Geo-Spatial Analysis in Hydrology

Geo-spatial analysis has become an essential component of hydrological studies to process and examine geo-spatial data such as hydrological variables (e.g., precipitation and discharge) and basin characteristics (e.g., DEM and land use land cover). The advancement of the data acquisition technique helps accumulate geo-spatial data with more extensive spatial coverage than traditional in-situ observations. The development of geo-spatial analytic methods is beneficial for the processing and analysis of multi-source data in a more efficient and reliable way for a variety of research and practical issues in hydrology. This book is a collection of the articles of a published Special Issue Geo-Spatial Analysis in Hydrology in the journal ISPRS International Journal of Geo-Information. The topics of the articles range from the improvement of geo-spatial analytic methods to the applications of geo-spatial analysis in emerging hydrological issues. The results of these articles show that traditional hydrological/hydraulic models coupled with geo-spatial techniques are a way to make streamflow simulations more efficient and reliable for flood-related decision making. Geo-spatial analysis based on more advanced methods and data is a reliable resolution to obtain high-resolution information for hydrological studies at fine spatial scale

Development and application of a non-point sources pollution model for hydrological processes and nutrient loadings in the Xitiaoxi catchment in South China

This dissertation describes the hydrology and non-point source pollution of the humid, subtropical Xitiaoxi catchment in the south-eastern China and comprises a hydrologic and nutrient dynamics simulation there. The study presents at first an interpretation of hydrological processes influenced by anthropological activities. Beyond that, it deals with nutrient cycles in both arable land with an intensive farming system and a natural forest dominated catchment

Proceedings of the 2021 DigitalFUTURES

This open access book is a compilation of selected papers from 2021 DigitalFUTURES—The 3rd International Conference on Computational Design and Robotic Fabrication (CDRF 2021). The work focuses on novel techniques for computational design and robotic fabrication. The contents make valuable contributions to academic researchers, designers, and engineers in the industry. As well, readers encounter new ideas about understanding material intelligence in architecture

Virtual Worlds and Conservational Channel Evolution and Pollutant Transport Systems (Concepts)

Many models exist that predict channel morphology. Channel morphology is defined as the change in geometric parameters of a river. Channel morphology is affected by many factors. Some of these factors are caused either by man or by nature. To combat the adverse effects that man and nature may cause to a water system, scientists and engineers develop stream rehabilitation plans. Stream rehabilitation as defined by Shields et al., states that restoration is the return from a degraded ecosystem back to a close approximation of its remaining natural potential [Shields et al., 2003]. Engineers construct plans that will restore streams back to their natural state by using techniques such as field investigation, analytical models, or numerical models. Each of these techniques is applied to projects based on specified criteria, objectives, and the expertise of the individuals devising the plan. The utilization of analytical and numerical models can be difficult, for many reasons, one of which is the intuitiveness of the modeling process. Many numerical models exist in the field of hydraulic engineering, fluvial geomorphology, landscape architecture, and stream ecology that evaluate and formulate stream rehabilitation plans. This dissertation will explore, in the field of Hydroscience , the creation of models that are not only accurate but also span the different disciplines. The goal of this dissertation is to transform a discrete numerical model (CONCEPTS) into a realistic 3D environment using open source game engines, while at the same time, conveying at least the equivalent information that was presented in the 1D numerical model

Changes of water clarity in large lakes and reservoirs across China observed from long-term MODIS

Water clarity is a well-established first-order indicator of water quality and has been used globally by water regulators in their monitoring and management programs. Assessments of water clarity in lakes over large temporal and spatial scales, however, are rare, limiting our understanding of its variability and the driven forces. In this study, we developed and validated a robust Secchi disk depth (ZSD) algorithm for lakes across China based on two water color parameters, namely Forel-Ule Index (FUI) and hue angle α, retrieved from MODIS data. The MODIS ZSD model shows good results when compared with in-situ measurements from 17 lakes, with a 27.4% mean relative difference (MRD) in the validation dataset. Compared with other empirical ZSD models, our FUI and α-based model demonstrates improved performance and adaptability over a wide range of water clarity and trophic states. This algorithm was subsequently applied to MODIS measurements to provide a comprehensive assessment of water clarity in large lakes (N = 153) across China for the first time. The mean summer ZSD of the studied lakes between 2000 and 2017 demonstrated marked spatial and temporal variations. Spatially, the ZSD of large lakes presented a distinct spatial pattern of “high west and low east” over China. This spatial pattern was found to be associated with the significant differences in lake depth and altitude between west and east China while China's population, GDP, temperature, and precipitation distribution have also contributed to a certain extent. Temporally, the ZSD of most lakes increased during this period, with an overall mean rate of 3.3 cm/yr for all lakes. Here, 38.6% (N = 59) of the lakes experienced a significant increase in their ZSD value during the past 18 years while only 8.5% (N = 13) showed a significant decreasing trend. Significant increases in lake ZSD were observed in west China, which were found to correlate with the increase of air temperature and lake surface area. This is possibly a response of the lakes in west China to climate change. In the lake systems of east China, which are predominately used as a drinking water source, the increase in lake ZSD was found to be strongly correlated with changes in local GDP (gross domestic production), NDVI (normalized difference vegetation index) and lake surface area, suggesting a combined effect of the implemented management practices and climatic variability. The results of this study provide important information for water quality conservation and management in China, and also highlight the value of satellite remote sensing in monitoring water quality over lakes at a large scale and long-term

