| 1. |
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| 2. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 3. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Luo, Yifei, et al.
(författare)
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Technology Roadmap for Flexible Sensors
- 2023
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Ingår i: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 17:6, s. 5211-5295
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Forskningsöversikt (refereegranskat)abstract
- Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.
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| 5. |
- Sampson, Joshua N., et al.
(författare)
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Analysis of Heritability and Shared Heritability Based on Genome-Wide Association Studies for 13 Cancer Types
- 2015
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Ingår i: Journal of the National Cancer Institute. - : Oxford University Press (OUP). - 0027-8874 .- 1460-2105. ; 107:12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Studies of related individuals have consistently demonstrated notable familial aggregation of cancer. We aim to estimate the heritability and genetic correlation attributable to the additive effects of common single-nucleotide polymorphisms (SNPs) for cancer at 13 anatomical sites. Methods: Between 2007 and 2014, the US National Cancer Institute has generated data from genome-wide association studies (GWAS) for 49 492 cancer case patients and 34 131 control patients. We apply novel mixed model methodology (GCTA) to this GWAS data to estimate the heritability of individual cancers, as well as the proportion of heritability attributable to cigarette smoking in smoking-related cancers, and the genetic correlation between pairs of cancers. Results: GWAS heritability was statistically significant at nearly all sites, with the estimates of array-based heritability, h(l)(2), on the liability threshold (LT) scale ranging from 0.05 to 0.38. Estimating the combined heritability of multiple smoking characteristics, we calculate that at least 24% (95% confidence interval [CI] = 14% to 37%) and 7% (95% CI = 4% to 11%) of the heritability for lung and bladder cancer, respectively, can be attributed to genetic determinants of smoking. Most pairs of cancers studied did not show evidence of strong genetic correlation. We found only four pairs of cancers with marginally statistically significant correlations, specifically kidney and testes (rho = 0.73, SE = 0.28), diffuse large B-cell lymphoma (DLBCL) and pediatric osteosarcoma (rho = 0.53, SE = 0.21), DLBCL and chronic lymphocytic leukemia (CLL) (rho = 0.51, SE = 0.18), and bladder and lung (rho = 0.35, SE = 0.14). Correlation analysis also indicates that the genetic architecture of lung cancer differs between a smoking population of European ancestry and a nonsmoking Asian population, allowing for the possibility that the genetic etiology for the same disease can vary by population and environmental exposures. Conclusion: Our results provide important insights into the genetic architecture of cancers and suggest new avenues for investigation.
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| 6. |
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| 7. |
- Kristanl, Matej, et al.
(författare)
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The Seventh Visual Object Tracking VOT2019 Challenge Results
- 2019
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Ingår i: 2019 IEEE/CVF INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW). - : IEEE COMPUTER SOC. - 9781728150239 ; , s. 2206-2241
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2019 is the seventh annual tracker benchmarking activity organized by the VOT initiative. Results of 81 trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis as well as the standard VOT methodology for long-term tracking analysis. The VOT2019 challenge was composed of five challenges focusing on different tracking domains: (i) VOT-ST2019 challenge focused on short-term tracking in RGB, (ii) VOT-RT2019 challenge focused on "real-time" short-term tracking in RGB, (iii) VOT-LT2019 focused on long-term tracking namely coping with target disappearance and reappearance. Two new challenges have been introduced: (iv) VOT-RGBT2019 challenge focused on short-term tracking in RGB and thermal imagery and (v) VOT-RGBD2019 challenge focused on long-term tracking in RGB and depth imagery. The VOT-ST2019, VOT-RT2019 and VOT-LT2019 datasets were refreshed while new datasets were introduced for VOT-RGBT2019 and VOT-RGBD2019. The VOT toolkit has been updated to support both standard short-term, long-term tracking and tracking with multi-channel imagery. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website(1).
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| 8. |
- Campbell, PJ, et al.
(författare)
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Pan-cancer analysis of whole genomes
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 578:7793, s. 82-
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Tidskriftsartikel (refereegranskat)abstract
- Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale1–3. Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4–5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter4; identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation5,6; analyses timings and patterns of tumour evolution7; describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity8,9; and evaluates a range of more-specialized features of cancer genomes8,10–18.
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| 9. |
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| 10. |
- Wang, Zhaoming, et al.
(författare)
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Imputation and subset-based association analysis across different cancer types identifies multiple independent risk loci in the TERT-CLPTM1L region on chromosome 5p15.33
- 2014
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 23:24, s. 6616-6633
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Tidskriftsartikel (refereegranskat)abstract
- Genome-wide association studies (GWAS) have mapped risk alleles for at least 10 distinct cancers to a small region of 63 000 bp on chromosome 5p15.33. This region harbors the TERT and CLPTM1L genes; the former encodes the catalytic subunit of telomerase reverse transcriptase and the latter may play a role in apoptosis. To investigate further the genetic architecture of common susceptibility alleles in this region, we conducted an agnostic subset-based meta-analysis (association analysis based on subsets) across six distinct cancers in 34 248 cases and 45 036 controls. Based on sequential conditional analysis, we identified as many as six independent risk loci marked by common single-nucleotide polymorphisms: five in the TERT gene (Region 1: rs7726159, P = 2.10 × 10(-39); Region 3: rs2853677, P = 3.30 × 10(-36) and PConditional = 2.36 × 10(-8); Region 4: rs2736098, P = 3.87 × 10(-12) and PConditional = 5.19 × 10(-6), Region 5: rs13172201, P = 0.041 and PConditional = 2.04 × 10(-6); and Region 6: rs10069690, P = 7.49 × 10(-15) and PConditional = 5.35 × 10(-7)) and one in the neighboring CLPTM1L gene (Region 2: rs451360; P = 1.90 × 10(-18) and PConditional = 7.06 × 10(-16)). Between three and five cancers mapped to each independent locus with both risk-enhancing and protective effects. Allele-specific effects on DNA methylation were seen for a subset of risk loci, indicating that methylation and subsequent effects on gene expression may contribute to the biology of risk variants on 5p15.33. Our results provide strong support for extensive pleiotropy across this region of 5p15.33, to an extent not previously observed in other cancer susceptibility loci.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Kato, Norihiro, et al.
