak was applied from Department of Irrigation and Drainage (DID) to be analysed and compared to the results from water quality assessments of water without/with treatment. The current values of water quality were captured in year 2012. The water quality index for Sungai Klang is 57.05 in Class III similar class to Sungai Batu valued is 54.7 and while the Sungai Gombak has no station to capture the values. The rivers are identified that contain polluted water but still suitable for fishery. The aim of the study at those polluted rivers is to reduce and remove the amount of high concentrations of nitrogen via zeolite reactions meantime to mitigate the foulant layer on the film surface

Suitability of ANN applied as a hydrological model coupled with statistical downscaling model: a case study in the northern area of Peninsular Malaysia

The increase in global surface temperature in response to the changing composition of the atmosphere will significantly impact upon local hydrological regimes and water resources. This situation will then lead to the need for an assessment of regional climate change impacts. The objectives of this study are to determine current and future climate change scenarios using statistical downscaling model (SDSM) and to assess climate change impact on river runoff using artificial neural network (ANN) and identification of unit hydrographs and component flows from rainfall, evaporation and streamflow data (IHACRES) models, respectively. This study investigates the potential of ANN to project future runoff influenced by large-scale atmospheric variables for selected watershed in Peninsular Malaysia. In this study, simulations of general circulation models from Hadley Centre 3rd generation with A2 and B2 scenarios have been used. According to the SDSM projection, daily rainfall and temperature during the 2080s will increase by up to 2.23 mm and 2.02 °C, respectively. Moreover, river runoff corresponding to downscaled future projections presented a maximum increase in daily river runoff of 52 m3/s. The result revealed that the ANN was able to capture the observed runoff, as well as the IHACRES. However, compared to the IHACRES model, the ANN model was unable to provide an identical trend for daily and annual runoff series

Spatial assessment of groundwater over-exploitation in northwestern districts of Bangladesh

Groundwater demand in northwestern districts of Bangladesh is increasing rapidly with the growth of population and the expansion of irrigated agriculture. Development and management of groundwater resources are essential to supply the growing population with sufficient water for economic development as well as for the sustainable environment of the region. In the present study, groundwater recharge-abstraction balance method has been used for the spatial assessment of groundwater development potential. The abstraction of groundwater is estimated from irrigation and domestic water demands in the study area. The net recharge calculated from groundwater table fluctuation data, whereas the abstraction of groundwater is estimated from irrigation and domestic water demands in the study area. The study shows that out of twenty-six sub-districts, groundwater exploitation has reached to a critical condition in fourteen subdistricts. Development of surface water resources and water conservation are essential to reduce the stress on groundwater exploitation

Modeling the distribution of inter-event dry spell for Peninsular Malaysia

The spatio-temporal distribution of rainfall and the corresponding inter-event dry period separating two rainfalls play a major role in the planning and management of water resources of a country. Knowledge of the distribution of inter-event dry period is necessary in storm water management related to designs of best management practices such as detention and retention ponds. In this paper, we aim to explore the characteristics of inter-event dry period for Peninsular Malaysia using long term hourly rainfall data. The data covering a period of 10 to 22 years were collected from 12 stations spread across the peninsular. The data were discretized into individual rainfall events using 2 hour separation time and its statistics were analyzed. Result of inter-event dry period indicates that rainfall frequency ranges between 133 events at Kota-Bahru to 260 events per annum at Kedah. Rainfall occurs over the peninsular, on the average, once in every two days. The distribution of mean inter-event dry period shows that Kota-Bahru and Segamat have the highest mean dry period while Kedah, Penang, Kuala Lumpur and Mersin recorded the lowest. Goodness-of-fit test ranking indicates that all the models selected can be used to describe the hourly inter-event dry period. However, generalized-pareto and Log-normal distributions are found to be the most preferable

Rainfall runoff simulation using MIKE11 NAM

Rainfall runoff estimation from a watershed is of vital importance as these values are required in most hydrologic analysis for the purpose of water resources planning. This study deals with Layang River rainfall runoff estimation using MIKE 11 NAM model. The calibration and validation procedures were carried out to provide a satisfactory estimation. The runoff discharges were simulated for a 12-year period (1988-2000). The simulated peak flow occurred in 1992 and 1995 with approximate values of 20.94 m3/s and 18.93 m3/s respectively. The optimum values of the model parameters obtained during the calibration procedure were presented. The reliability of MIKE11 NAM was evaluated based on the Efficiency Index (EI) and Root Mean Square Error (RMSE). The EI and RMSE obtained during this study are 0.75 and 0.08 respectivel