Analyses and quantification of modelling uncertainties in streamflow simulations with applications to two catchments: the small lowland Kielstau basin in Germany and the mesoscale mountainous XitaoXi basin in China

Models are the primary way to predict the values of various system performance indicators in hydrologic researches. The usefulness of any model depends in part on the accuracy and reliability of its output. This PhD thesis presents the development of a methodological framework to analyse the impacts of three sources of modelling uncertainty (namely model structure error, parameter estimation and input data resolution) on streamflow simulation and to quantify the associated modelling uncertainties. The case study includes two catchments: the small lowland Kielstau catchment (51.5 km²) in Northern Germany and the mesoscale mountainous XitaoXi basin (2271 km²) in Southern China. The river discharge simulation is completed through the KIDS model (Kielstau Discharge Simulation model, Hörmann et al. 2007; Zhang et al. 2007) using PCRaster modelling language (Van Deursen 1995; Wesseling et al. 1996). The main criterion of model output performance is the Nash-Sutcliffe efficiency (Nash & Sutcliffe 1970). The structural uncertainty is assessed by developing a set of model ensembles with increasing model complexity. The modelling uncertainty induced by parameter estimation is investigated through Monte Carlo based sampling strategy in the framework of SUFI-2 analysis routine (Sequential Uncertainty Fitting, ver. 2, Abbaspour et al. 2004). The uncertainty of changing input data resolutions is analysed by aggregating grid cells. For each of them, a method has been developed to quantify the inherent modelling uncertainties with two statistical measures: R factor and P factor (Abbaspour et al. 2004; Schuol & Abbaspour 2006). Considering the two different catchments of Kielstau and XitaoXi, investigating the effects of model structure on model performance helps to identify the most appropriate model adapted to local hydrological features. Also, result comparisons for the parameter estimation and resolution impacts are conducted between the two basins. It is shown that the uncertainties induced by the different model structures tested in this study are much higher than the ones induced by parameter calibration and input data resolutions using a fixed hydrological model structure. However, modelling uncertainties from different sources are not independent of each other, they can interact in various ways and it is hard to calculate them separately. All the uncertainties obtained here refer to the overall modelling uncertainty while focusing on one aspect of influencing sources. It indicates that model output and modelling efficiency highly depend on tradition and empirical assumptions concerning the choice of model structures, parameter estimation, and the selection of appropriate resolution level. This study may provide a methodology to investigate these issues in the study basins

Fluid mixing processes in enclosed shallow water flows and applications

PhD ThesisThis work develops a numerical modelling tool to investigate and better understand the fluid mixing processes in enclosed or semi-closed shallow water flows. The integrated fluid mixing modelling framework consists of two components, i.e. a shallow flow model for predicting hydrodynamics and a particle-tracking model for calculating the trajectories of passive particles released in the water bodies. The well-defined analysis method in dynamical system theory, Finite Time Lyapunov Exponent (FTLE), is used to extract the Lagrangian Coherent Structures (LCSs) to provide insight of the nonlinear particle dynamics in the time-dependant environmental shallow water flows under consideration. The fluid mixing modelling and analysis framework is firstly used to study the mixing properties of an oscillating environmental flow driven by two inflows and one outflow in an idealised shallow basin. The Eulerian velocity field of the flow is first predicted using the shallow flow model, which is then used by the particle-tracking model to calculate the particle trajectories and describe the transport and mixing properties of the inflows/outflow driven shallow water flow. The particle dynamics is found to be controlled by a dimensionless parameter and fluid mixing changes from regular to chaotic when the magnitude of the parameter increases. The integrated numerical modelling framework is then applied to reproduce the wind-driven flow hydrodynamics and investigate the corresponding fluid mixing in Taihu, one of the largest fresh water lakes in China, for continuous 12 months. The predicted flow field, which is used to drive the particle dynamics, compares favourably with the field measurements. The transport and mixing properties of the lake are analysed by calculating the FTLE and identifying the LCSs, clearly revealing the stagnant and well-mixing zones of the water body. The understanding of the underlying fluid mixing mechanism of the lake is also improved. Through successful application to one idealised and one realistic case studies, the potential of the current integrated numerical modelling framework is confirmed for analysing fluid mixing in (semi-)enclosed water bodies.‘The Henry Lester Trust Limited’ and ‘The Great Britain-China Educational Trust’, for their financial supporting in the third and fourth year of my progra