(författare)
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Trans-ancestry genome-wide association study identifies 12 genetic loci influencing blood pressure and implicates a role for DNA methylation
- 2015
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 47:11, s. 1282-1293
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Tidskriftsartikel (refereegranskat)abstract
- We carried out a trans-ancestry genome-wide association and replication study of blood pressure phenotypes among up to 320,251 individuals of East Asian, European and South Asian ancestry. We find genetic variants at 12 new loci to be associated with blood pressure (P = 3.9 × 10−11 to 5.0 × 10−21). The sentinel blood pressure SNPs are enriched for association with DNA methylation at multiple nearby CpG sites, suggesting that, at some of the loci identified, DNA methylation may lie on the regulatory pathway linking sequence variation to blood pressure. The sentinel SNPs at the 12 new loci point to genes involved in vascular smooth muscle (IGFBP3, KCNK3, PDE3A and PRDM6) and renal (ARHGAP24, OSR1, SLC22A7 and TBX2) function. The new and known genetic variants predict increased left ventricular mass, circulating levels of NT-proBNP, and cardiovascular and all-cause mortality (P = 0.04 to 8.6 × 10−6). Our results provide new evidence for the role of DNA methylation in blood pressure regulation.
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| 15. |
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| 16. |
- Du, Jinkang, et al.
(författare)
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Development and testing of a new storm runoff routing approach based on time variant spatially distributed travel time method
- 2009
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 369:1-2, s. 44-54
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a GIS based simple and easily performed runoff routing approach based on travel time was developed to simulate storm runoff response process with consideration of spatial and temporal variability of runoff generation and flow routing through hillslope and river network. The watershed was discretized into grid cells, which were then classified into overland cells and channel cells through river network delineation from the DEM by use of GIS. The overland flow travel time of each overland cell was estimated by combining a steady state kinematic wave approximation with Manning’s equation, the channel flow travel time of each channel cell was estimated using Manning’s equation and the steady state continuity equation. The travel time from each grid cell to the watershed outlet is the sum of travel times of cells along the flow path. The direct runoff flow was determined by the sum of the volumetric flow rates from all contributing cells at each respective travel time for all time intervals. The approach was calibrated and verified to simulate eight storm runoff processes of Jiaokou Reservoir watershed, a sub-catchment of the Yongjiang River basin in southeast China using available topography, soil and land use data for the catchment. An average efficiency of 0.88 was obtained for the verification storms. Sensitivity analysis was conducted to investigate the effect of the area threshold of delineating river networks and parameter K relating channel velocity calculation on the predicted hydrograph at the basin outlet. The effects of different levels of grid size on the results were also studied, which showed that good results could be attained with a grid size of less than 200 m in this study. (C) 2009 Elsevier B.V. All rights reserved.
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| 17. |
- Du, Jinkang, et al.
(författare)
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Development and testing of a simple physically-based distributed rainfall-runoff model for storm runoff simulation in humid forested basins
- 2007
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 336:3-4, s. 334-346
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Tidskriftsartikel (refereegranskat)abstract
- A distributed rainfall-runoff model was developed to predict storm runoff from humid forested catchments. The model is physically based and takes into account the saturation excess overland flow mechanism and preferential subsurface flow. The watershed is discretized into a number of square grids, which then are classified into overland flow and channel flow elements based on water flow properties. On the overland elements, Infiltration, overland flow and lateral subsurface flow are estimated, while on channel flow elements river flow routing is performed. Lateral subsurface flow is calculated using Darcy’s law and the continuity equation, whereas overland flow and channel flow are modeled using a one dimensional kinematic wave approximation to the St. Venant equations. The model governing equations are solved by an implicit finite difference scheme. While using process-based equations and physically meaningful parameters, the model still maintains a relatively simple structure. Most of the model parameters can be derived from digital elevation models (DEMs), digital soil and land use data, and the remainder of the parameters that are comparatively sensitive can be determined by model calibration. The model is tested using nine storm events in the Jiaokou watershed, a sub-basin of Yongjiang River in Zhejiang Province, China. Of these storms, one storm is used for calibrating the model parameters and the remaining eight storms are used to verify the model. When judged by the model efficiency coefficient (R2), volume conversation index (VCI), absolute error of the time to peak (ΔT), and relative error of the peak flow rate (δPmax), acceptable results are achieved. Sensitivity analysis shows that the model is sensitive to saturated hydraulic conductivity (Ks), Manning’s roughness coefficients (n) and the initial soil moisture content.
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| 18. |
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| 19. |
- Du, J., et al.
(författare)
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Storm runoff simulation based on the spatially distributed runoff curve number and time variant routing methods
- 2007
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Ingår i: Methodology in Hydrology. - Wallingford, England : IAHS. - 9781901502930 ; , s. 186-194
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this study, a GIS-based, simple and easily performed modelling approach was proposed to simulate storm runoff response processes with consideration of spatial and temporal variability of runoff generation and flow routing through the hillslope and river network. The watershed was discretized into grid cells, and the river network was delineated from the DEM by use of GIS. In the modelling approach, the US Department of Agriculture Soil Conservation Service (SCS) curve number (CN) method in its differential form was used to calculate surface runoff (or excess rainfall) for each grid cell. The surface runoff was then routed to the watershed outlet using an improved spatially distributed travel time method. The approach was applied to simulate eight storm runoff events in the Jiaokou Reservoir watershed, a sub-basin of the Yongjiang River basin in southeast China. The results showed that the proposed approach predicted the runoff processes with an average efficiency of 0.94.
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| 20. |
- Kristan, Matej, et al.
