| 1. |
- An, Dong, et al.
(författare)
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APPLICATION OF DIFFERENT HYDROLOGIC MODELS IN FLASH FLOODS SIMULATION
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, the flash flood occurs frequently and intensively. It has become a world-wide focus in the field of disaster prevention and mitigation. The flash flood critical rainfall determination method, flash floods forecasting model and experience forecasting method are the most commonly used methods. This study focused on the application of hydrological models for flash floods simulation.The research has adopted 7 flood forecasting models with different types and structures: topography-based API model, Xinanjiang Model, Xinanjiang Model with excess infiltration, Sacramento Model, IHACRES, BP-KNN Model and TOPKAPI. Every model will be applied in semi-humid and semi-arid watersheds Banqiao, Maduwang, Zhidan in China, which have high risk of flash floods. According to the characteristic of flash floods, a set of evaluation for the simulation results isput forward. The purpose is to find out one or several hydrological models fit for research area and to provide reference for future related research.Combining with topography and runoff characteristics of each watershed, the paper collected and compared various simulation results of different models. Results indicated that models performed varies in semi-humid and semi-arid basins because of the complicated runoff mechanism in these areas. Among the conceptual hydrological models, Xinanjiang Model with excess infiltration performed better than the models with single runoff mechanism. TOPKAPI has a better simulation results than the lumped models topography-based API model and IHACRES. However, it has higher data requirements. BP-KNN model contains no physical mechanism and performed best in calibration period, but the accuracy falls greatly in validation period.
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| 2. |
- An, Dong, et al.
(författare)
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Evidence of climate shift for temperature and precipitation extremes across Gansu Province in China
- 2020
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Ingår i: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 1434-4483 .- 0177-798X. ; 139:3-4, s. 1137-1149
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Tidskriftsartikel (refereegranskat)abstract
- Temperature and precipitation extremes are the dominant causes of natural disasters. In this study, seven indices of extreme temperature and precipitation events in Gansu Province, China, were analysed for the period 1961–2017. An abrupt climate shift was recorded during 1980–1981. Thus, the study period was divided into a preshift (before the climate shift) period 1961–1980 and an aftshift (after the climate shift) period 1981–2017. Comparison of mean extreme indices for preshift and aftshift periods was performed for the purpose of exploring possible increasing/decreasing patterns. Generalized extreme value (GEV) distribution was applied spatially to fit the extreme indices with return periods up to 100 years for preshift/aftshift periods. Singular value decomposition (SVD) was adopted to investigate possible correlation between the extreme climate events and indices of large-scale atmospheric circulation. The results indicate that changes in mean and return levels between the preshift and aftshift periods vary significantly in time and space for different extreme indices. Increase in extreme temperature regarding magnitude and frequency for the aftshift period as compared with the preshift period suggests a change to a warmer and more extreme climate during recent years. Changes in precipitation extremes were different in southern and northern parts of Gansu. The precipitation extremes in the north have increased that can result in more serious floods and droughts in the future. SVD analyses revealed a complex pattern of correlation between climate extremes and indices of large-scale atmospheric circulation. Strengthening of westerlies and weakening of the south summer monsoon contribute to the complex changing patterns of precipitation extremes. Results in this study will contribute to disaster risk prevention and better water management in this area.
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| 3. |
- Bengtsson, Lars, et al.
(författare)
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A decision support system for watershed flood design purpose in China
- 1995
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Ingår i: Proceedings of the Second International Conference on Hydro-science and Engineering. ; , s. 982-989
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Konferensbidrag (refereegranskat)abstract
- The paper presents a computer-based decision support system for watershed planning andflood design purposes including a conceptual rainfall-runoff model. The software package uses up-to-date programing techniques in Windows environment which makes it flexible to handle, adaptableto new areas, and easy to test for different design criteria. The package is suitable for designproblems in small as well as in large river basins. The case study area is the Hongru River basin incentral China where an application of the package with emphasize on rainfall-runoff modeling ispresented.
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| 4. |
- du, Yiheng, et al.
