Volume 5 Issue 3
Authors: M. Sahu; S. Lahari; A.K. Gosain; A. Ohri
Abstract: Hydrological modeling of river basins is a valuable tool for basin management and assessment of extreme event impacts. However, challenges with this type of modeling still remain, including issues with data acquisition, accuracy of meteorological data, model uncertainty, and operational patterns of dams/large water structure. This paper evaluates the performance and suitability of a Soil Water Assessment Tool (SWAT) model in predicting stream flow discharge, identifying sensitive parameters, and analyzing uncertainty in the Mahi river basin. This kind of assessment is useful for the hydrological community, water resources engineers involved in agricultural management and climate change concerns, as well as the government’s efforts in mitigating extreme natural hazards such as droughts and floods. Since any model uncertainty becomes replicated in management practices, this paper addresses the concerns of uncertainity in hydrological modelling of Water Resources in the Mahi River Basin. A GIS environment was used to delineate the basin and its watersheds, and SWAT-CUP was used to perform the uncertainty and sensitivity analyses. The model’s results were compared against five observation points spread across the basin. Statistical analysis showed that four of them resulted in good Nash–Sutcliffe model efficiency and correlation.
Keywords: SWAT; hydrological modelling; Mahi Basin; Uncertainty Analysis; Sensitivity Analysis; SWAT-CUP
Authors: Hayet Chihi; Guislain de Marsily; Matthieu Bourges; Habib Belayouni; Mohamed Sbeaa
Abstract: In this study, the problems of parameter estimation for systems with scarce measurements are examined. In this case, an original geostatistical methodology is applied to generate bathymetric surface models of a faulted aquifer system within the Jeffara Basin in southeastern Tunisia. The modelling workflow is based on i) the spatial analysis of the data configuration and ii) the conceptual stacking pattern. This allows provision of key concepts and geostatistical approaches to be undertaken during geomodelling procedures. In fact, two constraints have been integrated: i) inequality data provided by the end of the boreholes and ii) the faults that compartmentalize the aquifer system. First, kriging with inequality was used for depth estimation of the Turonian reservoir Top. The results are compared with those from classical kriging and evaluated through the estimation quality, the adopted assumptions and the method limitations. Validation analyses show that the model developed with the inequality data leads to a significant gain in mapping accuracy and geological realism. In the second step, the geostatistical approach was used to model the successive bounding surfaces of the aquifer system units. Consequently, the kriging constrained by inequality data could be applied in a variety of hydrogeological parameters interpolations to provide significantly better informative maps that are useful for hydrodynamic modelling.
Keywords: Geostatistics; Surface Interpolation; Exact Data; Inequality Data; Geological Constraints
Authors: F E Banze; R Ploszai; H D O A Fill
Abstract: Conflicts often arise for reservoirs with multiple water uses, such as hydropower generation, irrigation, and flood control. While high levels are desired to store water that will be used during the dry season for hydropower generation, low levels in the reservoirs may reduce flood damage. As most hydropower reservoirs are not designed for flood control, the operational planning usually seeks to minimize this conflict with careful allocation of appropriate space in the reservoirs for flood control. The present study compares the benefits provided by a reservoir for flood control versus those of a reservoir for hydropower generation, using a case study at the Zambezi River at the Cahora Bassa dam in Mozambique, Africa. The evaluation of these benefits was made using Monte Carlo simulations with synthetic series of natural inflows. The synthetic series were generated using inflow statistics from 1955 to 2012 at the Cahora Bassa dam. The results indicate that the consideration of flood control spaces in the reservoir results in a reduction of dependable energy, which in turn relies upon the return period considered and the proposed maximum outflow. Considering a return period of 100 years for flood control and 50 years for hydropower generation, an energy loss was observed of: 4 average MW for an outflow restriction of 15,000 m3.s-1; 90 average MW for an outflow restriction of 10,000 m3.s-1; and 196 average MW for an outflow restriction of 8,000 m3.s-1. Therefore, as expected, there is an increase in energy loss for lower outflow restriction.
