| 1. |
- Berndtsson, Ronny, et al.
(författare)
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Educating the compassionate water engineer - a remedy to avoid future water management failures?
- 2005
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 50:1, s. 7-16
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Tidskriftsartikel (refereegranskat)abstract
- The number of local and regional-scale water management failures appears steadily to increase despite an apparently higher level of engineering solutions at hand. The objective of this paper is to examine the challenges the existing education system needs to meet in order to produce water engineers capable of responding to the complexity of contemporary and future water problems in relation to societal needs. The next generation of water engineers may stay in their professional functions until 2040 or 2050. It is likely that in this period more critical water management and environmental problems will be experienced than have been encountered so far. The question then arises whether the present water engineers have the proper background education to understand environmental, hydrological, ecological and socio-economic problems to resolve related water management problems. Future water engineers must, to a greater extent, include socio-economic consequences in planned and/or designed water management systems and convey greater transparency regarding risks and societal effects.
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| 2. |
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| 3. |
- Bouksila, Fethi, et al.
(författare)
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Soil water content and salinity determination using different dielectric methods in saline gypsiferous soil
- 2008
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 53:1, s. 253-265
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedMeasurements of dielectric permittivity and electrical conductivity were taken in a saline gypsiferous soil collected from southern Tunisia. Both time domain reflectometry (TDR) and the new WET sensor based on frequency domain reflectometry (FDR) were used. Seven different moistening solutions were used with electrical conductivities of 0.0053-14 dS m(-1). Different models for describing the observed relationships between dielectric permittivity (K-a) and water content (theta), and bulk electrical conductivity (ECa) and pore water electrical conductivity (ECp) were tested and evaluated. The commonly used K-a-theta models by Topp et al. (1980) and Ledieu et al. (1986) cannot be recommended for the WET sensor. With these models, the RMSE and the mean relative error of the predicted theta were about 0.04 m(3) m(-3) and 19% for TDR and 0.08 m(3) m(-3) and 54% for WET sensor measurements, respectively. Using the Hilhorst (2000) model for ECp predictions, the RMSE was 1.16 dS m(-1) and 4.15 dS m(-1) using TDR and the WET sensor, respectively. The WET sensor could give similar accuracy to TDR if calibrated values of the soil parameter were used instead of standard values.
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| 4. |
- Chen, Y. D., et al.
(författare)
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Regional analysis of low flow using L-moments for Dongjiang basin, South China
- 2006
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 51:6, s. 1051-1064
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Tidskriftsartikel (refereegranskat)abstract
- Dongjiang water has been the key source of water supplies for Hong Kong and its neighbouring cities in the Pearl River Delta in South China since the mid-1960s. Rapid economic development and population growth in this region have caused serious concerns over the adequacy of the quantity and quality of water withdrawn from the Dongjiang River in the future. Information on the magnitude and frequency of low flows in the basin is needed for planning of water resources at present and in the near future. The L-moment method is used to analyse the regional frequency of low flows, since recent studies have shown that it is superior to other methods that have been used previously, and is now being adopted by many organizations worldwide. In this study, basin-wide analysis of low flows is conducted for Dongjiang basin using five distributions: generalized logistic, generalized extreme value, lognormal, Pearson type III and generalized Pareto. Each of these has three parameters estimated by the L-moment method. The discordancy index and homogeneity testing show that 14 out of the 16 study sites belong to a homogenous region; these are used for further analysis. Based on the L-moment ratios diagram, the Hosking and Wallis goodness-of-fit statistical criterion and the L-kurtosis criterion, the three-parameter lognormal distribution is identified as the most appropriate distribution for the homogeneous study region. The regional low-flow estimates for each return period are obtained using the index flood procedure. Examination of the observed and simulated low flows by regional frequency analysis shows a good agreement in general, and the results may satisfy practical application. Furthermore, the regional low-flow relationship between mean annual 7-day low flows and basin area is developed using linear regression, providing a simple and effective method for estimation of low flows of desired return periods for ungauged catchments.