(författare)
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The Visual Object Tracking VOT2017 challenge results
- 2017
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Ingår i: 2017 IEEE INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW 2017). - : IEEE. - 9781538610343 ; , s. 1949-1972
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2017 is the fifth annual tracker benchmarking activity organized by the VOT initiative. Results of 51 trackers are presented; many are state-of-the-art published at major computer vision conferences or journals in recent years. The evaluation included the standard VOT and other popular methodologies and a new "real-time" experiment simulating a situation where a tracker processes images as if provided by a continuously running sensor. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The VOT2017 goes beyond its predecessors by (i) improving the VOT public dataset and introducing a separate VOT2017 sequestered dataset, (ii) introducing a realtime tracking experiment and (iii) releasing a redesigned toolkit that supports complex experiments. The dataset, the evaluation kit and the results are publicly available at the challenge website(1).
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| 21. |
- Li, Z., et al.
(författare)
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Uncertainty issues of a conceptual water balance model for a semi-arid watershed in north-west of China
- 2013
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 27:2, s. 304-312
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Tidskriftsartikel (refereegranskat)abstract
- Hydrological models are useful tools for better understanding the hydrological processes and performing the hydrological prediction. However, the reliability of the prediction depends largely on its uncertainty range. This study mainly focuses on estimating model parameter uncertainty and quantifying the simulation uncertainties caused by sole model parameters and the co-effects of model parameters and model structure in a lumped conceptual water balance model called WASMOD (Water And Snow balance MODeling system). The validity of statistical hypotheses on residuals made in the model formation is tested as well, as it is the base of parameter estimation and simulation uncertainty evaluation. The bootstrap method is employed to examine the parameter uncertainty in the selected model. The Yingluoxia watershed at the upper reaches of the Heihe River basin in north-west of China is selected as the study area. Results show that all parameters in the model can be regarded as normally distributed based on their marginal distributions and the Kolmogorov-Smirnov test, although they appear slightly skewed for two parameters. Their uncertainty ranges are different from each other. The model residuals are tested to be independent, homoscedastic and normally distributed. Based on such valid hypotheses of model residuals, simulation uncertainties caused by co-effects of model parameters and model structure can be evaluated effectively. It is found that the 95% and 99% confidence intervals (CIs) of simulated discharge cover 42.7% and 52.4% of the observations when only parameter uncertainty is considered, indicating that parameter uncertainty has a great effect on simulation uncertainty but still cannot be used to explain all the simulation uncertainty in this study. The 95% and 99% CIs become wider, and the percentages of observations falling inside such CIs become larger when co-effects of parameters and model structure are considered, indicating that simultaneous consideration of both parameters and model structure uncertainties accounts sufficient contribution for model simulation uncertainty.
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| 22. |
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| 23. |
- Wu, Xiao-Ling, et al.
(författare)
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Coupled Hydraulic and Kalman Filter Model for Real-Time Correction of Flood Forecast in the Three Gorges Interzone of Yangtze River, China
- 2013
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Ingår i: Journal of hydrologic engineering. - 1084-0699 .- 1943-5584. ; 18:11, s. 1416-1425
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Tidskriftsartikel (refereegranskat)abstract
- The Three Gorges Project along the Yangtze River in China, as one of the biggest hydropower-complex projects in the world, plays a significant role in the economic development of the area even of the whole nation. An accurate and reliable flood forecast modeling system is of significant importance for flood control, flood warning, and operation of larger reservoirs. Kalman filter coupling with hydrological models or hydraulic models is one of the efficient methods to adjust real-time flood series for reducing errors from model structure, input data, and calibrated parameters. However, the coupling model is time consuming in computation because the state vectors in this kind of Kalman filter including both water stage and discharge are solved simultaneously. In this study, an alternative coupling method was developed, which separates system state equations and measurement equations allowing the water stage and discharge to be computed alternately. The new method was applied for real-time flood forecasting in the Three Gorges interzone of Yangtze River. The hydraulic model is calibrated and verified against the observed flood stage and discharge before and during Three Gorges Dam construction periods. Study results demonstrate that the new model is efficient in real-time flood forecasting. A comparative study shows that the newly developed approach outperforms the conventional methods in terms of modeling efficiency, root mean square error, as well as the forecasting errors in the maximum water stage and peak flow.
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| 24. |
- Zhang, Qiang, et al.
(författare)
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Multifractal analysis of measure representation of flood/drought grade series in the Yangtze Delta, China, during the past millennium and their fractal model simulation
- 2010
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 30:3, s. 450-457
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Tidskriftsartikel (refereegranskat)abstract
- Based on reconstructed flood/drought grade series, IFS (iterazed function systems) and RIFS[(recurrent) iterated function systems] models were used to reconstruct their measure representations. The goodness-of-fit of the simulation indicated good performance of IFS and RIFS models in simulation of the measure representaitons of the historical flood/drought grade series in the Yangtze Delta. Multifractal properties of the measures of the flood/drought grade series were analyzed using multifractal detrended fluctuation analysis (MF-DFA) technique. The DFA1 exponents of 0.6348 +/- 0.013 and 0.7215 +/- 0.013 indicated that the measures of the flood/drought grade series of the Yangtze Delta were characterized by long memory or persistence. Furthermore, the h(q) curves of the measure representations indicated that the measure representations of the flood/drought grade series in the Yangtze Delta were multifractal measures. The finding of this paper highlights possibility of prediction for future climatic changes based on historical records in the Yangtze Delta region. Copyright (C) 2009 Royal Meterological Society.
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| 25. |
- Zhang, Qiang, et al.
