International Journal of Hydrology Science and Technology (33 papers in press)

Regular Issues

• Determining the most suitable Sentinel-2 indices for turbidity and chlorophyll-a concentration for an oligotrophic to mesotrophic reservoir in Brazil  
  by Fernanda Mara Coelho Pizani, Camila Costa De Amorim, Philippe Maillard 
  Abstract: Water quality is a major issue for agencies responsible for the management and maintenance of reservoirs. In this article, Sentinel-2 (S-2) data is tested to produce reliable estimates of turbidity and chlorophyll-a concentrations in an oligotrophic to mesotrophic reservoir in Brazil. The spectral bands were all tested individually and jointly to determine the best and most stable features. Many indices are also tested. In situ data was acquired over a period of three years with synchronous S-2 data. The models were evaluated on their robustness and stability using a bundle of in situ dataset (all field campaigns). The results show that no model can be directly applied to other reservoirs or different dates without calibration. Conversely, calibrating the S-2 indices with two in situ measurementsa greatly reduces the errors. Average root mean square errors of 0.518 FNU and 1.1 _g/l were obtained for turbidity and chlorophyll-a concentrations respectively.
  Keywords: chlorophyll-a; turbidity; empirical models; Sentinel-2; reservoir.
  DOI: 10.1504/IJHST.2023.10057236
   
  
• Effect of hydrological model selection in climate change impact assessment in the Dano tropical catchment (Burkina-Faso)  
  by Yacouba Yira, Aymar Y. Bossa, Ngague Hisseine Ganda, Djigbo F. Badou, Kpade O. Laurentin Hounkpatin, Jean Hounkpè, Luc Ollivier Sintondji 
  Abstract: Applying a validated hydrological model is a common approach in climate change impact studies. The current study used an ensemble of five regional climate models and two hydrological simulation models (HBV-light and GR4J). Both models were successfully calibrated and validated with coefficients of determination-R 2 and Nash and Sutcliffe efficiencies-NSE ranging between 0.64 and 0.88. Compared to the reference period (1976-2005), the projected temperature shows an increase for the future periods 2021-2100, whereas for the projected precipitation change, a mixed trend is expected. The projected discharge change is very similar to the precipitation signal. The results further indicate for some climate datasets that, the climate-induced discharge change is lower than 50 mm per year for both HBV-light and GR4J, while the inter-comparison of discharges between the two hydrological models indicates differences exceeding 100 mm per year. Therefore, the choice of the hydrological model overscores the impact of the projected climate change.
  Keywords: climate change; CORDEX; discharge; HBV-light; GR4J; hydrological model selection; climate change impact; tropical catchment; Burkina Faso.
  DOI: 10.1504/IJHST.2023.10057775
   
  
• Integrated rainfall-runoff modelling using fuzzy logic considering soil moisture: case study of Damanganga Basin  
  by Vrushti C. Kantharia, Darshan J. Mehta 
  Abstract: The present study aims to develop integrated rainfall-runoff modelling considering soil moisture at three different depths (5 cm, 100 cm, and bedrock) for the Damanganga basin. To simulate the daily discharge Mamdani fuzzy-logic model and adaptive neuro-fuzzy inference system (ANFIS) are used. The analysis is carried out for the South-West Monsoon season, i.e., (June, July, August, and September) for 39 years, i.e., 1983-2022. Mamdanis fuzzy-logic and adaptive neuro-fuzzy inference system (ANFIS) model uses soil moisture and rainfall data as the input variables to simulate daily discharge. The model application result reveals that soil moisture at bedrock gives more precise results as compared to soil moisture at 5 and 100 cm. Comparison between both the models is also carried out on the basis of regression and the results demonstrate that the adaptive neuro-fuzzy inference system (ANFIS) model gives a more precise value of daily discharge as compared to the Mamdani fuzzy model. This study can be helpful to future research scholars and to hydrological scientists in selecting appropriate rainfall-runoff models.
  Keywords: ANFIS; Damanganga; discharge; fuzzy logic; Mamdani; rainfall; soil moisture.
  DOI: 10.1504/IJHST.2023.10058036
   
  
• Infiltration characteristics and hydraulic properties of soil as affected by tillage practices and biochar-poultry manure application.  
  by Chukwuebuka Vincent Azuka 
  Abstract: The study investigated the effect of biochar and poultry manure (PM) applications on infiltration characteristics and hydraulic properties of degraded Ultisols in Nsukka under two tillage practices. The treatments were tillage practices (conventional tillage; zero-tillage) and organic amendments (10 t/ha biochar, 10 t/ha PM, 10 t/ha biochar + 200 kg/ha NPK and 400 kg/ha NPK). The results showed significant (p < 0.05) higher values of cumulative and steady-state infiltration, saturated hydraulic conductivity (Ksat), microporosity and total porosity (TP) in tilled soils (1,266 mm, 0.772 cm/min, 25.88 cm/hr, 40.53% and 49.23% respectively) than in no-tilled soils (799 mm, 0.502 cm/min, 20.05 cm/hr, 36.88% and 45.81% respectively). Organic amendments had a significant (p < 0.05) effect on BD, cumulative and steady-state infiltration, Ksat and available water capacity (AWC). The highest values of cumulative and steady-state infiltration, Ksat and AWC (1,302 mm, 0.800 cm/min, 25.23 cm/hr and 0.290 respectively) and lowest values of BD (1.49 g/cm3) were obtained in biochar-amended soil.
  Keywords: organic amendment; soil degradation; soil quality; biochar; soil productivity.
  DOI: 10.1504/IJHST.2023.10058434
   
