Topics in Magnetic Resonance Imaging

The damage of geomembranes in dikes can result in leakage. In order to investigate the efficacy of heat tracing in the detection of geomembrane defects, a series of laboratory experiments were conducted utilising a self-made 2D sand trough and temperature sensors. The heat tracing response of geomembrane defects was evaluated. The findings indicate that the temperature distribution within the dike, resulting from geomembrane defects, exhibits a comparable spatial-temporal pattern to that of the seepage field. Furthermore, the heat tracing response is discernible. A flow-heat coupling model (FHCM) was constructed based on the heat transfer theory of porous media and the saturated-unsaturated seepage theory. The accuracy of the FHCM was tested by combining the laboratory experiment results. The The numerical simulation results show that the superposition of multiple geomembrane defects results in an acceleration of leakage. In order to reduce the amount of debugging work required for model parameters, the Morris method was employed to analyse the global sensitivity of six parameters within the FHCM. It was determined that the parameter exhibiting the greatest sensitivity is hydraulic conductivity. This work provides a reference for the wide application of heat tracing technique.

Water resources have been and continue to be of vital significance to every nation and country. They have been the focus of institutional management and legal regulation for centuries. The purpose of this paper is to provide the local and international community with a summary of the institutional and legal framework of the water sector in the Republic of Kosovo. In this regard, the institutional and legal framework are required for good administration, water rights division, and other functions related to water preservation and rational use. Water administration is organized at two levels in the Republic of Kosovo: central and local, with jurisdiction based on the Constitution of Kosovo as the highest legal act and acts derived from the constitution for the regulation of specific areas, including the water sector. As a result, the paper is divided into two major sections that examine the regulation and its impact on well administration and the use of national water resources in Kosovo.

In this study, the electrical conductivity (EC) of Ekbatan reservoir water in Hamedan Province (Iran) under the impact of thermal stratification changes and water temperature for seven scenarios of reducing inflow and outflow has been assessed using CE-QUAL-W2. Results showed that the highest and lowest EC is related to the scenarios of 10 and 30% reduction of outflow, respectively. Therefore, the EC largely depends on discharge, and this shows that policies of controlling the outflow can improve and reduce the salinity in water and soil. In autumn and winter, complete mixing has occurred; thermal stratification has begun in the middle of spring and continues until the end of summer. The highest EC was observed before the occurrence of thermal stratification and the lowest EC was observed at the end of the thermal stratification phenomenon. The lowest EC related to the fourth scenario is equal to 0.1 S/m occurred in the spring, and the highest value related to the second scenario is equal to 0.2 S/m and occurred in winter. The degree of EC sensitivity in relation to temperature changes is higher than that related to flow changes in the reservoir.

Since the operation of the Three Gorges Dam, the mid-channel bars (MCBs) in the Middle Yangtze River (MYR) experienced significant deformation, which is crucial to the stability of river regime. However, a systematic understanding of MCB’s morphodynamics and their linkage to upstream damming still remains largely unknown. Therefore, Landsat images were collected to perform an analysis of MCB’s deformation in the MYR. The following conclusions are obtained: (i) the total exposed area of MCBs presented a decreasing trend owing to upstream damming; moreover, the shrinking degree decreased in the longitudinal direction; (ii) the process of MCB’s deformation was consistent with the process of channel degradation during the dam-operation period (erosion, slight erosion and strong erosion); (iii) the deformation of MCBs is mainly attributed to the altered flow-sediment conditions. It can be found that the magnitude of sediment transport capacity changed slightly after the upstream damming, but the concentration of suspended sediment was greatly reduced, which resulted in a general erosion trend of MCBs; moreover, the sediment concentration recovered owing to channel degradation, and the differences between sediment transport capacity and suspended sediment concentration decreased along the MYR, which made the dam effect generally diminish in the longitudinal direction.

Hydraulic jumps frequently occur in natural river channels, impeding the movement of gravel particles within water flow. The sediment deposited in the jump region forms a sedimentary bar that moves upstream pushing against the hydraulic jump, and causing surges in upstream water levels potentially resulting in flood disasters. Hydraulic conditions and particle properties are pivotal in the hydraulic jump process. This study investigates the impact of these factors on the retrograde velocity of hydraulic jumps through experimental model tests. The retrograde movement of hydraulic jumps was captured through a high-definition camera and data acquisition system, enabling the systematic analysis of quantitative relationships between hydraulic conditions, particle properties, and retrograde velocity. The study identifies several significant factors, contributing to an increase in retrograde velocity: an elevated ratio of upstream to downstream Froude numbers, a reduction in inflow discharge, an increase in particle size, and intensified sediment supply. Furthermore, the study proposes a simple empirical formula for calculating hydraulic jump retrograde velocity, offering crucial insights into water-sand interactions in diverse water flows. These findings are indispensable for mitigating flash floods and sediment disasters in mountainous environments.