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| 5. |
- Di Baldassarre, Giuliano, et al.
(författare)
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Analysis of the effects of levee heightening on flood propagation : example of the River Po, Italy
- 2009
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 54:6, s. 1007-1017
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Tidskriftsartikel (refereegranskat)abstract
- The effects of human activities on flood propagation, during the period 1878-2005, in a 190-km reach of the middle-lower portion of the River Po (Northern Italy) are investigated. A series of topographical, hydrological and inundation data were collected for the 1878 River Po geometry and the June 1879 flood event, characterised by an inundated area of 432 km(2). The aim of the study is two-fold: (1) to show the applicability of flood inundation models in reconstructing historical inundation events, and (2) to assess the effects of human activities during the last century on flood propagation in the middle-lower portion of the River Po. Numerical simulations were performed by coupling a two-dimensional finite element code, TELEMAC-2D, with a one-dimensional finite difference code, HEC-RAS.
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| 6. |
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| 7. |
- Hamed Abd El Mageed, Yasser, et al.
(författare)
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Evaluation of the WET sensor compared to time domain reflectometry
- 2006
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 51:4, s. 671-681
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Tidskriftsartikel (refereegranskat)abstract
- This paper concentrates on the experimental calibration of a rapid, non-destructive sensor to investigate the salinization process by measuring the dielectric properties of the soil to estimate both the soil water content (theta) and pore water electrical conductivity (sigma(p)) for different soil types. The proposed sensor depends on the frequency domain reflectometry (FDR) technique and is called the WET sensor. It estimates the dielectric permittivity (K-a) and bulk electrical conductivity (sigma(a)) of soil. Then, it utilizes both of them to estimate theta and sigma(p). The new sensor is compared to time domain reflectometry (TDR) measurements. Time domain reflectometry is a well established technique for K-a and sigma(a) measurements in soils. The study involves experimental measurements in the laboratory using five different soil types and a range of theta values. In each soil type, three different electrical conductivity solutions (sigma(w)) were used. The results revealed that the calibration coefficients of water content and the soil parameter are significantly dependent on the soil type and slightly affected by electrical conductivity of the moistening solution.
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| 8. |
- Hamed, Yasser, et al.
(författare)
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Comparison of soil salinity and solute transport for different cultivated soil types in northeastern Egypt
- 2008
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 53:2, s. 466-478
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Tidskriftsartikel (refereegranskat)abstract
- The soil salinity distribution and solute transport properties of three different soil types were investigated and compared within a project area in northeastern Egypt. For this purpose, dye tracer experiments and salinity sampling were carried out. The resulting salinity maps showed that the soil salinity in the cultivated western site of the project area is 8-10 times higher than that in the cultivated eastern site. However, the cultivated soil displayed significantly lower salinity with higher uniformity as compared to the uncultivated soil. The preferential flow phenomenon was less apparent in the cultivated soil. This is mainly due to tillage which disrupts the structure of the soil so that deep cracks are no longer connected to the soil surface. This reduces the risk for groundwater contamination through preferential flow. The study showed that careful and continuous monitoring of the salinity status is needed now and in the future.
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| 9. |
- Jebari, Sihem, et al.
(författare)
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Regionalizing short-term rainfall affected by topography in semiarid Tunisia
- 2007
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 52:6, s. 1199-1215
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Tidskriftsartikel (refereegranskat)abstract
- The characteristics of fine time-scale rainfall are important in many hydrological applications, such as infiltration, erosion and flooding. The spatial properties of such rainfall are, however, seldom known, especially for arid and semi-arid areas. A better knowledge of fine time-scale rainfall and also comparison with daily rainfall may yield possibilities for disaggregation. For this purpose, rainfall data of different time scales, from 1-min to daily, from 25 stations during four years (1995–1998), were spatially analysed by means of spatial correlation, empirical orthogonal function (EOF) and hierarchical clustering. The results show that the spatial correlation is typically non-isotropic and varying, depending on topography and local meteorological settings. Similarly, spatial patterns of EOF are closely related to main atmospheric synoptic situations as influenced by orography and spatial dependence regarding areas with predominant convective and frontal rainfall. The clustering displayed different homogeneous sub-groups over the Tunisian Dorsal Mountains that can be used to better manage the limited water resources that often depend on fine time-scale rainfall variability.