(författare)
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Multifractal analysis of streamflow records of the East River basin (Pearl River), China
- 2009
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Ingår i: Physica A. - : Elsevier BV. - 0378-4371 .- 1873-2119. ; 388:6, s. 927-934
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Tidskriftsartikel (refereegranskat)abstract
- Scaling behaviors of the long daily streamflow series of four hydrological stations (Longchuan (1952-2002), Heyuan (1951-2002), Lingxia (1953-2002) and Boluo (1953-2002)) in the mainstream East River, one of the tributaries of the Pearl River (Zhujiang River) basin, were analyzed using multifractal detrended fluctuation analysis (MF-DFA). The research results indicated that streamflow series of the East River basin are characterized by anti-persistence. MF-DFA technique showed similar scaling properties in the streamflow series of the East River basin on shorter time scales, indicating universal scaling properties over the East River basin. Different intercept values of the fitted lines Of log-log Curve of F-q(s) versus s implied hydrological regulation of water reservoirs. Based on the numerical results, we suggested that regulation activities by water reservoirs Could not impact the scaling properties of the streamflow series. The regulation activities by water reservoir only influenced the fluctuation magnitude. Therefore, we concluded that the streamflow variations were mainly the results of climate changes, and precipitation variations in particular. Strong dependence of generalized Hurst exponent h(q) on q demonstrated multifractal behavior of streamflow series of the East River basin, showing ‘universal’ multifractal behavior of river runoffs. The results of this study may provide valuable information for prediction and assessment of water resources under impacts of climatic changes and human activities in the East River basin. (C) 2008 Elsevier B.V. All rights reserved.
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| 26. |
- Zhang, Qiang, et al.
(författare)
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Multifractal detrended fluctuation analysis of streamflow series of the Yangtze River basin, China
- 2008
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 22:26, s. 4997-5003
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Tidskriftsartikel (refereegranskat)abstract
- Scaling, and multifractal properties of the hydrological processes of the Yangtze River basin were explored by using a multifractal detrended fluctuation analysis (MF-DFA) technique. Long daily streamflow series from Cuntan. Yichang Hankou and Datong stations were analyzed. Using shuffled streamflow series, the types of multifractality of streamflow series was also studied. The results indicate that the discharge series of the Yangtze River basin are non-stationary. Different correlation properties were identified within streamflow series of the upper, the middle and the lower Yangtze River basin. The discharge series of the upper Yangtze River basin Lire characterized by short memory or anti-persistence while the streamflow series of the lower Yangtze River basin is characterized by long memory or persistence. h(q) vs q curves indicate multifractality of the hydrological processes of the Yangtze River basin. h(q) curves of shuffled streamflow series suggest that the multifractality of the streamflow series is mainly due to the correlation properties within the hydrological series. This may be of practical and scientific importance in regional flood frequency analysis and water resource management in different parts of the Yangtze River basin. Copyright (C) 2008 John Wiley & Sons, Ltd.
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| 27. |
- Zhang, Q., et al.
(författare)
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Observed trends of annual maximum water level and streamflow during past 130 years in the Yangtze River basin, China
- 2006
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 324:1-4, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- Annual maximum streamflow and annual maximum water level and their variations exert most serious influences on human society. In this paper, temporal trends and frequency changes at three major stations of Yangtze River, i.e. Yichang, Hankou and Datong representing upper, middle and lower reaches, respectively, were detected with the help of parametric t-test, Mann-Kendall (MK) analysis and wavelet transform methods. The results show that: (1) there is a significant upward trend in streamflow at middle Yangtze River, indicating that flood hazard in the middle reach of the river, the flood rich region, will be more serious; (2) there is a consistent increase of water level from upper to lower reaches of the river which does not always coincide with the maximum streamflow variations; and (3) the periods of water level changes are decreasing over time, indicating the increasing occurrence frequency of annual maximum water level over time. This phenomenon is more obvious from upper Yangtze River to the lower Yangtze River. Human activities like destruction of vegetation, land reclamation and construction of levees reduced lake sizes and filled up the river bed, reducing the flood storage capacity of lakes and fluvial channel. These factors led to higher water level even some times the streamflow is small. Human should adjust his activity to enhance his adaptive capacity to flood hazard in the future.
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| 28. |
- Bian, Guodong, et al.
(författare)
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Detection and attribution of flood responses to precipitation change and urbanization : A case study in Qinhuai River Basin, Southeast China
- 2020
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 51:2, s. 351-365
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Tidskriftsartikel (refereegranskat)abstract
- Both flood magnitude and frequency might change under the changing environment. In this study, a procedure combining statistical methods, flood frequency analysis and attribution analysis was proposed to investigate the response of floods to urbanization and precipitation change in the Qinhuai River Basin, an urbanized basin located in Southeast China, over the period from 1986 to 2013. The Mann–Kendall test was employed to detect the gradual trend of the annual maximum streamflow and the peaks over threshold series. The frequency analysis was applied to estimate the changes in the magnitude and frequency of floods between the baseline period (1986–2001) and urbanization period (2002–2013). An attribution analysis was proposed to separate the effects of precipitation change and urbanization on flood sizes between the two periods. Results showed that: (1) there are significant increasing trends in medium and small flood series according to the Mann–Kendall test; (2) the mean and threshold values of flood series in the urbanization period were larger than those in the baseline period, while the standard deviation, coefficient of variation and coefficient of skewness of flood series were both higher during the baseline period than those during the urbanization period; (3) the flood magnitude was higher during the urbanization period than that during the baseline period at the same return period. The relative changes in magnitude were larger for small floods than for big floods from the baseline period to the urbanization period; (4) the contributions of urbanization on floods appeared to amplify with the decreasing return period, while the effects of precipitation diminish. The procedure presented in this study could be useful to detect the changes of floods in the changing environment and conduct the attribution analysis of flood series. The findings of this study are beneficial to further understanding interactions between flood behavior and the drivers, thereby improving flood management in urbanized basins.
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| 29. |
- Cao, Yong-Xiao, et al.
(författare)
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Ligustilide induces vasodilatation via inhibiting voltage dependent calcium channel and receptor-mediated Ca(2+) influx and release.
