International Journal of Water (10 papers in press)
Urbanisation and hydraulic geometry response: a model approach
by Adeyemi Olusola, Toyin Fashae
Abstract: As the process of urbanisation continues within a river basin, the response of the river channels within the basin alters, resulting in a variety of responses from the river channel: increase in the area of low infiltration capacity and the efficiency or speed of water transmission in channels or conduits, variations in peakflow discharges and stream velocity along a channel, etc. This study pursues further to understand the impact of urbanization on channel geometry of the Ona River Basin using the Hydrological Modelling System (HEC-HMS). Additionally, the study seeks to provide answers on the downstream hydraulic geometry of the main segment of the Ona River as it relates to downstream discharge. The hydrograph of the basin shows that the present discharge of the channel from this study is 5177.32 cubic metres per second with a peak time of 10.52 min, while the moderated channel response due to increase in the level of urbanisation discharges 5342.19 cubic metres per second and peaks at 10.45 min. This shows an increase of about 3% in discharge. This study has been able to show that the rate at which urbanisation contributes to an increase in discharge of urban rivers is not high. This suggests that urban flooding is attributable to many factors, one of which is the present level of urbanisation and which may not necessarily carry a very high weight. The exponents of the hydraulic geometry of the river, 0.15, 0.28, 0.57 (width, depth and velocity, respectively) indicate the variability within these three variables and supports the fact that f and m increase while b decreases for cross-sections studied within the basin. The implication of DHG suggests that with increasing bankfull discharge, the bankfull variables of mean depth, mean width and mean velocity also increase systematically downstream.
Keywords: Ona River; HEC-HMS; hydrograph; bankfull discharge; urbanisation.
Modelling non-stationary extreme streamflow in peninsular Malaysia
by Nur Amalina Mat Jan, Ani Shabri, Jean Hounkpe, Basri Badyalina
Abstract: Global change and global warming have raised concerns among hydrologists about the use of the stationary assumption (independent and identically distributed flood series) in infrastructure-designed methods. This confirms the necessity of evaluating the stationary or non-stationary behaviour of hydrological variables before deriving designed flood for infrastructure projects and flood mitigation. Trends were evaluated in the annual maximal streamflow of 49 stations in peninsular Malaysia, over 50 years (1960-2009) using the Mann-Kendall and Spearman Rho trend tests. Three models, a stationary model (GEV0), a non-stationary model with location parameter linear function of time (GEV1) and a non-stationary model with location and log-transformed scale parameters as a linear function of time (GEV2), were considered for stations with a significant trend. The likelihood ratio test, the Akaike information criteria and the Bayesian information criteria were used to determine the best-fitting model. It was found that a quarter of the analysed stations show statistically significant trends in their annual maximal streamflow. Among the 14 stations showing statistically significant trend at 5% level, 10 stations were found to better fit with the non-stationary models (GEV1 and GEV2) based on three goodness of fit measures. These results indicate the importance of taking into consideration the non-stationary behaviour of the flood series in order to improve the quality of flood estimation.
Keywords: stationary; non-stationary; streamflow; flood frequency analysis; generalised extreme value distribution; Mann-Kendall and Spearman Rho trend test.
Investigating of relationship between physical characteristics of watersheds and nonlinearity of daily streamflow processes
by Mahshid Khazaiee Athar, Keivan Khalili, Javad Behmanesh
Abstract: Using time series models is one of the practical methods for simulation and prediction of hydrological data. But often, without examining linear or nonlinear system, common linear time-series models are used. On the other hand, due to the relationship between physiographic characteristics of the watershed and river flow, it is expected that streamflow nonlinearity is heavily influenced by physiographic characteristics of the watershed. In this study, using BDS test, nonlinearity of daily streamflow was examined, then its relationship with the watershed slope and area of hydrometric stations was examined. ADF test was used to test stationarity of data time series. The results of ADF test revealed that with the elimination of non-stationarity factors, streams' flow series become stationary. Also, BDS test results showed that flow was nonlinear. In examining the relationship between streamflow nonlinearity and watershed area, the results revealed that despite R
Keywords: ADF test; Watershed Area; BDS test; Nonlinearity streamflow; Slope; Time series.