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| 10. |
- Jinno, Kenji, et al.
(författare)
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Effects of land-use change on groundwater recharge model parameters
- 2009
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 54:2, s. 300-315
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Tidskriftsartikel (refereegranskat)abstract
- Land development usually induces large changes in flood peak and infiltration properties, thus affecting the entire hydrological environment of the area. In order to evaluate such negative effects caused by land-use change, it is necessary to estimate the changes in surface runoff and groundwater recharge rate. The effects of land-use changes on the parameter values of a groundwater recharge model were studied and are presented. The response of groundwater level was examined at several observation wells for two different unconfined aquifers consisting of weathered granite. The spatially calibrated parameters of the groundwater recharge model were classified in order to evaluate the effects of land-use change. It was shown that the parameter values most affected by land-use change were the surface runoff coefficient, F-infinity, followed by the shape parameter, (r)(1/2). The field capacity parameter, R-0, was also greatly affected. By defining the land-use change for these three parameters the hydrological change can be predicted.
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| 11. |
- Jonsdottir, Jona Finndis
(författare)
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A runoff map based on numerically simulated precipitation and a projection of future runoff in Iceland
- 2008
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 53:1, s. 100-111
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Tidskriftsartikel (refereegranskat)abstract
- The runoff of Iceland has been evaluated for the period 1961-1990, and changes in runoff from then to the period 2071-2100 predicted according to a future projection of climate change. The hydrological model WASIM-ETH was used, with meteorological data from the PSU/NCAR MM5 numerical weather model. The evaluation of the effects of climate change on water resources was based on a future climate simulation from the HIRHAM regional climate model with boundary conditions from the HadAM3H global climate model using A2 and B2 emissions scenarios. Future runoff was shown to become much higher in 2071-2100 compared to 1961-1990, predominantly due to increased glacial melt caused by increased temperature. Furthermore, changes in runoff seasonality would be substantial. Thus, according to this projection there could be great changes in hydropower production potential associated with climate change in Iceland.
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| 12. |
- Kalteh, Aman Mohammad, et al.
(författare)
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Interpolating monthly precipitation by self-organizing map (SOM) and multilayer perceptron (MLP)
- 2007
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 52:2, s. 305-317
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Tidskriftsartikel (refereegranskat)abstract
- There are needs to find better and more efficient methods to interpolate precipitation data in space and time. Interpolation of precipitation is explored using a self-organizing map (SOM) in a region with large complexity of precipitation mechanisms (northern Iran). The technique is used both for regionalization and for interpolating monthly precipitation for stations with missing data for 1-, 2-, 5- and 10-year periods using a jack-knife procedure to obtain objective results. The SOM is able both to find regions with similar precipitation mechanisms and to interpolate with accuracy. The results show that precipitation interpolation can be improved considerably by taking into account the regionalization properties in the SOM modelling. The SOM results are compared with those from a well-defined multilayer perceptron (MLP). The findings suggest that, without regionalization, MLP modelling is generally better than SOM. However, when regionalization is included, SOM performs better than MLP. Il est nécessaire de trouver des méthodes meilleures et plus efficaces pour interpoler des données de précipitation dans l'espace et le temps. L'utilisation d'une carte auto-organisée (SOM) pour l'interpolation des précipitations est explorée dans une région aux mécanismes de précipitation très complexes (nord de l'Iran). La technique est utilisée pour la régionalisation et pour l'interpolation des précipitations mensuelles de stations qui présentent des lacunes pour des périodes de 1, 2, 5 et 10 ans, à l'aide d'une procédure jack-knife pour obtenir des résultats objectifs. La SOM est capable d'identifier les régions dont les mécanismes de précipitation sont similaires et d'interpoler avec précision. Les résultats montrent que l'interpolation des précipitations peut être considérablement améliorée en tenant compte des propriétés de régionalisation dans la modélisation SOM. Les résultats de SOM sont comparés avec ceux d'un perceptron multi-couches (PMC) bien défini. Les résultats suggèrent que, sans régionalisation, la modélisation par PMC est généralement meilleure que par SOM. Cependant, lorsque la régionalisation est introduite, la SOM donne de meilleurs résultats que le PMC.