The evolution of the bar-pool configurations in response to the upstream damming has significant impacts on channel regulations, navigations, water intakes and protection projects. Herein, this paper reports and analyses the evolution of bar-pool configurations in the bends along the Lower Jingjiang Reach (LJR) after the impoundment of the Three Gorge Dam (TGD), which is distinguished from the natural evolution of the bends. The main factors to the different adjustments of bar-pool configurations are the changes in incoming flow and sediment regime during pre- and post-TGD periods. To capture the changes in the bar-pool configurations, we have presented a new cross-sectional geometrical characteristic - relative lateral distance of the centroid (RLDC). RLDC has close relations with incoming sediment coefficient (i.e. incoming discharge divided by suspended sediment concentration during flood season). RLDC is better than the conventional cross-sectional geometrical characteristic (e.g. width to depth ratio) to indicate the bar-pool configurations of the downstream of the large dam projects. Based on the delayed response model, the values of RLDC in the bends of the LJR are related to the previous 4-6 years’ incoming sediment coefficient, and the correlation coefficient is about 0.90. RLDC is expected to capture the variations of bar-pool configurations in the bends downstream of the large dam project.

Labyrinth weirs are commonly used hydraulic structures to increase discharge efficiency in free-overflow discharges. These weirs provide higher discharge efficiency than conventional linear weirs at the same headwaters. This study investigated hydraulic performance of rectangular labyrinth weirs under different geometries and flow conditions experimentally and numerically. The numerical model was verified and validated using the grid convergence index method recommended in the literature and the experimental data. The numerical modelling results showed that the increase in performance of the labyrinth weir was caused by the distribution of lateral velocities in the inlet keys, while the nappe interference in the downstream keys was responsible for the decrease in performance at high headwater. Within the limitations of 1.5≤L/B≤2.33 and 0.1<Ho/P<0.61, a performance increase of 44% on average and a maximum of 67% for unit channel width was found for rectangular labyrinth weirs compared to linear weirs. For given limitations, two new empirical formulas with high correlation were derived to estimate the discharge coefficients of rectangular labyrinth weirs based on channel width (B) and weir crest length (L) for Ho/P>0.1 in which are widely used in practice. It is concluded that, when compared with some of the data in the literature, the empirical formulas give satisfactory results.

This article investigates twenty-five experiments of one-dimensional shallow thin-surface flow on wide carriageway pavements, undertaken as part of wider investigations to avoid aquaplaning. Analysis of their predictive equations for surface water depths are assessed, along with informative background papers. Issues regarding rainfall intensity and the macrotexture structure of pavement materials and their inter-relationship are considered. Current international best-practice guidance is contrasted and observations for the practising highway engineer are provided, as well as recommendations for future research.

In the UK, hydropower produces 1.65 GW of energy, only 2% of the national capacity. With most large-scale storage-based hydropower potential sites already utilised in the UK, further development is minimal due to financial, environmental and construction time concerns. However, run of river (RoR) is a type of hydropower that has the potential for further development. While there are studies that estimate different ranges of RoR hydropower potential, the last UK-wide study was undertaken in 1989, meaning it is outdated. In this study, a methodological framework was created to assess the potential of RoR hydropower in Great Britain (GB) (Northern Ireland was omitted from this study due to a lack of river flow data). The hydrological, technical, financial and realisable potentials for pico, micro, mini and small RoR hydropower were determined. The results show that the total hydrological potential is 20 GW, the technical potential is 11 GW, the financially viable potential is 320–420 MW and the realisable potential is 290–320 MW. Most realisable schemes are either mini or small, situated in the west and north-west parts of GB. This study adds to the understanding of the RoR potential in GB and offers a reliable estimate of RoR hydropower that can be produced alongside suitable RoR scheme locations.

The increasing effect of drought causes negative effects on water resources. To prevent these negative effects, it is of great importance to know the trend of drought over time. Many methods are used in the literature to determine the severity of drought. One of these methods is the Standard Precipitation Index (SPI), which is calculated based on precipitation data. The SPI method was chosen in this study because it is widely used in the literature for its simplicity, flexibility, and effectiveness in characterizing drought duration and intensity. There are different classifications for drought severity in the SPI method. Therefore, it is of great importance to know the individual trends for each classification. Classical trend detection methods (such as Mann-Kendall) require a separate analysis for each drought classification. However, with Şen’s Innovative Trend Analysis (ITA) method, it becomes possible to determine the trends for all drought classifications on a single graph. In this way, the change of drought events over time can be easily determined for all drought classifications.

