Estimation of temporal variation of sediment yield using GIS / Estimation de la variation temporelle de l'exportation sédimentaire grâce à un SIG

Abstract

A GIS-based method is proposed for computation of temporal variation of sediment yield during isolated storm events. Data from three Indian catchments, namely Karso and Nagwa in Jharkhand and Kharkari in Rajasthan, have been used. The Integrated Land and Water Information System (ILWIS) GIS package was used for (a) catchment discretization into cell areas using grid networks, (b) evaluation of the spatial variation in catchment topographical characteristics and land use, and (c) presentation of the results obtained. The process of sediment delivery from grid cells to the catchment outlet is represented by the topographical characteristics of the cells. Unit sediment graphs for the catchments are derived by translation of the sediment yield from the grid cells and routing through a linear storage reservoir. The proposed method is found to provide satisfactory estimates of the temporal variation of sediment yield during isolated storm events. The total sediment yield of a storm event may also be computed using the proposed method.     

On-line estimation of unit hydrographs using the wavelet-based LMS algorithm / Estimation en ligne des hydrogrammes unitaires grâce à l'algorithme des moindres carrés moyens à base d'ondelettes

Abstract

This study applies the discrete wavelet transform (DWT) to decompose the unit hydrograph, thereby generating parsimonious reparameterizations of the unit hydrograph. A model compression method is then employed to significantly compress the unit hydrograph requiring that fewer coefficients be estimated. Moreover, a wavelet-based linearly constrained least mean squares (WLCLMS) algorithm is also used to estimate on-line the wavelet coefficients of the unit hydrograph. The updated wavelet coefficients of the unit hydrograph, convoluted with effective rainfall input in the wavelet domain, allow for accurate prediction of one-step-ahead runoff in the time domain. The proposed approach allows the unit hydrographs to vary in time and accurately predicts runoff from a basin in Taiwan, thus making it highly promising for flood forecasting.     

Modelling uncertainties in short-term reservoir operation using fuzzy sets and a genetic algorithm / Modélisation d’incertitudes dans la gestion de barrage à court terme grâce à des ensembles flous et à un algorithme génétique

Abstract

Abstract Various uncertainties are inherent in modelling any reservoir operation problem. Two of these are addressed in this study: uncertainty involved in the expression of reservoir penalty functions, and uncertainty in determining the target release value. Fuzzy set theory was used to model these uncertainties where the preferences of the decision maker for the fuzzified parameters are expressed as membership functions. Nonlinear penalty functions are used to determine the penalties due to deviations from targets. The optimization was performed using a genetic algorithm with the objectives to minimize the total penalty and to maximize the level of satisfaction of the decision maker with fuzzified input parameters. The proposed formulation was applied to the problem of finding the optimal release and storage values, taking Green reservoir in Kentucky, USA as a case study. The approach offers more flexibility to reservoir decision-making by demonstrating an efficient way to represent subjective uncertainties, and to deal with non-commensurate objectives under a fuzzy multi-objective environment.     

Soil moisture estimation using ERS 2 SAR data: a case study in the Solani River catchment/Estimation de l’humidité du sol grâce à des données ERS-2 SAR: étude de cas dans le bassin de la rivière Solani

Abstract

Abstract The information regarding spatial and temporal variation of soil moisture in a catchment is of utmost importance in hydrological, as well as many other studies. Point measurements from gravimetric and other methods for soil moisture determination are insufficient to understand the spatial behaviour of soil moisture in a region. Microwave remote sensing data from active sensors on board various satellites are increasingly being used to map spatial distribution of soil moisture within the 0–10 cm top surface. The northern part of India has a network of large rivers and canals and, therefore, spatial and temporal distribution of soil moisture in this region has a significant bearing on the hydrology of the region. In this paper, results on estimation of soil moisture from an ERS-2 SAR image in the catchment of the Solani River (a tributary to the River Ganga) in and around the town of Roorkee, India, have been presented. The radar backscatter coefficient for each pixel of the image has been modelled from the digital numbers of the SAR image. Gravimetric measurements have been made simultaneously during the satellite pass to determine the concurrent value of volumetric soil moisture at a large number of sample points within the satellite sweep area. The backscatter coefficient is found to vary from –30 dB to –42 dB for a variation in soil moisture from 30 to 75%. Regression analyses between volumetric soil moisture and both the digital numbers and backscatter coefficients were performed. Strong correlations between volumetric soil moisture and digital number were observed with R ² values of 0.84, 0.75 and 0.83 for bare soil, vegetative and combined surfaces, respectively. A similar trend was observed with the relationship between backscatter and volumetric soil moisture with R ² values of 0.60, 0.89 and 0.67 for bare soil, vegetative and combined surfaces, respectively. These results demonstrate the utilization of SAR data for estimation of spatial distribution of soil moisture in the region of the present study.     

