Water Quality Modeling and Dissolved Oxygen Balance in Streams: A Point Source Streeter‐Phelps Application in the Case of the Harsit Stream

The Harsit Stream flowing into the Black Sea is an important watershed in the northeastern part of Turkey. The monthly averages of dissolved oxygen, carbonaceous biochemical oxygen demand, temperature, pH, total suspended solids, total phosphorus and total nitrogen were obtained for the water samples taken from the Tekke, Akcakale and Haciemin sites of the Harsit Stream. Water quality parameters were analyzed and evaluated according to the WHO standards and the Turkish Water Pollution Control Regulation. Initially, the variations in the dissolved oxygen profile were determined from dissolved oxygen, temperature and carbonaceous biochemical oxygen demand measurements by using the point source Streeter‐Phelps equation. Critical dissolved oxygen deficit values were calculated for the monthly average from January–December 2005, which are below the limit value (4 mg L^–1) excluding April (7.26 mg L^–1) and May (5.98 mg L^–1) in the Harsit Stream, resulting in it having second class water quality in terms of dissolved oxygen concentration, temperature, pH and biochemical oxygen demand. It is also seen that the minimum dissolved oxygen limit value (8 mg L^–1), which is a desired quantity for drinking water, is under the limit value for all months in the case of the water mixture. In particular, during the summer months, the consumption speed of oxygen is greater than the production speed of oxygen with increasing temperature and decreasing discharge, and negative values (anoxia) of dissolved oxygen sag are seen. These situations call for significant precautions and treatment criteria.     

Effect of Bank Deformations on Pollutant Transport in Rivers in Cryolithozone: Laboratory and Mathematical Modeling

The study is focused on pollution transport in rivers flowing in cryolithozone and takes into account possible channel deformations caused by thawing of permafrost rocks in which the channel runs. The methods used are laboratory and mathematical modeling. The mathematical model consists of four blocks: hydrodynamic, thermal, deformation, and pollutant transport. The model was validated and tested against the data of a laboratory experiment. Numerical experiments suggested conclusions regarding the propagation of pollutants entering the flow from sources in thawing bank slopes and on river floodplain.     

The effect of temperature on the seepage transport of suspended particles in a porous medium

The main purpose of this study is to experimentally investigate the effect of temperature on the seepage transport of suspended particles (SP) with a median diameter of 10–47 μm in a porous medium for various seepage velocities. The results show that the rise of temperature accelerates the irregular movements of SPs in the porous medium and reduces their migration velocity. As a result, the pore volume corresponding to the peak value of the breakthrough curves is apparently delayed, and the peak value in the effluent is decreased. The migration velocity of SPs decreases with increasing particle size, regardless of the Darcy velocity and temperature. The longitudinal dispersivity of SPs decreases slightly with increasing temperature and then remains almost unchanged. Larger particles experience more irregular movements induced by the limit of pore size, which leads to a larger dispersivity. The deposition coefficient increases with increasing temperature, especially in the case of a high seepage velocity, and then tends to be stable. The deposition coefficient for large‐sized particles is higher than that for small‐sized particles, which can be attributed to the restriction of large‐sized particles by the narrow pores in the porous medium. The recovery rate decreases slightly with the increase of temperature until a critical value is reached, beyond which it remains almost unchanged. In summary, temperature is a significant factor affecting the transport and deposition of SPs in the porous medium, and the transport parameters such as particle velocity, dispersivity, and deposition coefficient.     

Modeling boulder transport by coastal waves on cliff topography: Case study at Hachijo Island,Japan

Clifftop coastal boulders transported by storm waves or tsunamis have been reported around the world. Although numerical calculation of boulder transport is a strong tool for the identification of tsunami or storm boulders, and for estimation of the wave size emplacing boulders, models which can reasonably solve boulder transport from below a cliff or from a cliff-edge onto a cliff-top do not yet exist. In this study, we developed a new numerical formulation for cliff-top deposition of boulders from the cliff edge or below the cliff, with validation from laboratory tests. We then applied the model using storm and tsunami wave forcing to simulate the observed boulder deposits at the northwest coast of Hachijo Island, Japan. Using the model, the actual distribution of boulders was explained well using a reasonable storm wave height without assumption of anomalously high-water level by storm surge. Results show that boulder transport from the cliff edge or under the cliff onto the cliff-top was possible from a tsunami with periods of 5~10 min or storm waves with no storm surge. However, the actual distribution of boulders on the cliff was explained only by storm waves, but not by tsunami. Therefore, the boulders distributed at this site are likely of storm wave origin. Our developed model for the boulder transport calculation can be useful for identifying a boulder's origin and can reasonably calculate cliff-top deposition of boulders by tsunami and storm waves. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Effect of the Mahanadi River on the Development of Storm Surge Along the Orissa Coast of India: A Numerical Study