- 2006
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Ingår i: Vascular Pharmacology. - : Elsevier BV. - 1537-1891. ; 45:3, s. 171-176
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to investigate the effect of ligustilide on vasodilatation in rat mesenteric artery and the mechanisms responsible for it. Isometric tension of rat mesenteric artery rings was recorded by a sensitive myograph system in vitro. The results showed that ligustilide at concentrations more than 10 mu M relaxed potassium chloride (KCl)-preconstricted rat mesenteric artery in a con centration-dependent manner. The vasodilatation effect of ligustilide was not dependent on endothelium. Ligustilide rightwards shifted concentration-response curves induced by KCl, calcium chloride (CaCl2), noradrenaline (NA) or 5-hydroxytryptamine (5-HT) in a non-parallel manner. This suggests that the vasodilatation effects were most likely via voltage-dependent calcium channel (VDCC) and receptor-operated calcium channel (ROCC). Propranolol, glibenclamide, tetraethylammonium and barium chloride did not affect the vasodilation induced by ligustilide, showing that beta-adrenoceptor, ATP sensitive potassium channel, calcium-activated potassium channel and inwardly rectifying potassium channel were not involved in the vasodilatation. Ligustilide concentration-dependently inhibited the vasoconstriction induced by NA or CaCl2 in Ca2+-free medium, indicating that the vasodilatation relates to inhibition of extracellular Ca2+ influx through VDCC and ROCC, and intracellular Ca2+ release from Ca2+ store. Since caffeine-induced contraction was inhibited by ligustilide, inhibition of intracellular Ca2+ released by ligustilide occurred via the ryanodine receptors. Our results suggest that ligustilide induces vasodilatation in rat mesenteric artery by inhibiting the VDCC and ROCC, and receptor-mediated Ca2+ influx and release. (c) 2006 Elsevier Inc. All rights reserved.
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| 30. |
- Chen, D., et al.
(författare)
-
A high-resolution, gridded dataset for monthly temperature normals (1971 – 2000) in Sweden
- 2007
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 89:4, s. 249-261
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Tidskriftsartikel (refereegranskat)abstract
- A baseline climatology is required in evaluating climate variability and changes on regional and local scales. Gridded climate normals, i.e. averages over a 30-year period, are of special interest since they can be readily used for validation of climate models. This study is aimed at creating an updated gridded dataset for Swedish monthly temperature normals over the period 1971–2000, based on standard 2-m air temperature records at 510 stations in mainland Sweden. Spatial trends of the normal temperatures were modelled as functions of latitude, longitude and elevation by multiple linear regression. The study shows that the temperature normals are strongly correlated with latitude throughout the year and especially in cold months, while elevation was a more important factor in June and July. Longitude played a minor role and was only significant in April and May. Regression equations linking temperature to latitude, longitude and elevation were set up for each month. Monthly temperature normals were detrended by subtracting spatial trends given by the regressions. Ordinary kriging was then applied to both original data (simple method) and de-trended data (composite method) to model the spatial variability and to perform spatial gridding. The multiple regressions showed that between 82% (summer) and 96% (winter) of the variance in monthly temperature normals could be explained by latitude and elevation. Unexplained variances, i.e. the residuals, were modelled with ordinary kriging with exponential semivariograms. The composite grid estimates were calculated by adding the multiple linear trends back to the interpolated residuals at each grid point. Kriged original temperature normals provided a performance benchmark. The cross–validation shows that the interpolation errors of the normals are significantly reduced if the composite method rather than the simple one was used. A gridded monthly dataset with 30-arcsecond spacing was created using the established trends, the kriging model and a digital topographic dataset.
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| 31. |
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| 32. |
- Chen, David, et al.
(författare)
-
CHANGE-POINT ALTERATIONS OF EXTREME WATER LEVELS AND UNDERLYING CAUSES IN THE PEARL RIVER DELTA, CHINA
- 2009
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Ingår i: Rivers Research and Applications. - : Wiley. - 1535-1459 .- 1535-1467. ; 25, s. 1153-1168
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the Bayesian model and Lepage test were used to detect change point and to analyse associated statistical properties of high/low water levels in summer (June, July and August (JJA)) and winter (December, January and February (DJF)) months across the PRD (Pearl River Delta). The results indicate that: (1) two time intervals, that is 1979-1981 and 1988-1995, witness abrupt changes of SmH/SmL (summer mean high water level/summer mean low water level). The lower PRD is dominated by increased mean and coefficient of variation (Cv) of SmH. Increased mean but decreased Cv of SmL can be observed in the Mainstem Pearl River; (2) WmL (winter mean low water level) and WmH (winter mean high water level) of about 74% of the total stations have two change points occurred roughly during 1969-1971 and 1993-1995. First change points of WmH are mainly characterized by increased mean and Cv, but decreased mean and increased Cv of WmL can be observed across major parts of the PRD. The driving factors causing abrupt changes of water levels are various. Intensive human activities cannot be ignored, for example in-channel dredging and reallocation of the streamflow within the river channels due to human-induced topographical changes of river channel. Different responses of high/low water levels to externally influencing factors and interactions between influencing factors make the alterations of the water levels across the PRD more complicated. The findings of this paper will be helpful for the management of the PRD and human mitigation to natural hazards under the changing environment. Copyright (C) 2008 John Wiley & Sons, Ltd.
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| 33. |
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| 34. |
- Chen, David, et al.
(författare)
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Hydrologic alteration along the Middle and Upper East River (Dongjiang) basin, South China : a visually enhanced mining on the results of RVA method
- 2010
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Ingår i: Stochastic environmental research and risk assessment (Print). - : Springer Science and Business Media LLC. - 1436-3240 .- 1436-3259. ; 24, s. 9-18
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a visually enhanced evaluation of the spatio-temporal patterns of the dam-induced hydrologic alteration in the middle and upper East River, south China over 1952-2002, using the range of variability approach (RVA) and visualization package XmdvTool. The impacts of climate variability on hydrological processes have been removed for wet and dry periods, respectively, so that we focus on the impacts of human activities (i.e., dam construction). The results indicate that: (1) along the East River, dams have greatly altered the natural flow regime, range condition and spatial variability; (2) six most remarkable indicators of hydrologic alteration induced by dam-construction are rise rate (1.16), 3-day maximum (0.91), low pulse duration (0.88), January (0.80), July (0.80) and February (0.79) mean flow of the East River during 1952-2002; and (3) spatiotemporal hydrologic alterations are different among three stations along Easter River. Under the influence of dam construction in the upstream, the degree of hydrologic changes from Lingxia, Heyuan to Longchuan station increases. This study reveals that visualization techniques for high-dimensional hydrological datasets together with RVA are beneficial for detecting spatio-temporal hydrologic changes.
