Open Channel Networks Research Articles

A semi-quantitative risk model for dairy farms to pinpoint and break source-pathway connections between nutrient sources and open drainage channel sections

IntroductionOn intensive grassland dairy farms in high rainfall areas with poorly drained soils, networks of open drainage channels linked to in-field drainage systems are needed to enable farm operations. Nitrogen and phosphorus point and diffuse sources may be connected to this open drainage channel network along surface and subsurface pathways, with negative impacts upon delivery to the downstream aquatic system.MethodsThis study developed a semi-quantitative risk assessment model by: (1) selecting parameters (categorical or continuous) representing the nutrient transfer continuum and (2) scoring (relative magnitude and impact) the risk of nutrient source connectivity and delivery for every open drainage channel section across seven dairy farms.Results and DiscussionA Risk Index Classification System consisting of low, medium, high, or very high-risk class was developed, with high or above requiring a mitigation plan. Results showed that 23%, 68%, 9% and 0% of all open drainage channels on study farms were identified as low, moderate, high and very high-risk, respectively. A range from 2% to 25% per farm of the open drainage channels was classified as high-risk that potentially needed mitigation, although none was identified as very high-risk. Two-thirds of the high-risk open drainage channels were connected to the farmyards, with potential for high nutrient loss from point sources. A combined approach of source management and targeted breaking of the pathway (e.g., in-channel filters, water diversion bars) may help minimise nutrient losses from high risk open drainage channels on poorly draining soils.

Skeletonization of open-channels networks - New approaches

Due to the complexity of open-channel networks in which a lengthy procedure is required to understand and analyze their behavior. This paper introduces a methodology for the skeletonization of complex tree-shaped open channel systems. The aim is to aggregate separate branches into one equivalent branch, which has a new skeletonization factor. Three different illustrative examples of river systems using two approaches are analyzed. The software package HEC-RAS is employed to simulate the proposed open channel networks as a one-dimensional steady, gradually varied flow state. Results show that there is a strong correlation between the skeletonization factor required for the equivalent branch and the flow rate of the equivalent branch. The skeletonization factor is also significantly affected by an increase in the ratio of the bed width of each branch canal to that of the main channel in Approach A. The water depth along the main channel has increased more significantly in approach B than in approach A, with average increases of 49.5 %, 29.2 %, and 14.1 % for a number of branches equal to 2, 4, and 6, respectively. Finally, the developed skeletonization concept can be used to represent complex open-channels network models.

Adaptive Consensus-Based Reference Generation for the Regulation of Open-Channel Networks

Adaptive Consensus-Based Reference Generation for the Regulation of Open-Channel Networks

Managing a cyanobacteria harmful algae bloom “hotspot” in the Sacramento – San Joaquin Delta, California

Cyanobacterial harmful algal blooms (CHABs) have become a persistent seasonal problem in the upper San Francisco Estuary, California also known as the Sacramento-San Joaquin Delta (Delta). The Delta is comprised of a complex network of open water bodies, channels, and sloughs. The terminus of the Stockton Channel is an area identified as a CHAB “hotspot.” As CHABs increase in severity, there is an urgent need to better understand CHAB drivers to identify and implement mitigation measures that can be used in an estuarine complex like the Delta. We investigated water quality conditions and nutrient dynamics in the Stockton Channel by measuring nutrients in the water column, sediments, and pore waters. In situ nutrient addition bioassay experiments were used to assess the effects of nutrient enrichment on total algal/cyanobacterial growth and pigment concentrations. In both June and September, relative to unamended controls, total chlorophyll and cyanobacterial pigment concentrations were unaffected by nutrient additions; hence, the study area showed signs of classical hypereutrophication, with ambient nitrogen and phosphorus present in excess of algal growth requirements. A cyanobacterial bloom, dominated by Microcystis spp. was present throughout the study area but was most severe and persistent at the shallowest site at the channel terminus. At this site, Microcystis spp. created water quality conditions that allowed for a prolonged bloom from June through September. While targeted nutrient reductions are recommended for long term mitigation, on a shorter timescale, our findings suggest that physical/mechanical controls are the more promising alternative approaches to reduce the severity of CHABs in the terminus of the Stockton Channel.