Keywords: Hydropower Generation; Flood Control; Synthetic Flow Series Generation
Authors: Meiling Wang; Lei Zhang; Thelma D Baddoo
Abstract: In this study, the Hydrologic Engineering Centre’s Hydrologic Modeling System (HEC-HMS) model was employed to simulate runoff in the semi-arid region of northwestern China, specifically the Hailiutu watershed. The Hydrologic Engineering Centre’s Geospatial Hydrologic Modeling Extension (HEC-GeoHMS) was used in conjunction with ArcHydro tools in an ArcMap geographical information system (GIS) environment to create input files of the catchment physical characteristics for the HMS model. The model was calibrated for the time period of 1978-1992. The results showed that the model systematically underestimated winter and spring hydrographs as well as a few summer flows. This was due to the discrepancy between the nonlinear rainfall-runoff response in the watershed and the linear structure of the Soil Moisture Accounting (SMA) model used. Also, the results pointed out that, due to data unavailability on hydraulic engineering in the Hailiutu watershed, the model faced challenges in simulating runoff properly and therefore could not be validated. Ultimately, the model’s general performance in simulating runoff in the Hailiutu watershed was found unsatisfactory.
Keywords: China; GIS; Hailiutu; HEC-HMS; Semi-Arid Region; Runoff Simulation
Authors: Z. Fuat TOPRAK
Abstract: It is common knowledge that both fresh water and precipitation have no homogeneous mixture temporally or spatially on the earth planet. Transportation of water from one region to another has always been a part of human existence. The transfer is achieved by water conveyance structures (i.e. channels, pipes, tunnels, galleries, and drains). However, the flow in such structures occurs hydraulically and can be divided into two main classes: (1) pipe flow and (2) open channel flow. There are many published studies in the current literature on modeling pipe or open canal flows. In this study, following a relevant discussion on existing literature, a new concept of “ideal velocity” is introduced. Furthermore, ideal discharge and Reynolds and Froude numbers, which are currently used in computational hydraulics, are re-modified following the new concept. The simplification of such equations by the new concept will conveniently solve many hydraulic problems, particularly in pipe and open canal manufacturing sectors.
Keywords: Ideal Velocity; Open Canal Hydraulics; Open Canal Flows; Open Canal Manufacturing
A Review of Proposed Techniques for Modeling Longitudinal Dispersion Coefficient in Natural Channels
Authors: Z. Fuat TOPRAK
Abstract: The World is facing a global climate change, while the world’s population continues to grow. Therefore, providing sufficient water has become increasingly difficult in the last few decades. Artificially providing fresh water requires complex technology and economic investment. This is almost impossible, especially in underdeveloped countries. Due to these issues, water scarcity and/or stress is expected to rise dramatically in many regions in the world in the near future. Furthermore, current fresh water resources are vulnerable to pollutants (nuclear, biological, physical, and chemical). Conservation of fresh water resources has therefore become a critical issue. As is well known, the main fresh water sources are rivers and natural streams. Convective longitudinal dispersion is the most effective parameter in such sources. The longitudinal dispersion coefficient represents the rate of pollution and it is mostly used in water pollution modeling studies. Hence, learning the longitudinal dispersion mechanism in natural channels is vitally important to control water pollution. This paper’s main purpose is to present a significant review and criticism on the literature related to both the longitudinal dispersion mechanism and the modeling techniques proposed for determining longitudinal dispersion coefficient in natural channels.
Keywords: Dispersion; Dimensional and Dimensionless Longitudinal Dispersion Coefficient; Natural channels; Water Pollution Control
Authors: REN Hong-wei; LIU Yao-wei; ZHANG Lei
Abstract: In order to investigate whether the groundwater moving state is affected after Three Gorges Reservoir impoundment, this study tested the velocity and direction of the groundwater seepage in the monitoring wells around Three Gorges Dam using the method of isotope tracing, and gained good results. Test results showed that the groundwater seepage directions in Gaojiaxi well (W1) and Hanjiawan well (W4) are respectively 25°east by south and 2° south by east, according with the previous hydro-geological inference. These indicated that the groundwater seepage directions around the Three Gorges Dam are not affected significantly after reservoir impoundment. The groundwater seepage velocities in W1 and W4 wells are respectively 0.72m/d and 1.29m/d. There is small difference between them and this may be related to the tectonic setting of the two wells.