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| 35. |
- Chen, Deliang, 1961, et al.
(författare)
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Spatial Interpolation of Daily Precipitation in China : 1951-2005
- 2010
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Ingår i: Advances in Atmospheric Sciences. - : Springer Science and Business Media LLC. - 0256-1530 .- 1861-9533. ; 27:6, s. 1221-1232
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Tidskriftsartikel (refereegranskat)abstract
- Climate research relies heavily on good quality instrumental data; for modeling efforts gridded data are needed. So far, relatively little effort has been made to create gridded climate data for China. This is especially true for high-resolution daily data. This work, focuses on identifying an accurate method to produce gridded daily precipitation in China based on the observed data at 753 stations for the period 1951-2005. Five interpolation methods, including ordinary nearest neighbor, local polynomial, radial basis function, inverse distance weighting, and ordinary kriging, have been used and compared. Cross-validation shows that the ordinary kriging based on seasonal semi-variograms gives the best performance, closely followed by the inverse distance weighting with a power of 2. Finally the ordinary kriging is chosen to interpolate the station data to a 18 kmx 18 km grid system covering the whole country. Precipitation for each 0.5A degrees x 0.5A degrees latitude-longitude block is then obtained by averaging the values at the grid nodes within the block. Owing to the higher station density in the eastern part of the country, the interpolation errors are much smaller than those in the west (west of 100A degrees E). Excluding 145 stations in the western region, the daily, monthly, and annual relative mean absolute errors of the interpolation for the remaining 608 stations are 74%, 29%, and 16%, respectively. The interpolated daily precipitation has been made available on the internet for the scientific community.
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| 36. |
- Chen, H., et al.
(författare)
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Historical temporal trends of hydro-climatic variables and runoff response to climate variability and their relevance in water resource management in the Hanjiang basin
- 2007
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 344:3-4, s. 171-184
-
Tidskriftsartikel (refereegranskat)abstract
- The Danjiangkou reservoir lies in the upper Hanjiang basin and is the source of water for the middle route of the South-to-North Water Diversion Project (SNWDP) in China. Any significant change in the magnitude or timing of runoff from the Danjiangkou reservoir induced by changes in climatic variables would have significant implications for the economic prosperity of the area in the Hanjiang basin as well as for the South-to-North Water Diversion Project. In this paper the following issues are investigated: (1) Temporal trends of annual and seasonal precipitation and temperature from 1951 to 2003 in the Hanjiang basin are analyzed using the Mann–Kendall and the linear regression methods; spatial distributions of precipitation and temperature are interpolated by the inverse distance weighted interpolation method. (2) Temporal trends of runoff, precipitation and temperature from 1951 to 2003 in the Danjiangkou reservoir, an upper stream basin of the Hanjiang River, are further tested. (3) To assess the impact of climate change on water resources and predict the future runoff change in the Danjiangkou reservoir basin, a two-parameter water balance model is used to simulate the hydrological response for the climate change predicted by GCMs for the region for the period of 2021–2050. The results indicate that (1) at the α = 0.05 significance level precipitation in the Hanjiang basin has no trend, but the temperature in the same region has significant upward trends in most parts of the Hanjiang basin. (2) The mean annual, spring, and winter runoffs in the Danjiangkou reservoir basin have decreasing trends. (3) The results simulated for the period 2021–2050 show that runoff of the Danjiangkou reservoir would increase in all the seasons, mainly in response to the predicted precipitation increase in the region. Sensitivity analysis shows that a 1 °C and 2 °C increase in temperature would reduce the mean annual runoff to about 3.5% and 7%, respectively. A decrease/increase of the mean monthly precipitation of 20% and 10% would decrease/increase the mean annual runoff to about 30% and 15%, respectively. The results of this study provide a scientific reference not only for assessing the impact of the climate change on water resources and the flood prevention in the Hanjiang basin, but also for dimensioning the middle route of the SNWDP in China.
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| 37. |
- Chen, X., et al.
(författare)
-
A distributed monthly hydrological model for integrating spatial variations of basin topography and rainfall
- 2007
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 21:2, s. 242-252
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrological models at a monthly time-scale are important tools for hydrological analysis, such as in impact assessment of climate change and regional water resources planning. Traditionally, monthly models adopt a conceptual, lumped-parameter approach and cannot account for spatial variations of basin characteristics and climatic inputs. A large requirement for data often severely limits the utility of physically based, distributed-parameter models. Based on the variable-source-area concept, we considered basin topography and rainfall to be two major factors whose spatial variations play a dominant role in runoff generation and developed a monthly model that is able to account for their influences in the spatial and temporal dynamics of water balance. As a hybrid of the Xinanjiang model and TOPMODEL, the new model is constructed by innovatively making use of the highly acclaimed simulation techniques in the two existing models. A major contribution of this model development study is to adopt the technique of implicit representation of soil moisture characteristics in the Xinanjiang model and use the TOPMODEL concept to integrate terrain variations into runoff simulation. Specifically, the TOPMODEL topographic index ln(a/tan) is converted into an index of relative difficulty in runoff generation (IRDG) and then the cumulative frequency distribution of IRDG is used to substitute the parabolic curve, which represents the spatial variation of soil storage capacity in the Xinanjiang model. Digital elevation model data play a key role in the modelling procedures on a geographical information system platform, including basin segmentation, estimation of rainfall for each sub-basin and computation of terrain characteristics. Other monthly data for model calibration and validation are rainfall, pan evaporation and runoff. The new model has only three parameters to be estimated, i.e. watershed-average field capacity WM, pan coefficient and runoff generation coefficient . Sensitivity analysis demonstrates that runoff is least sensitive to WM and, therefore, it can be determined by a prior estimation based on the climate and soil properties of the study basin. The other two parameters can be determined using optimization methods. Model testing was carried out in a number of nested sub-basins of two watersheds (Yuanjiang River and Dongjiang River) in the humid region in central and southern China. Simulation results show that the model is capable of describing spatial and temporal variations of water balance components, including soil moisture content, evapotranspiration and runoff, over the watershed. With a minimal requirement for input data and parameterization, this terrain-based distributed model is a valuable contribution to the ever-advancing technology of hydrological modelling.