Dehumidification efficiency in the conditions of climate change in the Novgorod region

Agricultural production is closely related to natural and climatic factors, of which meteorological factors are the most variable and active. The analysis of climatic precipitation and temperature norms according to the data of 4 meteorological stations of the Novgorod region for the period 1891-2020 showed their steady increase, except for the Novgorod meteorological station, where the annual precipitation rate by 2020 decreased against the background of temperature growth. Analysis of the results of meteorological observations over the past 60 years has shown that there is a steady trend in the Novgorod region to increase the degree of humidification: the hydrothermal coefficient has increased from 1.36 to 1.46. This happened due to the excess of the increase in precipitation over the increase in temperature, so agricultural production of crop production is impossible without reclamation measures. The aim of the research was to gain new knowledge in the formation of soil moisture regimes under the influence of drainage reclamation in the conditions of climate change. In the Non-Chernozem zone, two main methods of drainage are common - a network of open channels and closed drains. Studies on the formation of soil moisture regimes were carried out during 2019-2021 on experimental production sites of closed and open drainage on 8 variants of structures. The conducted studies of the efficiency of the drainage systems of closed and open drainage allowed us to conclude that closed drainage systems better provide the water-air regime of the soil compared to open drainage: the period of soil being in a waterlogged state is 2 times shorter (50 days on open drainage structures and 25 days on closed drainage structures).The most optimal water-air regime of the soil among the options with closed drainage was provided by drainage systems with filling the drainage trench with wood chips, on which the range of moisture changes in the root-inhabited soil layer during 3 years of observation was closest to optimal and amounted to 210-114 mm. Among the options for open drainage are systems of runoff hollows in combination with cultivation strips.

Inverse task of pollution spreading – Localization of source in extensive open channel network structure

Abstract This paper is focused on the problem of the pollutant source localisation in streams in other words the solution of the inverse problem of pollution spreading with in an extensive open channel network structure, i.e. in a complex system of rivers, channels and creeks in natural catchments or sewer systems in urban catchments. The design of the overall localisation procedure is based on the requirement that the entire localization system be operative and fast enough to enable quick operative interventions and help prevent the spread of pollution. The proposed model, as well as, the overall localisation procedure was calibrated and tested on a real sewer system, which represents in this case an extensive open channel network structure with free surface flow. The test results are successful and confirmed applicability of proposed localization tool in simple real conditions. However, the localisation procedure has pros and cons, which are discussed in the paper.

Two-Step Solvothermal Process for Nanoarchitectonics of Metastable Hexagonal WO3 Nanoplates

Hexagonal tungsten trioxide (h-WO3) has shown great potential for application in electrochromic devices, gas sensors, battery electrodes, and as photo-catalysts. The h-WO3 structure features a unique large network of open hexagonal channels that allow for intercalation. The hydrothermal synthesis of h-WO3 using sodium tungstate dihydrate as a precursor is widely explored, however, the residual alkaline ions are difficult to eliminate during the synthesis. The solvothermal synthesis using tungsten hexachloride as starting materials largely avoids the use of alkaline ions, but the effect of various synthesis parameters is not well-understood yet. To resolve these ambiguities, this study provides a reliable route to obtain h-WO3 via solvothermal synthesis and dehydration annealing. The effects of precursor concentration, water content, synthesis temperature, and synthesis time, as well as dehydration temperature, on the as-synthesized crystal structure and crystal morphology are studied.

The PDP feedback control design and exponential stability for a star-shaped network of open channels

This paper investigates the stability of a star-shaped network of open channels under the position and delayed position (PDP) feedback controller. Firstly, we deal with the special case of a single channel, and the well-posedness and exponential stability of the closed-loop system are established by using the semi-group theory and a strict Lyapunov function. The explicit dissipative conditions for system parameters and time-delay are presented. Then, we analyze the delay-independent stability of the closed-loop system by the method of characteristic. Next, we extend the PDP control design to the star-shaped network of [Formula: see text] channels with [Formula: see text] inlet channels and one outlet channel, and the exponential stability can be obtained similarly. Finally, we give some numerical simulations for the special case of three channels.