  
• Extreme value modelling using the peaks over threshold method, an inverse cumulative uniform distribution approach  
  by Justin Chirima 
  Abstract: This paper proposes an inverse continuous uniform distribution approach for selecting the threshold when performing the peaks over threshold (POT) method to data with outliers. Applying results from the mean residual life plot (MRLP) and the threshold stability plot (TSP), the threshold is assumed to follow a continuous uniform distribution between values a and b. An inverse uniform distribution algorithm for threshold selection is developed and applied to hypothetical data and Zimbabwean precipitation data. The proposed method is capable of determining optimal thresholds which give reasonable fits for historical data.
  Keywords: uniform distribution; threshold; generalised Pareto distribution; GPD; peaks over threshold; POT.
  DOI: 10.1504/IJHST.2023.10058520
   
  
• Assessment of recharge dam performance in arid regions based on satellite data, case study: Jalajil and Rawdah Dams  
  by Raied Saad Alharbi, Jerome Arunakumaren 
  Abstract: Effective water resources management in arid regions necessitates accurate information on their current condition and how they change due to resource use and development, land-use patterns, and climate change. Due to a lack of data collected on the ground, it is challenging to evaluate the condition of the resources and implement effective management strategies. Recent developments in earth observation and satellite remote sensing offer valuable data for water resource management and better knowledge and control of the natural and anthropogenic processes that affect changes in water resources. This paper discusses how historical surface water area variations at dam sites, derived from remote sensing data, can be used to assess current conditions and long-term trends in water resource availability. The Jalajil Dam’s water balance model was developed using the GoldSIM modelling framework by linking precipitation-runoff inflow components and reservoir storage variation processes. Based on the model results, the dam recharge component is much higher than the evaporation component, and the dam act to save collected water from evaporation. Enhancement of recharge at dam sites has become necessary in arid regions to develop water resources from availability to times of need, reduce water supply issues, and even mitigate climate change.
  Keywords: remote sensing; water balance model; GoldSIM; managed aquifer recharge; modified normalised difference water index; MNDWI.
  DOI: 10.1504/IJHST.2023.10059786
   
  
• Identification of flood hazard zones in Afghanistan using GIS and multi-criteria decision approach  
  by Hamidullah Tani, Gokmen Tayfur 
  Abstract: This study assessed Afghanistans potential flood hazard zones using the geographic information systems (GIS) and the analytical hierarchy process (AHP). Six different thematic layers were selected, and the AHP was applied to estimate the influence weights of each parameter. The final flood hazard zones map (FHZM) was reclassified into five zones. Sensitivity analysis was employed to create the flood hazard sensitivity map (FHSM) based on effective weights. It was found that the land use land cover (LULC) and rainfall are less sensitive compared to the other parameters. The FHZM and FHSM comparatively indicate the same regions regarding flood hazard levels. The methodology was tested against the recorded flood events in the region. The results showed that about 44% of the study area is under Low and Very Low flood hazards, whereas 56% is subjected to high and very high. Low-lying areas are highly prone to flooding.
  Keywords: flood prone regions; flood hazard; sensitivity analysis; geographic information systems; GIS; analytical hierarchy process; AHP; Afghanistan.
  DOI: 10.1504/IJHST.2023.10059873
   
  
• Mauritius oil spill detection using transfer learning approach for oil spill mapping and wind impact analysis using Sentinel-1 data  
  by Koushik Das, Prashanth Janardhan, Harish Narayana 
  Abstract: The oil spill detection and mapping using Sentinel-1 (S-1) data for the Mauritius oil spill event have been done in this study. The convolutional neural network (CNN)-based on pre-trained models such as AlexNet, VGG-16, and VGG-19, have been used to classify the S-1 images by the transfer learning approach. The S-1 images are classified into two classes: with and without the oil spill. Then, the oil spill detection was done in the sentinel application platform (SNAP), and the oil spill mapping was done in ArcGIS. The VGG-16 network performs the best among the other pre-trained networks with an accuracy of 96.88%, precision of 95.92%, and recall of 97.92%. The impact of wind on the spreading of oil is also analysed using remote sensing and GIS techniques. It has been observed that the spreading of oil doesn’t only depend on sea wind but also other environmental factors.
  Keywords: transfer learning; convolutional neural network; CNN; Sentinel-1; sentinel application platform; SNAP; oil spill; image classification; remote sensing; GIS.
  DOI: 10.1504/IJHST.2023.10059874
   