Usability-enhanced coordination design of geovisualisations to communicate coastal flood risk information

For at least two millennia and probably much longer, the traditional vehicle for communicating geographical information to end-users has been the map. With the advent of computers, the means of both producing and consuming maps have radically been transformed, while the inherent nature of the information product has also expanded and diversified rapidly. This has given rise in recent years to the new concept of geovisualisation (GVIS), which draws on the skills of the traditional cartographer, but extends them into three spatial dimensions and may also add temporality, photorealistic representations and/or interactivity. Demand for GVIS technologies and their applications has increased significantly in recent years, driven by the need to study complex geographical events and in particular their associated consequences and to communicate the results of these studies to a diversity of audiences and stakeholder groups. GVIS has data integration, multi-dimensional spatial display advanced modelling techniques, dynamic design and development environments and field-specific application needs. To meet with these needs, GVIS tools should be both powerful and inherently usable, in order to facilitate their role in helping interpret and communicate geographic problems. However no framework currently exists for ensuring this usability. The research presented here seeks to fill this gap, by addressing the challenges of incorporating user requirements in GVIS tool design. It starts from the premise that usability in GVIS should be incorporated and implemented throughout the whole design and development process. To facilitate this, Subject Technology Matching (STM) is proposed as a new approach to assessing and interpreting user requirements. Based on STM, a new design framework called Usability Enhanced Coordination Design (UECD) is ten presented with the purpose of leveraging overall usability of the design outputs. UECD places GVIS experts in a new key role in the design process, to form a more coordinated and integrated workflow and a more focused and interactive usability testing. To prove the concept, these theoretical elements of the framework have been implemented in two test projects: one is the creation of a coastal inundation simulation for Whitegate, Cork, Ireland; the other is a flooding mapping tool for Zhushan Town, Jiangsu, China. The two case studies successfully demonstrated the potential merits of the UECD approach when GVIS techniques are applied to geographic problem solving and decision making. The thesis delivers a comprehensive understanding of the development and challenges of GVIS technology, its usability concerns, usability and associated UCD; it explores the possibility of putting UCD framework in GVIS design; it constructs a new theoretical design framework called UECD which aims to make the whole design process usability driven; it develops the key concept of STM into a template set to improve the performance of a GVIS design. These key conceptual and procedural foundations can be built on future research, aimed at further refining and developing UECD as a useful design methodology for GVIS scholars and practitioners

Development of the Community Water Model (CWatM v1.04) – a high-resolution hydrological model for global and regional assessment of integrated water resources management

We develop a new large-scale hydrological and water resources model, the Community Water Model (CWatM), which can simulate hydrology both globally and regionally at different resolutions from 30 arcmin to 30 arcsec at daily time steps. CWatM is open source in the Python programming environment and has a modular structure. It uses global, freely available data in the netCDF4 file format for reading, storage, and production of data in a compact way. CWatM includes general surface and groundwater hydrological processes but also takes into account human activities, such as water use and reservoir regulation, by calculating water demands, water use, and return flows. Reservoirs and lakes are included in the model scheme. CWatM is used in the framework of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP), which compares global model outputs. The flexible model structure allows for dynamic interaction with hydro-economic and water quality models for the assessment and evaluation of water management options. Furthermore, the novelty of CWatM is its combination of state-of-the-art hydrological modeling, modular programming, an online user manual and automatic source code documentation, global and regional assessments at different spatial resolutions, and a potential community to add to, change, and expand the open-source project. CWatM also strives to build a community learning environment which is able to freely use an open-source hydrological model and flexible coupling possibilities to other sectoral models, such as energy and agriculture