Water Sensitive Cities: An Integrated Approach to Enhance Urban Flood Resilience in Parma (Northern Italy)

Climate change is globally causing more intense meteorological phenomena. Our cities experience increased rainfall intensity, more intense heat waves, and prolonged droughts providing economic, social, health and environmental challenges. Combined with population growth and rapid urbanization, the increasing impact of climate change will make our cities more and more vulnerable, especially to urban flooding. In order to adapt our urban water systems to these challenges, the adoption of newly emerging water management strategies is required. The complexity and scale of this challenge calls for the integration of knowledge from different disciplines and collaborative approaches. The water sensitive cities principles provide guidance for developing new techniques, strategies, policies, and tools to improve the livability, sustainability, and resilience of cities. In this study, the DAnCE4Water modeling approach promoting the development of water sensitive cities was applied to Parma, an Italian town that has faced serious water issues in the last few years. The city, indeed, had to face the consequences of flooding several times, caused by the inadequacy of both the network of open channels and the sewerage network due to the urban expansion and climate change of the last 30 years. Through the model, the efficiency of decentralized technologies, such as green roofs and porous pavement, and their integration with the existing centralized combined sewer system was assessed under a range of urban development scenarios. The obtained results show that the adoption of an integrated approach, including soft engineering hydraulic strategies, consisting in the use of natural and sustainable solutions, can increase resilience to urban flooding. Further, the study shows that there is a critical need for strategic investment in solutions that will deliver long-term sustainable outcomes.

Hydrostatic Pressure Wheel for Regulation of Open Channel Networks and for the Energy Supply of Isolated Sites

The Hydrostatic Pressure Wheel is an innovative solution to regulate flow discharges and waters heights in open channel networks. Indeed, they can maintain a water depth while producing energy for supplying sensors and a regulation system. To prove the feasibility of this solution, a complete model of water depth–discharge–rotational speed relationship has been elaborated. The latter takes into account the different energy losses present in the turbine. Experimental measurements achieved in IMFT laboratory allowed to calibrate the coefficients of head losses relevant for a large range of operating conditions. Once the model had been validated, an extrapolation to a real case showed the possibility of maintaining upstream water level but also of being able to produce sufficient energy for supplying in energy isolated sites. The solution thus makes it possible to satisfy primary energy needs while respecting the principles of frugal innovation: simplicity, robustness, reduced environmental impact.

Automated Detection of Instability-Inducing Channel Geometry Transitions in Saint-Venant Simulation of Large-Scale River Networks

A new sweep-search algorithm (SSA) is developed and tested to identify the channel geometry transitions responsible for numerical convergence failure in a Saint-Venant equation (SVE) simulation of a large-scale open-channel network. Numerical instabilities are known to occur at “sharp” transitions in discrete geometry, but the identification of problem locations has been a matter of modeler’s art and a roadblock to implementing large-scale SVE simulations. The new method implements techniques from graph theory applied to a steady-state 1D shallow-water equation solver to recursively examine the numerical stability of each flowpath through the channel network. The SSA is validated with a short river reach and tested by the simulation of ten complete river systems of the Texas–Gulf Coast region by using the extreme hydrological conditions recorded during hurricane Harvey. The SSA successfully identified the problematic channel sections in all tested river systems. Subsequent modification of the problem sections allowed stable solution by an unsteady SVE numerical solver. The new SSA approach permits automated and consistent identification of problem channel geometry in large open-channel network data sets, which is necessary to effectively apply the fully dynamic Saint-Venant equations to large-scale river networks or for city-wide stormwater networks.

Garnet as a monitor for melt–rock interaction: Textural, mineralogical, and compositional evidence of partial melting and melt‐driven metasomatism

AbstractIn this study, we focus on a partially melted garnet‐bearing granulite from the Salvador–Esplanade Belt (Salvador da Bahia, Brazil), and examine the behaviour of major and trace elements during partial melting and melt‐driven metasomatism. Phase equilibria modelling and U–Th–Pb geochronology show that the sample underwent partial melting during the heating segment of the decompression path from ~1.2 GPa and 675–700°C to ~0.8 GPa and 790°C at c. 2.06 Ga. During the final stage of decompression, from 0.8 to ~0.5 GPa, physical segregation of melt resulted in the establishment of chemical potential gradients and mass transfer between the host granulite and the leucosome. Modelling shows that H2O, CaO, K2O, and Na2O diffused from the melt into the host residue, whereas SiO2 was transferred from the host granulite into the adjacent leucosome. Opposed senses of diffusional transfer resulted in the formation of a quartz‐rich anhydrous leucosome and a quartz‐depleted selvedge in the host granulite. Compositional maps show that garnet exhibit contrasting major and trace element distributions depending on their textural position. The largest garnet located in the quartz‐depleted selvedge preserve their original Ca and trace element growth zoning. A transition from bell‐shaped profiles for Y and heavy rare earth elements to bowl‐shaped profiles for light rare earth elements is consistent with a typical Rayleigh fractionation model, fast intergranular element mobility, and rock‐wide equilibrium during prograde partial melting. In contrast, smaller garnet away from the leucosome show prograde growth zoning modified by intragranular diffusion, as evidenced by a network of open channels and healed cracks that act as connecting pathways between the matrix and garnet core. This results in either subtle modification of both major and trace elements adjacent to the inner core inclusions, or a complete re‐equilibration. Recognition that the original Ca growth zoning was later modified by intragranular diffusion implies that misleading thermobarometric results and tectonic interpretations would be obtained if the core composition was used to fingerprint the early garnet nucleation stage. This study demonstrates that at high temperature (>750°C) and in the presence of melt, REE are not less vulnerable to diffusive resetting than divalent cations like Ca2+.

