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Diversion head works, also called weirs or barrages, are structures constructed across rivers or canals to store water or raise the water level. The design of diversion weir structures involves calculating the depth, length and thickness of the horizontal and sloping aprons and sheet pile cut-offs. The design parameters of a diversion weir structure, which have complex non-linear relationships, are traditionally determined using empirically derived recommendations and iterations to achieve structural stability against failures due to scour, uplift, sliding, piping and overturning. However, current design approaches do not explicitly explore the trade-offs between the many relevant design objectives and thus fail to reveal possibly superior designs. A multi-objective optimisation design approach for a diversion weir structure is proposed in this article. A free and open-source code that can be used as a design tool is also provided. The method is demonstrated on a stylised design problem. The results show that the method reveals solutions with diverse balances of stability metrics and cost, with the optimal relationships of parameter values of components also varying based on the relative cost of the construction materials for sheet piles and aprons. [ABSTRACT FROM AUTHOR]

Deep-sea aquaculture has developed rapidly in the world in recent years. Aquaculture equipment is required for largescale, mechanization, automation, and intelligence. Among them, the vacuum fish pump has been used widely in the process of fish catching and conveying. However there is a large range of strong vortexes in the tank during operation, leading to the mutual friction and collision injury between fish. In this study, the structure of the tank and the operation mode were improved to reduce the fish injury for the high working efficiency using a improved fish pump. The inlet pipe passed through the bottom of the tank and then entered the inside of the tank. A trumpet-shaped diversion structure was placed upside down at the top of the inlet pipe. An industrial centrifugal pump was selected as the driving device to replace the water ring vacuum pump. The water inlet of the centrifugal pump was connected to the water outlet of the tank. The fish-water mixture entered the tank, where the fish was separated from the water, due to the suction effect of the centrifugal pump. The incoming fish stayed in the tank, but the incoming water was discharged from the tank by the centrifugal pump. The baseline ratio of fish to water was 1:1 in the pool and the tank. When the ratio of fish to water in the pool was 1:2, 1:3, 1:4, and 1:5, respectively, it was calculated that the conveying time of the improved fish pump was reduced by 20.4%, 30.6%, 36.8%, and 40.8%, respectively, compared with the vacuum fish pump for conveying fish with the same quality. The numerical simulation was carried out to compare the water absorption of the vacuum and the improved fish pump using computational fluid dynamics. The results showed that there was a small vortex range in the tank of the improved fish pump, indicating the weak vortex intensity. An improved fish pump prototype was also designed and then manufactured to verify the numerical simulation in the performance experiments. Compared with the performance of the vacuum fish pump prototype, there was a relatively small vortex in the tank of the improved fish pump, and the conveying capacity did not changed with the change of fish lifting height. The improved fish pump was more friendly to fish conveying. The probability of fish injury was greatly reduced as well. The findings can provide a strong reference for the design of a large fish pump. [ABSTRACT FROM AUTHOR]

A shift in reservoir stratification and mixing significantly affects the water column ecosystem, which in turn leads to changes in phytoplankton abundance and community structure. To explore the effects of stratification and mixing on the phytoplankton community structure of a diversion reservoir, a 1-year survey was divided into a stratification period in 2020, a mixing period in 2020, and a stratification period in 2021, and redundancy analysis (RDA), variance partitioning analysis (VPA) and Pearson correlation analysis were used to analyse the key drivers affecting the phytoplankton functional groups, using Xikeng Reservoir as a case study. During the study period, 8 phyla, 69 genera and 9 major functional groups were observed in this reservoir. The dominant functional groups varied significantly, being X1 in the stratified period in 2020; P and D in the mixing period in 2020; and D, X1, and M in the stratified period in 2021. The phytoplankton diversity index was greater in the mixing period than in the stratification period, in agreement with the results of the aquatic ecological status evaluation (Q index, higher in the mixing period than in the stratification period). However, phytoplankton diversity of Xikeng Reservoir was of limited value in assessing the degree of water pollution, so should be considered in combination with the Q index. Water temperature (WT), mixing depth (Zmix), nitrogen-phosphorus ratio (N/P), and total nitrogen (TN) were important drivers of phytoplankton functional group dynamics in different periods. The study provides a valuable reference for assessing the relationship between environmental factors and phytoplankton communities, as well as for the evaluation and conservation of aquatic ecosystems in southern China's water diversion reservoirs. [ABSTRACT FROM AUTHOR]

In response to the issue of suboptimal thermal performance in traditional data centers, four distinct airflow management structures, namely, composite, linear, convex, and concave diversion plates, were proposed. Utilizing Airpak 3.0, numerical simulations were conducted on five different data centers, including the original configuration of the computer room air conditioner (CRAC). The objective was to assess the impact of various airflow management structures on the thermal performance of data centers, with experimental validation of the model. The findings demonstrate that these airflow management structures significantly enhance the thermal performance of data centers. Among them, the composite diversion plate yielded moderate improvements, the convex diversion plate effectively optimized velocity distribution, although with limitations in temperature optimization, and the concave diversion plate exhibited non-uniform temperature distribution. Overall, considering all factors, the linear diversion plate proved to be the most effective. [ABSTRACT FROM AUTHOR]

In a study to reduce Mojave Desert Tortoise (Gopherus agassizii) mortality along roadways, we tested the feasibility of structures that discourage tortoises from 1) walking or "pacing" along barriers or 2) crossing areas where gates or openings occur. The diversion designs we tested (one straight and one curved structure, each 7.6 m long) deflected tortoises away from fences at nearly the same rate as tortoises who continued walking along barriers despite the diversion (36.8% vs. 35.7%). No "tortoise guard" structures that we tested, similar to cattle guard structures, were 100% effective at preventing tortoises from crossing the opening. We identified essential characteristics of an effective "tortoise guard" such as minimum gap sizes in the structure and a construction design that allowed a tortoise to climb out of a trench under the structure. [ABSTRACT FROM AUTHOR]