VASPCALM module for frequency regulation as a pump control method in EPANET
by Drazen Vouk, Domagoj Nakic, Ivan Halkijevic
Abstract: Frequency regulation as a pump control method is an efficient method for pressure control in pressurised water supply systems, and consequently for water loss control and power consumption control. Operation of pumps with frequency regulation can be successfully simulated by means of mathematical modelling. This paper describes the basic principles of frequency regulation and analyses its control and operation in the free computer software EPANET. The developed auxiliary module VASPCALM automatically generates a number of pump operation controls for constant or proportional pressure value at the required model junction. The application of the module on the actual water supply system Velika Gorica (Croatia) proves that simple and efficient modelling of pump operation with frequency regulation in EPANET is possible, with an acceptable degree of accuracy. Also, the use of the VASPCALM module considerably facilitates the mathematical modelling of variable speed pumps in EPANET.
Keywords: VASPCALM; frequency regulation; EPANET; water supply; water losses; mathematical modelling.
Hydrological response to climate change in a high altitude catchment
by Yasir Altaf, Manzoor Ahanger, Mohammad Fahimuddin
Abstract: Different climate models were linked to the coupled river and hydrological model MIKE SHE-MIKE-11 to evaluate the future impact of climate change on hydrology in the Lidder sub-basin of the Jhelum Basin. The coupled hydrological model was calibrated against the observed streamflow data at Sheeshnag gauging station. The output of the model in the form of snow cover percentage was validated with the high-resolution satellite-based Modis data. The outputs from five different global climate models for IPCC A1B emission scenarios for the future (2025, 2050, 2075 and 2100) were applied to the hydrological model. It was observed that at the end of the 21st century the ET losses in the region are increasing and the snow storage component is decreasing, which is further causing the runoff in the river to increase at the end of 21st century. The contribution of base flow to the discharge in the Lidder river is increasing under all climate models, except for the incm3 model.
Keywords: global climate models; hydrological models; downscaling; MIKE-SHE; MIKE-11.
Groundwater quality assessment and mapping using multivariate statistics and analytic hierarchy process in Bhubaneswar city, Odisha, India
by Madhumita Das, Ashok K. Nayak, Bishnupriya Das, O.P. Verma
Abstract: Groundwater, the major drinking water source in urban areas, is vulnerable to deterioration of its quality due to population pressure and developmental activities. Assessment and understanding of the groundwater chemistry is therefore imperative. Using multivariate statistics and the Analytic Hierarchy Process (AHP), the groundwater quality of Bhubaneswar, an ever-growing city in eastern India, is assessed and elaborated in this paper. Samples collected from the city were found to be dominated by NaClHCO3, NaCaClHCO3, NaCl and mixed hydrochemical facies through Piper trilinear diagrams. Silicate weathering had come up as a dominating process for influencing ionic constituents in bore well (>20 m depth), while anthropogenic intervention was responsible for excess nitrate, potassium, sulphate and chloride contents in the dug well (≤310 m depth) water. Samples were classified into four clusters using hierarchical cluster analyses, and cluster-wise discriminating variables were identified through discriminant function. The discriminating variables (turbidity, Fe, Mn, NO3-, K and pH) that determine the drinkability of water were then ranked through the AHP, and a hierarchy was prepared and used to generate the vulnerability map distinguishing low to high quality groundwater localities in the study area.
Keywords: groundwater quality; hydrochemical facies; hierarchical cluster analyses; discriminant functions; analytic hierarchy process; vulnerability map.