(författare)
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Integrated large‐scale circulation impact on rainy season precipitation in the source region of the Yangtze River
- 2020
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Ingår i: International Journal of Climatology. - : Wiley. - 1097-0088 .- 0899-8418. ; 40:4, s. 2285-2295
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Tidskriftsartikel (refereegranskat)abstract
- Monthly precipitation data at regular grids of 0.5° × 0.5° derived from observations during June–August 1961–2016 were used to reveal characteristics of large‐scale circulations associated with rainy season precipitation over the source region of the Yangtze River (SRYR). The integrated impact of major influencing circulation patterns was examined by principal component analysis and composites. Results showed that the first rainy season precipitation mode associates with the Southern Oscillation Index (SOI) and the Pacific Decadal Oscillation (PDO), explaining 64% of spatial and temporal rainy season precipitation variance in the region. Composites of precipitation pattern under different phases of SOI and PDO revealed that the effect of PDO on precipitation varies with the SOI phase. When out of phase with the SOI, PDO‐induced precipitation anomalies are magnified. When they are in phase, anomalies weaken or even disappear. Composites of moisture flux patterns show that large‐scale atmospheric circulation affects the strength of westerlies that transport moisture to the study area and formation of convergence. In coming decades, the PDO is likely to continue in a negative phase with La Niña (positive SOI) events, implying more precipitation during the rainy season. Consequently, this knowledge can be used to improve decision making regarding water supply and flood risk management in the SRYR.
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| 5. |
- du, Yiheng, et al.
(författare)
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Multi-Space Seasonal Precipitation Prediction Model Applied to the Source Region of the Yangtze River, China
- 2019
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Ingår i: Water. - 2073-4441. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- This paper developed a multi-space prediction model for seasonal precipitation using a high-resolution grid dataset (0.5° × 0.5°) together with climate indices. The model is based on principal component analyses (PCA) and artificial neural networks (ANN). Trend analyses show that mean annual and seasonal precipitation in the area is increasing depending on spatial location. For this reason, a multi-space model is especially suited for prediction purposes. The PCA-ANN model was examined using a 64-grid mesh over the source region of the Yangtze River (SRYR) and was compared to a traditional multiple regression model with a three-fold cross-validation method. Seasonal precipitation anomalies (1961–2015) were converted using PCA into principal components. Hierarchical lag relationships between principal components and each potential predictor were identified by Spearman rank correlation analyses. The performance was compared to observed precipitation and evaluated using mean absolute error, root mean squared error, and correlation coefficient. The proposed PCA-ANN model provides accurate seasonal precipitation prediction that is better than traditional regression techniques. The prediction results displayed good agreement with observations for all seasons with correlation coefficients in excess of 0.6 for all spatial locations.
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| 6. |
- Du, Yiheng, et al.
(författare)
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SPATIAL VARIATION OF PRECIPITATION IN THE HUANG-HUAI-HAI RIVER BASIN UNDER CLIMATE CHANGE
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Huang-Huai-Hai River Basin covers the major political and socioeconomic centers of China. Thus, flood protection and economic development by sustainable water supply are important. Due to this, it is imperative to study distribution and variation of precipitation characteristics under climate change. As hydrological observations are limited, scholars have done more research on daily, monthly, and annual data but less research on hourly data. Meanwhile, short-term extreme precipitation is the main cause of urban flooding and related rural disasters and analysis of these patterns can reflect trend changes of extreme hydrological events. This paper uses daily and hourly data from six rainfall stations in the Huang-Huai-Hai Basin representing the precipitation characteristics over the basin. A variety of statistical methods is used to analyze the observations. Intensity-duration curves are used for extreme value characteristics. The results show that the annual precipitation amount is increasing in the northern area of the Huang-Huai-Hai Basin. Similarly, the southern areas display a decreasing trend. The annual effective rainfall intensity shows an overall increasing trend. Analyzing the extreme values of precipitation in the basin shows that short-term rainfall intensity displays both increasing and decreasing trends depending on the latitude. Thus, there is no general trend but instead changes in rainfall climate that is spatially dependent. This may be connected to spatial changes in the occurring East-Asian monsoon that is influencing the general rainfall climate in the area.