Hydropower dams affect freshwater biodiversity by virtue of modifying flow regimes and degrading habitat conditions both above and below the water impoundment and diversion structure. In recent decades, there has been a global proliferation of Small Hydropower Plants (SHPs) propelled by incentive policies and a general perception that small dams are less harmful to the environment. However, limited science is available on the effects of SHPs on freshwater biodiversity, which is concerning considering their sheer numbers and the high variability in the size and operation of dams classified as SHPs.We investigated the ecological effects of 12 SHPs on macroinvertebrate and fish assemblages of the Chapecó River Basin, Brazil. Our study included sites located upstream of the SHPs and sites directly affected by their operations (i.e., reservoir, dewatering section and downstream of the powerhouse). This design allowed us to quantify shifts in taxonomic composition and examine the relative role of different SHP attributes (e.g., dam height, reservoir area, age) in explaining these changes.Our results reveal that SHPs modify the composition of both macroinvertebrate and fish assemblages, but the magnitude of such changes vary widely among dams. Both assemblages exhibited directionality in taxonomic shifts, resulting in a gradual replacement of taxa associated with fast‐flowing habitats by other groups more commonly associated with standing waters. We also found that changes in assemblage structureare related to structural (dam height, reservoir area) and spatial attributes (distance from headwaters) of SHPs, although the predictive power of these attributes varied taxonomically and among reservoir, dewatering and downstream sites.Overall, our results demonstrate that SHPs have important and heterogeneous effects on freshwater assemblages, which may manifest individually or cumulatively across the riverscape. This suggests that it is unlikely that a priori classifications of dams based on their structural attributes can replace site‐specific and cumulative impact assessments. The results also shed light on the need for better understanding of how SHP attributes shape their ecological effects, so that a full assessment of the potential environmental impacts of the wide range of "small" dams is possible. [ABSTRACT FROM AUTHOR]

Simple Summary: The water quality of reservoirs in water transfer projects is key as these reservoirs provide water directly to people. In general, the composition and structure of fish assemblage can reflect reservoir water quality and can also be regulated for its improving. We compared monitoring results of fish assemblages carried out by the traditional and environmental DNA methods in three-terminal reservoirs of the South-to-North Water Transfer project in China. The fish assemblages determined by both methods showed similar assemblage structure and patterns of diversity and spatial distribution; however, obvious differences in fish composition across the three reservoirs examined were found. Demersal and small fishes were the most common in all sites. Moreover, a strong association between water transfer distance and the distribution of non-native fish was found. Our findings highlight the importance of fish assemblage monitoring and the impact of water transfer distance on fish assemblage, providing valuable information that can be used in future water transfer projects. The terminal reservoirs of water transfer projects directly supply water for domestic, agricultural, and industrial applications, and the water quality of these reservoirs produce crucial effects on the achievement of project targets. Typically, fish assemblages are monitored as indicators of reservoir water quality, and can also be regulated for its improvement. In the present study, we compared traditional fish landing (TFL) and environmental DNA (eDNA) metabarcoding methods for monitoring fish assemblages in three terminal reservoirs of the East Route of the South-to-North Water Transfer Project, China. Results of TFL and eDNA showed similar assemblage structures and patterns of diversity and spatial distribution with obvious differences in fish composition across three examined reservoirs. Demersal and small fish were dominant in all reservoirs. In addition, a strong association between water transfer distance and assemblages and distribution of non-native fish was found. Our findings highlight the necessity of the fish assemblage monitoring and managing for water quality and revealed the impact of water diversion distance on the structure of fish assemblages and dispersal of alien species along the water transfer project. [ABSTRACT FROM AUTHOR]

Heat reflow in the fan rotation center of a forced convection cooling system has a great influence on heat dissipation. In this research, a calculation model of the external flow field of an engine compartment's cooling module was established. Computational fluid dynamics method was used to calculate and analyze the heat flow characteristics of the existing radiator. By comparing the calculations with the experimental results, the regions and the reasons for the heat reflow were found. The existing heat dissipation scheme was recalculated by using the secondary heat dissipation model, and an optimized and improved scheme was proposed to introduce a deflector cone structure to eliminate heat reflow. This structure was connected to the fan hood by four blades. The front end of the structure acted as a diversion for the conical structure, and the back end was a hollow cylinder structure, making it easier for the fluid to transition to the conical structure. Both ends and the distance between the vertebrae were set to range from 2–5 mm. The research results showed that the secondary heat dissipation model could more accurately describe the heat reflow problem of the engine compartment, the heat flow organization of the improved structure was more reasonable, and the temperature distribution was more uniform. Moreover, the theoretical heat dissipation effect of the improved structure was more than 10 % higher than that of the existing structure. [ABSTRACT FROM AUTHOR]

Tropical island streams are heavily impacted by water withdrawals to the detriment of native ecosystems. Freshwater fauna in the tropics often exhibit diadromous life‐history strategies, requiring hydrologic connectivity between upstream and nearshore habitats. During some or most of the year, this connectivity is generally lost at points of water withdrawal, typically constructed as a low‐head dam diversion. In 2010, instream flow standards (i.e., minimum environmental flows) were established for streams in East Maui, Hawai'i, which led to the partial restoration of flow in certain streams. In 2016, flow in several of these streams was then fully restored. We surveyed 10 streams before (2012) and after (2017) varying degrees of flow restoration (none, partial, full) to explore the short‐term consequences of reestablishing natural streamflow for the migratory fauna of high‐elevation tropical streams. Using visual point‐quadrat surveys, we quantified density and habitat usage of the endemic atyid shrimp (Atyoida bisulcata) and sampled A. bisulcata populations using seine‐netting to assess size frequency, sex ratio, percent ovigerous (egg bearing) females, and percent juveniles. In streams with full flow restoration, shrimp density increased in 2017 compared to 2012, while mean body size declined, suggesting increased recruitment following restoration. By contrast, streams that did not experience any flow restoration had similar shrimp densities and body sizes across years. Further, the male: female ratio declined from 18:1 in 2012 to 6.5:1 in 2017, suggesting an increase in reproductive potential of the population. Our results demonstrate that freshwater ecosystems upstream of diversion structures may respond rapidly to the restoration of hydrologic connectivity via increased recruitment of amphidromous species. [ABSTRACT FROM AUTHOR]

Groundwater depletion is a problem in many parts the world. We developed an approach to investigate the drivers of groundwater depletion in data-scarce regions. The approach combines natural and human-induced drivers, with the latter focusing on the link between human activities and government policies. We tested the approach in Wadi Zabid, Yemen. Forty years of rainfall-runoff data were analyzed, alongside changes in land cover, groundwater abstraction and related policies. No decrease in rainfall was observed, but runoff did decrease slightly. Significant expansion of agricultural lands led to increased demand for irrigation water, which was provided by drilling wells and building water harvesting/diversion structures. In Wadi Zabid, human activities, stimulated by policy measures, were the main drivers of groundwater depletion (water table here fell by 1 m/yr on average over 1972–2016). We conclude that combining natural and human-induced factors is indeed a valuable approach for investigating groundwater depletion drivers. [ABSTRACT FROM AUTHOR]