  
• Modelling drought as a climate change indicator in the southwest coastal region of Bangladesh  
  by Noor-E-Ashmaul Husna, Sheikh Hefzul Bari, G.M. Tarekul Islam, A.K.M. Saiful Islam, Md. Manjurul Hussain 
  Abstract: In this study, we conducted a comprehensive analysis of meteorological drought in the southwest region of Bangladesh using the reconnaissance drought index (RDI) and the Mann-Kendall trend test. Furthermore, trends in the initial form of RDI (?k) are assessed using the Mann-Kendall and sequential Mann-Kendall tests to find any indication of climate change. The results show that the study area has experienced moderate to extreme droughts in the past, with an increasing frequency in recent years showing a seasonal nature. The negative trend in the annual and most seasonal standardised RDI (RDIst) series suggests that drought severity will increase in the future. At the same time, trends in the initial RDI (?k) suggest a potential change in the climate, especially after 1990. The resulting change in precipitation, or potential evapotranspiration (PET), may significantly affect surface water sources during dry seasons.
  Keywords: climate change; meteorological drought; Southwest Bangladesh; reconnaissance drought index; RDI; drought management; drought monitoring; sequential Mann-Kendall test.
  DOI: 10.1504/IJHST.2023.10059979
   
  
• Smart irrigation planning in water deficit area (case study: Pench Irrigation Project, India)  
  by Narendra Bonde, Vivek Manekar, Dinesh V. Morankar 
  Abstract: As the climate is changing, more and more area is turning into water deficit for irrigation. It is always challenging for the authority to allocate crop area and water resources in such a way that farmers should not be in the loss. Genetic algorithm (GA) optimisation model is used in this for optimisation of surface and groundwater (GW) resources in the Pench Irrigation Project. The results show that the command area’s GW allotment is significantly reduced, and GW withdrawal may also be limited to recharge in order to preserve the equilibrium between rivers and aquifers. The optimisation problem for constrained conjunctive use was solved using a GA. To enhance the net benefit to the farmers and keep the water demand within the volume of water available, the results show that paddy, cotton, and wheat should be grown less and Sugarcane, other perennial crops, and chillies should be grown more.
  Keywords: conjunctive use; irrigation; crop area optimisation; linear programming; India.
  DOI: 10.1504/IJHST.2023.10061259
   
  
• Analysis of flood severity using intelligent deep networks and sentinel image for the Kerala region  
  by Supriya Kamoji, Mukesh Kalla 
  Abstract: Accurate flood prediction and the classification of severity levels are vital for assessing the impact of floods and ensuring the safety of affected populations. Despite introducing numerous systems, many existing models require significant time to generate prediction results. Intelligent techniques like neural networks have been proposed to enhance prediction accuracy to address this. However, the complexity of data sources, such as satellite or sentinel data, poses challenges due to their unstructured nature and noisy attributes. This study introduces a pioneering approach known as the virtual bee-based recurrent model (VBRM) for flood prediction and severity classification. Specifically, the model categorises floods into low, medium, and high severity levels. The initial step involves gathering sentinel data related to the floods in Ernakulum, Kerala. This data is then used to train the VBRM, followed by a pre-processing stage that effectively filters out irrelevant features and noise. Subsequently, the refined data is fed into the classification layer, where the model extracts pertinent features and determines the severity level of floods. The ultimate objective is to achieve high prediction accuracy with minimal errors. Various performance metrics are employed, and a comparative analysis is conducted against other existing models to evaluate the model’s performance.
  Keywords: deep networks; feature extraction; flood severity classification; optimisation; sentinel data; virtual bee-based recurrent model; VBRM.
  
  
• Long-range forecasting of daily rainfall using machine learning techniques  
  by Syamantak Bhunia, Ujjwal Saha 
  Abstract: Around the world, awareness of the value of rainfall forecasting and its social and economic advantages is rapidly growing. Nation like India, where agriculture is one of the main economic drivers, accurate rainfall forecasting is essential for managing water resources and reducing hydrological extremes. To predict daily rainfall for a year in the drought-prone Kangsabati river basin, long short-term memory (LSTM) and random forest (RF) techniques were utilised using the data of 52 years (1969 to 2020). Finding the right associated variable and a substantial lag in the time series that allows for future value prediction is essential when developing time series forecasting models. The partial auto correlation function and Pearson correlation technique were applied in this context. Furthermore, comparisons were made between the suggested models and the well-known statistical model, the seasonal auto-regressive integrative moving average (SARIMA). The study shows that for this region, the proposed LSTM model and SARIMA model had higher accuracy than the RF model. Additionally, this research suggests that machine learning algorithms may be used to analyse daily rainfall for a particular catchment or station and, to a certain extent, forecast extreme hydrological events.
  Keywords: hyperparameter; long short-term memory; LSTM; machine learning; rainfall forecasting; RF; SARIMA.
  DOI: 10.1504/IJHST.2024.10061937
   
  
• Investigating the effect of watershed management on land use, groundwater recharge, and irrigation potential in Tigray region, northern Ethiopia  
  by Tsige Yenalem, Yilma Kidanie, Ahmed Mohammed Degu, Teame Yisfa 
  Abstract: This study was conducted to investigate the effect of watershed management on groundwater recharge and irrigation expansion in northern Ethiopia. The GIS-based water and energy transfer between soil, plants, and atmosphere under the quasi-steady state (WetSpass) hydrological model was implemented. Two scenarios, before watershed management (1997-2007) and after watershed management (2008-2018), were investigated. After watershed management, groundwater recharge increased from 9.7, 44.4, and 54.15 mm for dry, rainy, and annual conditions, respectively, to 9.9, 96.2, and 106.13 mm for these conditions. The relationship between calculated and observed groundwater depths results in a coefficient of determination of 0.81. After watershed management, the water balance system had evapotranspiration, surface runoff, and groundwater recharge of 83.7%, 3.0%, and 13.3%, respectively, of total precipitation. Excess groundwater recharge of 6.51% resulted in extending the irrigation area by 12.7 hectares. Results show that WetSpass is effective in estimating groundwater recharge and irrigation area expansion.
  Keywords: groundwater recharge; hydrology; water balance; watershed management; WetSpass; Ethiopia.
  