Evaluating the performances of a flexible mechanism of water diversion: application on a northern Italy gravity-driven irrigation channel

Improving the management of irrigation schemes is a priority in the Mediterranean countries of the EU to achieve the objectives of the Water Framework Directive 2000/60EC. In the case of schemes based on open-channel networks for water conveyance and delivery, a limitation to the management efficiency is the huge number of gates that need to be controlled and regulated manually to adapt the flow to the actual irrigation water demand. Automated and coordinated gate regulation of large irrigation schemes has been successfully implemented in some areas of the world (e.g., NSW, Australia), but it implies huge public investments that are often unavailable. Opposite to this top–down approach, the Lombardy region (the largest irrigated region in the EU) has explored an approach based on funding small projects, which should demonstrate the potential of innovation in irrigation practice and foster the expansion of the most effective measures. In this paper, we analyze the effects of one of these projects, consisting in the substitution of a manual gate, controlling the supply of irrigation to a 150 ha irrigation district, with an automated, remotely controlled gate. Nine years of daily flow measurements at the district inlet, provided by the irrigation consortium that manages the gate, were compared with the rigid flow regulation that was applied when the inlet gate was manually regulated and with the irrigation water requirements simulated with a distributed agro-hydrological model widely used in the region for irrigation accounting and planning. The results show that the flexible regulation allowed by the new gate provided an average water saving of 12,000 m3/ha/year compared to the rigid regulation system. A further, though smaller, margin of improvement of 5000 m3/ha/year can be achieved with an optimal regulation that follows exactly the crop water requirements. A further interesting empirical evidence is that the simulation model fits very well the irrigation water requirements of the district using only easily accessible meteorological input data, without exploiting any information from ground or remote sensors to update soil moisture or crop developments during the season. This indicates that it could be effectively used, with very limited costs and effort, to support and improve the gate management. Finally, a preliminary economic analysis shows that the cost of the gate installation is sustainable, but the upscaling of this type of intervention to larger areas requires the support of public funding to cover approximately half of the cost of investment needed for the networking infrastructures.

CONVEYANCE LOSSES ESTIMATION FOR OPEN CHANNELS IN MIDDLE EGYPT CASE STUDY: ALMANNA MAIN CANAL, AND ITS BRANCHES

Whereas the irrigation water transmission open channel network in Egypt, is one of the largest and longest networks all over the world that dogged in permeable soil (Its length reaches about 33500 km). In a country that suffers greatly from an increasing shortage of limited available irrigation water quantities, ignoring the expected huge quantities of irrigation water losses through transport operations is a path of madness, to bridge the accelerated gap between what is required, and what is exist. Irrigation water conveyance losses include seepage, evaporation, and transpiration losses. The used data in this research was collected from the field and through the official Ministry of water resources and irrigation authority in Assiut governorate. The analysis of the data proved that, the total loss of irrigation water from Almanna canal and its branches reaches about 16.05 Million cubic meters monthly. The lost water through only seepage reaches about 15.95 Million cubic meters monthly, representing 99% of all lost irrigation water. While, the rate of increase in the evaporation losses at earthen sections more than the designed sections losses can be neglected. Thus, the lining of Almanna canal and its branches is the most effective solution for saving such a huge amount of water, and directed it to irrigate some newly reclaimed areas, in addition, to solve the problems of non-arrival of the irrigation water to the ends of some irrigation canals. At the same time, improving the environmental situation of the surrounding agricultural community.