In water-rich karst area, the lining structure of diversion tunnels is prone to cracking and gushing water problems under high water pressure, so water drainage design is often adopted for these diversion tunnels, that is, to drill holes on the lining structure and install drainage equipment to lower the external water pressure of the lining, therefore, accurately calculating the external water pressure of the lining is a very important work for the safety of the lining structure of tunnels. Based on the method of equivalent permeability coefficient, this paper regarded the drainage capacity of drainage equipment installed on the lining and the permeability of lining itself as a whole, and used the virtual equivalent permeability coefficient of the lining to describe it; then, this paper proposed a method for determining the equivalent permeability coefficient of lining and used it to analyze the drainage effect. Main conclusions of this paper are: 1) By designing tests for the drainage model of the tunnel drainage equipment and theoretically analyzing the seepage field of hydraulic tunnel, the equivalent permeability coefficient of the lining was determined and its accuracy was verified via numerical calculation; 2) Analytical calculation results and numerical simulation results of the tunnel were analyzed, and their conclusions about the effect of drainage capacity on the external water pressure of the lining were consistent; 3) The tunnel drainage design is an effective measure to reduce the external water pressure of the lining, the pressure reduction effect is obvious when k<1×10-6, and the groundwater level around the tunnel could be reduced at the same time. This paper provides a useful evidence for the design of high-pressure water diversion tunnels. [ABSTRACT FROM AUTHOR]

• Graded adaptable regulation of cane seed transfer flux. • Flexible seed metering device enables orderly and quantitative delivery of irregular stalk-shaped seeds. • Logistics response models address synergistic relationship between seed supply and discharge processes. Considering that the rigid seed metering device has difficulty adapting to the irregular geometry of cane seeds and the gradual change in required conveying capacity, it is very prone to defects as passage blockage, missed sowing and bud damage. In order to achieve continuous and orderly seed supply for quantitative seeding, a novel design methodology of seed metering device underlying the flexible regulation of transfer flux was proposed for the rolling stalk-shaped seed flow. The effective action modes of compliant wall constraint, elastic de-redundancy and vibration-excited blockage relief were dynamically analyzed, and their synergistic utilization was confirmed to generate adaptive control effects for graded cane seed flux. The principle of reducing obstruction by dynamic balance between supply and discharge rates was also clarified. Regarding the interaction process between guided seeds and their restrictive passage, a rigid-flexible coupling DEM-MBD model was established to reveal the combined functional mechanism of various diversion wall properties, including driving, axial and flexible constraints, and elastic boundaries, on particle groups in terms of contact mechanics. Based on bench experiments, the impact of regulatory factors in the diversion structure on the comprehensive seeding performance in terms of smoothness and discharge quantity was further studied, and a logistics response relationship model was created accordingly. Through optimizing the coordinated effects involved in the supply and discharge processes, confirmatory tests indicated that the optimal qualified rate of discharge quantity was increased by 43.7%, while the incidences of blockage and local congestion were reduced by 23.4% and 6.7% respectively. This provided direct evidence for improved control accuracy in terms of seeding rate and smoothness by strengthening the particle deliverability of irregular stalk seeds. [ABSTRACT FROM AUTHOR]

• Numerical simulation method is used to optimize the high-speed seeding performance. • The relationship between velocity and wind pressure is obtained by high-speed camera. • Designed a diversion and disturbance stirring wheel to regulate the motion path. • Working conditions of different speeds are determined to achieve efficient seeding. • The seeding evaluation process is improved by using the number of internal seeds. Numerical simulation and high-speed photography technology are used in this work to obtain the key factors affecting the seeding performance of a novel high-speed centrifugal filling-cleaning precision seeding metering device under different conditions. The effects of key parameters, including seed-metering diversion turbine structure, dynamic wind pressure, seed quantity, and ground speed, on the seeding performance of the high-speed seed metering device are investigated. The results show that a diversion turbine structure with diversion and controlled disturbance flow increases seed pressure and enhances the filling process. Meanwhile, a correlation between dynamic wind pressure and seed movement velocity is established using a high-speed camera-based experimental approach. Maintaining 24 internal seeds is crucial to guaranteeing the quality of feed index. Specifically, under the simulation conditions, when the ground speed is 14 km/h (corresponding to a rotation speed of 194.5 rpm), the corresponding dynamic wind pressure is identified as 1.5 kPa, the corresponding seed plate speed is 2 m/s, the corresponding optimal feeding rate should be maintained at about 14 seeds/s, and the seed inlet velocity is 3 m/s. Additionally, the results of comprehensive bench and field seeding performance experiments demonstrate that, as the seeding speed increases, there is no apparent seeding performance decline, and even under high-speed operational conditions, the quality of feed index under different ground speeds exceeds 90%. [ABSTRACT FROM AUTHOR]

This study focuses on the start-up optimization strategies for a Hydroelectric Generating System (HGS). A mathematical model of HGS to describe the complex hydraulic coupling relationship, between the water diversion pipes, the hydro-turbine, the governor and the generator, is proposed. This allows to accurately describe the start-up process and identifying the effect of successive start-up time interval (ΔT) and the pipe structure on the water head and the rotational speed of HGS. The result shows that the successive start-up strategy with ΔT = 9s maximally reduces the water head fluctuation of units #1 and #2 by 30.94% and 25.77% compared with the simultaneous start-up strategy when the branch pipe is symmetric. For the asymmetric branch pipe, the unit behind branch B# starts up first is beneficial to reduce the water head fluctuation of the unit behind branch #A when the flow inertia time constant of branch #A is larger. Finally, the parameters of the start opening as well the PID governor parameters are optimized by a multi-objective particle swarm optimization for the asymmetric pipe in order to minimize the unit speed overshoot and the speed rise time. These results in this work provide a theoretical guidance for the selection of optimal start-up strategy in the case of symmetric and asymmetric HGS branch pipe structures. • A hydroelectric generating system is established, which can describe the start-up process. • The optimization algorithm is applied to the start-up process of hydro-turbine. • The optimal start-up strategy of hydro-turbine with symmetric or asymmetric pipe are analyzed. • The work can improve the start-up quality of hydro-turbine in practical engineering. [ABSTRACT FROM AUTHOR]