River-ocean coupled models are described for the evaluation of the interaction between river discharge and surge development along the Orissa coast of India. The models are used to study the effect of fresh water discharge from the Mahanadi River on the surge response along the Orissa coast due to the October 1999 super cyclone which led to severe flooding of the coastal and delta regions of Orissa. The so-called 1999 Paradip cyclone was one of the most severe cyclones; causing extensive damage to property and loss of lives. The present study emphasizes the impact of the Mahanadi River on overall surge development along the Orissa coast. Therefore, we have developed a location specific fine resolution model for the Orissa coast and coupled it with a one–dimensional river model. The numerical experiments are carried out, both with and without inclusion of fresh water discharge from the river. The bathymetry for the model has been taken from the naval hydrographic charts extending from the south of Orissa to the south of west Bengal. A simple drying scheme has also been included in the model in order to avoid the exposure of land near the coast due to strong negative sea-surface elevations. The simulations with river-ocean coupled models show that the discharge of fresh water carried by the river may modify the surge height in the Bay, especially in the western Bay of Bengal where one of the largest river systems of the east coast of India, the Mahanadi River, joins with the Bay of Bengal. Another dynamic effect of this inlet is the potentially deep inland penetration of the surge originating in the Bay. The model results are in good agreement with the available observations/estimates.     

The impact of storm events on solute exports from a glaciated forested watershed in western New York,USA

This study analysed the importance of precipitation events from May 2003 to April 2004 on surface water chemistry and solute export from a 696 ha glaciated forested watershed in western New York State, USA. The specific objectives of the study were to determine: (a) the temporal patterns of solutes within individual storm events; (b) the impact of precipitation events on seasonal and annual export budgets; and (c) how solute concentrations and loads varied for precipitation events among seasons as functions of storm intensity and antecedent moisture conditions. Analysis of solute trajectories showed that NH₄⁺, total Al and dissolved organic nitrogen (DON) peaked on the hydrograph rising limb, whereas dissolved organic carbon (DOC) concentrations peaked following the discharge peak. Sulphate and base‐cations displayed a dilution pattern with a minimum around peak discharge. End‐member mixing analysis showed that throughfall contributions were highest on the rising limb, whereas valley‐bottom riparian waters peaked following the discharge peak. The trajectories of NO₃^? concentrations varied with season, indicating the influence of biotic processes on the generation, and hence flux, of this solute. Storm events had the greatest impact on the annual budgets for NH₄⁺, K⁺, total dissolved Al, DON and DOC. Storm events during summer had the greatest impact on seasonal solute budgets. Summer events had the highest hourly discharges and high concentrations of solutes. However, NO₃^? and DOC exports during a spring snowmelt event were considerably more than those observed for large events during other periods of the year. Comparisons among storms showed that season, precipitation amount, and antecedent moisture conditions affected solute concentrations and loads. Concentrations of solutes were elevated for storms that occurred after dry antecedent conditions. Seven of the largest storms accounted for only 15% of the annual discharge, but were responsible for 34%, 19%, 64%, 13%, 39% and 24% of the annual exports of NH₄⁺, K⁺, Al, NO₃^?, DON and DOC respectively. These results suggest that the intense and infrequent storms predicted for future climate‐change scenarios will likely increase the exports of solutes like DOC, DON, NH₄⁺, Al and K⁺ from watersheds. Copyright © 2006 John Wiley & Sons, Ltd.     