  
• Modeling of scour depth in the existing bridge piers with and without an adjacent parallel bridge  
  by Biswajit Dalal, Subhrajyoti Deb 
  Abstract: This paper presents a hydraulic simulation conducted to assess the stability of the Netaji Subhas Bridge on the Gomti River in Tripura. The simulation takes into account different scour profiles and numerous flood events. The calculation of local scour at various piers takes into account four different flow profiles: PF1 (1,495 m3 /s), PF2 (1,147 m3 /s), PF3 (711 m3 /s) and PF4 (475 m3 /s). The analysis of the HEC-RAS model reveals that the scour depth (Ys) and the Froudes number (Fr) exhibit a decrease for all flow profiles when a parallel bridge is constructed upstream of the existing bridge. But, if the new bridge is constructed on the downstream side then Ys and Fr are increased for PF2, PF3 and PF4 but in the case of PF1, only the Ys decreased. Therefore, the safer and more serviceable option is to construct the parallel bridge on the upstream side of the existing bridge.
  Keywords: Gomti River; parallel bridges; HEC-RAS; modelling; scour depth.
  DOI: 10.1504/IJHST.2024.10062372
   
  
• Estimation of groundwater recharge in Southern Ghana  
  by Delaiah Antwi Nyarko, Larry Pax Chegbeleh, Elikplim Abla Dzikunoo, Edward Kofi Ackom, Sandow Mark Yidana 
  Abstract: The rainfall infiltration breakthrough (RIB) model has been applied to estimate groundwater recharge over parts of the saprolite aquifer unit in southern Ghana. This method relies on rainfall and groundwater level data monitored simultaneously over a period, and properties of the aquifer material. The water table fluctuations (WTF) technique was applied independently to validate the results of RIB technique. Both methods were executed based on specific yield (Sy) values in the range of 1%-5%. The results suggest a wide range of variations in groundwater recharge rates over the terrain. Groundwater recharge rates fall in the range of 0.58%-21.36% of annual precipitation based on the RIB. The results indicate that the lag period between rainfall and eventual groundwater recharge ranges between 0 and 9 months, depending on the thickness and content of the unsaturated zone. Estimates of groundwater recharge suggest variably good fortunes for groundwater.
  Keywords: RIB model; WTF method; groundwater level fluctuation; groundwater recharge; shallow unconfined aquifer; saprolite aquifer system; lag time; lag length.
  DOI: 10.1504/IJHST.2024.10062601
   
  
• Evaluation of mesoscale physical habitats in sediment and water quality improvement - a mesocosm study for urban canals  
  by Sanjana De Zoysa, Kurugama A. T. Chandeep, Pathirathne H. D. R. Pathirathne, Pattiyage I.A. Gomes 
  Abstract: This study investigated the applicability of different types of attenuation processes (i.e., aeration and stirring) with and without dilution in nutrients (nitrogen and phosphorous) and sulphide-polluted sediment cleanup via laboratory mesocosms. Attenuation refers to the decline in contaminant concentration, a phenomenon driven by processes like dilution, mixing, and dispersion. Dilution, a remedial method involving the blending of contaminated water with uncontaminated often happens with uncontaminated runoff or a tributary. Regardless of the seasons, aeration, stirring, combined aeration and stirring, and dilution generally resulted in better removal efficiency of pollutants. Aeration combined with stirring showed notable improvements across multiple water quality parameters, and parameters seemed to be treatment type dependent, but without any significant differences. Dilution reduced electrical conductivity and increased dissolved oxygen but did not influence ammoniacal nitrogen and phosphate. The energy consumption for a unit percentage improvement via aeration and stirring was 0.04-0.25 and 0.03-0.15 USD, respectively. Therefore, relying solely on attenuation processes without dilution is deemed economically infeasible in real or prototype applications. This research sheds light on potential applications including pros and cons, emphasising the need for a balanced approach, and setting the stage for future studies.
  Keywords: aeration; dilution; energy; mesocosms; mesoscale physical habitats; sediment; stirring; water quality.
  