To reduce local scour around bridge piers, a mitigation measure requiring a submerged triangular flow diversion structure is proposed. Different dimensions, locations, and submergence ratios were examined experimentally. Using Taguchi's method to minimize the number of alternative tests, 27 alternative tests were undertaken to ascertain the optimum size and location for the structure. Compared to the no flow diversion structure situation, it was found that the optimized structure resulted in a 40% reduction in the maximum scour depth and a 60% reduction in scour volume. Also, an experimental study of the flow field was conducted to investigate the influence of the structure on flows. Results showed that the structure influenced the down-flow and horseshoe vortex and consequently reduced the scour. Based on the investigation presented herein, a flow diversion structure is a simple and easy approach for mitigation of scour at existing and new bridges. [ABSTRACT FROM AUTHOR]

With the continuous increase of railway transportation volume, the aging problem of railway tunnel bottom structure is becoming more and more serious, which seriously threatens the safe operation of trains. Based on the cause analysis and field detection of the defects at the railway tunnel bottom structure, the "Anchor-Grouting-Drainage" treatment technology of the railway tunnel bottom structure is summarized. The research shows that (1) the technology is simple and can effectively repair the defects of railway tunnel bottom structure under the conditions of the narrow site, short time of maintenance skylight, strict requirements of track size variation, and no interference with the normal operation of the train, which has great significance and broad application prospect. (2) The drainage system of the existing railway tunnel bottom structure can be applied to the reconstruction of the railway tunnel bottom structure. The high-strength transverse diversion structure at the bottom of the tunnel has the advantages of strong bearing capacity, large drainage capacity, and corrosion resistance, which can provide a reference for the subsequent implementation of the reconstruction project at the railway tunnel bottom structure. [ABSTRACT FROM AUTHOR]

Determining beneficial operation rules for complex reservoir cascades is challenging due to the variability of river inflows, multiple water users, and the computational burden imposed by optimization calculations. Water managers of Sri Lanka face the challenge of balancing water releases for hydropower and for irrigated agriculture in the Mahaweli project. This study derived Mahaweli reservoir operation policies—reservoir rule curves and water allocation rules—by optimizing hydropower generation and agricultural yield. We derived operation rules for three reservoirs and one water diversion structure, because these offer the main opportunities for controllability of hydropower and irrigation. We used a multiobjective evolutionary algorithm to optimize hydropower and agriculture yields for 1,000 synthetically generated reservoir inflows that capture the natural variability of the monsoon seasons. The optimization problem was simplified by focusing on the main components of the cascade and by carrying out the computation in two stages. Despite the simplification, the operation rules derived using multiobjective optimization enhanced hydropower and agriculture yield compared with the values from current rules. The solution set exposed the trade-off between energy and agricultural yield objectives. Risk-neutral and risk-averse optimized rules and trade-offs between the objectives provide information that can be used to adapt water management practices for different hydrological conditions, which can be beneficial to thousands of people. Water managers of similar reservoir cascades can use the method to select policies considering trade-offs among objectives. [ABSTRACT FROM AUTHOR]

Mapping the streambed morphology is crucial for understanding fluvial forms and processes, for advancing both our knowledge and best management practice of riverine systems. It is often done by wading streams but recently topobathymetric Light Detection and Ranging (LiDAR) and imagery captured from airborne platforms are becoming promising and effective surveying methodologies. The recent use of remotely piloted aerial systems (RPAS) combined with structure-from-motion (SfM) photogrammetric processing provides a novel, high-resolution approach to modelling fluvial morphology. Nevertheless, a complicating factor of such data acquisition in fluvial settings is linked to water bodies, whose presence introduces errors and distortions because of light reflection and refraction at the air–water interface. Although proof-of-concept research has shown it is possible to reduce the effects of refraction in certain settings (e.g., clear waters, unbroken surfaces), corresponding validation methods remain limited to point-based assessments of error, these being typically limited to accessible parts of the channel. Here, we provide the first high-resolution, spatially continuous validation of a stream reach bathymetry surveyed with SfM and corrected with an advanced refraction method. This method required only the camera co-ordinates and is available as open source, coded in C++. We used RPAS imagery from a regulated reach of the Palancia River, Spain, where a diversion structure fully dewatered the reach and let us obtain the entire streambed topography, which we used as spatially continuous control topography to compare the bathymetry surveyed from imagery during normal flow conditions. We compared this method with the small angle refraction correction (SARC), which has less data requirements, and analysed the error distribution across habitat types (i.e. pools and riffles). These results showed that our approach had smaller errors than SARC in both habitat types, especially in the riffle. By analysing the relationship between error and channel roughness obtained from our dry-bed model, we found that the greatest errors arise in the peripheral zones of the water surface and in its areas where streambed roughness generates more turbulence. Quantitative validation confirmed the reliability of our method as a relatively low-cost tool for the modelling and management of geomorphology and habitat within small – to medium-sized streams. [ABSTRACT FROM AUTHOR]

Abstract: Direct seeding of rice is widely expected as one of the most important technology in mechanized rice planting. At present, two ways were mainly divided into the transplanting and direct seeding. The direct seeding can reduce the input of procedures and costs, while the growth cycle. In the complex field environment, direct-seeded rice seeds are easily affected by diseases, pests, weeds, and flooding, leading to greatly reduce the emergence rate and the yield. Alternatively, the seed coating technology can be used to provide micro-fertilizers, growth regulators and pesticides for the germination of seeds and the growth of seedlings. Specifically, the film-forming agents, adhesives, and other ingredients are generally used to uniformly bond the active ingredients on the surface of seeds. Since its convenient application, low cost, as well as resistance to pests and diseases, the seed coating technology can greatly contribute to enhance the seedling rate in the field, and the growth potential of seedlings. Particularly, small environmental pollution can meet the harsh requirement of ecological agriculture. In recent years, the mechanical direct seeding technology of rice has been commonly used in a large area in China, one of which the precision hole direct seeding technology of rice has good ventilation and permeability in the paddy field. The rice seeds are distributed evenly in the field, according to the agronomic requirements of rice varieties. The main types of direct seeding rice are the conventional rice and hybrid rice. The sowing rate is normally 5~10per hole of conventional rice, while the sowing rate is generally 2-4 grains per hole for the hybrid rice with strong tillering ability. With the emergence of super hybrid rice and some high-quality rice varieties, the single-grain sowing has become particularly important, due to it meets the requirements of agronomic planting. In this study, a single-grain pneumatic seed metering device was designed for the coated rice to meet the demand of single-grain sowing of super rice. The physical parameters of coated rice seeds were measured. A movement model was established between rice seed and diversion suction plate during adsorption, according to the movement process of rice seed under the action of suction tray. The optimal negative pressure was calculated under the ideal condition of seed suction disk. Taking the coated rice variety (Super Rice Wuyou 1179) as the experimental object, the three-factor and three-level all-factor test was used to analyze the seed absorption of rice varieties at the speed of suction tray, negative pressure of suction chamber, and structure of seed suction tray. The experimental results show that the seed suction effect was the best, when the rotating speed of diversion suction tray was 30 r/min, and the negative pressure of suction chamber was 1 400 Pa. The seed sucking effect was best in the seed sucker structure with diversion groove and auxiliary seed sucking device, where the maximum of single seed sucking rate was 81.58%, and the leakage rate was 2.89%. Therefore, the suction tray can effectively improve the seed absorption rate per grain, suitable for the needs of single-grain sowing of super rice. The finding can provide a theoretical basis for the rapid development of single-grain sowing of rice. [ABSTRACT FROM AUTHOR]