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| 13. |
- Mo, X G, et al.
(författare)
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Parameter conditioning and prediction uncertainties of the LISFLOOD-WB distributed hydrological model
- 2006
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 51:1, s. 45-65
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Tidskriftsartikel (refereegranskat)abstract
- Distributed hydrological models are considered to be a promising tool for predicting the impacts of global change oil the hydrological processes at the basin scale. However, distributed models typically require values of many parameters to be specified or calibrated, which exacerbates model prediction uncertainty. This study uses the generalized likelihood uncertainty estimation (GLUE) technique to analyse the parameter sensitivities of a distributed hydrological model, LISFLOOD-WB. Discharge time series and event volume data of the Luo River at upstream and downstream sites, Lingkou and Lushi, are used to analyse parameter uncertainty. Eight key parameters in the model are selected for conditioning and sampled using the Monte Carlo method under assumed prior distributions. The results show that maximum efficiency of model performance is lower and the number of behavioural parameter sets giving acceptable performance is fewer in the Lingkou sub-basin than in the Lushi sub-basin with the same criteria of acceptability. For both sub-basins the distribution shape parameter B in the fast runoff generation scheme is the most sensitive in predicting both discharge time series and event volume at the Outlet. It is also shown that the value of parameter B at which the highest efficiency is derived is shifted from a high value for Lushi to a low value for Lingkou, consistent with past experience of model calibration that the larger the basin, the larger the B value is. The channel Manning coefficient N-c shows some sensitivity in the prediction of discharge time series, but less in the prediction of event volumes. The other key parameters show little sensitivity and good simulations are found across the full range of parameter values sampled. The uncertainty bounds of predicted discharges at the Lushi sub-basin are broad in the peak and narrow in the recession. The normalized difference between the upper and lower uncertainty bounds for both discharge and evapotranspiration are broad in summer and narrow in winter and that of recharge is the opposite.
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| 14. |
- Pillco Zola, R, et al.
(författare)
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Long-term and extreme water level variations of the shallow Lake Poopo, Bolivia
- 2006
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 51:1, s. 98-114
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Tidskriftsartikel (refereegranskat)abstract
- Lake Poopo, within the large Altiplano basin of Bolivia, is connected upstream to Lake Titicaca and downstream to the salares, the big salt fields. Small changes in precipitation and river inflows strongly affect the extent of the lake surface area. For times when there are no satellite images, it is difficult to determine the extent of the lake from observations. Water balance computations were performed to create a water-level series for Lake Poopo extending back in time. The dominant water inflow to Lake Poopo is from the River Desaguadero, which constitutes the outflow of Lake Titicaca. The water-balance computations confirm the crude peasant knowledge about historical lake status. It is found that if the lake level is less than I in during the wet season, there is a risk that this shallow lake dries out in the dry season.
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| 15. |
- Wang, XP, et al.