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| 38. |
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| 39. |
- Chen, Xiaohong, et al.
(författare)
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Hydrological Design of Nonstationary Flood Extremes and Durations in Wujiang River, South China : Changing Properties, Causes, and Impacts
- 2013
-
Ingår i: Mathematical problems in engineering (Print). - : Hindawi Limited. - 1024-123X .- 1563-5147. ; , s. 527461-
-
Tidskriftsartikel (refereegranskat)abstract
- The flood-duration-frequency (QDF) analysis is performed using annual maximum streamflow series of 1-10 day durations observed at Pingshi and Lishi stations in southern China. The trends and change point of annual maximum flood flow and flood duration are also investigated by statistical tests. The results indicate that (1) the annual maximum flood flow only has a marginally increasing trend, whereas the flood duration exhibits a significant decreasing trend at the 0.10 significant level. The change point for the annual maximum flood flow series was found in 1991 and after which the mean maximum flood flow increased by 45.26%. (2) The period after 1991 is characterized by frequent and shorter duration floods due to increased rainstorm. However, land use change in the basin was found intensifying the increased tendency of annual maximum flow after 1991. And (3) under nonstationary environmental conditions, alternative definitions of return period should be adapted. The impacts on curve fitting of flood series showed an overall change of upper tail from "gentle" to "steep," and the design flood magnitude became larger. Therefore, a nonstationary frequency analysis taking account of change point in the data series is highly recommended for future studies.
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| 40. |
- Chen, Xi, et al.
(författare)
-
Simulating the integrated effects of topography and soil properties on runoff generation in hilly forested catchments, South China
- 2010
-
Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 24:6, s. 714-725
-
Tidskriftsartikel (refereegranskat)abstract
- Estimation of runoff components associated with catchment topography and soil properties is critical for planning water resources utilization and evaluating hydrological changes due to artificially induced land surface manipulation. In this study, the modified TOPMODEL by Scanlon et al. (2000) was applied to simulate runoff-generating processes and to separate runoff components in two hilly forested catchments within the Dongjiang Basin of Southeast China. The modified TOPMODEL was improved by integrating an evapotranspiration package with the model algorithms. Influences of catchment topography and soil properties on runoff generation were analysed on the basis of explicit expression of catchment field capacity distribution derived from the topographic index and catchment average field capacity. Study results demonstrate that the model is capable of simulating hydrological processes and separate hydrological components in both hourly and daily time steps. Total runoff generation primarily depends on the effective storage capacity of unsaturated zone. A 50% decrease of the effective storage capacity from 0.22 to 0.11 m over the soil zone leads to a 6.6% increase in total runoff. Topography plays a dominant role in formation of runoff components. When the catchment mean slope increases by 87%, subsurface storm flow could increase by 50% whilst overland flow decreases by 7.5% and baseflow by 6.7%. Vertical changes of soil permeability influence runoff components as well. Decrease of the lower layer hydraulic transmissivity may result in 2-3% increase of overland flow and subsurface storm flow and 5% decrease of baseflow.
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| 41. |
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| 42. |
- Chen, Yongqin David, et al.
(författare)
-
Multiscale streamflow variations of the Pearl River basin and possible implications for the water resource management within the Pearl River Delta, China
- 2010
-
Ingår i: Quaternary International. - : Elsevier BV. - 1040-6182 .- 1873-4553. ; 226:1-2, s. 44-53
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Tidskriftsartikel (refereegranskat)abstract
- Long monthly streamflow series of three control hydrological stations of the Pearl River basin were analyzed by using the scanning t-test and the scanning F-test. Possible implications of the changing properties of streamflow variations for the water resource management of the Pearl River Delta are also discussed. The results indicated that: 1) more complicated changes were observed in terms of the second center moment when compared to the first original moment More significant abrupt changes of the second center moment imply more sensitive response of streamflow stability to climate changes and human activities; 2) abrupt behaviors of the first (second) center moment of the streamflow variations tend to be more sensitive to climate changes and/or human activities in the larger river basin when compared to those in the smaller river basin. These phenomena are attributed to buffering functions of more storage space of longer river channel, and more complicated and longer runoff yield and concentration processes in the river basin of larger drainage area; 3) annual minimum streamflow of the Pearl River basin tends to be increasing. This will be helpful for better human mitigation of the salinity intrusion in dry seasons across the Pearl River Delta. Annual maximum streamflow, when compared to annual minimum streamflow, shows larger-magnitude variability reflected by larger standard deviation, implying unfavorable conditions for flood mitigation in the Pearl River Delta. The results of this paper are of scientific and practical merits for water resource management and sound human mitigation to water hazards across the Pearl River Delta, and also are a good case study for similar researches in other river deltas in the world under the changing environment. (C) 2009 Elsevier Ltd and INQUA. All rights reserved.
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| 43. |
- 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
-
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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| 44. |
- Cheng, Qin-Bo, et al.