The book concludes with dam safety; Chapter 11 introduces the dam breach problem and then moves to the temporal evolution of an embankment dam breach and empirical correlations with historic dam failures. Chapter 3 expands on the topic of overflow structures to include the side channel weir, labyrinth weir, piano key weir, siphon, and morning glory spillway. Hydraulic engineering is the application of hydraulic science to problems dealing with water management and use. [Extracted from the article]

Water diversions for hydropower and other applications can potentially affect wild fish populations. Although some evidence indicates that acoustic barriers can prevent fish from entrainment into such infrastructures, few studies have been conducted on filtering candidate sound stimuli. Here, the effectiveness of three types of sounds acting as acoustic barriers to prohibit the movement of tu‐fish Schizopygopsis younghusbandi (Regan) was evaluated. The phonotaxic response of the fish to recordings of hissing sound (sound of Chinese alligator Alligator sinensis hissing), outboard motorboat and pile driving noise, compared to control conditions (recordings of ambient riverine noise), was investigated using playback approaches in a fibreglass tank. The tu‐fish reacted to the hissing sound at relatively low sound intensity by exhibiting negative phonotaxis with significantly more responses (F3,79 = 49.590, p < 0.01) and faster swimming (F3,219 = 310.086, p < 0.01) away from the sound source during the 10‐min trials than to control conditions. However, the fish were relatively impervious to the outboard motorboat and pile driving noise even when the sound intensities were increased. These results indicate that the potential use of the hissing sound to manipulate fish behaviour and to help protect them from water diversion structures. [ABSTRACT FROM AUTHOR]

A sharp-crested side compound weir is a flow diversion structure provided on one or both side walls of a channel to divert water from the main channel. Compound sharp-crested weirs are widely used in irrigation, hydraulics, and environmental engineering. This article presents results of experimental and numerical studies conducted on sharp-crested side compound weirs in open channels. Owing to the complex mechanism of flow through a side compound weir it is difficult to establish a regression model to accurately predict the coefficient of discharge (Cd). In this study, an alternative approach to the conventional regression modelling in the form of artificial neural network (ANN) has been used to predict the values of Cd. A network architecture with trained values of connection weights and biases is recommended to predict Cd. The input to ANN model consists of grouped parameters pertaining to the ratio of weighted crest height to the length of the side compound weir (--> W ¯ / L -->), the ratio of upstream depth to length of the side compound weir (Y1/L), and upstream Froude number (F1). The results of the ANN model applied herein were found to be superior to those obtained through regression modelling by previous researchers. The sensitivity analysis of the ANN model shows that --> W ¯ / L --> is the most important parameter for the estimation of Cd; followed by Y1/L and F1. [ABSTRACT FROM AUTHOR]

Bucket-based structure is a new type of structure suitable for offshore soft soil foundation, which has been successfully applied in Xuwei dike of Lianyungang. Based on the successful experience of the semi-circular structure in the Yangtze estuary phase I regulation project, a new type of semi-circular bucket-based composite diversion dike structure is proposed, which takes the advantages of diversion and wave resistance of the semi-circular structure and combines the stability of the bucket-based. Based on theoretical analysis and experimental study of the Jiuduansha diversion dike project in the south channel of the Yangtze estuary, it is concluded that the semi-circular bucket composite dike is safe, reliable, controllable in displacement, simple in construction and green in environmental protection. Its design method, experimental research and research conclusions can provide a reference for similar engineering design, and the research results will be applied to engineering practice. [ABSTRACT FROM AUTHOR]

The flood peak and flood volume are generally considered to be independent random variables in early-term dam construction diversion risk simulation, while the cofferdam elevation is a definite value. Due to the continual construction of high dams at the 200 m-level in southwest China, the effect of flooding on dams lasts longer than before due to greater filling volumes and longer construction periods. The correlation between the flood peak and the volume has been shown to affect the accuracy of mid-term diversion risk analysis. Aiming at determining the mid-term diversion risk of high rockfill dams, this paper presents a joint distribution for the construction flood peak and volume using the copula function. Then, a simulation model for the monthly filling height during the flood season is given considering the filling intensity and effective construction days, in which the daily rainfall and the stoppage standards for rain, which affect the effective construction days, were analysed. Additionally, stochastic factors such as the hydrology, hydraulics, stop days, and filling intensity were considered to resolve the diversion risk rate by using the Monte Carlo method. Finally, an example of a high rockfill dam in southwest China was provided to verify the correlation between the flood peaks and volumes and to calculate the mid-term diversion risk during its construction by incorporating historical flood data, rainfall days, and diversion standards. The results reflect the probability distribution of a construction flood more accurately, avoiding the overestimation of a low-probability flood event, with a high peak but a small volume, that leads to a lower risk rate and lower designed reliability for diversion structures. In addition, the monthly diversion risk and its corresponding maximum water level in the equivalent reappearance period can provide design references for coordination between flood prevention measures and construction schedules. [ABSTRACT FROM AUTHOR]