Spatio-temporal analysis of the Karun River water quality
by Mojtaba Moravej, Iman Karimirad, Kumars Ebrahimi
Abstract: In recent years, the water quality of the Karun River has been degraded by different pollutant loads, from agricultural drainages and municipal and industrial wastewaters. This paper aims to analyse spatio-temporal variations of the water quality of the Karun River using National Sanitation Foundation Water Quality Index (NSFWQI), time series analysis, and a geographic information system (GIS). Monthly data, including pH, temperature, dissolved oxygen, five-day biochemical oxygen demand, total solids, PO43-, NO3-, turbidity and fecal coliform, were analysed during 2007-2012. Calculated NSFWQI time series during the study period shows that the water quality of the river lies in the medium class, which implies that the use of the Karun river water is subjected to advanced treatment. The results of time series analysis show that periodicity and trend are not significant in the majority of stations. The spatial analysis results demonstrate that the water quality in Ahwaz urban area is slightly poorer than in the rest of the river. Overall, the spatio-temporal distribution of the NSFWQI values indicates that changes are negligible and show a balance between the pollutant input and self-purification capacity of the river.
Keywords: Karun River; NSFWQI; spatio-temporal analysis; time series analysis; water quality.
A new equation to predict the total potential longshore sediment transport rate in the beach ocean area
by Saeed Khorram, Mahede Vahedi
Abstract: In such coastal engineering applications, such as the sediment budget derivation for coastal regions (with/without structures, breakwaters, groynes) and long-term beach stability (without/with nourishments or coarse-grained protections), a reliable estimate of the longshore sand transport is of considerable practical importance.
An effort has been made in this paper to propose a novel predictive formula for the estimation of the TLSTR (total longshore sediment transport rate) using the ISS (incomplete self-similarity) and sediment transport physics principles with the assumption that sediments are mobilised by breaking waves that occur in the coastal environment at spatio-temporal scales and multiple interacting forces (porosity, wave conditions at breaking, water/sediment density, K-value, breaker index, etc.). The key factor in this study is the use of dimensional analysis and self-similarity concepts based on the number of independent variables to develop an integrated classical formula for the non-cohesive TLSTR in marine coastal regions. To assess the prediction capability of the proposed formula, high-quality sediment transport and hydrodynamics datasets were gathered, and six well-known formulae were employed for both the field and laboratory test conditions. Results show that the novel formula agrees well with both the flume and field data, and it is quite suitable both for practical applications in coastal regions and for the numerical modelling of sediment transport and nearshore variations.
Keywords: dimensional analysis; longshore sediment transport; incomplete self-similarity; combined wave-current; sediment transport.
Application of global precipitation dataset for drought monitoring and forecasting over the Lake Urmia basin with the GA-SVR model
by Edris Ahamdebrahimpour, Babak Aminnejad, Keivan Khalili
Abstract: Drought monitoring and forecasting are known as the key components of water resource management; however, in developing countries, one of the major impediments to carrying out studies in this field is a deficiency of required data. Therefore, in the present study, the accuracy of the Climatic Research Unit (CRU) precipitation data was assessed as an alternative source instead of in situ data for monitoring the drought in the Lake Urmia basin area of Iran during the period from 1984 to 2013. Drought monitoring was performed based on SPI and in 3-, 6-, 9-, 12-, and 24-month time scales. Later, a genetic algorithm-support vector regression (GA-SVR) model, which is a data-driven model, was used to forecast drought conditions up to four months ahead. The results demonstrated that the CRU data had acceptable accuracy in drought monitoring so that, in at least 75% of the cases, there was no difference between the monitored drought classed through observed data and CRU data. In the forecasting section, the results showed two general patterns. The first pattern indicated a descending trend of forecast accuracy with an increase in the lead-times ahead of forecasts; the second pattern revealed the ascending trend of forecast accuracy, with an increase in the SPI scale. As an example, the CC values in the one-month-ahead forecasts of SPI-3 and SPI-24 have been 0.52 and 0.86, respectively; whereas, in the four-month-ahead forecasts, these values have been 0.02 and 0.31, respectively.
Keywords: climatic research unit; genetic algorithm; support vector regression; gridded precipitation.
Evaluating uncertainty in nonlinear hydrological models using VIC-3D model on the Ume
by Saeed Khorram, Mahedeh Vahedi
Abstract: A considerable environmental and developmental challenge that the water resources management is now facing is the climate change for the evaluation of which a macro-scale model (physically based with high resolution) has been designed to be tested on the Ume
Keywords: physically based macro-scale; simulation; variable infiltration capacity model; water resources management.