Using peak discharge estimation methods in urban flood modeling for WADI AL-AQIQ

Environment, Development and Sustainability - Several large floods have hit city areas in various regions of Saudi Arabia as a result of significant rainfall with significant effects on economic...     

Impact of climate change on regional irrigation water demand in Baojixia irrigation district of China

Water scarcity in China would possibly be aggravated by rapid increase in water demand for irrigation due to climate change. This paper focuses on the mechanism of climate change impact on regional irrigation water demand by considering the dynamic feedback relationships among climate change, irrigation water demand and adaptation measures. The model in implemented using system dynamics approach and employed in Baojixia irrigation district located in Shaanxi Province of China to analyses the changes in irrigation water demand under different climate change scenarios. Obtained results revealed that temperature will be the dominant factor to determine irrigation water demand in the area. An increase of temperature by 1 °C will result in net irrigation water demand to increase by about 12,050?×?10⁴ m³ and gross water demand by about 20,080?×?10⁴ m³ in the area. However, irrigation water demand will not increase at the same rate of temperature rise as the adaptation measures will eventually reduce the water demand increased by temperature rise. It is expected that the modeling approach presented in this study can be used in adopting policy responses to reduce climate change impacts on water resources.     

Possibility of converting indigenous Salvadora persica L. seed oil into biodiesel in Pakistan

In this research study, biodiesel has been successfully produced from vegetable seed oil of an indigenous plant Salvadora persica L. that meets the international biodiesel standard (ASTM D6751). The biodiesel yield was 1.57 g/5 g (31.4% by weight) and the in-situ transesterification ester content conversion was 97.7%. The produced biodiesel density was 0.894 g/mL, its kinematic viscosity 5.51 mm²/s, HHV 35.26 MJ/kg, flash point 210°C, cetane no. 61, and sulfur content 0.0844%. Thermal analysis of the biodiesel showed that 97% weight loss was achieved at 595°C with total oxidation of the biodiesel. The production energy efficiency was 0.46% with a lab scale setup, assuming the volume fraction ratio (volume of the sample/total volume of the equipment used). The results revealed that single-step in-situ transesterification method is suitable for the production of biodiesel from S. persica seed oil.     

Evaluating the Applicability of a Two‐dimensional Flow Model of a Highly Heterogeneous Domain to Flow and Environmental Management

Two‐dimensional simulation of highly heterogeneous domains, especially those with disparate length scales, roughness conditions, and geometries, often leads to challenges such as long computation times and numerical instability. Simulation of challenging domains is often needed to guide flood management and environmental regulation agencies in operation and potential domain modifications. This work evaluates the ability of a two‐dimensional unsteady hydrodynamic model to represent long‐duration transient flows over a domain with highly heterogeneous roughness, geometric characteristics, and length scales through bed roughness representation. The domain includes 13 km of Cache Creek and the 14.5 km² Cache Creek Settling Basin, which traps both sediment and mercury. Calibration under different bed roughness methods, validation, and modeling results of bathymetric modification scenarios are presented. The modeling approach's performance supports its application as a tool for management of similar domains, such as settling basins, leveed floodplains, and reservoirs. Accurate representation of flow dynamics can also inform environmental management that involves transport of sediments, nutrients, and heavy metals. This study found that a two‐dimensional unsteady flow model can accurately represent long‐duration transient flow in a large settling basin with highly heterogeneous characteristics without parsing of the domain or flow events simulated.     

Effects of Spatial and Temporal Data Aggregation on the Performance of the Multi‐Radar Multi‐Sensor System

The objectives of this study were to (1) evaluate the performance of the Multi‐Radar Multi‐Sensor (MRMS) system in capturing precipitation compared to gauge data, and (2) assess the effects of spatial (1–50 km) and temporal (15–120 min) data aggregation scales on the performance of the MRMS system. Point‐to‐grid comparisons were conducted between 215 rain gauges and the MRMS system. The MRMS system at 1 km spatial and 15 min temporal resolutions captured precipitation reasonably well with average R², root mean square error (RMSE), and percent bias (PBIAS) values of 0.65, 0.5 mm, and 11.9 mm; whereas Threat Score, probability of detection, and false alarm ratio were 0.57, 0.92, and 0.40, respectively. Decreasing temporal resolution from 15 min to two hours resulted in an increase in R² and a decrease in RMSE, whereas PBIAS was not affected. Reducing spatial resolution from 1 to 50 km resulted in increases in R² and PBIAS, whereas RMSE was decreased. Increasing spatial aggregation scale from 1 to 50 km resulted in an R² increase of only 0.08. Similarly, improvement in R² was only modest (0.17) compared to an eightfold reduction in temporal resolution (from 15 min to two hours). While aggregating data at coarser temporal resolutions resolved some of the under/overestimation issues of the MRMS system, it was apparent even at coarser spatial and temporal resolutions the MRMS system inherently overestimated smaller precipitation events while underestimated bigger events.     