Salinity in estuaries affects numerous ecological processes, and is strongly driven by river outflow interacting with the tide. We used an exponential decay function to model the relationship between salinity and freshwater flow (i.e., river discharge) to characterize and map salinity dynamics over the tidal flats of the Fraser River delta, British Columbia, Canada. The model has three parameters: the horizontal asymptote Asym that represents the average weekly salinity at very high river flows; the theoretical intercept R 0 that represents salinity conditions during very low river flows; and the natural log of the rate constant lrc that reflects the relationship between river discharge into the estuary and resultant average salinity. Using data from 47 salinity-monitoring stations deployed from 2015 to 2021, we found that Fraser River discharge had a strong and inverse relationship with average weekly salinity on the outlying tidal mudflats, which is expressed by the lrc value of −8.56. Model estimates indicate that weekly salinity (on the Practical Salinity Scale) at very low discharge rates (R 0) had a value of 22.4, which decreased at high discharge rates (Asym) to a value of 3.7. This predictable decrease in salinity for increasing river discharge means that the salinity regime of the Fraser River delta tidal flats is poikilohaline, and undergoes a regular and biologically relevant transition from brackish to nearly fresh water as the river outflow increases and abates seasonally. The resulting spatial gradients in salinity dynamics were associated with distance to river outflows and existing water diversion structures (i.e., jetties and causeways), meaning the timing and extent of this transition varied across the tidal flats. As estuaries become increasingly modified by coastal development and climate change, this simple model can be used to evaluate management interventions and river discharge scenarios that affect salinity gradients over tidal flats. • Salinity on tidal flats of the Fraser River delta transitions seasonally from marine to fresh water. • River training infrastructure has a footprint on the salinity regime of tidal flats. • A hydrological approach can be used to evaluate management of estuaries. [ABSTRACT FROM AUTHOR]

Cofferdams are widely used temporary structures at construction sites. Two of the main parameters required in designing a cofferdam are the flow rate and exit hydraulic gradient at the bottom of the excavation. Commonly, these two parameters are evaluated by using two-dimensional (2D) ground water flow models. However, when the flow pattern is three-dimensional (3D), such as flow into the square or rectangular cofferdams, predictions by the 2D models underestimate the flow rate and exit gradients considerably. Therefore, it is necessary to incorporate the 3D flow effect through a correction factor. It is shown that treating a square cofferdam as a circular one of the same width or treating a rectangular cofferdam as a 2D double-walled cofferdam significantly underestimates the flow rate. In this study, simple expressions are developed and validated for accurately estimating the flow rate and exit hydraulic gradient values of square and rectangular cofferdams, based on hundreds of finite element simulations in both 2D and 3D. It is suggested that the expressions given in the Canadian foundation engineering manual be improved. [ABSTRACT FROM AUTHOR]

Prediction models are essential in dam crack behavior identification. Prototype monitoring data arrive sequentially in dam safety monitoring. Given such characteristic, sequential learning algorithms are preferred over batch learning algorithms as they do not require retraining whenever new data are received. A new methodology using the genetic optimized online sequential extreme learning machine and bootstrap confidence intervals is proposed as a practical tool for identifying concrete dam crack behavior. First, online sequential extreme learning machine is adopted to build an online prediction model of crack behavior. The characteristic vector of crack behavior, which is taken as the online sequential extreme learning machine input, is extracted by the statistical model. A genetic algorithm is introduced to optimize the input weights and biases of online sequential extreme learning machine. Second, the BCa method is proposed to produce confidence intervals based on the improved online sequential extreme learning machine prediction. The improved online sequential extreme learning machine for identifying crack behavior is then built. Third, the crack behavior of an actual concrete dam is taken as an example. The capability of the built model for predicting dam crack opening is evaluated. The comparative results demonstrate that the improved online sequential extreme learning machine can provide highly accurate forecasts and reasonably identify crack behavior. [ABSTRACT FROM AUTHOR]

The diversion tunnel of high arch dam located in canyon areasruns through the initial to middlestages of dam construction. Investigating the creation and solution of a diversion risk model of the initial and middle stages of high arch dam construction is therefore important to the design optimization of diversion tunnels. The present work focuses on the engineering design stage and makes use of the dynamic simulation technology of high arch dam construction to collect morphological data covering water retaining and dam protection from the initial to middle stages of construction. We here established a risk model of flow diversion in the initial through middle stages for high arch dam construction considering the factors of hydrology and hydraulic randomness, and a method of solving the risk model using Monte Carlo method, which couples with the water retaining and dam protection morphological data and the major random factors, is proposed in this work. Based on the principle of risk analysis, a risk recognition method for the design of diversion tunnel is proposed, and the mathematical model and detailed steps for the design optimization of diversion tunnel dimensions are given. The results of the case study of a high arch dam in the upper reaches of Jinsha River show that the proposed risk model and the solution method are applicable and effective; the model can be used to determine the risk rate of the initial to middle stages of the entire construction project, and it can objectively reflect the two possible water retaining conditions of the high arch dam during the middle stage of the dam protection period and overcome the limitations of the initial diversion risk model; during the middle stage of construction, the diversion risk rate decreases with the increase in diversion tunnel dimensions; and the feasible scheme set of diversion tunnel dimension designs has a boundary, i. e. the optimal scheme. The outcomes of this study can provide theoretical support for risk decision-making and design optimization for the construction of diversion structures for high arch dams. [ABSTRACT FROM AUTHOR]

Slit dams are open-type structures used to mitigate debris-flow hazards by constricting the flow and attenuating the kinetic energy. However, slit dams are often filled up as they are designed to impede debris volume instead of reducing kinetic energy of debris flows. To better understand the regulation function of slit dams against debris flows, physical model tests were carried out using a 7-m-long flume. The water content and relative post spacing were varied to discern their influence on the regulation function. Results reveal that the velocity attenuation and trapping efficiency is strongly controlled by water content and relative post spacing. Water content fundamentally reflects the degree of liquefaction (effetive grain-contact stress) and capacity of energy dissipation of debris flows. When water content < 26%, relative post spacing has a noticeable effect on velocity attenuation, trapping efficiency, and run-out distance. In contrast, when water content ≥ 26%, the influence relative post spacing is negligible. Furthermore, a new relationship between velocity attenuation and trapping efficiency for the design of slit dams is proposed to avoid the slit dam being easily filled up by sediments contained in debris flows. [ABSTRACT FROM AUTHOR]

Flood is common phenomena worldwide since time immemorial. Recently the change in climatic parameters has drastically affected the pattern and magnitude of flood. India being one of the tropical country face flood and drought situations every year, therefore it needs accurate assessment and forecast of flood for proper management of natural resources.An attempt has been made through the present study which consists frequency analysis on maximum daily discharge data in Betwa river at Basoda, Mohana and Shahijina gauging stations in Madhya Pradesh state using Gumbel’s Extreme value distribution and Log Pearson Type-3 distribution for 20 years period (1993-2012).The result shows that Log Pearson Type-3 distribution is better suited for Betwa basin. The results can be used by civil engineers for deciding the dimensions of hydraulic structures such as spillways, dams, bridges etc. Floods are forecasted for the different return periods for Betwa river. [ABSTRACT FROM AUTHOR]

