Single Recharge Research Articles

Upscaling Hillslope‐Scale Subsurface Flow to Inform Catchment‐Scale Recession Behavior

AbstractThe subsurface flow contribution to a basin hydrograph is often conceptualized as a single lumped reservoir parameterized by a power law function fit through the observed recession behavior of the basin. However, basins may be better represented as multiple independent subsurface hillslope reservoirs characterized with variable, transient recession behavior as a function of the time history of recharge. In this work, we unify the latter, more complex understanding of the subsurface with the large‐scale power law recession behavior convenient in hydrologic modeling applications. This unification is achieved by deriving upscaling relationships capable of converting simple metrics of basin hillslope topography into a signature basin response characterizing the subsurface‐flow‐induced recession from a single recharge event. Event superposition may then be used to simulate the application of a time series of recharge and a simple scaling relationship may be used to handle basins with homogeneous conductivity. The signature response is informed by numerical simulations of the hillslope‐storage Boussinesq equation for unconfined saturated flow through sloping hillslopes applied to 30 basins in the CAMELS database. The efficacy of the upscaled signature response in replicating numerical simulations in 50 CAMELS basins is demonstrated, as is the practical efficacy of the upscaling relationships for predicting transient recession in 17 of these basins. The upscaled signature response method thus provides a tool for hydrologic modelers to estimate transient recession parameters using the insights of subsurface flow modeling, although the predictions made by this method are unable to capture the full variability of observed recession behavior.

Performance of Passive and Active Balancing Systems of Lithium Batteries in Onerous Mine Environment

To use lithium-iron-phosphate battery packs in the supply systems of any electric mining equipment and/or machines, the required conditions of work safety must be met. This applies in particular to coal mines endangered by fire and/or explosion. To meet the spark-safety conditions, the cells (together with the battery management system—BMS) must be isolated from the influence of the environment, and therefore placed in special fire-tight housings. This significantly degrades the heat dissipation, thus affecting the operating conditions of the cell-packs. Therefore, their usage without the so-called BMS is not recommended, as shown in the authors’ preliminary research. In practice, various BMS are used, most often with the so-called passive balancing. However, their application in mines is uncertain, due to the effect of heating under operation. When it comes to active BMS, they usually possess a quite complex structure and hence, are relatively expensive. Therefore, the authors conducted research for two specially developed active and one commercial passive BMS cooperating with selected lithium-iron-phosphate (LiFePO4) batteries when used in a suspended mining vehicle type PCA-1. The tests were carried out under environmental temperatures ranging from +5 °C to +60 °C. The effect of mismatching (12.5% to 37.5% of total cells number) of the cell parameters on the temperature distribution and voltage fading at the terminals of individual cells was checked. As a result of the investigations, the practical usefulness of the developed active BMS was determined, enabling the extension of the lithium-iron-phosphate battery life under onerous mine conditions, for a single recharge, which is a novelty. On the basis of the obtained results, appropriate practical conclusions were formulated.

Modeling the Matrix-Conduit Exchanges in Both the Epikarst and the Transmission Zone of Karst Systems

Usual conceptual models of karst hydrodynamics highlight the important role of unsaturated subsystems in recharge repartition. However, few of them have been compared with scarce suitable physically-based numerical models. Hybrid models that couple single continuum medium with discrete features promise an improved consideration of karst specificities. Here we evaluate their capability to properly reproduce interactions between a vertical conduit and the surrounding unsaturated matrix. We simulate the response of such a configuration to a single recharge event for various sets of parameters. We show the ability of hybrid models to reproduce the most significant behaviors described in the literature, i.e., transient storage and distribution of recharge, flow concentration towards conduits in the epikarst, and matrix-conduit exchanges varying in time and space. In addition to the explicit conduits, simulating variably saturated flows with the Richards equation and distinguishing the epikarst and the transmission zone are key elements to reproduce most processes. The contrasts between subsystems necessary to observe desired behaviors have been quantified. They are reinforced by the varying matrix saturation that causes realistic competition between matrix and explicit conduits. The study also highlights the need to deepen knowledge of the scaled medium properties we need to know to apply such models to actual cases.