Fitting the distributions of wet spell duration with probability models

The long term rainfall characteristics of an area are best understood if the statistical distributions describing the various rainfall parameters have been modeled. The distributions can be used in applications that need rainfall information such as stormwater management, agriculture and many others. In this paper the suitability of four different types statistical distributions in modeling wet spell duration in Peninsular Malaysia have been tested. Hourly rainfall data, of 10 to 22 years period, from 12 representative stations spread across the Peninsular were collected. Four statistical distributions, namely, Generalized pareto, Exponential, Gamma and Beta distributions were proposed to model the distribution of the wet spell. Kolmogorov-Sminov, Anderson-Darling and Chi-squared goodness-of-fit tests were used to evaluate the model fitness. Based on 6hr storm separation time; the mean rainfall frequency ranges from 115 to 198 events per annum. Statistics of duration shows that Kuala-Lumpur receives the lowest mean duration of 4.08hr per event while Khota-Bahru receives the highest value of 10.47hr. Goodness-of-fit indicates that Generalized pareto, exponential and Gamma distributions can be used at 5% level of significance. However, Generalized pareto is found to fit better than the remaining distributions

Optimization of active to permanent pool volumes ratio for wet ponds in tropical catchments

Urban stormwater is the second major urban flow of concern to the drainage engineer and the second largest source of impairment to lakes and estuaries. Safe and efficient removal of urban stormwater is important to maintain public health and safety and to protect the receiving water environment. Detention ponds are stormwater best management practices used for the treatment and control of urban stormwater. Wet detention ponds have two zones: the active and the permanent pool volumes. In this research, long term hourly rainfall and case study catchment's data were collected and the effect of varying the ratio of active to permanent pool volumes investigated using analytical probabilistic models. It was observed that the pollution control performance of wet ponds increase with increase in the ratio reaching a peak value of 82% at a ratio of 0.6 and declines. For optimum benefit, design of the wet ponds in tropical catchments should target this point where the pollution control is highest although other design considerations might also need to be considered

Uncertainty of phosphorus loadings estimation using vollenweider model for reservoir euthrophication control

Eutrophication process downgraded lake or reservoir water quality, if the system is not monitored and managed properly. Recent investigation seems to favor phosphorus as the limiting factor for reservoir productivity. The purpose of this study is to estimate the uncertainty of phosphorus loadings for the Layang reservoir using Vollenweider-IHACRES model. The incorporation of IHACRES Model had helped to compute better hydrological estimation. This model is used to predict the streamflow into the reservoirs that later be used in the Vollenweider model. Rainfall data were obtained from the Department of Irrigation and Drainage Malaysia for the Station 1539001, Loji air Sungai Layang. Five water samples were taken randomly near the inlet and upstream of reservoir. The water samples were tested with reagent phos Ver 3 phosphate using DR 4000 (Hach Co. CO 80539-9987, USA) to indicate the dissolved phosphorus content in mg/l. The total phosphorus concentration obtained from the three site visits were observed. The average phosphorus content was 0.214 mg/l. The highest phosphorus content observed was 0.622 mg/l and the lowest concentration was 0.053 mg/l. Fuzzy membership function is then used to describe phosphorus content, hydraulic loadings and the phosphorus loadings that represent the current conditions of the reservoir. By using fuzzy membership function, a range of estimation could be obtained. The most likely range of phosphorus content obtained was 0.1 mg/l to 0.3 mg/l and for hydraulic loadings was 1350 m/yr to 1400 m/yr. Estimated phosphorus loadings range from 0.26 g/m2/yr to 0.81 g/m2/yr (7.81 ton/yr to 24.28 ton/yr). The average phosphorus content was 0.214 mg/l and average hydraulic loading was 1452.25 m/yr. The average phosphorus loading calculated was 0.6g/m2/yr, within the estimated range of 0.26g/m2/yr to 0.81g/m2/yr. The largest bias from the IHACRES model simulation is -0.5546 mm/day and the smallest bias is -0.0076 mm/day. The highest R2 value is 0.9925 while the lowest is 0.9208. Both statistics showed that the model is able to perform well. This fuzzy phosphorus loadings estimation will help lake water quality improvement and management in the future. In order to ensure the phosphorus level reduction and overall lake water quality, the development and overall activities within the watershed should be properly and systematically managed