On the basis of literature analysis and field investigations it was found that piers in spillway culverts suffer most from the ice impacts. Floating ice is a significant hazard to structures - jamming between piers or rubble pile development will modify the effective size of the structure and possibly increase the loads. Ice loads are generally described as ice forces or pressures acting over an area of structure. Ice loads are classified as: static loads, dynamic loads, global loads, local loads. Local ice loads from ice-structure interaction are highly irregular and very hard to model exact. The aim of this work - to evaluate ice loads formed in the ponds of Lithuania and their impact on the spillway culverts piers structures. The ice loads were analysed in this work: 1) the force of moving ice fields in contact with single pier; 2) the force of standing ice field, in the impact due wind and water drag forces; 3) the force from ice jam cutting by pier; 4) the force of ice jam in the perpendicular contact with structure front, 5) the force, which is cutting pier of the ice plug. [ABSTRACT FROM AUTHOR]

The forebay of pumping stations is an important hydraulic structure that connects the channel with the inlet channel. Actual test observations and theoretical studies have shown that poor precursors produce backflow, vortex, and water flow disturbances in the forebay water. In this paper, taking a lateral inlet pump station as an example, we study the nonmeasures and five rectification measures—“Y” type diversion pier, “T” shaped diversion pier, narrow bottom hole, high and wide bottom, and diversion wall—through adopting the method of numerical simulation and model test. For the numerical simulation, the corresponding three-dimensional model is established by UG solid modeling software, and then the computational fluid is simulated numerically with CFX. Based on the analysis and comparison of the results during the test of numerical simulation and model test, the stability of the rectification measures is considered after taking into consideration the results of the uniformity test of the velocity distribution of the surface layer, the bottom layer, and the front section of each scheme. The proposed scheme 3 (“T” diversion pier) is regarded as the pumping station flow control measures. [ABSTRACT FROM AUTHOR]

For embankment dams, the modelling of influences in the dam response becomes more difficult if the empirical model cannot be used due to changing external influences. In this work, an attempt at modeling the measured deformations as a dynamic stochastic process is presented. A discrete Wiener process acceleration model (DWPAM), which is based on Kalman filtering, is implemented on geodetically measured displacements of the point on a rock-fill embankment dam. The acceleration is modelled as a zero-mean white sequence. The verification of a filter design and choosing an appropriate value of the process noise intensity scalar is controlled primarily with the compliance of the statistical tests in the domain of measurements and in the system state domain. In the case study, it was shown that the DWPAM can detect statistically significant changes in measured displacements according to the previous behaviour and can be used for the identification of potential anomalies. [ABSTRACT FROM AUTHOR]

Sluice gates are commonly used in canals for control and measurement of the flow. The discharge under sluice gates can be determined through the energy-momentum method (EM), the orifice flow rate equations and the application of the Π-theorem of the dimensional analysis. The different discharge methods available, for free and submerged hydraulic jump including the transition between flows, were compared with experimental data. The performance of the different calibration methods was analyzed. The test program was conducted in the laboratory flume and in the experimental irrigation canal of the University of Évora, Portugal. The test program shows that the evaluation of the discharge under sluice gates for free and submerged flows and for the transition between both flows through the methods based in the EM were those who had better results. For the studied gates openings, the results also show that the methods that consider the division of the submerged flow in partial and totally submerged did not improve the discharge results. [ABSTRACT FROM AUTHOR]

We have studied the effects of aquatic habitat connectivity interruption upon the fish fauna in the riverbed of the upper sector of Crisul Negru River (ROSCI 0049). Earlier, a small barrage was built in that area, and we have analyzed its affects onto the species distribution of local fish fauna. Sampling of nine km sections each of the river above and below the barrage in 2015 yielded the total of 28 fish species. We have noticed that species were not affected evenly by the habitat fragmentation caused by the barrage. The population size of small-sized fish species (Sabanejewia balcanica, Romanogobio kessleri, R. uranoscopus, Gobio carpathicus (sin. Gobio gobio) and Zingel streber) and also potamodromous species (Chondrostoma nasus, Vimba vimba and Barbus barbus) has affected by biotope fragmentation in the barrage region. The increased number of specimensbelow the barrage is caused principally by their inability to pass this barrier. In addition, reduction of the water speed and the resulting increase in sediment accumulation upstream the barrage has favored population overgrowth of several exotic invasive species, including Pseudorasbora parva, Carassius gibelio and Lepomis gibbosus. [ABSTRACT FROM AUTHOR]

A new methodology is proposed to estimate earthquake damage of gravity dams. In this methodology the static pushover analysis is used to formulate a systematic and rational procedure to estimate the level of damage from the linear seismic analysis results. The tensile cracking of concrete is considered as the main potential damage. Examples of three existing concrete gravity dams are provided to illustrate the methodology and discuss the probable nonlinear response and failure mechanisms. The damage state of the dams under twelve proper earthquake ground motions scaled to increasing intensity levels is estimated using the new proposed criteria and verified using the actual nonlinear time-history analysis. Finally, a damage index is defined to quantitatively predict the earthquake damage of gravity dams. [ABSTRACT FROM AUTHOR]

This paper describes the development and application of a spreadsheet model to evaluate effects of water management on diversion modified flow regimes, enabling the exploration of novel ways to meet proposed environmental flow standards. Mill Creek, a northern California river with an altered flow regime that impacts aquatic species, was used as a case study. Test cases examined how water management alternatives, such as groundwater pumping, water rights transfers, and water exchange agreements, can improve environmental flow allocations given irrigation water demands. Four test cases include passage flows for Chinook salmon and steelhead trout, a minimum instream flow, 80% of natural flow, and a spring recession flow with functional flow components. The model identified late October as consistently water-scarce, even in wet years. These analyses suggest that fall shortages for fish migration could be eliminated through a water exchange agreement combined with use of wells. All cases except the minimum fish passage flow case required acquisition of the largest water rights to decrease environmental shortages by over 80%, with a substantial curtailment in irrigation. [ABSTRACT FROM AUTHOR]

