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A new approach is proposed for image denoising. The approach involves edge preservation relying on image multiresolution decomposition using a redundant wavelet transform.

This paper reports the results of statistical analyses for the detection of time trend in 48 rainfall records from sites in the Amazon Basin with more than 15 yr of record. Using a nonparametric test for trend in monthly rainfall, three results emerge: (a) irrespective of the statistical significance of time trends, positive and negative trends occur with approximately equal frequencies over the Brazilian Amazon hydrographic basin; (b) the number of statistically significant time trends, whether positive or negative, is very much greater than can be ascribed to chance variation; (c) significantly negative time trends are more common than significantly positive time trends in monthly rainfall. Over the period of approximately 30 yr covered by the records, during which deforestation has been rapid, negative trends seem to have occurred more frequently in two regions of western and central Amazonia, and positive trends more frequently in eastern Amazonia. There is some qualitative agreement between the disposition of contours defining regions of negative trend (reduced rainfall) in the rainfall records, and the contours defining regions of reduced rainfall following 50% deforestation, as predicted by the U.K. Hadley Centre for Climate Prediction and Research. However, the rainfall records show positive trends (increased rainfall, confirming the conclusion of Chu et al.) in some parts of the region where the Hadley Centre predicts reduced rainfall, following deforestation of 50% or more.

Regionalization of flow duration curves make up an important part of any project in water resources planning and development. Maximum likelihood estimators can be used to obtain asymptotically unbiased and minimum variance estimates for parameters of the flow-duration curve model. However, multivariate regression equations should be developed to improve derived confidence intervals for an estimated flow duration curve.

Abstract: Sediments produced from eroding cultivated land can cause on‐site and off‐site effects that cause considerable economic and social impacts. Despite the importance of soil conservation practices (SCP) for the control of soil erosion and improvements in soil hydrological functions, limited information is available regarding the effects of SCP on sediment yield (SY) at the catchment scale. This study aimed to investigate the long‐term relationships between SY and land use, soil management, and rainfall in a small catchment. To determine the effects of anthropogenic and climatic factors on SY, rainfall, streamflow, and suspended sediment concentration were monitored at 10‐min intervals for 14 years (2002–2016), and the land use and soil management changes were surveyed annually. Using a statistical procedure to separate the SY effects of climate, land use, and soil management, we observed pronounced temporal effects of land use and soil management changes on SY. During the first 2 years (2002–2004), the land was predominantly cultivated with tobacco under a traditional tillage system (no cover crops and ploughed soil) using animal traction. In that period, the SY reached approximately 400 t·km−2·year−1. From 2005 to 2009, a soil conservation programme introduced conservation tillage and winter cover crops in the catchment area, which lowered the SY to 50 t·km−2·year−1. In the final period (2010–2016), the SCP were partially abandoned by farmers, and reforested areas increased, resulting in an SY of 150 t·km−2·year−1. This study also discusses the factors associated with the failure to continue using SCP, including structural support and farmer attitudes. [ABSTRACT FROM AUTHOR]

When 'fingerprinting' is used to identify what proportions Ps ( s = 1, ..., g) of suspended sediment come from g different source areas, measures of the uncertainties in estimates of the Ps are also required. These uncertainties are influenced by two kinds of correlation whose effects are rarely recognized in the literature. These are (i) correlation between the estimated Ps because they must add to 1 and (ii) correlation between the geochemical tracers measured in sediment samples. This paper uses bootstrap procedures to identify joint confidence regions for the estimated proportions [responding to correlation of type (i)] and to explore alternatives to the 'standard' least-squares criterion used to estimate the proportions when tracer measurements are correlated [correlation of type (ii)]. Using a limited dataset with three sediment source areas for illustration ( g = 3), results were obtained from 5000 bootstrap samples, using two criteria (standard and generalized least squares, GLS) with two inequality constraints: (a) 0 ≤ Ps ≤ 1, where Ps is the fraction of suspended sediment contributed by the s-th source area ( s = 1, 2, 3) and (b) 0 < Ps < 1, which, the paper argues, better represents reality. Approximate 95% confidence regions for the Ps, given by the two criteria and two inequality constraints, were compared. Using inequality constraint (a), the confidence region given by the GLS criterion was slightly smaller than that given by the standard; using constraint (b), the two confidence regions' boundaries were almost identical, suggesting that the effects of correlations between tracers were not large for the dataset used. For both criteria, the scatter amongst estimated proportions Ps obtained by bootstrapping was large, raising issues concerning the efficiency of sampling and the allocation of sampling effort, both in source areas and in transported suspended sediment. The results suggest that apparently small differences in the constraints applied to the proportions Ps can give quite different numerical results. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Since the 1970s, there has been both continuing and growing interest in developing accurate estimates of the annual fluvial transport (fluxes and loads) of suspended sediment and sediment-associated chemical constituents. This study provides an evaluation of the effects of manual sample numbers (from 4 to 12 year−1) and sample scheduling (random-based, calendar-based and hydrology-based) on the precision, bias and accuracy of annual suspended sediment flux estimates. The evaluation is based on data from selected US Geological Survey daily suspended sediment stations in the USA and covers basins ranging in area from just over 900 km2 to nearly 2 million km2 and annual suspended sediment fluxes ranging from about 4 Kt year−1 to about 200 Mt year−1. The results appear to indicate that there is a scale effect for random-based and calendar-based sampling schemes, with larger sample numbers required as basin size decreases. All the sampling schemes evaluated display some level of positive (overestimates) or negative (underestimates) bias. The study further indicates that hydrology-based sampling schemes are likely to generate the most accurate annual suspended sediment flux estimates with the fewest number of samples, regardless of basin size. This type of scheme seems most appropriate when the determination of suspended sediment concentrations, sediment-associated chemical concentrations, annual suspended sediment and annual suspended sediment-associated chemical fluxes only represent a few of the parameters of interest in multidisciplinary, multiparameter monitoring programmes. The results are just as applicable to the calibration of autosamplers/suspended sediment surrogates currently used to measure/estimate suspended sediment concentrations and ultimately, annual suspended sediment fluxes, because manual samples are required to adjust the sample data/measurements generated by these techniques so that they provide depth-integrated and cross-sectionally representative data. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]