  
• Performance evaluation of commonly used infiltration models  
  by Redahegn Sileshi, Robert Pitt, Shirley Clark 
  Abstract: Soil infiltration rate is a critical parameter in the design and evaluation of stormwater control facilities. The aim of this research was to evaluate selected infiltration models (Horton’s, Kostiakov’s, and Green-Ampt’s) used to estimate final soil infiltration rate. Parameters of the models were estimated. The goodness of fit of the three equations for infiltration was tested using the root mean squared error (RMSE). Comparison of the field and predicted infiltration rate evaluated at each time interval indicated that the infiltration rate predicted by the Green-Ampt’s and Horton’s models were much closer to the measured data.
  Keywords: infiltration rate; stormwater; infiltration models; model parameter; root mean squared error; RMSE.
  DOI: 10.1504/IJHST.2024.10063206
   
  
• Minimising greenhouse gas emissions from small and medium-sized wastewater treatment plants  
  by Jerzy Mikosz 
  Abstract: Municipal wastewater treatment plants often use the activated sludge process in single-stage reactors with nitrification or in two-stage reactors with nitrification and denitrification. Both processes, if operated under unfavourable environmental conditions, can lead to excessive production of nitrous oxide (N2O), a gas with a high global warming potential (GWP) of about 300). In turn, the decomposition of organic pollutants leads to the release of CO2 and CH4 into the atmosphere. When analysing greenhouse gas emissions from wastewater treatment, it is also necessary to consider indirect emissions, mainly related to the use of energy from external sources. Estimating the magnitude of these emissions based on actual measurements is difficult. This article presents the results of simulation studies on the potential for reducing greenhouse gas emissions from small and medium-sized wastewater treatment plants with aerobic sludge digestion (AD) through operational optimisation of existing plants or the application of new technologies.
  Keywords: wastewater treatment plant; WWTP; activated sludge; multiphase reactors; nitrification; enitrification; aerobic digestion; greenhouse gases; GHG; GHG emission; nitrous oxide; N2O; computer simulation.
  DOI: 10.1504/IJHST.2024.10063324
   
  
• Using artificial neural network with clustering techniques to predict the suspended sediment load  
  by Abdelghafour Dellal, Abdelouahab Lefkir, Yamina Elmeddahi, Samir Bengherifa 
  Abstract: Rivers are natural water channels that are influenced by a variety of factors, including erosion and sedimentation, which have a detrimental impact on the ecosystem’s health and water quality. Recently, researchers resorted to using an artificial neural network (ANN) to model the suspended sediment load. This study addressed the application of a multi-layer ANN model. Feed-forward with a backpropagation algorithm based on five different collection methods for the input data. To model the daily suspended sediment load in the Sacramento River, California, USA, current and delayed Ql flow discharge data and solid flow Qs data were used. The accuracy of the five methods was compared in 10 different input groups based on proficiency criteria: standard deviation ratio RSR, coefficient of determination R2, percentage bias (PBIAS), and Nash-Sutcliffe efficacy (NSE). The ANN model with the k-mean clustering technique provides the best results. The RSR values varied between 0.30 to 0.42, and the R2 values ranged from 0.82 to 0.91. While the range of NSE values was from 0.79 to 0.90.
  Keywords: artificial neural network; ANN; clustering technique; flow discharge; suspended sediment.
  DOI: 10.1504/IJHST.2024.10063467
   
  
• Site selection and hydropower potential assessment in Upper Sutlej River Basin: a case study of Indian and Tibetan regions using RS-GIS, SWAT and T-F models  
  by Nikki Chanda, Madhusudana Rao Chintalacheruvu, Anil Kumar Choudhary 
  Abstract: This research explores the untapped hydropower potential in India and Tibets Upper Sutlej River Basin (USRB). By leveraging remote sensing and GIS methods, the study identifies 901 new sites in India and 95 sites in Tibet for potential hydropower generation. The present study estimates that the Indian sites have 2,923 megawatt (MW), 1,830 MW and 1,274 MW, while the Tibetan sites have 289 MW, 178 MW and 98 MW hydropower potential at 50%, 75% and 90% dependability flows, respectively for medium or high-head in the USRB. The future hydropower generation potential is also assessed at the Bhakra dam site, a significant project in the USRB region, utilising historical streamflow data (19932013) and projected streamflows (20142053) through calibrated SWAT and T-F models results. This research offers valuable insights for sustainable development and highlights the immense hydroelectric power possibilities in the USRB region.
  Keywords: hydropower; Upper Sutlej River Basin; USRB; RS-GIS; soil water assessment tool; SWAT; Thomas-Fiering model; T-F model.
  DOI: 10.1504/IJHST.2024.10063572
   
  
• Electrolised oxidised water using rainwater synthesis as an environmentally friendly disinfectant  
  by Agus Maryono, Daniel Timotius, Muhammad Sulaiman, Andhika Puspito Nugroho, Heni Wahyu Sartika, Cristina M. Talakua, Pratama Tirza Surya Sembada, Yosef Prihanto, Eko Handoko, Agus Prasetyo, Himawan Tri Bayu Murti Petrus 
  Abstract: Electrolytic oxidising water (EOW) is a disinfectant and sanitary material that is classified as easy to obtain, inexpensive, safe, and environmentally friendly. This study aims to determine the effect of electrodes and mineral salt concentration on changes in the properties of EOW such as potential hydrogen (pH), oxidation-reduction potential (ORP), and total dissolved solids (TDS) at various times, determine the toxicity of EOW to earthworms (Lumbricus sp.), and the disinfecting ability against bacteria (both gram-positive and gram-negative) was measured with disc diffusion method. The water used for EOW is rainwater in Yogyakarta. The study results show that EOW water is successfully produced by an electrolysis device and the EOW water used as a disinfectant is environmentally friendly. Furthermore, the use of EOW water as a disinfectant shows the ability to inhibit gram-positive and gram-negative bacteria, which is comparable to 70% ethanol.
  Keywords: electrolytic oxidising water; EOW; rainwater; disinfectant; toxicity; disinfection.
  