Concrete-faced rockfill dams (CFRDs) can be configured as concrete-faced sand-gravel dams (CFSGDs) during design and planning stages based on geological conditions and available rockfill materials at the construction site. Karacasu Dam, located in Turkey, is a pioneering example of a CFSGD and is built primarily on marl. The primary purpose of this study is to examine the monitored performance of the Karacasu Dam by using data collected from 18 earth pressure cells and 30 displacement cells embedded within the dam body, as well as 15 joint meters installed on its concrete face. This quantitative examination provides various crucial insights for building dams of this type in the future. [ABSTRACT FROM AUTHOR]

The labyrinth spillway as an upstream regulator is a hydraulic structure that, regardless of the flow rate, can keep its upstream level fairly constant within acceptable bounds. This study demonstrates that there is a variation in the discharge coefficient and in the free dumping limit, as a function of the location of the work with respect to the canal flow direction: apex upstream or apex downstream. This variation has significant importance for the design and operation of this work, which by its structural simplicity and easy hydraulic design, is a convenient regulatory solution for supply systems to canal network users. [ABSTRACT FROM AUTHOR]

The state of the art about labyrinth spillways is presented in a very tight synthesis. Main experimental results about the subject are introduced and expressed in the form of graphics, tables and equations. Additionally included are two work sheets that have been elaborated by the authors of this paper to facilitate the hydraulic design process of this type of spillways. Finally, the need to continue experimental studies of this type of structure is made apparent, specially regarding two aspects which the authors consider of primary importance: the use of other spillway types different from the free fall ones and the structures located downstream of the labyrinth. [ABSTRACT FROM AUTHOR]

River damming and other anthropogenic disturbances of natural habitats are among the main drivers of species loss through a range of direct and indirect effects. While the effects of river damming on aquatic species are relatively well studied, particularly with regard to their impacts on diadromous species and stenotopic riverine specialists, there is a paucity of studies quantifying the effects of dam construction on whole communities., We conducted a global meta-analysis focussed on fish communities, comparing species richness, abundance and proportion of alien species between dammed and undammed rivers. Both longitudinal and cross-sectional studies were examined., We found that construction of dams did not have a noticeable effect on fish richness and abundance, but the increase in proportion of alien species was significant (mean effect size of 0.62)., Our findings suggest that the conversion of lotic waterbodies into lentic habitats result in the extirpation of species unable to withstand a drastic change in environmental conditions, but the loss is compensated by colonising lacustrine or eurytopic species taking advantage of reduced competition and the availability of new niches specific to lentic habitats. However, when eurytopic natives are absent from waterbodies connected to the newly constructed reservoirs, vacant niches are instead exploited by alien species, resulting in impoverishment of native species richness although overall species richness may be maintained. [ABSTRACT FROM AUTHOR]

Large-scale river diversions have been proposed as a way to transport sediment to the deteriorating Mississippi River deltaic plain. These diversions would also transport immense nutrient loads to shallow receiving estuaries, including open water areas where there may be potential for blooms of toxin-producing cyanobacteria. We examined environmental variables and cyanobacteria dynamics in the Lake Pontchartrain Estuary during the spring-summer period of two years: (a) 2011 when the system received a massive inflow of diverted Mississippi River water from the Bonnet Carré Spillway, and (b) 2012 when no diversion occurred. Cluster analysis of 180 samples collected over the course of both years identified five distinct water types grouped according to salinity, temperature, clarity, bioavailable nutrients, and chlorophyll a . Three of these water types were unique to the 2011 diversion event. We found no evidence of immediate, direct cyanobacteria bloom stimulation by diverted nutrients in the “high phytoplankton biomass” cluster associated with the 2011 diversion. Substantial nitrate assimilation by non-harmful phytoplankton occurred as the plume of diverted freshwater traveled through the system that year. The “summer” cluster characterized by nitrogen-limited conditions and including data from both years was characterized by significantly greater cyanobacteria abundance than all other clusters. There was no difference in cyanobacteria abundance between years within the summer cluster. Microcystin levels detected suggested low probability of acute health risks for recreational waters and were not correlated to cyanobacteria abundance. Site-specific understanding of the following is needed to guide diversion management: (i) interannual phytoplankton community variability in non-diversion years, (ii) cyanobacteria inputs from local tributaries, (iii) interactions between plume physics, chemistry, and phytoplankton dynamics, (iv) internal phosphorus feedbacks that may indirectly link diversions to summer blooms, and (v) controls on cyanotoxin production. [ABSTRACT FROM AUTHOR]

On a gabion stepped chute, the steps contribute to the dissipation of turbulent kinetic energy, free-surface aeration may be intense, and there are complex interactions between the free-surface flow and seepage motion. Detailed measurements were conducted in a relatively large gabion stepped spillway model. Using a combination of high-speed movies and phase-detection probe measurements, the air--water flow properties in the step cavities and in the gabions were documented. Strong air--water exchanges between seepage and stepped cavity flows were observed. The data showed a complex bubbly seepage motion in the gabions associated with a high level of interactions between seepage and free-surface flows, leading to a modification of the step cavity recirculation and lesser flow resistance. [ABSTRACT FROM AUTHOR]

Dam safety programs are informed by numerical model solutions of dam-break flood depth, extent, and timing that are uncertain owing to an imperfect mathematical and numerical representation of system dynamics as well as uncertain model parameters and input data, yet model uncertainty is rarely reported. The most extreme and damaging events of greatest interest are also the most infrequent to occur and, thus, seldom studied and poorly understood from a model uncertainty perspective. Here an extraordinary event is considered that occurred in Gangneung, South Korea, on August 31, 2002, when Typhoon Rusa dropped nearly 90 cm of rainfall over a 24 h period, causing two dams in tributary valleys to fail only a few moments apart. A two-dimensional (2D) hydrodynamic flood model is developed using the best available data, calibrated, and validated, and uncertainty is systematically examined. Sources of uncertainty include topographic and bathymetric data, breach geometry data, precipitation data, storm surge data, resistance parameters, and structural model errors that represent deficiencies in the flood model formulation. An uncalibrated solution yields a flood height root-mean square error (RMSE) of 0.4 m and a flood-extent agreement of 86% when the best available measurements are used as data input, including precipitation. Additionally, the calibration of resistance parameters reduces the flood height RMSE to 0.33 m, which is close to the estimated uncertainty in flood height measurements (0.2 m) and RMSE of the best available topographic data (0.2 m). Results show that many factors contribute to solution uncertainty and in different ways depending on whether the focus is flood height, flood extent, or flood discharge and timing, and strategies to reduce uncertainties are presented. [ABSTRACT FROM AUTHOR]