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| 7. |
- Khadka, Jeevika, et al.
(författare)
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Using HEC-HMS and HEC-RAS Models for Rainfall-Runoff Simulation and Flood Inundation Mapping: Case Studies from Nepal and Sweden
- 2018
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Konferensbidrag (refereegranskat)abstract
- Understanding catchment behaviour through rainfall-runoff models allows decision makers for proper planning and operation in context of flood risk management. However accurate rainfall-runoff and flood modelling at high spatio-temporal resolutions still remains a significant challenge in any hydrologic and hydraulic studies. This study seeks to develop Hydrologic Engineering Centre’s Hydrologic Modelling System (HEC-HMS) and Hydrologic Engineering Centre’s River Analysis System (HEC-RAS) models to simulate the effects of rainfall on surface runoff and generate flood inundation maps for Kankai and Kävlinge river. The Kankai River is rainfed perennial river of eastern Nepal which recieves concentrated precipitation mostly during summer months. Whereas Kävlinge river is situated in the southern part of Sweden in Skåne county and has temperate climate with precipitation, mostly in the form of snow occurring throughout the year. Being in a complete different hydrological and geographical setting, model parameters of these catchment models have varied significance level to modelling methods, which have been critically analyzed here through sensitivity analysis. Using HEC-RAS 1D model, flood inundation maps for 100-year flood are also generated and their potential impacts across the adjoing area have been discussed with possible recommendation on flood management strategies for each region.
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| 8. |
- Liu, Fang, et al.
(författare)
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Synthesis of Reduced Graphene Oxide over CeO2 nanowires for hydrogen production from photocatalytic water decomposition
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Energy deficiency is currently an emergency issue in society. Hydrogen has been considered an environment-friendly energy carrier with high energy capacity. Hence, in this study a simple and effective method was used to synthesize Cerium-oxide Nanowires doped with Reduced Graphene Oxide (CNW-RGO) via the hydrothermal reaction as hydrogen evolving catalysts. Results showed that the composite photocatalyst demonstrated obvious absorption in the visible-light region and the highest hydrogen production was 7.14 mmol g−1 with CNW-RGO of 4 wt.% RGO. So, the as-prepared CNW-RGO was favorable for charge separation and light harvesting. In addition, this study is helpful not only for photocatalytic water splitting of hydrogen production but also for practical application during waste to energy conversion which provides new insights.
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| 9. |
- Luo, Ziteng, et al.
(författare)
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Quantifying Characteristics of Fine Roots Contributing to Water Flow Process in Rocky Mountainous Area Using Dye Tracer Experiment and Monolith Method
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Root channel serve as one major type of pathway for water flow in forest soil. In this paper, we combined a dye tracer experiment and a monolith method to distinguish the fine roots (0 < d ≤ 5 mm) that served as preferential water flow pathways in rocky mountainous areas. The characteristics of these types of roots among different soil layer and different root diameter were discussed. In this modified method, two typical forest species in Mount JiuFeng were selected. One was broad-leaved forest (BF) with Quercus variabilis, and the other one was needle-leaved forest (NF) afforested with Platycladus orientalis (L.) Franco. Monoliths were taken from horizontal profiles along with the soil depth after the dye tracer experiment was conducted. Fine roots contributing to water flow processes were defined as being dyed by the colour of the tracer and selected from the soil. Our results showed that not all of the fine roots can contribute to water flow, even in the soil layer of 0 to 10 cm. In the soil layer of 0 to 30 cm, the proportion of fine roots with 0 < d ≤ 1 mm made more than approximately 50% contributions to water flow in every soil layer. Meanwhile, the share of stained fine roots with a diameter of 1 < d ≤ 5 mm had an increased trend along soil depth, which was more clear in NF than in BF.
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| 10. |
- Yang, Xiaoliu, et al.