  
• Application of CE-QUAL-W2 model for optimal selective withdrawal of reservoir concerning water quality (case study: Shahr Bijar Dam Reservoir, Iran)  
  by Seyed Abolfazl Ebrahimi 
  Abstract: Reservoirs, essential for human water supply, experience thermal stratification affecting water quality. Utilising the CE-QUAL-W2 model, this study simulates thermal stratification and water quality in Shahr Bijar Reservoir, Iran, spanning September 2019 to 2020. Simulations identify the optimal intake gate for selective withdrawal, considering parameters such as dissolved oxygen, phosphate, ammonium, and total dissolved solids. Calibration and validation demonstrate a reasonable correlation between simulated and observed data. Thermal stratification leads to variable water quality at different intake gate levels. Three seasonal management scenarios determine the optimal outlet for selective withdrawal. Results indicate that the third intake gates, with IRWQISC indices of 83.1, 85.5, and 79.8 in fall, spring, and summer, deliver superior-quality water. In winter, all three intake gates, each with an index of 87, exhibit identical quality. This study introduces an innovative approach to reservoir withdrawal optimisation, emphasising seasonal variations and practical implications for water resource management.
  Keywords: water quality modelling; CE-QUAL-W2; selective withdrawal; dam operation; reservoir management.
  DOI: 10.1504/IJHST.2024.10063982
   
  
• Predictive hydraulic conductivity modeling of wide gradation spectrum sandy soils using stepwise multiple linear and LASSO regression  
  by Mohammad Aasif Khaja, Shagoofta Rasool Shah, Ramakar Jha 
  Abstract: Accurate estimation of soil hydraulic conductivity (K) is crucial in groundwater hydrology and geo-environmental engineering applications. This study introduces novel K predictive modelling for wide gradation spectrum sandy soils, employing stepwise multiple linear regression (SMLR) and least absolute shrinkage and selection operator (LASSO) techniques. Using an 81-sample dataset with key variables, including particle sizes, gradation parameters, porosity, and dry density, this study addresses limitations in existing K prediction methods. Correlation analysis reveals variable associations and multicollinearity issues, necessitating feature selection and the development of SMLR and LASSO regression models. While both models perform well on the training dataset, LASSO excels in mitigating overfitting, achieving a high coefficient of determination (R2) of 0.82 and 0.87 on the training and testing datasets. Comparative analyses with existing models in the literature underscored LASSO’s superiority in approximating laboratory-measured K-values, establishing it as the preferred choice for hydraulic conductivity estimation.
  Keywords: hydraulic conductivity; sandy soils; predictive modelling; stepwise multiple linear regression; SMLR; LASSO regression.
  DOI: 10.1504/IJHST.2024.10064217
   
  
• Accessing the accuracy of modified Schlumberger (Hummel) array of vertical electrical sounding: a pivotal to groundwater exploration  
  by Abayomi Adesola Olaojo, Prekibina Tamunoimama Oti, Kehinde David Oyeyemi 
  Abstract: Space constraints encountered in areas with well-developed housing layouts impede geophysical exploration for groundwater. The study aims to evaluate the effectiveness of the modified Hummel array in groundwater exploration. 32 vertical electrical sounding (VES) data were obtained using both the full and half Hummel and Schlumberger arrays on a migmatite gneiss, revealing its applicability in a complex geology. The data were processed by curve matching and computer iteration. The curve types (H, KH, and QH) and geoelectric sequences inferred from the arrays showed similar layer distributions. The correlated raw data and geoelectric parameters generated moderate to strong coefficients (0.5224-0.9999), indicating a high degree of similarity. The T-values (>2) confirmed the reliability of the coefficients used as predictors. The closeness of data around 1:1 line revealed half Hummel to be a better substitute for Schlumberger, especially in built-up areas where mirror electrode spread is not achievable due to space constraints.
  Keywords: Hummel; Schlumberger; sounding; geoelectric; groundwater; resistivity; correlation; exploration; gneiss; curve-type.
  DOI: 10.1504/IJHST.2024.10064540
   
  
• Analysis of groundwater resources in the Majene coastal aquifer - Indonesia based on a hydrogeological conceptual model  
  by Muhammad Ramli, Aryanti Virtanti Anas 
  Abstract: Many cities do not have sufficient groundwater availability information. As a result, meeting the communitys water needs can become a problem, as in Majene City - Indonesia. Therefore, it is necessary to gain an understanding of groundwater through a hydrogeological conceptual model. The conceptual model was developed based on rock resistivity, hydro-chemical, and climatological data. The rocks that make up this area form an unconfined aquifer which receives a recharge of 277 mm/year. The resistivity data characterises the rock layer/aquifer as being relatively uniform down to a depth of 150 metres. The hydro-chemical groundwater data in the aquifer was indicated to have been contaminated with seawater intrusion. An interpretive model of 2D areal simulation using the developed conceptual model to figure out the current condition based on estimated model parameters and boundary conditions. The numerical results could provide groundwater flow patterns according to the field observations and indicate significant river influence on seawater intrusion into the aquifer.
  Keywords: groundwater; hydro-chemical; seawater intrusion; salinity; aquifer; resistivity; numerical model; recharge; water balance; Indonesia.
  DOI: 10.1504/IJHST.2024.10064608
   