Sur l'influence de la loi de répartition des densités à l'intérieur de la Terre dans les variations luni-solaires de la gravité en un point

Résumé Les observations des variations luni-solaires de la gravité en divers points du globe ne donnent pas des valuers très concordantes pour le facteur lié au module de rigidité de la Terre. On démontre ici que la répartition croissante des densités vers le centre de la Terre a pour conséquence d'amplifier encore les effets dus à l'élasticité. En adoptant la répartition deBullen, on aurait =1+0.244h>1, (h étant le premier nombre deLove). En outre une relation simple lie les facteurs et (déviations de la verticale). La valuer deh déduite de telles observations ne peut conduire directement à une valeur significative du module de rigidité du globe car il faut encore tenir compte des variations de la période et de l'amplitude du mouvement chandlérien du pôle.

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Summary Observations of luni-solar variations of gravity at various points of the Earth do not give values in agreement for the factor bound to the Earth's modulus of rigidity. It is shown here that the law of increasing of density toward the center of the Earth emphasizes the effect of elasticity: following the law ofBullen, we should have =1+0.244h>1, (h is the firstLove's number). Further, there is a simple relation between the factors and (deviations of the vertical). The value ofh deduced from such observations could not give directly a significative value of the modulus of rigidity because we must take into account the variations of period and amplitude of the chandlerian motion of the pole.

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Riassunto Le osservazioni delle variazioni luni-solari della gravità in diversi punti della Terra non dànno valori concordanti per il fattore legato al modulo di rigidità del Globo. Si dimostra che la ripartizione crescente della densità verso il centro della Terra ha per conseguenza di amplificare ancora gli effetti dell'elasticità; adottando la legge diBullen, abbiamo =1+0.244h>1, (h essendo il primo numero diLove). Inoltre, una semplice relazione lega i fattori e (deviazioni della verticale). Il valore dih dedotto da tali osservazioni non può condurre ad un valore significativo del modulo di rigidità del Globo poiché bisogna considerare anche le variazioni del periodo e dell'ampiezza del moto polare diChandler.

     

Study of Dongting Lake area variation and its influence on water level using MODIS data / Etude de la variation de la surface du Lac Dongting et de son influence sur le niveau d’eau,grâce à des données MODIS

Abstract

Abstract MODerate-resolution Imaging Spectroradiometer (MODIS) is a new generation remote sensing (RS) sensor and its applications in hydrology and water resources have attracted much attention. To overcome the problems of slow response in flood disaster monitoring based on traditional RS techniques in China, the Flood Disaster Monitoring and Assessing System (FDMAS), based on MODIS and a Geographic Information System (GIS), was designed and applied to Dongting Lake, Hunan Province, China. The storage curve of Dongting Lake for 1995 was obtained using 1:10 000 topographic map data and then a relationship between water level at the Chenglingji hydrological station and lake area was derived. A new relationship between water level and lake area was obtained by processing MODIS images of Dongting Lake from April 2002 to April 2003 and the influence of lake area variation on water level was analysed with the 1996 flood data. It was found that the water level reduction reached 0.64 m for the 1996 flood if the original lake area curve was replaced with the area curve of 2002. This illustrates that the flood water level has been considerably reduced as a result of the increased area of Dongting Lake since the Chinese Central Government’s ?return land to lake? policy took effect in 1998.     

Soil water content and salinity determination using different dielectric methods in saline gypsiferous soil / Détermination de la teneur en eau et de la salinité de sols salins gypseux à l'aide de différentes méthodes diélectriques

Abstract

Measurements 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 (θ), and bulk electrical conductivity (EC _a ) and pore water electrical conductivity (EC _p ) were tested and evaluated. The commonly used K _a –θ 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 θ were about 0.04 m³ m^?3 and 19% for TDR and 0.08 m³ m^?3 and 54% for WET sensor measurements, respectively. Using the Hilhorst (2000) model for EC _p 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.     