(författare)
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Institutional Arrangement for Integrated River Basin Management
- 2016
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- This study concerns the management functions, institutional and legal frameworks to foster IRBM in the Yangtze River Basin. It is implemented as part of the EU China River Basin Management Programme funded by the EU.The overall objective of the study is to contribute to an enabling framework of policies, legislation and institutions that will promote IRBM in China and assist the government to harmonise social and economic development and water and environmental protection within the Yangtze River Basin. Specifically, the study will provide the CWRC with a better basis for informed decisions on adjustment of its organization, responsibilities and management functions to be incorporated in the Yangtze River Master Plan. Based on stakeholder mapping an assessment has been made to characterise the present situation of water resources management in China and provide direction for future changes. The assessment found that 1) China has established a legal framework supporting water management in a river basin context, 2) plans embodying IRBM are drafted at national, river basin and provincial levels, and 3) the existing funding of water management is dominated by government investment. A diagnosis and evaluation of the management functions of the CWRC is presented with focus on gaps and overlaps providing recommendations for a more effective governance structure in accordance with internationally accepted principles that have emerged during the past 10 years. The diagnosis is based on key informant interviews and questionnaires and indicated that 1) Chinese legislation enables decentralized river basin management, 2) river basin, regional and provincial management functions are not clearly defined, 3) some management functions of the CWRC are difficult to implement due to discrepancies between authority and responsibilities 4) there are no efficient consultation and coordination mechanisms among stakeholders within the river basin, 5) the implementation of IRBM lacks support of provincial and local authorities, and 6) the CWRC sees stakeholder participation as the key to better river basin governance. Water management in the Yangtze River Basin has been analysed with the Rhine River, Danube River, France and the European Union as reference. The comparisons indicate that 1) legislation or formal agreements between different administrative units, nations or provinces, are required for efficient cooperation, 2) an inter-provincial river basin organization is an ideal platform to promote IRBM and resolve conflicts between nations or provinces within a river basin, 3) political governance and technical support should be separated, 4) stakeholder participation is imperative for efficient IRBM, and 5) pollution of the Yangtze River is at risk of increasing while the Rhine River and to some extent the Danube River have passed a turning point (top of Kuznet’s curve), where pollution is effectively managed and declining.Strategically institutional arrangements for IRBM will be conditional on central government initiative. At the national level four initiatives are proposed as umbrella for basin level action, 1) a national water framework plan to be inspired by the EU Water Framework Directive (WFD), 2) an assessment of basin institutional arrangements inspired by the Rhine and Danube rivers, 3) an assessment of provincial institutions inspired by France and 4) an assessment of legal efficiency taking the EU WFD as benchmark.In close consultation with the CWRC an action plan to foster IRBM in the Yangtze River Basin has been formulated in terms of legislation, institutions, capacity building, financing, information disclosure and stakeholder participation.The principal recommendations of the study are:1) Water Law to be amended or supplemented with legislation, which clearly defines the division of responsibilities between the national, river basin and provincial level authorities.2) A National Water Resource Commission to be established to strengthen cross-sectorial coordination and cooperation and mitigate the current fragmentation of responsibilities, especially the overlapping responsibilities of the Ministry of Water Resources (MWR) and Ministry of Environmental Protection (MEP) in water pollution management and of the Ministry of Water Resources and Ministry of Land and Resources in groundwater management.3) Reform of the CWRC may take one of three basic models: Unified management as branch of central government, essentially the current structure; Coordinated management governed by stakeholders, including central government; Autonomous enterprise authorised by central government.4) Institutions and responsibilities for water resources management and water service delivery to be separated and clearly defined.5) River basin commissions to be assigned responsibility for coordination of water resources management at basin scale and provinces for implementation in accordance with overall management objectives.6) River basin commissions to be responsible for operation of multipurpose infrastructure and bulk water supply.7) Provinces and municipalities to be the responsible for management and delivery of water supply and sanitation services in both rural and urban areas.8) Cost recovery for water resources management, bulk water supply, water supply and sanitation services to be scaled up and serve as water demand management tool as well as a significant source of funding for infrastructure development.9) National Water Resources Council to be set up at national level to supervise and regulate water resources management and services delivery by benchmarking of river basin commissions, provincial administrations and water utility companies using clear and well defined performance indicators.
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