  
• Comparative assessment of LSTM approaches for enhanced prediction of rainfall climatology with minimum uncertainty  
  by Akshay Kumar, Saumitra Rai, Gaurav Kumar, Rajiv Gupta 
  Abstract: Forecasting precipitation is highly challenging for scientific modellers due to the complexity and uncertainty of atmospheric data and weather prediction models. To investigate the hydrological alternations such as rising sea levels, increasing floods and evaporation, and changes in snowpack caused by climate change, it is essential to accurately predict precipitation, a function of several interrelated climatic variables. This study presents a unique approach to predicting precipitation with minimum uncertainty by performing a comparative assessment of long-short-term memory (LSTM) approaches. The LSTM prediction models were run using quarterly, semi-annual, annual, and biannual precipitation data and other data such as temperature, vapour pressure, cloud cover, rainy days, and potential evaporation. Bivariate models using potential evaporation and temperature produced equivalent results to the multivariate model as the mean absolute error (MAE) was found to be 23.89% and 26.35%, respectively, compared to the univariate model (MAE 76.29%).
  Keywords: precipitation prediction; machine learning; LSTM; climate change.
  DOI: 10.1504/IJHST.2024.10064994
   
  
• Bias correction of regional climate model simulation for hydrological climate change over Bouregrag watershed in Morocco  
  by F. Gadouali, T. Benabdelouahab, A. Boudhar, R. Hadria, N. Semane, A. Fadil, K. Elrhaz 
  Abstract: General and regional climate models (GCMs/RCMs) exhibit many systematic biases, which affects the simulation accuracy of the real precipitation patterns and consequently the associated hydrological changes. The common approach used to reduce errors in the climate model output is to apply bias correction methods (BCMs) which attempt to adjust the climate simulation by its observation counterpart. In this study, we applied BCM on simulated rainfall over the Bouregrag basin (Morocco) from CanRCM₄ CORDEX RCM using linear SCALING method (SCALING), gamma quantile mapping (GQM) and empirical quantile mapping (EQM). Owing to its high performance compared to the others, we applied the EQM method on climate projections under the RCP_4.5 scenario. Results showed a decrease up to -50% in the monthly rainfall for the period 2041-2060 with the exception of August and December exhibiting an increase between +20% and +78%. This study supports the need to bias correct climate data before their use in hydrological models where the bias could be irreversible.
  Keywords: regional climate model; RCM; bias correction methods; BCMs; hydrological models; quantile mapping; Morocco.
  DOI: 10.1504/IJHST.2023.10056362
   
  
• Identifying the optimum location of the dewatering pumping wells around excavations using numerical FEFLOW model: a theoretical study  
  by Hayder H. Kareem 
  Abstract: A theoretical study has been explored the dewatering process in an excavation pit has dimensions (600 × 600) m² and depth 6 m in an area (4,000 × 4,000) m² with a total depth 30 m using FEFLOW programme. A mathematical model is created to reduce the water table at least 1 m below the bottom level of the excavation. The model is run in the steady state (one year) and transient flow (45 days, 60 days, 90 days and 120 days) conditions. Pumping wells are installed at distances of 50 m, 100 m, 150 m, 300 m, 450 m and 600 m away from the excavation. The total tested scenarios are 27: 15 (steady state) and 12 (transient state). Only 13 scenarios succeeded in achieving the required condition: 4 (steady state) and 9 (transient state). Economically, over the succeeded scenarios, scenario (S₁₆) is considered the best dewatering one with the lowest extraction rate (157,500 m³/45 days) and minimal distance away from the excavation (50 m).
  Keywords: construction excavation pit; dewatering; FEFLOW; optimum location; mathematical modelling.
  DOI: 10.1504/IJHST.2023.10056098
   
  
• The effect of reactor H/D ratios on the cultivation of aerobic granular sludge  
  by Fengli Zhao, Shenjie Zhou 
  Abstract: Height to diameter ratios (H/D ratios) of the sequencing batch reactors (SBRs) are of great significance in the cultivation of the aerobic granular sludge (AGS). In this study, the gas-liquid two-phase flow patterns in the reactors with two different H/D ratios of 5 and 3 were simulated based on computational fluid dynamics (CFD). The results showed that higher H/D ratios of the reactors provided smaller liquid velocity and shear rate, but more small vortices and longer circulations compare with the lower H/D ratio reactor. Moreover, the cultivation of AGS in the two H/D ratio reactors was further investigated. It was found that reactors with higher H/D ratios can accelerate sludge granulation and retain more sludge than reactors with lower H/D ratios. However, the two reactors achieved the similar pollutant removal efficiency during the stable period, demonstrating that a high H/D ratio can enhance granulation but is not necessary for practical applications, which can reduce construction difficulties.
  Keywords: aerobic granular sludge; AGS; H/D ratios; computational fluid dynamics; CFD; flow patterns; granular performance.
  DOI: 10.1504/IJHST.2023.10055671
   