Routing electric vehicles with a single recharge per route

AbstractDriven by environmental considerations, regulations on vehicle emissions, and the offer of major subsidies, electric commercial vehicles (ECVs) are receiving ever stronger attention in logistics companies. Route planning for ECV fleets requires consideration of the special characteristics of ECVs, like limited driving range and the potential need to recharge en route at dedicated recharging stations. From a practical viewpoint, the number of recharge operations of each vehicle can very often be restricted to one recharge per route because (i) typical route distances in the most important application areas of ECVs, like small package shipping and food or beverage distribution, do not require more than one recharge given the current driving range of ECVs, and (ii) operations managers are very reluctant to plan vehicle routes with two or more recharges because recharging operations are perceived as unproductive idle times. We develop a simple hybrid of large neighborhood search and granular tabu search to solve the resulting electric vehicle‐routing problem with time windows and single recharge (EVRPTWS), considering the possibility of both full and partial recharge. The heuristic works on routes represented as customer sequences, and recharge operations are implicitly considered by determining the recharging position in the route, the recharging station to visit, and the amount to be recharged in optimal fashion. We discuss how our algorithm can be extended to handle nonlinear recharging times, different recharging times per station, and time‐dependent waiting times at stations. In numerical studies on EVRPTWS instances from the literature, the method provides optimal or near‐optimal solutions for instances with up to 100 customers within reasonable runtimes. Additional studies investigate the cost savings potential of partial recharges in comparison to full recharges in the presence of time‐window constraints, and examine the factors that influence this cost saving potential.

Novel rechargeable calcium phosphate nanoparticle-filled dental cement.

The objectives were to develop a novel rechargeable cement containing amorphous calcium-phosphate nanoparticles (nanoACP) to suppress tooth decay. Five cements were made with: (1) 60% glass particles (experimental control); (2) 40% glass+20% nanoACP; (3) 30% glass+30% nanoACP; (4) 20% glass+40% nanoACP; (5) 10% glass+50% nanoACP. Groups 1-4 had enamel bond strengths similar to Transbond XT (3M) and Vitremer (3M) (p>0.1). The nanoACP cement had calcium and phosphate ion release which increased with increasing nanoACP fillers. The recharged cement had substantial ion re-release continuously for 14 days after a single recharge. Ion re-release did not decrease with increasing recharge/re-release cycles. Groups 3-5 maintained a safe pH of medium (>5.5); however, control cements had cariogenic pH of medium (<4.5) due to biofilm acid. Therefore, nanoACP cement (1) had good bond strength to enamel, (2) possessed calcium and phosphate ion recharge/re-release capability, and (3) raised biofilm pH to a safe level to inhibit caries.

Electric vehicle routing problem with single or multiple recharges

Abstract Nowadays, due to the new laws and policies related to the greenhouse gas emissions, and the rise of social and ecological awareness of transport sustainability, logistic companies started to incorporate green technologies in their distribution activities. Here, electric vehicles, as a cleaner mode of transport than conventional vehicles come to the fore and many companies are already integrating electric vehicles in their delivery fleets. Compared to the conventional vehicles, electric vehicles have a shorter driving range due to the limited battery capacity, and they need to recharge at charging stations more frequently. To efficiently manage the fleet of electric vehicles, new algorithms that take into account visits to charging stations have to be developed. In this paper, we observed the Electric Vehicle Routing Problem with Time Windows (E-VRPTW) and multiple or single recharge policies during the route. The homogeneous fleet of battery electric vehicles with limited load and battery capacity, customer time windows and full linear recharge at charging stations are considered. The objective is to minimize total traveled distance while operating a minimal number of vehicles. To find the solution of the problem, on larger instances we applied the metaheuristic based on the ruin-recreate principle and on the small instances we solved the mixed integer program with commercial software.

Enabling fast charging – Vehicle considerations

To achieve a successful increase in the plug-in battery electric vehicle (BEV) market, it is anticipated that a significant improvement in battery performance is required to increase the range that BEVs can travel and the rate at which they can be recharged. While the range that BEVs can travel on a single recharge is improving, the recharge rate is still much slower than the refueling rate of conventional internal combustion engine vehicles. To achieve comparable recharge times, we explore the vehicle considerations of charge rates of at least 400 kW. Faster recharge is expected to significantly mitigate the perceived deficiencies for long-distance transportation, to provide alternative charging in densely populated areas where overnight charging at home may not be possible, and to reduce range anxiety for travel within a city when unplanned charging may be required. This substantial increase in charging rate is expected to create technical issues in the design of the battery system and the vehicle's electrical architecture that must be resolved. This work focuses on vehicle system design and total recharge time to meet the goals of implementing improved charge rates and the impacts of these expected increases on system voltage and vehicle components.

Exact Algorithms for Electric Vehicle-Routing Problems with Time Windows

Effective route planning for battery electric commercial vehicle (ECV) fleets has to take into account their limited autonomy and the possibility of visiting recharging stations during the course of a route. In this paper, we consider four variants of the electric vehicle-routing problem with time windows: (i) at most a single recharge per route is allowed, and batteries are fully recharged on visit of a recharging station; (ii) multiple recharges per route, full recharges only; (iii) at most a single recharge per route, and partial battery recharges are possible; and (iv) multiple, partial recharges. For each variant, we present exact branch-price-and-cut algorithms that rely on customized monodirectional and bidirectional labeling algorithms for generating feasible vehicle routes. In computational studies, we find that all four variants are solvable for instances with up to 100 customers and 21 recharging stations. This success can be attributed to the tailored resource extension functions (REFs) that enable efficient labeling with constant time feasibility checking and strong dominance rules, even if these REFs are intricate and rather elaborate to derive. The studies also highlight the superiority of the bidirectional labeling algorithms compared to the monodirectional ones. Finally, we find that allowing multiple as well as partial recharges both help to reduce routing costs and the number of employed vehicles in comparison to the variants with single and with full recharges.

Analyses of infrequent (quasi-decadal) large groundwater recharge events in the northern Great Basin: Their importance for groundwater availability, use, and management

There has been a considerable amount of research linking climatic variability to hydrologic responses in the western United States. Although much effort has been spent to assess and predict changes in surface water resources, little has been done to understand how climatic events and changes affect groundwater resources. This study focuses on characterizing and quantifying the effects of large, multiyear, quasi-decadal groundwater recharge events in the northern Utah portion of the Great Basin for the period 1960–2013. Annual groundwater level data were analyzed with climatic data to characterize climatic conditions and frequency of these large recharge events. Using observed water-level changes and multivariate analysis, five large groundwater recharge events were identified with a frequency of about 11–13 years. These events were generally characterized as having above-average annual precipitation and snow water equivalent and below-average seasonal temperatures, especially during the spring (April through June). Existing groundwater flow models for several basins within the study area were used to quantify changes in groundwater storage from these events. Simulated groundwater storage increases per basin from a single recharge event ranged from about 115 to 205 Mm3. Extrapolating these amounts over the entire northern Great Basin indicates that a single large quasi-decadal recharge event could result in billions of cubic meters of groundwater storage. Understanding the role of these large quasi-decadal recharge events in replenishing aquifers and sustaining water supplies is crucial for long-term groundwater management.

The Improved Trial Method of Hydrogeological Parameters Inversion by Using Single Well Recharge Formula

Based on the related theory under recharge condition, the trial method solving the hydrogeological parameters of unsteady flow by single well recharge test according to Theis Formula can be gotten. Integrating the cubic spline interpolation curve of the parameters into the said trial method, the improved trial method of inversion hydrogeological parameters is worked out by using single well recharge formula. In this method, the cubic spline interpolation curve is constructed from three groups of initial adjacent comparison points at first. Then the fussy trial process of the traditional trial method can be replaced by line-line intersection. It can be seen from the practical verification of the data of underground water manual recharge test somewhere in Xi’an City that the calculation steps here are greatly simplified comparing to the traditional trial method. And the calculation result is basically the same with the existing data, which shows that this method is simple and effective.

Unsaturated zone travel time to groundwater on a vulnerable site

A bromide (Br) tracing experiment was conducted to ascertain unsaturated zone travel time to groundwater on a site with a karstified limestone aquifer overlain by a thin free-draining overburden. Br tracer was applied to areas surrounding two boreholes; soil solution and groundwater Br concentrations were monitored. Bromide was first detected after eight and 34 days in the soil solution and groundwater. The quick break-through of the applied Br in the soil solution and groundwater indicates the presence of preferential flow in the soil at this site. The time to maximum groundwater Br concentration supports a dominant matrix flow path through the overburden and then preferential flow through the unsaturated limestone bedrock. The results indicated that the transport of conservative contaminants, such as nitrate, can be expected to occur in a single recharge season. The occurrence of preferential flow raises concerns over rapid transport of non-conservative contaminants such as faecal coliforms and this merits further investigation.

An analytical study of groundwater fluctuations in unconfined leaky aquifers induced by multiple localized recharge and withdrawal

&lt;p&gt;Commonly used analytical methods for assessing the effects of recharge and withdrawal on the groundwater flow system are based on an idealistic assumption that the aquifer&amp;rsquo;s base is fully impervious. In reality, the hydrostratigraphic conditions are often complex and involve leakage induced flow between aquifer and the confining layers. In this study, a simple analytical procedure is presented for determining the spatial and temporal distribution of water head in an unconfined aquifer system due to multiple localized recharge and withdrawal at time-varying rates. A new transient function is introduced that can conveniently approximate the rising and recession limbs of any single recharge hydrograph. Solution of linearized two-dimensional groundwater flow equation under Dirichlet and Neumann boundary conditions is obtained using finite Fourier cosine transform with analytic inversion. The study has at least one clear advantage over the existing solutions that it accounts for the vertical leakage in water table buildup and drawdown analysis. A computational example demonstrates that the leakage induced flow plays an important role in recharge and withdrawal processes of unconfined aquifer system. The model results can be used for estimating aquifer&amp;rsquo;s hydraulic properties and validation of numerical models.&lt;/p&gt;

A new approach to model the spatial and temporal variability of recharge to karst aquifers

Abstract. In karst systems, near-surface dissolution of carbonate rock results in a high spatial and temporal variability of groundwater recharge. To adequately represent the dominating recharge processes in hydrological models is still a challenge, especially in data scarce regions. In this study, we developed a recharge model that is based on a conceptual model of the epikarst. It represents epikarst heterogeneity as a set of system property distributions to produce not only a single recharge time series, but a variety of time series representing the spatial recharge variability. We tested the new model with a unique set of spatially distributed flow and tracer observations in a karstic cave at Mt. Carmel, Israel. We transformed the spatial variability into statistical variables and apply an iterative calibration strategy in which more and more data was added to the calibration. Thereby, we could show that the model is only able to produce realistic results when the information about the spatial variability of the observations was included into the model calibration. We could also show that tracer information improves the model performance if data about the spatial variability is not included.

Unsaturated zone travel time to groundwater on a vulnerable site

A bromide (Br) tracing experiment was conducted to ascertain unsaturated zone travel time to groundwater on a site with a karstified limestone aquifer overlain by a thin free-draining overburden. Br tracer was applied to areas surrounding two boreholes; soil solution and groundwater Br concentrations were monitored. Bromide was first detected after eight and 34 days in the soil solution and groundwater. The quick break-through of the applied Br in the soil solution and groundwater indicates the presence of preferential flow in the soil at this site. The time to maximum groundwater Br concentration supports a dominant matrix flow path through the overburden and then preferential flow through the unsaturated limestone bedrock. The results indicated that the transport of conservative contaminants, such as nitrate, can be expected to occur in a single recharge season. The occurrence of preferential flow raises concerns over rapid transport of non-conservative contaminants such as faecal coliforms and this merits further investigation.

The hydrothermal system of Volcan Purac�, Colombia

This paper presents chemical and isotopic data for thermal waters, gases and S deposits from Volcan Purace (summit elevation ∼4600 m) in SW Colombia. Hot gas discharges from fumaroles in and around the summit crater, and thermal waters discharge from three areas on its flanks. The waters from all areas have δD values of-75±1, indicating a single recharge area at high elevation on the volcano. Aircorrected values of3He/4He in thermal waters range from 3.8 to 6.7 RA, and approach those for crater fumarole gas (6.1–7.1 RA), indicating widespread addition of magmatic volatiles. An economic S deposit (El Vinagre) is being mined in the Rio Vinagre fault zone at 3600 m elevation. Sulfur isotopic data are consistent with a magmatic origin for S species in thermal waters and gases, and for the S ore deposit. Isotopic equilibration between S species may have occurred at 220±40°C, which overlaps possible equilibration temperatures (170±40°C) determined by a variety of other geothermometers for neutral thermal waters. Apparent CH4−CO2 equilibration temperatures for gases from thermal springs (400±50°C) and crater fumaroles (520±60°C) reflect higher temperatures deeper in the system. Hot magmatic gas ascending through the Rio Vinagre fault zone is though to have precipitated S and generated thermal waters by interaction with descending meteoric waters.

Hydraulic calculation of groundwater flow velocity and age: examination of the basic premises

The equations applied to the calculation of groundwater flow velocity and hydraulic age are based on assumptions that are frequently invalidated or not satisfactorily met by actual field conditions. Problem areas that account for significant errors in the calculated values of groundwater flow velocity and age include: (1) poorly defined hydraulic variables; (2) lack of single recharge and discharge areas; (3) extremely small or nonexistent discharge areas and entrapment of ground water in ‘dead’ volumes in deep confined systems; (4) topographic and geologic controls affecting the flow path; (5) fractures/conduits affecting groundwater flow in supposed homogeneous porous media; (6) concealed structural and lithological barriers; (7) mixing of ground water of various ages; (8) slow hydraulic response to climatic or geologic changes. Checks based on physical, chemical, and isotopic data are advocated as a means to validate the basic assumptions used for calculating groundwater flow velocity and age. Hydraulic and isotopically determined groundwater ages provide essential and complementary hydrologic information. Both ages have to be computed with the utmost care, and the validity of the basic premises in each case study must be checked.

Radial fuel-water transport in aquifer near an injection well

A new physico-mathematical approach is developed for modelling of fuel migration in an axisymmetric groundwater flow by considering the various dimensionless parameters governing the transport processes. The self-similar solution scheme developed for a time-dependent water injection rate describes the evolution of the fuel saturation in the aquifer near a single recharge well. It is found that the capillary forces prevent the fuel from being removed downstream by injecting water through the well. The time dependent saturation profiles calculated from several exact analytical solutions exhibit the effects of various dimensionless parameters in fuel migration in radial water flow.

Some analytical solutions for seawater intrusion control with recharge wells

Closed-form solutions are obtained for the steady-state location of the salt-water interface and stagnation points when either a single recharge well or an infinite number of recharge wells are used to inject freshwater into a coastal aquifer. It is shown how the solutions can be applied to either confined or unconfined flows, and the results are illustrated with a numerical example.

The isotope hydrology of the Mereenie Sandstone aquifer, Alice Springs, Northern Territory, Australia

The town of Alice Springs is situated within the arid zone of central Australia and derives its water supply from production bores in Mereenie Sandstone. Twenty-nine samples of this water and other surrounding water have been analysed for their chemical, radiocarbon, stable carbon, deuterium and 18O composition to investigate recharge to the aquifer system. The measured 14C contents range from 5.1 to 63.4% modern. There is no correlation between borehole depth and percentage modern carbon; however, the samples fall into several groups when the percentage modern carbon is plotted against the reciprocal of the total carbonate content. Within each group, the δ D and δ 18O values are constant and isotopically much lighter than the average annual rainfall value. It is believed that each group represents a single recharge event, and that recharge to the aquifer system occurred at intervals of a few millennia, when climatic conditions were different from those of today.