The establishment of improved water supplies is one of the United Nation’s Sustainable Development Goals (SDGs). Many water schemes have provided wells and pumps to enhance the life of local communities across Africa. However, in numerous cases these schemes fail over time due to a lack of established maintenance regimes and trained staff. One of the ways that resilience might be improved is the introduction of remote monitoring systems to allow detection of not only failed pumps but to enable predictions of when a pump might fail without intervention, thus allowing the associated loss of service to be minimised, ensuring that the community is not without safe drinking water for extended periods. This paper pulls together the knowledge and details of the remote monitoring systems that are available in the field today and provides a coherent knowledge base of the work that is being done. The paper also reviews how each of the systems are compiled, their strengths and weaknesses and provides background knowledge that should encourage future research and development in the field. It also queries whether such systems, with their reliance on microprocessors are appropriate for the Global South.

Debris generated by the destruction of houses in a floodplain can cause damage to the structure in the way of floodwater by the impact of different hydraulic forces. In the present study, the impact of different hydraulic forces including impact force, hydrostatic force, hydrodynamic force, fluid force index, and moment index on the house model of different porosity were examined and also the impact of these hydraulic forces on a house model for different types of debris including rectangular and cylindrical debris was investigated. The results showed that cylindrical debris of type D5 has a greater specific gravity of 0.206 compared to the other types of debris which is why it results higher magnitude of impact force (40%) for the double porous house model. D3 type of cylindrical debris showed the highest values of hydrostatic force (40%) as D3 has a greater length (26.5cm) and diameter (1.5cm). The higher velocity of flow causes a greater magnitude of fluid force index (60%) on the impermeable house model that reduces with the porosity of the house model. The highest moment index (97% ) acts on the impermeable house model because of greater flow velocity and water depth on the upstream side. Vegetation provided as a countermeasure on the upstream side of the house model reduced impact force from 10% to 22% for the double porous house model compared to the single house model (1-12%) and hydrostatic force reduced from 12-59% for different types of debris. Hydrodynamic force reduction was observed to be 30% when vegetation was provided on the upstream side of the house model of different porosity. Providing vegetation as countermeasures reduced the fluid force index and moment index up to 70% and 63.39% for the impermeable house model respectively.

The waste of potable water is a problem that affects a population’s supply and the environment, raising the need for studies focusing on the adoption of efficient actions and modern technological resources, such as artificial intelligence (AI), for sustainable water management. However, in the literature there are few studies on the operational, economic and environmental benefits of using AI in dam management. In addition, no study has been found on this topic addressing the Cantareira system, located in the metropolitan region of São Paulo, Brazil, which is one of the largest water supply systems in the world. This work presents an approach combining an artificial neural network and the Monte Carlo simulation method for floodgate control in the Cantareira system. Furthermore, parameters are explored that make the simulations of water collection and distribution more realistic. The results (root mean squared error (RMSE) = 0.076 and R2 = 0.963) confirm the viability of using the proposed approach to minimize water waste and flood risks, as well as to increase efficiency in water resource management. Furthermore, this study advances the state of the art by presenting a set of operational, economic and environmental benefits directly associated with the adoption of AI in floodgate management.

Excess scour developing around tandem and eccentric piers of side-by-side bridges may aggravate bridge failure. Thinking differently, this kind of pier-like structure combination may increase scour and shift sediments towards the bank which may help in self-dredging. Therefore, accurate estimation of temporal scour depth (dst) around such piers is getting the utmost priority nowadays. However, very little work has been done in this regard. Most of the previous equations predict dst only for isolated pier. In the present study, 2-3 piers were placed eccentrically inline in addition to isolated piers to empirically derive equations for accurately predicting dst considering circular, triangular and square pier shapes. Present experimental results for isolated circular pier are validated using literature equations and also cross-validated with other literatures experimental data. Predictive equations are proposed for 2-3 piers with eccentrically inline arrangements, taking their intermediate spacing's as key variables. These equations are established based on dimensional analysis and non-linear regression. Overall analysis reveals that the estimated temporal scour depths based on the proposed integrated equation are closely within the ±80% accuracy band. The proposed equations can be used to accurately predict temporal scour for selected combinations of piers within the given experimental ranges.

By decreasing the entrained air flow discharge and improving the hydraulic characteristics of vertical shaft spillways, the Marguerite-shaped inlets can mitigate the effects of swirling flow surrounding their inlet. This study numerically investigates the hydraulic and hydrodynamic characteristics of flow around the Marguerite-shaped inlets under orifice flow regime, applying different geometrical parameters. This configuration of the inlet can decrease the strength of swirling flow and increase the flow discharge through the shaft. The finite volume method and the RNG k-ε turbulence model were employed to solve the governing equations of motion in a cylindrical coordinate system and a two-phase air-water flow on the water free-surface. Increasing the height and length of the blades of the Marguerite-shaped inlets was found to increase area of the barriers against the swirling flow, weaken the swirling flow strength, engender a more uniformed flow and lower the water free-surface level. Extremely long or high blades, however, causes an intense collision of the flow with the spillway and increases the water free-surface level and the swirling flow strength at the Marguerite-shaped inlets.