Markovian–Octant analysis based stable turbulent shear stresses in near-bed bursting phenomena of vortex settling chamber

The coherent structure in near-bed turbulent boundary layer of vortex chamber, particularly the bursting events and their associated shear stresses play the main role in sediment flushing process and consequently the trap efficiency of the vortex settling chamber. Hence, three-dimensional velocity measurements were made at 48 points near the bed of physical model of vortex chamber by using Micro-ADV. The pattern of sediment deposition at the bed of vortex settling chamber reveals three separate regions formed by three predominant currents of inlet flow, flushing flow and outlet over flow. Additionally, due to the instability and three-dimensional nature of the bursting events near the bed of chamber, the new method of Markovian–Octant analysis was applied to study the different classes of near-bed stable shear stresses of vortex chamber in three dimensions. Moreover, the role of each class of stable shear stresses on Sediment transport mechanism at the bed of vortex chamber is investigated.     

Investigation of acute toxicity of cadmium sulfate (CdSO4 x H2O) and behavioral changes of grass carp (Ctenopharyngodon idellus Val., 1844)

This study attempts to determine the 96-h LC50 values of CdSO4 x H2O, a metal salt widely used in industry, for grass carp (Ctenopharyngodon idellus Val., 1844). The study was carried out in two stages with 120 grass carp individuals using statistic method of aquatic toxicity. In addition, the behavioral changes of grass carp at different CdSO4 x H2O concentrations were determined. The results were evaluated using probit analysis method and the LC50 value for grass carp species was calculated as 9.42 mg/l.     

Investigation of acute toxicity of cadmium chloride (CdCl2 . H2O) metal salt and behavioral changes it causes on water frog (Rana ridibunda Pallas, 1771)

The 96-h LC(50) value of cadmium chloride (CdCl(2).H(2)O), a metal salt widely used in industry, was determined in the water frog (Rana ridibunda Pallas, 1771). The experiments were conducted in two series and a total of 140 frogs were used to determine acute toxicity. In addition, behavioral changes in the water frog were determined for each cadmium chloride concentration. Data obtained from the cadmium chloride investigation were evaluated by using the probit analysis statistical method and the 96 h LC(50) value for water frog was estimated to be 51.2 mg/l.     

Potential of immobilized bitter gourd (Momordica charantia) peroxidases in the decolorization and removal of textile dyes from polluted wastewater and dyeing effluent

Immobilized peroxidases from Momordica charantia were highly effective in decolorizing reactive textile dyes compared to its soluble counterpart. Dye solutions, 50-200 mg/l, were treated with soluble and immobilized bitter gourd peroxidases (specific activity of 99.0 EU per mg protein). The decolorization of dyes with soluble and immobilized enzyme was maximum in the range of pH 3.0-4.0. The effect of different temperatures on the dye decolorization was monitored and it was observed that all the dyes were maximally decolorized at 40 degrees C. In order to examine the operational stability of the immobilized preparation, the enzyme was repeatedly exploited for the decolorization of the dyes from fresh batch of dye solutions. Even after 10 cycles in each case the immobilized preparation retained nearly 50% of the initial enzyme activity. The immobilized enzyme exhibited more than 90% of the original activity while the soluble enzyme lost 33% of the initial activity when stored for 40 d at room temperature. Mixtures of three, four and eight dyes were prepared and treated with soluble and immobilized bitter gourd peroxidase. Each mixture was decolorized by more than 80% when treated with immobilized enzyme. Dyeing effluent collected from local dyers was treated with both types of enzyme preparations. Immobilized enzyme was capable of removing remarkably high concentration of color from the effluent. TOC content of soluble and immobilized enzyme treated individual dyes, mixture of dyes and dyeing effluent was determined and it was observed that higher TOC was removed after treatment with immobilized enzyme.     

Physico-chemical characteristics and pollution level of Lake Nainital (U.P., India): role of macrophytes and phytoplankton in biomonitoring and phytoremediation of toxic metal ions

Lake Nainital is the sole source of drinking water for the local people and even to majority of tourists. In background of lake utility and its importance at national level, such study is essential which is focused on toxic metal pollution and current nutrient status of the lake and their magnification by algae and macrophytes. Study has shown that lake water is rich in nutrients which supports growth of many aquatic macrophytes and algal blooms. Besides, water is contaminated with metals like Cr, Cu, Fe, Mn, Ni, Pb and Zn. Concentration of some of them like Fe, Pb and Ni were higher than the recommended maximum permissible limits. Concentration of these metals were also found high in lake sediments. The level of metals amongst various components of lake varied considerably in different season. Plants and algae growing therein accumulated appreciable amount of metals and water roots of Salix being more efficient than others. High metal removing potential of these plants may be significant for biomonitoring studies and could be a useful phytoremediation technology to restore water quality by harvesting submerged and floating biomass inhabiting littoral zone of the lake.