Fuzzy logic model approaches to daily pan evaporation estimation in western Turkey / Estimation de l’évaporation journalière du bac dans l’Ouest de la Turquie par des modèles à base de logique floue

Abstract

Abstract Evaporation is one of the fundamental elements in the hydrological cycle, which affects the yield of river basins, the capacity of reservoirs, the consumptive use of water by crops and the yield of underground supplies. In general, there are two approaches in the evaporation estimation, namely, direct and indirect. The indirect methods such as the Penman and Priestley-Taylor methods are based on meteorological variables, whereas the direct methods include the class A pan evaporation measurement as well as others such as class GGI-3000 pan and class U pan. The major difficulty in using a class A pan for the direct measurements arises because of the subsequent application of coefficients based on the measurements from a small tank to large bodies of open water. Such difficulties can be accommodated by fuzzy logic reasoning and models as alternative approaches to classical evaporation estimation formulations were applied to Lake Egirdir in the western part of Turkey. This study has three objectives: to develop fuzzy models for daily pan evaporation estimation from measured meteorological data, to compare the fuzzy models with the widely-used Penman method, and finally to evaluate the potential of fuzzy models in such applications. Among the measured meteorological variables used to implement the models of daily pan evaporation prediction are the daily observations of air and water temperatures, sunshine hours, solar radiation, air pressure, relative humidity and wind speed. Comparison of the classical and fuzzy logic models shows a better agreement between the fuzzy model estimations and measurements of daily pan evaporation than the Penman method.     

Estimation de L'équivalent en Eau du Couvert Nival en Montagne Libanaise à Partir des Images RADARSAT-1/Estimation of Water Equivalent of the Snow Cover in Lebanese Mountains by Means of RADARSAT-1 Images

Abstract

The assessment of the spatial and temporal distribution of water resources in Mediterranean region is crucial for the better management of available resources. In Lebanon in particular, the snow is a crucial parameter for water supply. However, few research works were performed until now to study this potential resource because of difficulties inherent to the measurement of the water volume stored by snow. Remote sensing, and more specifically radar imaging, is the favourite tool for investigating the now water equivalent. This study aims to assess the potential of synthetic aperture radar (SAR) imaging for estimating the snow water equivalent in relation with eight experimental sites distributed over the high plateaus of the Lebanese mountains. With this purpose, an algorithm was tested, which links the backscattering coefficient to physical parameters of the snow and underlying soil, and which allows to assess the water equivalent from the backscattering ratios of a winter scene and a reference scene taken during a period with no snow. To this end, four RADARSAT images were acquired during winter 2001, concurrently to field observations. The model was developed in Quebec for regions with low relief, whereas relief has a decisive influence on the radar signal and on the geometry of images, in a context of high mountains. Consequently, radiometric and geometric corrections were compulsory in order to reduce distortions dues to topographical effects. The preliminary results corroborate the existence of a series of limitations to the application of the algorithm to the particular conditions of the Lebanese snow cover: heterogeneity, accelerated metamorphism and high content of liquid water.     

Application of linear and nonlinear techniques in river flow forecasting in the Kilombero River basin,Tanzania / Application de techniques linéaires et non-linéaires à la prévision des débits dans le bassin de la Rivière Kilombero,en Tanzanie

Abstract

Modelling of the rainfall–runoff transformation process and routing of river flows in the Kilombero River basin and its five sub-catchments within the Rufiji River basin in Tanzania was undertaken using three system (black-box) models—a simple linear model, a linear perturbation model and a linear varying gain factor model—in their linear transfer function forms. A lumped conceptual model—the soil moisture accounting and routing model—was also applied to the sub-catchments and the basin. The HEC-HMS model, which is a distributed model, was applied only to the entire Kilombero River basin. River discharge, rainfall and potential evaporation data were used as inputs to the appropriate models and it was observed that sometimes the system models performed better than complex hydrological models, especially in large catchments, illustrating the usefulness of using simple black-box models in datascarce situations.     