  
• Anomalous behaviour of Indian summer monsoon rainfall due to the change in some of the monsoon semi-permanent features in surplus and deficit years  
  by Ghulam G. Zahid, Nuzhat Fatima, Aparna Sinha, Ajhar Hussain, Firoz Ahmad 
  Abstract: The purpose of this research is to better understand the Indian summer monsoon's insufficient rainfall in 2002 and excess rainfall in 2007, as well as their relationship with large-scale circulation features and land-sea heating contrast. Zonal and Meridional wind at 850 Hpa and mean sea level pressure and monthly mean rainfall are the parameters used to describe the semi-permanent features and anomalous behaviour of ISMR. Over extensive portions of the Indian Ocean, Arabian Sea, and much of India, significant mean sea level pressure and rainfall anomalies are present. Negative rainfall anomalies prevailed over some parts in the centre of the monsoon core zone (MCZ). By evaluating the Somali jet, the Mascarene high and ISMR observed that heavy rainfall occurs in the MCZ. Mascarene high show stronger anticlockwise circulation in deficit year but due to the effects of El Niño wind and moisture transferred towards the East-Pacific region.
  Keywords: Indian summer monsoon rainfall; ISMR; monsoon semi-permanent features; ENSO; convection; cross-equatorial low-level jet; monsoon core zone; MCZ.
  DOI: 10.1504/IJHST.2023.10056541
   
  
• Impact of large dam reservoirs on slight local season shifting (case study: Three Gorges Dam)  
  by Yongzhen Deji, Jihui Fan, Majid Galoie, Artemis Motamedi 
  Abstract: The monthly data (1980-2018) from 54 stations, which were classified into three altitude levels, were extracted. The analysis showed TGD had a minor effect on the variation of the precipitation data. Also, due to the variation in dominant wind direction and speed, the spatial distribution of rainfall was altered significantly. The Standardised Precipitation Evapotranspiration Index (SPEI) analysis in 1, 3, and 12 months showed degradation in the positive drought index downstream of the dam after impounding. The data analysis showed that TGD had a strong impact on the increase in monthly temperature and relative humidity both upstream and downstream of the dam such that for the regions with altitudes of higher than 400 m.a.s.l., the month with the maximum monthly RH and temperature was shifted from December to June and from July to June, respectively. This shifting in lower altitude regions was not seen.
  Keywords: Three Gorges Dam; TGD; meteorological data analysis; season shifting; local climate change.
  DOI: 10.1504/IJHST.2023.10056527
   
  
• A systematic review on the sustainability of micro hydropower in Nepal  
  by Hari Prashad Joshi 
  Abstract: Micro hydropower plants not only provide electricity but also enrich the socio-economic status of rural areas of Nepal. Hence, the sustainability of smaller-scale hydropower plants is an exceptionally imperative viewpoint for poverty reduction in Nepal. This review paper aims to find a sustainability evaluation to demonstrate for smaller-scale hydropower plants in Nepal. We searched research articles from three popular databases: Google Scholar, Scopus, and JSTOR, starting from 2010 to 2022. And we have only included the data of the hydropower whose capacity is less than 100 KW. The result shows that the development of small-scale hydropower ventures gives viable decision-making support for the rural electrification and advancement sector. Despite that, some huge issues and challenges must be resolved in time for the development of micro-hydropower in Nepal. If those issues are resolved on time, there is huge potential for micro-hydropower in Nepal.
  Keywords: sustainability; micro-hydropower; development; financial barrier; Nepal; technical difficulties; decentralisation; environment; energy; rural electrification.
  DOI: 10.1504/IJHST.2024.10065307
   
  
• Rainfall trend analysis in Gujarat's semi-arid zone: a modified approach with autocorrelation consideration  
  by Ramiz F. Tasiya, Naveena K. Kannegowda, Shilpesh C. Rana 
  Abstract: Precise identification of rainfall movement is very essential during climate change scenarios for better water resources management. Erratic and violent monsoon rainfall movements are observed in the coastal region of Maharashtra, Gujarat, and Kerala within a very short period. The aim of the research is to identify the changes that occurred in the South-West monsoon rainfall trend using advance statistical package of R-software, for the semi-arid region of Gujarat. From the Wallis and Moore phase-frequency test, it is found that 6 out of 29 stations are having significant autocorrelation. Modified Mann-Kendall and Sen's slope tests are used to carry out rainfall trend analysis. Spatial representation of mean SW-monsoon rainfall and Sen's slope shows lower magnitude near coastal region and higher magnitude at higher elevation range. As a result, it is concluded that in monsoon two stations (7%) and particularly during June month seven (24%) stations are showing a significantly decreasing trend.
  Keywords: R-software; Sen's Slope test; Wallis and Moore phase-frequency test (Z- test); modified Mann-Kendall test.
  DOI: 10.1504/IJHST.2023.10056997