Keywords: Isotope Tracing; Seepage Velocity; Seepage Direction; The Three-Gorges of the Yangtze River
Authors: M. Bhushan; L. B. Roy; R. Kumar
Abstract: The present study focuses on the trend analysis of some parameters of climate change. These include annual mean temperature, rainfall, potential evapotranspiration and reference crop evapotranspiration for the 37 districts of Bihar, which is an eastern state in India. The study focuses on the period 1901-2002. The moving average method was for smoothening the time series curve. In order to detect the trend, MATLAB software was. For this study, in order to test the significance, the widely used Mann-Kendall test was run at a 5% significance level on a time series data. For annual mean temperature, all districts indicate a statistically significant increasing trend, whereas in the case of annual rainfall and a potential evapotranspiration trend, all districts indicate a statistically significant decreasing trend. However, this decreasing trend excludes the Araria and Kisanganj districts where a potential evapotranspiration trend indicates an increasing trend. For annual reference crop evapotranspiration, all districts show a statistically insignificant increasing trend. For the Bihar state as a whole, the annual mean temperature and reference crop evapotranspiration show an increasing trend of 0.0047°C/year and 0.07248 mm/year, respectively. Further rainfall and potential evapotranspiration for the state indicate a decreasing trend of 1.974 mm/year and 0.02672 mm/year, respectively.
Keywords: Climate Change; Statistically Significant Value; Rainfall Deficit; Moving Average; Trend Analysis
Authors: Claudia Plünnecke; João Marcelino
Abstract: The safety and operability of the Massingir embankment dam have been limited since its inauguration in 1977. This is mainly because of uncontrolled, excessive under-seepage. As extensive rehabilitation measures, concluded in 2007, could not completely solve this problem, a new rehabilitation concept, consisting of a free-draining seepage berm with an integrated inverted filter, has been developed. In this paper, several rehabilitation alternatives are discussed, the schematic rehabilitation concept is elaborated and a survey is given of the subsequent seepage analysis by means of the numerical 2D program, PlaxFlow.
Keywords: Finite Element Seepage Analysis; Massingir Embankment Dam
Authors: Abbas E. Rahma; Hassan I. Mohammed; Tingwu Lei; Eiman G. Mohamed
Abstract: Food production for the increasing population in the world is limited by water scarcity. One attempt to overcome the water shortage is to utilize water from different sources. To use Saline water blended with fresh water as alternative water source for irrigation requires the experimental quantification of the effects of such blended water on plant growth rate and germination at the early growth stages of Sorghum. The laboratory experiments used five salinity levels (Ec. 0.24, 4, 6, 9, and 18 dS.m-1), and two main local cultivars (Wad Ahmed and Tabat) of Sorghum (Sorghum bicolor L. Moench). Germination percentage, seedling length and mean germination time were taken as growth evaluation parameters. The results obtained showed that cultivars did not vary significantly in their ability to grow at various salinity values in clay cracking soils. At a higher salinity (Ec. 18 dS.m-1), the rate of germination was decreased and the mean germination time was increased for Sorghum seeds irrigated with saline water of Ec. 0.3- 4 dS. m-1. It was found that in Tabat cultivars, there was a significantly higher percentage of geminated seeds. Data obtained indicated that plant height was indirectly related to salinity levels with higher stem lengths for all cultivars grown in fresh water or saline water of Ec. 4 dS.m-1. Growth of Tabat cultivar expressed via stem length was found to supersede the Wad Ahmed cultivar. Blended water with salinities up to Ec of 9 dS. m-1 resulted in no negative impacts on germination and growth of both Tabat and Wad Ahmed cultivars. The results may be used as a tool to screen salt tolerance in the early growth stages of large quantities of sorghum genotypes.
Keywords: Sorghum; Germination; Seedling; Salinity; Sea Water; Water Blending