Effective 3D open-channel nanostructures of a MgMn2O4 positive electrode for rechargeable Mg batteries operated at room temperature

Room-temperature operations of rechargeable Mg coin-cell batteries have been achieved using a spinel MgMn2O4 powder having a large specific surface area > 200 m2 g–1 and more than 90% porosity with a triple-tiered 3D open-channel network.

Productivity of hydraulic fractures with heterogeneous proppant placement and acid etched walls

Production estimation for hydraulic fractures with heterogeneous proppant placement is not straightforward and requires numerical solution. Contrasts in hydraulic conductivity are intentionally created by channel fracturing, when proppants are injected by pulses in stages, or as a result of fracture wall etching by acids. In both types of fracturing treatment, a connected network of open channels is expected to form within a fracture. The channels not only create primary pathways for producing fluids, they are also very compliant regions that are subject to closure and pinching under large effective stresses. We develop a numerical model of hydraulic fracture productivity considering heterogeneous distribution of conductivity and channels. For various geometries of proppant pillars and etched walls, reservoir properties, and size of perforation intervals, we calculate total production rates from a hydraulic fracture as a function of pressure drawdown. We evaluate other productivity indicators such as skin factor and effective dimensionless conductivity traditionally used by field engineers. We show that our numerical solution agrees with exact solutions of several problems with rectangular and circular fracture geometry, with uniform or stepwise conductivity profile. The presented model can be used for accurate evaluation of pressure-dependent well productivity after channel fracturing and acid fracture treatments. An important application of our model is the optimization of the pressure drawdown schedule to reach the maximum production rates in the created fractures, which is often ignored by oilfield companies.

Efficient Solution Algorithm for Unsteady Flow in Channel Networks Using Subtiming Technique

AbstractThis paper describes a computationally efficient numerical model for unsteady flow computations in open channel networks using the four-point Preissmann implicit scheme. The proposed algori...

Stability of a Class of Controllers for a Sequence of Canals and Structures

Networks of open channels form an important category of environmental systems. They are used not only to transport irrigation and drainage water, but also as highways for barges transporting raw materials and goods. Automatic control of these systems poses specific problems. A local stability analysis for an open canal that is split into several parts by sluice gates under discrete time control is proposed. Theoretical justification is provided, and the method is tested for a simple controller. The method allows the examination of local stability of a series of canals when equipped with a controller from a large class, linear and non-linear. The analysis is based on the analysis of the eigenvalues of a matrix derived from the controlled system that is small enough to allow for parameter optimization.

Influence of bed elevation discordance on flow patterns and head losses in an open-channel confluence

Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common. Studies of schematized confluences with a step at the interface between the tributary and the main channel bed reveal that bed elevation discordance is an important additional control for the confluence hydrodynamics. This study aimed to improve understanding of the influence of bed elevation discordance on the flow patterns and head losses in a right-angled confluence of an open channel with rectangular cross-sections. A large eddy simulation (LES)-based numerical model was set up and validated with experiments by others. Four configurations with different bed discordance ratios were investigated. The results confirm that, with increasing bed elevation discordance, the tributary streamlines at the confluence interface deviate less from the geometrical confluence angle, the extent of the recirculation zone (RZ) gets smaller, the ratio of the water depth upstream to that downstream of the confluence decreases, and the water level depression reduces. The bed elevation discordance also leads to the development of a large-scale structure in the lee of the step. Despite the appearance of the large-scale structure, the reduced extent of the RZ and associated changes in flow deflection/contraction reduce total head losses experienced by the main channel with an increase of the bed discordance ratio. It turns out that bed elevation discordance converts the lateral momentum from the tributary to streamwise momentum in the main channel more efficiently.

Numerical modelling of open channel junctions using the Riemann problem approach

ABSTRACTThe solution of an extended Riemann problem is used to provide the internal boundary conditions at a junction when simulating one-dimensional flow through an open channel network. The proposed approach, compared to classic junction models, does not require the tuning of semi-empirical coefficients and it is theoretically well-founded. The Riemann problem approach is validated using experimental data, two-dimensional model results and analytical solutions. In particular, a set of experimental data is used to test each model under subcritical steady flow conditions, and different channel junctions are considered, with both continuous and discontinuous bottom elevation. Moreover, the numerical results are compared with analytical solutions in a star network to test unsteady conditions. Satisfactory results are obtained for all the simulations, and particularly for Y-shaped networks and for cases involving variations in channels' bottom and width. By contrast, classic models suffer when geometrical channel effects are involved.