(författare)
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Measurement of rainfall interception by xerophytic shrubs in re-vegetated sand dunes
- 2005
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 50:5, s. 897-910
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Tidskriftsartikel (refereegranskat)abstract
- More than 40 years of re-vegetation using mainly xerophytic shrubs Artemisia ordosica Krasch. and Caragana korshinskii Kom. at Shapotou Desert Experimental Research Station near Lanzhou, China has resulted in established dwarf-shrub and herbaceous cover on sand dunes. Precipitation, as the sole source of water replenishment in the semiarid area, plays a pertinent role in sustaining the desert ecosystem. A field study was conducted to (a) measure interception loss on shrub canopies during individual rainfall events, (b) determine the canopy storage capacity of individual plants, and (c) explore the relationship between interception and rainfall parameters. The total rainfall and its respective partitions as throughfall were determined and the interception losses in the studied ecosystem were quantified. Interception loss was shown to differ among the xerophyte taxa studied. During the growing seasons, the average shrub community interception loss is 6.9% and 11.7% of the simultaneous overall precipitation, for A. ordosica and C. korshinskii, respectively. Taking into account the observed rainfall conditions and vegetation cover characteristics, it was concluded that the interception loss was 2.7% of the total annual precipitation verified in the period for the A. ordosica community with an average cover of 30%, canopy projection area of 0.8 m(2) and canopy storage capacity of 0.75 mm. In contrast, interception loss for the C korshinskii community was 3.8% with an average cover of 46%, canopy projection area of 3.8 m(2) and canopy storage capacity of 0.71 mm. For individual plants of both shrubs, the proportion of interception loss to gross rainfall decreased notably as the rainfall intensity increased between 0 and 2 min h(-1), while it tended to remain constant at about 0.1-0.2 for A. ordosica and 0.1-0.3 for C. korshinskii when the rainfall intensity was > 2 mm h(-1).
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| 16. |
- Zhang, Qiang, et al.
(författare)
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Periodicity of sediment load and runoff in the Yangtze River basin and possible impacts of climatic changes and human activities
- 2008
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 53:2, s. 457-465
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Tidskriftsartikel (refereegranskat)abstract
- Periodicity of the runoff and the sediment load, and possible impacts from human activities and climatic changes, in the Yangtze River basin during 1963-2004 are discussed based oil the monthly sediment and runoff data, and using the wavelet approach. Research results indicated that: (a) Sediment load changes are severely impacted by the different types of human activity (e.g. construction of water reservoirs, deforestation/afforestation); and the runoff variability is the direct result of climatic changes, e.g. the precipitation changes. (b) The impacts of human activity and climatic changes on the sediment load and runoff changes are greater in smaller river basins (e.g. the Jialingjiang River basin) than in larger river basins. The response of sediment load and runoff changes to the impacts of human activities and climatic changes are prompt and prominent in the Jialingjiang River basin relative to those in the mainstem of the Yangtze River basin. (c) Construction of the Three Gorges Dam has already had obvious impacts on the sediment transport process in the middle and lower Yangtze River basin, but shows no obvious influence on the runoff changes. Construction of the Three Gorges Dam will result in further re-adjustment of the scouring/filling process within the river channel in the middle and lower Yangtze River basin, and have corresponding effects on the altered sediment load because of the Dam’s operation for the river channel, ecology, Sustainable social economy and even the development of the Yangtze Delta. This will be of concern to local governments and policy makers.
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| 17. |
- Persson, Magnus, et al.
(författare)
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Scaling analyses of high-resolution dye tracer experiments
- 2008
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Ingår i: Hydrological Sciences Journal. - 0262-6667. ; 53:6, s. 1286-1299
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Tidskriftsartikel (refereegranskat)abstract
- Four unsaturated solute transport experiments with different water fluxes were conducted in a Hele-Shaw cell filled with uniform sand. The transport of the dye tracer used was recorded with a camera and the dye concentration was calculated using image analysis. The concentrations fields were analysed in terms of time moments and converted into vertical solute transport velocity V. Both mean value and standard deviation of V increased with water flux. The autocorrelation function exhibited a linear decrease for short lags. The pronounced variability of V suggested a description in terms of scaling properties, and a scaling regime was indeed found from the resolution 1.8 mm up to almost 0.1 m. The upper limit corresponds roughly to a characteristic scale of fingering structures seen in the dye concentration images. Indications of a second scaling regime at larger scales were found. In the small-scale scaling regime, the power spectrum exponent beta was generally slightly below 1 and the intermittency parameter C-1 was on average 0.00025. The moment scaling K-q functions were convex, implying a multiscaling process.
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