(författare)
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Improvement and comparison of likelihood functions for model calibration and parameter uncertainty analysis within a Markov chain Monte Carlo scheme
- 2014
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 519:Part B, s. 2202-2214
-
Tidskriftsartikel (refereegranskat)abstract
- Summary In this study, the likelihood functions for uncertainty analysis of hydrological models are compared and improved through the following steps: (1) the equivalent relationship between the Nash–Sutcliffe Efficiency coefficient (NSE) and the likelihood function with Gaussian independent and identically distributed residuals is proved; (2) a new estimation method of the Box–Cox transformation (BC) parameter is developed to improve the effective elimination of the heteroscedasticity of model residuals; and (3) three likelihood functions—NSE, Generalized Error Distribution with BC (BC-GED) and Skew Generalized Error Distribution with BC (BC-SGED)—are applied for SWAT-WB-VSA (Soil and Water Assessment Tool – Water Balance – Variable Source Area) model calibration in the Baocun watershed, Eastern China. Performances of calibrated models are compared using the observed river discharges and groundwater levels. The result shows that the minimum variance constraint can effectively estimate the BC parameter. The form of the likelihood function significantly impacts on the calibrated parameters and the simulated results of high and low flow components. SWAT-WB-VSA with the NSE approach simulates flood well, but baseflow badly owing to the assumption of Gaussian error distribution, where the probability of the large error is low, but the small error around zero approximates equiprobability. By contrast, SWAT-WB-VSA with the BC-GED or BC-SGED approach mimics baseflow well, which is proved in the groundwater level simulation. The assumption of skewness of the error distribution may be unnecessary, because all the results of the BC-SGED approach are nearly the same as those of the BC-GED approach.
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| 45. |
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| 46. |
- El Tahir, M. El Haj, et al.
(författare)
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Comparison of Methods for Estimation of Regional Actual Evapotranspiration in Data Scarce Regions : Blue Nile Region, Eastern Sudan
- 2012
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Ingår i: Journal of hydrologic engineering. - 1084-0699 .- 1943-5584. ; 17:4, s. 578-589
-
Tidskriftsartikel (refereegranskat)abstract
- Remote sensing techniques enable estimation of regional evapotranspiration (AE) over large areas instead of point calculation and it also saves resources otherwise invested in monitoring instruments. The aim of this paper is to compare actual evapotranspiration (AE) estimated using the remote sensing method, the modified Thornthwaite water balance method (WB), and the complementary relationship method (GG) in the Blue Nile, Eastern Sudan. The satellite based Surface Energy Balance Algorithm for Land (SEBAL) model is used with Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data to estimate daily AE. The WB method is used as benchmark data when comparing the three methods. The results show that: (1) In the dry season (November-April), the SEBAL and GG methods give higher values than the WB method; (2) during the rainy season (May-October), the three methods give comparable results, where there is better agreement between SEBAL and WB than between GG and WB; (3) the spatial distribution pattern of monthly AE estimated by the SEBAL method during the dry season is mainly determined by the land-use type and whether there is irrigation taking place or not. However, in the rainy season, the spatial distribution pattern of monthly AE is mainly determined by the seasonal spatial distribution pattern of rainfall in the region.
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| 47. |
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| 48. |
- Fuentes-Andino, Diana, 1984-, et al.
(författare)
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Event and model dependent rainfall adjustments to improve discharge predictions
- 2017
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 62:2, s. 232-245
-
Tidskriftsartikel (refereegranskat)abstract
- Most conceptual rainfall–runoff models use as input spatially averaged rainfall fields which are typically associated with significant errors that affect the model outcome. In this study, it was hypothesised that a simple spatially and temporally averaged event-dependent rainfall multiplier can account for errors in the rainfall input. The potentials and limitations of this lumped multiplier approach were explored by evaluating the effects of multipliers on the accuracy and precision of the predictive distributions. Parameter sets found to be behavioural across a range of different flood events were assumed to be a good representation of the catchment dynamics and were used to identify rainfall multipliers for each of the individual events. An effect of the parameter sets on identified multipliers was found; however, it was small compared to the differences between events. Accounting for event-dependent multipliers improved the reliability of the predictions. At the cost of a small decrease in precision, the distribution of identified multipliers for past events can be used to account for possible rainfall errors when predicting future events. By using behavioural parameter sets to identify rainfall multipliers, the method offers a simple and computationally efficient way to address rainfall errors in hydrological modelling.
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| 49. |
- Fuentes-Andino, Diana, 1984-
(författare)
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Flood Hazard Assessment in Data-Scarce Basins : Use of alternative data and modelling techniques
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Flooding is of great concern world-wide, causing damage to infrastructure, property and loss of life. Low-income countries, in particular, can be negatively affected by flood events due to their inherent vulnerabilities. Moreover, data to perform studies for flood risk management in low-income regions are often scarce or lacking sufficient quality.This thesis proposes new methodologies and explores the use of unconventional sources of information in flood hazard assessment in areas where the quantity or sufficient quality of traditional hydrometrical data are lacking. One method was developed to account for errors in spatially averaged rainfall, from a sparse rain-gauge network, used as input to a rainfall-runoff model. A spatially-averaged and event-dependent rainfall depth multiplier led to improvements of the hydrographs at calibration. And by using a distribution of the multiplier, identified from previous events in the catchment, improvement in predictions could also be obtained.A second method explored the possibility of reproducing an unmeasured extreme flood event using a combination of models, post-event data, precipitation and an uncertainty-analysis framework. This combination allowed the identification of likelihood-associated parameter sets from which the flood hazard map for the extreme event could be obtained.A third and fourth study made at the regional scale explored the value of catchment similarities, and the effects of climate on the hydrological response of catchments.Flood frequency curves were estimated for 36 basins, assumed ungauged, using regional information of short flow records, and local information about the frequency of the storm. In the second regional study, hydro-climatic information provided great value to constrain predictions of series of daily flow from a hydrological model.Previously described methods, used in combination with unconventional information within an uncertainty analysis, proven to be useful for flood hazard assessment at basins with data limitations. The explored data included: post-event measurements of an extreme flood event, hydro-climate regional information and local precipitation data. The methods presented in this thesis are expected to support development of hydrological studies underpinning flood-risk reduction in data-poor areas.
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| 50. |
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