Comparison of grey and phase-space rainfall forecasting models using a fuzzy decision method / Comparaison grâce à une méthode de décision floue des modèles gris et d’espace des phases pour la prévision de pluie

Abstract

Abstract This work applies a fuzzy decision method to compare the performance of the grey model with that of the phase-space model, in forecasting rainfall one to three hours ahead. Four indices and two statistical tests are used to evaluate objectively the performance of the forecasting models. However, a trade-off must be made in choosing a suitable model because various indices may lead to different judgements. Therefore, a fuzzy decision model was applied to solve this problem and to make the optimum decision. The results of fuzzy decision making demonstrate that the grey model outperforms the phase-space model for forecasting one hour ahead, but the phase-space model performs better for forecasting two or three hours ahead.     

Utility of high-resolution climate model simulations for water resources prediction over the Korean Peninsula: a sensitivity study / Utilité de simulations de modèle climatique à haute résolution pour la prévision des ressources en eau dans la Péninsule Coréenne: étude de sensibilité

Abstract

Abstract The utility of simulations of Global Climate Models (GCMs) for regional water resources prediction and management on the Korean Peninsula was assessed by a probabilistic measure. Global Climate Model simulations of an indicator variable (e.g. surface precipitation or temperature) were used for discriminating high vs low regional observations of a target variable (e.g. watershed precipitation or reservoir inflow). The formulation uses the significance probability of the Kolmogorov-Smirnov test for detecting differences between two distributions. High resolution Atmospheric Model Intercomparison Project-II (AMIP-II) type GCM simulations performed by the European Centre for Medium-Range Weather Forecasts (ECMWF) and AMIP-I type GCM simulations performed by the Korean Meteorological Research Institute (METRI) were used to obtain information for the indicator variables. Observed mean areal precipitation and temperature, and watershed-outlet discharge values for seven major river basins in Korea were used as the target variables. The results suggest that the use of the climate model nodal output from both climate models in the vicinity of the target basin with monthly resolution will be beneficial for water resources planning and management analysis that depends on watershed mean areal precipitation and temperature, and outlet discharge.     

Spatial distribution of resistivity in the hydrogeological systems,and identification of the catchment area in the Rharb basin,Morocco / Répartition spatiale de la résistivité dans les systèmes hydrogéologiques et détection des zones de captages dans le bassin du Rharb,Maroc

Abstract

Abstract Geophysical results obtained in the Rharb basin, Morocco are reported. Correlations between hydrogeological well logs reveal several water-bearing Plio-Quaternary units resting on a substrate of blue marls. Geo-electrical borehole analyses were interpreted using bi-logarithmic diagrams which indicate the permeable layers of the aquifer and also its basement. Resistivity data from NE–SW and NW–SE electrical sections allow definition of the permeable/impermeable levels, and identification of ?ditches? that may be favourable sectors for hydrogeological exploitation. Resistivity anomalies were investigated by analysing maps of resistivity at 400 and 1000 m AB. Anomalies identified in the Rharb basin are related to the thickening of the permeable bodies (sand, limestone, sandstone deposits). In the coastal zone (AB = 1000 m), there is a strong decrease of the resistivity gradient (35–10 Ω m), which is probably linked to marine intrusion. Electrical anomalies allow detection of the water-bearing zones notably in the western and southwestern parts of the Rharb basin.     

Soil moisture assessment in the alluvial basins associated with seismic activity of northwest Anatolia,Turkey, using Landsat TM/ETM satellite imagery / Estimation de l’humidité du sol associée à l’activité sismique dans les bassins alluviaux du nord-ouest de l’Anatolie (Turquie) par l’imagerie satellitaire Landsat TM/ETM

Abstract

Abstract The aim of this study is to detect seasonal surface temperature changes and to estimate soil moisture conditions based on the evaporative cooling principle of damp ground in the alluvial basins of northwest Anatolia, Turkey, using Landsat TM/ETM data. According to analysis of satellite sensor data acquired on different dates, soil moisture is greatest in the spring season in the basins. Soil moisture decreases toward the summer and autumn. The 17 August 1999 earthquake occurred in the high surface temperature (low soil moisture) period, and the 12 November 1999 earthquake occurred in the low surface temperature (high soil moisture) period. It is possible to conclude that the urban-rural settlements and industrial developments on the loose deposits of the Adapazari, ?zmit and Düzce depressions have been affected by the seasonal changes in the local ground conditions.