摘要:

A novel approach for mapping river runoff is presented. It is based on a disaggregation of the mean annual streamflow measured at the outlet of a basin to estimate water depths on elements of an exact partition of this basin. The developed technique is based on geostatistical interpolation procedures to which a global constraint of water balance has been added. The methodology is illustrated by a case study from a tributary to the Rhône River, France. The results were compared to an established method-the nested approach, and a cross-validation was performed for each mapping technique. The disaggregation approach appears to give the most consistent results. Finally, two gridded maps were derived by applying the disaggregation twice to assess water depth on an increasingly finer grid mesh. The global constraint of water balance was applied to each element of the coarser mesh to give estimates for the finer one.

ISSN:0262-6667    

DOI:10.1080/02626660009492385

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The caesium-137 technique affords both an alternative to conventional measurement methods and an effective quantitative estimate of soil redistribution at the basin scale. Among the available calibration relationships which link the degree of increase or depletion of the137Cs activity relative to the baseline137Cs input and sediment yield, the mass balance approach has received increased application for its physical basis. First, the applicability of the refined simplified point-based mass balance (RSPMB) model of Zhang et al. (1999) at the scale of the morphological unit is proposed herein. The137Cs spatial distribution measured in a small Sicilian basin and the spatial distribution of the sediment yield calculated by a sediment delivery distributed approach are used to estimate values of the two key parameters of the RSPMB model, φ1and φ2, the fraction of137Cs fallout incorporated into soil and a particle size correction factor, respectively. Finally, the best procedure for experimental testing of a distributed sediment yield model by using caesium-137 measurements is investigated.

ISSN:0262-6667    

DOI:10.1080/02626660009492386

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Clayey and saline soils have been shown to be problematic for time domain reflectometry (TDR) measurements. This study presents some of these problems and discusses solutions to them. Thirteen solute transport experiments were carried out in three undisturbed soil columns of swelling clay soil from Tunisia, labelled S1, S2, and S3 respectively. The columns were collected at three different physiographical regions within a catchment. Water fluxes ranged from 1.2 to 7.2 cm day−1. The large solute transport heterogeneity and large tailing indicated that preferential flow was most pronounced in S1. The preferential flow took place in voids between structural elements and in wormholes. In S3, preferential flow was also evident, but not to the same extent as in S1. In S2, the solute transport was more uniform with little preferential flow. The heterogeneity of the solute transport increased with the water flux in S1 and to a smaller extent in S3, whereas it remained constant in S2. In a previous dye experiment in the field, preferential flow in cracks was observed at those sites where S1 and S3 were collected. In the column experiments, preferential flow in these cracks was less due to the higher initial water content compared to the dye experiments, indicating that the desiccation cracks were closed by the swelling clay.

ISSN:0262-6667    

DOI:10.1080/02626660009492387

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this first paper in a set of two, the problem of estimating missing segments in streamflow records is described. The group approach, different from the traditional single-valued approach, is proposed and explained. The approach perceives the hydrological data as sequence of groups rather than single-valued observations. The techniques suggested to handle the group approach are regression, time series analysis, partitioning modelling, and artificial neural networks. Pertinent literature is reviewed and background material is used to support the group approach. Implementation and comparisons of models' performance are deferred to the second paper.

ISSN:0262-6667    

DOI:10.1080/02626660009492388

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The group approach that treats hydrological data as groups rather than as single-valued observations was proposed in a companion paper. Various models representing four techniques are briefly presented and applied to single series and bi-series cases, respectively, in this paper. The techniques represented by these models are regression, time series analysis, partitioning modelling, and artificial neural networks. The utility of the models for estimating missing streamflow data using the group approach is investigated. It turns out that the group approach is valid for estimating missing values, and possibly other applications, when data are significantly auto-correlated.

ISSN:0262-6667    

DOI:10.1080/02626660009492389

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The main aim of this study is the experimental investigation of friction velocities and shear stresses in rivers under unsteady flow conditions. Special measurements of mean velocities and other hydraulic parameters were made in two small lowland rivers in central Poland. Four controlled flood waves were released and analysed in the selected reaches. The main hydrometric characteristics and the relationship between water level and discharge were established. Friction velocities were obtained directly from the full St Venant equations of motion, as well as from only the steady momentum equation, and their time-dependent forms were established. Both these approaches provided similar results when the unsteadiness parameter was relatively low. It appeared that real friction velocities were much larger than those obtained from the common uniform flow formula. The passing hydrograph influenced the value of the shear velocity significantly.

ISSN:0262-6667    

DOI:10.1080/02626660009492390

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The hydrology and sediment yield of the relatively undisturbed Sungai Air Terjun catchment on the forested Penang Hill was investigated in 1993–1994. Baseflow accounted for 87.3% of the total runoff, while quickflow comprised 12.7%. The suspended sediment concentration varied from an average concentration of 11.36 mg 1−1(range: 0.5–60.5 mg 1−1) during low flow to an average concentration of 125.5 mg 1−1(range: 11–668.7 mg 1−1) during storms. Suspended sediment transport during storms accounted for as little as 0.69% of the total sediment transport in the driest month, but as much as 52.35% in the wettest month, November 1993. The frequent high-intensity storms on the hill account for the removal of sediment from the hill. Natural disturbances, such as both landslides and human interference, affect the availability of sediment and thus influence variations in sediment output.

ISSN:0262-6667    

DOI:10.1080/02626660009492391

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Since 1995, hydrologists of the HiBAm (Hydrology and Geochemistry of the Amazon Basin) Research Program carried out several hundred discharge measurements in the Amazon basin. Implementation of modern discharge measurement techniques using ultrasonic devices (ADCP), give evidence of a systematic error linked to the displacement of the river bottom due to high water velocity close to the bottom. This error leads to an underestimation of discharge value. It was possible to establish a correlation between the water velocity close to the river bottom and the error between real position and position computed by ADCP when the boat returns to its starting point after a two-way crossing of the river. When there is no bottom displacement, i.e. during low flow period, this return position error is weak (less than 50 m). This has allowed quantification of river bed load speed, or bottom displacement speed. A correction method was developed on the basis of this correlation. This method, systematically applied to ADCP discharge measurements obtained at Óbidos hydrometric station, allowed all measured discharges to be corrected, especially for 1997 and 1999 floods. Another method, based on the analysis of real trajectory of the boat (obtained from topographic measurement or GPS positioning) compared with the ADCP computed trajectory, is under study.

ISSN:0262-6667    

DOI:10.1080/02626660009492392

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626660009492393

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626660009492394

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor