Natural Discharge Research Articles

Needle-disk electrospinning inspired by natural point discharge

Point discharge is a natural phenomenon which principle and application are both under active investigation. In this work, a needle-disk electrode spinneret was designed through the combination of the point discharge concept and the merits of typical needleless electrospinning (disk as spinneret). The desired outcome for point electrode system is to produce a controllable process of jet formation, with respect to the control of jet site and amount of jets under a lower applied voltage value. Two comparisons were used: (i) in comparison to the typical needleless electrospinning method (disk electrospinning), the needle-disk electrospinning produce finer and more uniform nanofibers. Further numerical simulation results confirmed that the needle-disk electrode induced electric field intensity which is 5.33 times higher than that of disk electrode under the same parameters; (ii) both the numerical simulation and experimental results showed that needle-disk electrospinning can produce competitive quality of nanofibers accompanied by enhanced throughput, compared with the traditional single-needle electrospinning method. Finally, we demonstrate that needle-disk electrospinning produces nanofiber with super-high throughput of 13.5 g/h, which is 183 times higher than traditional electrospinning under similar spinning conditions.

Organic compounds in thermal water: The Mutnovskii area and the Uzon caldera

New data are reported relating to the presence and relative concentrations of organic compounds of medium volatility in samples from the water of hot springs and in the condensate of a steam–water mixture from wells drilled in the Mutnovskii geothermal area and from a well and springs in the Uzon caldera. The Mutnovskii area was found to contain 95 compounds belonging to 16 homologous series, with 71 compounds (12 series) in the Uzon caldera. Among these we found homologous series of biologically important compounds: carbonic acids, alcohols, ethers, aldehydes, ketones, and others. Evidence was obtained for a contribution of the abiogenic component in organic matter from sterile condensates of an overheated steam–water mixture from wells (alkanes, aromatic hydrocarbons, ketones, alcohols, and others) and in thermal water from natural discharges (in particular, alkanes and chlorine-containing hydrocarbons). The results of this study can be used for the preparation and conduction of laboratory experiments in prebiological chemistry under conditions that simulate a hydrothermal environment.

Assessing the role of climate and resource management on groundwater dependent ecosystem changes in arid environments with the Landsat archive

Abstract Groundwater dependent ecosystems (GDEs) rely on near-surface groundwater. These systems are receiving more attention with rising air temperature, prolonged drought, and where groundwater pumping captures natural groundwater discharge for anthropogenic use. Phreatophyte shrublands, meadows, and riparian areas are GDEs that provide critical habitat for many sensitive species, especially in arid and semi-arid environments. While GDEs are vital for ecosystem services and function, their long-term (i.e. ~ 30 years) spatial and temporal variability is poorly understood with respect to local and regional scale climate, groundwater, and rangeland management. In this work, we compute time series of NDVI derived from sensors of the Landsat TM, ETM +, and OLI lineage for assessing GDEs in a variety of land and water management contexts. Changes in vegetation vigor based on climate, groundwater availability, and land management in arid landscapes are detectable with Landsat. However, the effective quantification of these ecosystem changes can be undermined if changes in spectral bandwidths between different Landsat sensors introduce biases in derived vegetation indices, and if climate, and land and water management histories are not well understood. The objective of this work is to 1) use the Landsat 8 under-fly dataset to quantify differences in spectral reflectance and NDVI between Landsat 7 ETM + and Landsat 8 OLI for a range of vegetation communities in arid and semiarid regions of the southwestern United States, and 2) demonstrate the value of 30-year historical vegetation index and climate datasets for assessing GDEs. Specific study areas were chosen to represent a range of GDEs and environmental conditions important for three scenarios: baseline monitoring of vegetation and climate, riparian restoration, and groundwater level changes. Google's Earth Engine cloud computing and environmental monitoring platform is used to rapidly access and analyze the Landsat archive along with downscaled North American Land Data Assimilation System gridded meteorological data, which are used for both atmospheric correction and correlation analysis. Results from the cross-sensor comparison indicate a benefit from the application of a consistent atmospheric correction method, and that NDVI derived from Landsat 7 and 8 are very similar within the study area. Results from continuous Landsat time series analysis clearly illustrate that there are strong correlations between changes in vegetation vigor, precipitation, evaporative demand, depth to groundwater, and riparian restoration. Trends in summer NDVI associated with riparian restoration and groundwater level changes were found to be statistically significant, and interannual summer NDVI was found to be moderately correlated to interannual water-year precipitation for baseline study sites. Results clearly highlight the complementary relationship between water-year PPT, NDVI, and evaporative demand, and are consistent with regional vegetation index and complementary relationship studies. This work is supporting land and water managers for evaluation of GDEs with respect to climate, groundwater, and resource management.

A Statistical Model for Managing Water Temperature in Streams with Anthropogenic Influences

AbstractStreams in the Pacific Northwest (Oregon, Washington, British Columbia) face rising summer temperatures and increasing anthropogenic influence, with consequences for fish populations. Guidance is needed in small managed watersheds for setting reservoir release rates or for the restriction of water extractions to meet the needs of fish and aquatic ecosystems. Existing environmental flow methods focus on discharge rates and do not typically consider water temperatures, and detailed thermal models are too complex for widespread implementation. We used multiple logistic regression to develop statistical models for estimating the probability of exceeding a salmonid stream temperature threshold of 22 °C as a function of discharge and maximum daily air temperatures. Data required are air temperature, stream temperature and stream discharge over a minimum of one summer. The models are used to make minimum discharge recommendations under varying forecast weather conditions. The method was applied to nine streams in the Pacific Northwest. Minimum recommended discharge generally ranged from 23% to 86% of mean annual discharge and was higher than observed low flows in most streams. Comparison of the new method to existing methods for Fortune Creek in British Columbia indicated that total season discharge volumes could be reduced while meeting thermal requirements. For other streams, it was evident that high water temperatures cannot be managed by increasing discharge, as the discharge required would be greater than natural discharge and higher than achievable by management. The statistical method described in this paper allows for a risk‐based approach to discharge management for fish habitat needs.

Numerical groundwater flow modeling of the northern river catchment of the Lake Tana, Upper Blue Basin, Ethiopia

The study area is found North Western plateau in the North Gondar zone, Amhara regional state, Ethiopia. Its total surface coverage is 1887km2.The study area boundary was delineated from 90m Shutter Radar Terrain Mapping (SRTM) digital elevation model (DEM) using Global Mapper 8 software. Based on geologic information of the study area, unconfined subsurface flow condition was considered and simulated using MODFLOW 2000. The model calibration accounts the matching of the 58 observation point with simulated head with a permissible residual head of ±10m. 75% of the difference the observed and measured water level head in the study area is 5m. . The model was calibrated with mean error 0.506, absolute mean error 4.431m and standard deviation 6.083m. Based on the calibration process, the model is very sensitive in decreasing order change in recharge, hydraulic conductivity, and stream bed conductance. The simulated out flow of the model is 205.7Mm3/year which is nearly equal to simulated inflow with difference 2,887.45m3/yr. The base flow simulated discharge Megech River holds 35.8% of the out flow. The river contributed as recharge in to the aquifer that accounts to 15.3% of the inflow. Steady state withdrawal rates were increased by 15%, 35%, 55%, 75% and 100% to study the response of the system in this scenario. From the simulation results, one can observe that the development of a new groundwater sources would not pose appreciable impact in case of 15% and 35% withdrawal the head declines in this case is insignificant relative to the steady state withdrawal rate and the natural discharges were not altered highly. The simulation result indicated that the stream leakage decreased by 7.9% relative to the whole steady state value, but showed 14.9% decrease for Angereb, Keha, and Shinta river segments near the well field area. The water tables decline by 3.6m to18.8m in head observation in the well field area. The steady state simulated recharge was decreased by 32% and the simulation results showed on average head decrease of 8.06m over the whole area; with the highest fall 32m in wells to north and a minimum of about 1m in wells to the south of the catchment. In addition, the stream leakage, compared to the simulated steady state value and it was decreased by 75.36%. The simulated value showed an average 2.74m increased head over the whole area. High difference values were observed at Tseda (7.83m) and Koladiba (7.3m). The minimum difference 1.08m was recorded at Angereb well field (observation 94). In addition, the stream leakage compared with the steady state value the change was about 87.43%. Keywords: MODFLOW 2000, Groundwater, Modelling, Sensitivity analysis, Simulation, Recharge

Using the light emission measurement in assessment of electrical discharge development in different liquid dielectrics under lightning impulse voltage

This article presents the results of studies concerning the assessment of propagation modes of electrical discharges developing in different liquid dielectrics. This assessment was performed on the basis of measurements of light emitted during discharge development. For liquid dielectrics such as natural ester, synthetic ester and mineral oil tested under standard lightning impulse voltage of both polarities, two propagation modes of discharges were identified: slow developing discharges of propagation velocities of few mm/μs and fast developing discharges of velocities of tens mm/μs. Comparing the results concerning the liquids tested in synthetic ester and natural ester fast discharges appeared at much lower testing voltage than in the case of mineral oil. Simultaneously, at the same voltage level, the frequency of light pulses corresponding with the discharges developing in esters was higher than frequency of pulses observed when discharges developed in mineral oil. Thus the results showed that both esters are less resistant to the appearance of fast and energetic discharges, which means that esters may have a lower ability to protect against the lightning impulses in real insulation systems. It is suggested that this disadvantage of the ester liquids should be necessarily taken into account during the design process of transformers filled by them.

Groundwater flow dynamics of weathered hard-rock aquifers under climate-change conditions: an illustrative example of numerical modeling through the equivalent porous media approach in the north-western Pyrenees (France)

A numerical groundwater model of the weathered crystalline aquifer of Ursuya (a major water source for the north-western Pyrenees region, south-western France) has been computed based on monitoring of hydrological, hydrodynamic and meteorological parameters over 3 years. The equivalent porous media model was used to simulate groundwater flow in the different layers of the weathered profile: from surface to depth, the weathered layer (5 · 10−8 ≤ K ≤ 5 · 10−7 m s−1), the transition layer (7 · 10−8 ≤ K ≤ 1 · 10−5 m s−1, the highest values being along major discontinuities), two fissured layers (3.5 · 10−8 ≤ K ≤ 5 · 10−4 m s−1, depending on weathering profile conditions and on the existence of active fractures), and the hard-rock basement simulated with a negligible hydraulic conductivity (K = 1 10 −9 ). Hydrodynamic properties of these five calculation layers demonstrate both the impact of the weathering degree and of the discontinuities on the groundwater flow. The great agreement between simulated and observed hydraulic conditions allowed for validation of the methodology and its proposed use for application on analogous aquifers. With the aim of long-term management of this strategic aquifer, the model was then used to evaluate the impact of climate change on the groundwater resource. The simulations performed according to the most pessimistic climatic scenario until 2050 show a low sensitivity of the aquifer. The decreasing trend of the natural discharge is estimated at about −360 m3 y−1 for recharge decreasing at about −5.6 mm y−1 (0.8 % of annual recharge).

Distribution patterns of mobile heavy metals in the inshore sediments of the Red Sea

The mobile forms of heavy metals are the exchangeable phases of these metals that represent the bioavailable toxic hazards in the marine environment. The exchangeable forms of Fe, Zn, Cu, Mn, and Pb were measured using atomic absorption spectrophotometry in the inshore sediments at five locations along the Red Sea coast in areas under natural and anthropogenic discharges. The fine sediment group (FSG) reached the average of 51.29 % representing the controlling and vital factor in the different geochemical processes that occur in seabed sediments. Hamrawin Bay recorded the highest averages of Mn (283.55 μg/g), Zn (99.63 μg/g), and Pb (73.35 μg/g). Abu Dabab recorded the highest average of Fe (1336.41 μg/g), Shalateen exhibited the highest Cu average (35.62 μg/g) and the lowest averages of Mn, Zn, and Pb (50.18, 24.28, and 18.44 μg/g), and Qula’an showed the lowest averages of Fe and Cu (944.61 and 17.39 μg/g). The estimated results indicated that the exchanges from one phase to another were active in all locations due to the continuous reworking processes in the surface sediments. Under the oxic conditions, oxides, hydroxides, and carbonates of Fe, Mn, and Zn were expected to be the dominant metal forms associated with the sand fraction at the different locations. Under the reducing environments (anoxic conditions), sulfide forms of Fe, Pb, Mn, and Cu were associated with fine sediment fractions (very fine sand, silt, and mud) were dominant. Ionic exchanges were active in the near bottom and the interstitial water during the transformation operations from one phase to another at the different locations. The continuity of the forms transformation in the marine ecosystem at the studied locations provide the favorable environment for benthos growing up.

Interactive effects of urban stormwater drainage, land clearance, and flow regime on stream macroinvertebrate assemblages across a large metropolitan region

AbstractUrban impacts on streams are mediated by alteration of land cover and subsurface drainage. Understanding interactions of these 2 effects is critical for urban land and water management. We used boosted regression trees to analyze relationships between environmental predictors, including land-cover measures that indicate urban impacts, and Stream Invertebrate Grade Number Average Level (SIGNAL) or the occurrence of 60 macroinvertebrate families across the Melbourne (Australia) region. SIGNAL and 51 families were negatively correlated with attenuated imperviousness (AI). Twenty-four families exhibited a steep decline in probability of occurrence between 0 and ≤3% AI, consistent across the range of natural discharge (Q). Responses to attenuated forest cover (AF) were more variable among families (39 positive, 15 negative). AF had a less positive influence on SIGNAL at high than at low AI because the many (high SIGNAL-grade) families that were strongly negatively correlated with AI were likely to be a...

기후예측 시나리오 기반의 단기가뭄피해 예측기법: 금강유역을 대상으로

There has been a very serious drought since June 2015 in Korea. This study seeks to quantify the ongoing water deficit in the first half of 2016 in the Geum river basin, which has been the most effected by severe drought in Korea. Weather time series were generated from the climate forecast results of the GFDL GCM that is a part of IRI Monthly Multi-model ensemble (MME) seasonal prediction system. Natural discharge was estimated in 14 subbasins using a rainfall-runoff model. A water balance model was built and used to predict the amount of water deficit in the first half of 2016 given the initial conditions in December 2015. Under the scenario predicted by the GCM, more precipitation than nornal is expected and consequently, water supplies in the basin will be sufficient to meet water demands. However, if only 75% or 50% of expected precipitation occurs, water supply will be inadequate to meet the water demands in spite of considering the regional supply water.

Observation of 2.45 MeV neutrons correlated with natural atmospheric lightning discharges by Lead‐Free Gulmarg Neutron Monitor

AbstractThe first experimental evidence of detecting the neutrons correlated with the natural atmospheric lightning discharges (NALD) was obtained with Lead‐Free Gulmarg Neutron Monitor (LFGNM) operating at High Altitude Research Laboratory, Gulmarg, Kashmir, India, and was reported in the year 1985. The neutron observations still continue with LFGNM. However, the current configuration of LFGNM is the upgraded version of the system used earlier to record neutron bursts (in the recording period of 320 μs in four successive electronic gates of 80 μs each) supposedly originating from an NALD. In the current system the neutron recording time period/interval has been extended to 1260 μs with 63 successive gates of 20 μs each. The system also simultaneously records the differential times—maximum up to 14—between the consecutive strokes of a multistroke lightning flash. The distance between an NALD channel and LFGNM setup is determined empirically by making use of the time delay (td)/time of flight (TOF) measurement of the first detected neutron subsequent to the sensing of the electrostatic field variation caused by the initiation of an NALD in the ambient atmosphere of the LFGNM setup. Assuming a priori incident energy as 2.45 MeV of the detected neutrons supposedly generated due to the fusion of deuterium ions in the lightning discharge channel leads to quantifying the neutron emission flux if the NALD channel distance with respect to the LFGNM setup is established. In this paper we discuss the experiment and the time profiles of several of a large number of the major neutron burst events recorded with LFGNM in association with NALDs. Moreover, a rare and an extraordinary neutron burst event, in terms of its associated “td/TOF” of first detected neutron after triggering, recorded by this system is specifically discussed. In this event, the recorded TOF of 14 μs of the escaping neutron detected by the system immediately after getting triggered by the NALD that struck a nearby tree found located just around 300 m (physically measured) away from the detector position indicates the energy of the detected neutron ϵn ≈2.45 MeV. In the light of this only event, we, therefore, cautiously suggest deuteron‐deuteron fusion reaction, 2H(2H,n)3He, as one of the possible mechanisms of the neutron generation correlated with an NALD. Nonetheless, the observations so far have reconfirmed production of neutrons in an NALD.

Groundwater fluoride enrichment in an active rift setting: Central Kenya Rift case study

Groundwater is used extensively in the Central Kenya Rift for domestic and agricultural demands. In these active rift settings groundwater can exhibit high fluoride levels. In order to address water security and reduce human exposure to high fluoride in drinking water, knowledge of the source and geochemical processes of enrichment are required. A study was therefore carried out within the Naivasha catchment (Kenya) to understand the genesis, enrichment and seasonal variations of fluoride in the groundwater. Rocks, rain, surface and groundwater sources were sampled for hydrogeochemical and isotopic investigations, the data was statistically and geospatially analyzed. Water sources have variable fluoride concentrations between 0.02–75mg/L. 73% exceed the health limit (1.5mg/L) in both dry and wet seasons. F− concentrations in rivers are lower (0.2–9.2mg/L) than groundwater (0.09 to 43.6mg/L) while saline lake waters have the highest concentrations (0.27–75mg/L). The higher values are confined to elevations below 2000masl. Oxygen (δ18O) and hydrogen (δD) isotopic values range from −6.2 to +5.8‰ and −31.3 to +33.3‰, respectively, they are also highly variable in the rift floor where they attain maximum values. Fluoride base levels in the precursor vitreous volcanic rocks are higher (between 3750–6000ppm) in minerals such as cordierite and muscovite while secondary minerals like illite and kaolinite have lower remnant fluoride (<1000ppm). Thus, geochemical F− enrichment in regional groundwater is mainly due to a) rock alteration, i.e. through long residence times and natural discharge and/or enhanced leakages of deep seated geothermal water reservoirs, b) secondary concentration fortification of natural reservoirs through evaporation, through reduced recharge and/or enhanced abstraction and c) through additional enrichment of fluoride after volcanic emissions. The findings are useful to help improve water management in Naivasha as well as similar active rift setting environments.

Improved thermal energy discharge rate from a temperature-controlled heating source in a natural draft chimney

Simulations by computational fluid dynamics using Phoenics were performed for a chimney, represented by a vertical cylinder of diameter 100 m and height of 200 m, located at clearances of 14.68 m, 10 m and 5 m above ground to provide for increasingly higher inlet resistances, with a temperature-controlled heater near the cylinder inlet (bottom) set at a temperature of 50 °C and ambient air temperature of 30 °C in still surroundings. The simulated results, in particular the cold inflow pattern, agreed with heat flux-controlled experiments previously carried out and two earlier simulation results by other workers; in addition, draft enhancement was also achieved as in the case when cold inflow had been impeded with the heat flux-controlled experiments. The wire mesh simulated as a flow resistor was found to effectively impede cold inflow for cylinders of these arrangements. Favre-averaging was found to provide closer values to true averages in maldistributed flows and overcame the problem of area-averaging in cold inflow situations, where poor heat balances were likely experienced. By impeding cold inflow or flow reversal, the average draft flow rate and the heat discharge rate were found to have improved significantly by up to 34 per cent, on the basis of Favre-averaged heat loads for the cases examined. The analysis showed that the natural convection thermal energy discharge rate and the draft from a temperature-controlled heating source in a chimney were enhanced, contrary to the normal expectation that it would be reduced, when cold inflow is impeded by installing wire mesh at the chimney top exit.

Experimental hydrological studies of processes of failure of beaver dams and pond draining

Beaver dams on small rivers significantly alter their hydrological regime. Formation of maximum break discharges on small rivers and flooding of areas are one of the detrimental consequences caused by the failure of such dams. Based on our survey of 11 dams and ponds in the Vereshchaginskii district (Perm oblast), as well as on cartographic modeling of 20 ponds, the dependences of the pond basin volume on the length of the pond and the maximum height of the dam have been established, which can be used to estimate the approximate volume of these ponds. When the dam height changes from 0.5 to 3.4 m and its length changes from 5 to 50 m, the volume of the pond basin alters from 0 to 850 m3. According to the results of artificial dam failure, the following aspects have been established: the nature of simulated flood propagation, the dependence of hydrological characteristics on stages; runoff hydrographs and volumes, as well as the nature of the drained pond bed. It has also been found that the development of the closure channel in the body of dams is unlikely to take place and that erosion mainly occurs on riverbank soils. Based on calculations, it has been revealed that the quantities of natural full-scale break discharges are equal to the maximum rain flood discharge with a 10% probability of exceedance. Full-scale break discharges differ from those calculated according to the hydraulics formulas by 10 to 30%. The maximum discharge values during our experiment ranged from 50 to 500 L/s; the amount of time to empty the ponds varied from 100 to 180 min.

Lightning attachment processes of three natural lightning discharges

Using a high-speed optical imaging system specifically designed for observing the lightning attachment process, we have documented the attachment process for six strokes in three natural lightning flashes. All strokes initiate at a height above ground and propagate bidirectionally from that height, similar to the return strokes of artificially initiated (triggered) lightning previously reported by Wang et al. (2013, 2014). Though the data are quite limited, these natural return strokes suggest a correlation between larger peak current and greater initiation height. Initiation heights determined here span 12–60 m with a typical uncertainty of less than 10 m. The initial upward return stroke luminosity speeds range from (0.8 ± 0.2) to (2.0 ± 0.4) × 108 m/s. Two first return strokes downward luminosity speeds are assessed as (1.6 ± 0.3) × 107 m/s and (1.4 ± 0.3) × 108 m/s. One of the first return strokes appeared to be initiated with a stepping pulse discharge of its leader as an inseparable part of the return stroke.

Use of mean residence time and flowrate of thermal waters to evaluate the volume of reservoir water contributing to the natural discharge and the related geothermal reservoir volume. Application to Northern Thailand hot springs

Tritium-based mean residence time, τw, and flowrate, Qw, of thermal waters from eleven different sites of Northern Thailand were used to evaluate the volume of reservoir waters contributing to the natural discharge, Vw, and the volume of the related geothermal reservoirs, Vres, assuming steady-state conditions and using simple relationships.Measured 3H contents of the thermal waters of interest, apart from San Kamphaeng, range from 0.4 to 1.3 TU. Based on the well-mixed reservoir model, mean fluid residence times between 500 and 1700 years are obtained. For most thermal waters of Northern Thailand, calculated Vw range from 0.13 to 0.68km3, whereas Vres vary from 13 to 68km3, assuming an effective porosity of 0.01. The only exception is San Kamphaeng, that has a high discharge leading to a calculated Vw of 2.2km3 and Vres of 220km3, although its mean fluid residence time of 955 years is within the range of other Northern Thailand thermal waters.Even though the uncertainties on both Vw and Vres are relatively high, the simple approach used here may be used to evaluate geothermal resources during the exploration stage. The obtained Vres may be used in the volume method of geothermal resource assessment (which is usually utilized to evaluate the productive potential of unexploited and minimally exploited geothermal fields) and may be compared with the Vres estimated by means of other approaches.

A conectividade hidrogeológica de uma nascente salina de baixa vazão em turfeiras topotróficas na região de areias betuminosas de Athabasca, Canadá

Saline springs can provide clues as to the nature of groundwater flow, including how it relates to subsurface wastewater storage and the distribution of solutes in the landscape. A saline-spring peatland neighboring a proposed in-situ oil facility was examined near Fort McMurray, Alberta (Canada). The study area is situated just north of a saline groundwater discharge zone, which coincides with the erosional edge of the Cretaceous Grand Rapids Formation. Na+ (mean 6,949 mg L−1) and Cl− (mean 13,776 mg L−1) were the dominant salts within the peatland, which increased by an order of magnitude in the opposite direction to that of the local groundwater flow. Rivers and freshwater wetlands within the study area had anomalously high salinities, in some cases exceeding 10,000 mg L−1 total dissolved solids within deeper sediments. Saline-spring features were observed as far as 5 km from the study area. A low-permeability mineral layer underlying the peatland restricted vertical groundwater exchange (estimated to be less than several mm over the 4-month study period). Sand and gravel lenses underlying the fen’s high-salinity zone may function as areas of enhanced discharge. High Cl/Br ratios point to halite as a potential source of salinity, while δ18O and δ2H signatures in groundwater were lower than modern-day precipitation or Quaternary aquifers. The complex connectivity of saline-spring wetlands within the landscape has implications for industry and land-use managers, and justifies incorporating them into monitoring networks to better gauge the magnitude and flow history of natural saline discharge in the oil sands region.

Prebreakdown air ionization in the atmosphere

This chapter is devoted to the analysis of electron-ionization and -elimination processes at early stages of electric-discharge development in air at altitudes of mainly 0–90 km. In this chapter, ionization processes in an external electric field, as well as background ionization by fast particles and electron attachment and detachment with participation of atomic and molecular oxygen, are considered. Temperature and concentration dependences of rate constants are described. Analysis of ionization models allowing simplified approaches to detailed computation models is undertaken. It is shown that the electric breakdown process in air, under the influence of an external electric field, comprises several stages that are different with respect to different altitudes over the Earth. Numerical modeling on the basis of a detailed plasma chemical model, taking into account the heating of gas by the discharge, has shown that the relaxation processes leading to gas heating also lead to the appearance of a nonlinear stage of electric breakdown. The considered phenomena can be convenient in the consideration of a high-altitude origination of natural discharges in fields of thunderstorm clouds.

Effect of Observed Discharge Data on Regional Flood Frequency Analysis in the Han River Basin

This study assessed the impact of uncertainties in flood data on the results of flood frequency analysis for Han river basin. To meet this aim, this study quantified assessment focused on the index flood and quantile by regional flood frequency analysis using the flood data from 17 water level gauges in Han river basin. We analysed the results categorized by three cases according to the characteristics of the measured data. Firstly, we analyzed the regional flood frequency for the water level gauge in the Pyungchang river basin to investigate the impact of water level data. The results has the error of 0.240 with respect to the mean flood. Secondly, we examined the impact of uncertainty in measurement data generated by the application of rating on the results of regional flood frequency analysis. We have compared the results by applying the rating estimated for each year to the one by the recently estimated rating. The results showed that the mean error has 0.246 in terms of the mean flood. Finally, we have inferred the regional flood frequency analysis results with the regulated flow in the downstream area of dams. The regulated specific discharge in the downstream area of dams controlled by dam operation showed a large difference to the estimated specific discharge in the downstream area of dams by extension of the natural specific discharge in the upstream area using the regionalization method.

A hydrologic assessment of a saline‐spring fen in the Athabasca oil sands region, Alberta, Canada – a potential analogue for oil sands reclamation

AbstractCanada's post‐mined oil sands will have a higher concentration of salts compared with freshwater peatlands that dominate the landscape. While rare, naturally occurring saline wetlands do exist in Alberta's Boreal Plains and may function as analogues for reclamation, however, little is known about their hydrology. This paper investigates the geochemical and hydrologic characteristics of a natural saline‐spring peatland in Alberta's oil sands region. The fen is located within a saline groundwater discharge area connected to the erosional edge of the Grand Rapids Formation. Na+(195–25,680 mgl−1) and Cl−(1785–56,249 mg l−1) were the dominant salts, and the fen transitioned sharply to freshwater along its margins because in part of subsurface mineral ridges that restricted shallow groundwater exchange. Salinity decreased from hypersaline to brackish along the local groundwater flow path but no active spring outlets were observed over the two‐year study. Vertical groundwater discharge was minimal because of the very low permeability of the underlying sediments. Subsurface storage was exceeded during periods of high flow, resulting in flooding and surface runoff that was enhanced by the ephemerally connected pond network. These findings have implications for reclamation, as mechanisms such as subsurface mineral ridges may function as effective saline groundwater‐control structures in the post‐mined environment. Incorporating saline wetlands into regional monitoring networks will help to better quantify natural discharge, which has implications for belowground wastewater storage related toin situbitumen extraction. Copyright © 2015 John Wiley &amp; Sons, Ltd.