磁暴K指数与云南地区中强震相关性统计分析

应用云南通海地磁台K≥6的磁暴数据,对云南省内M≥5．0地震发震时间关系进行统计分析发现：K≥7的大磁暴对云南省M≥5．0地震触发作用显著,且不同强度的磁暴对地震的触发作用有差异,磁暴强度增加,触发作用也增大。这一分析结果对云南地区5级以上地震发生时间的预测有一定的意义、     

Modeling and Validating Long‐Term Dynamics of Diel Dissolved Oxygen with Particular Reference to pH in a Temperate Shallow Lake (Turkey)

Long‐term monitoring of changes in dissolved oxygen (DO) and pH is of great importance to quantifying aquatic ecosystem metabolism, particularly for lakes under the changing global environment. During 173 days, diel DO cycles were measured in situ along with the main driving variables of pH, wind speed (WS), and net solar radiation (Rn) in a temperate shallow lake. Best‐fit multiple non‐linear regression (MNLR) models of diel DO time series were built and validated on a monthly basis, with R² values ranging from 42.4% in September to 95.4% in November for validation. The strong relationship between diel DO and pH (r = 0.6) appeared to be related to the patterns of ecosystem productivity and respiration, and sensitivity of decomposing bacteria to changes in pH. pH‐driven lake metabolism appears to have significant implications for diel and seasonal lake metabolism in a changing global environment.     

基于数学建模的潜在地震破裂面源检测方法研究

大多数地震破裂面源检测方法都是通过简化地震震源,将地震震源表示成线源或者点源,无法有效描述地震带地震破裂面源产状和大小,不适用地震震级较大的情况下地震危险性检测。因此提出基于数学建模的潜在地震破裂面源检测方法,在地震震级较大时仍能检测出地震危险性概率。选取适宜的地震基岩水平峰值加速度衰减关系,分析地震震级、破裂长度、破裂宽度相互关系,确定地震引起的潜在地震破裂面源大小,计算给定地震动小于在场点处产生地震动的概率,将该概率同地震动加速度衰减关系结合,得到地震动年超越概率,分析地震危险性。经过实验检测发现,所提方法检测出的年超越概率与峰值加速度、最大震级有关,该概率能精准表示地震带地震破裂面源产状和大小,说明该方法检测地震危险性是合理的。     

Impact of climate indicators on continental‐scale potential groundwater recharge in Africa

In the last decades, human activity has been contributing to climate change that is closely associated with an increase in temperatures, increase in evaporation, intensification of extreme dry and wet rainfall events, and widespread melting of snow and ice. Understanding the intricate linkage between climate warming and the hydrological cycle is crucial for sustainable management of groundwater resources, especially in a vulnerable continent like Africa. This study investigates the relationship between climate‐change drivers and potential groundwater recharge (PGR) patterns across Africa for a long‐term record (1960–2010). Water‐balance components were simulated by using the PCR‐GLOBWB model and were reproduced in both gridded maps and latitudinal trends that vary in space with minima on the Tropics and maxima around the Equator. Statistical correlations between temperature, storm occurrences, drought, and PGR were examined in six climatic regions of Africa. Surprisingly, different effects of climate‐change controls on PGR were detected as a function of latitude in the last three decades (1980–2010). Temporal trends observed in the Northern Hemisphere of Africa reveal that the increase in temperature is significantly correlated to the decline of PGR, especially in the Northern Equatorial Africa. The climate indicators considered in this study were unable to explain the alarming negative trend of PGR observed in the Sahelian region, even though the Standardized Precipitation‐Evapotranspiration Index (SPEI) values report a 15% drought stress. On the other hand, increases in temperature have not been detected in the Southern Hemisphere of Africa, where increasing frequency of storm occurrences determine a rise of PGR, particularly in southern Africa. Time analysis highlights a strong seasonality effect, while PGR is in‐phase with rainfall patterns in the summer (Northern Hemisphere) and winter (Southern Hemisphere) and out‐of‐phase during the fall season. This study helps to elucidate the mechanism of the processes influencing groundwater resources in six climatic zones of Africa, even though modelling results need to be validated more extensively with direct measurements in future studies. Copyright © 2016 John Wiley & Sons, Ltd.     

基于走航高频监测的水库冬季水体溶解甲烷浓度分布:以湖北西北口水库为例

水库是大气甲烷(CH4)的重要来源之一,但目前对水库(尤其是河道型水库)中溶解CH_4浓度及释放潜力的空间异质性的认识仍不足.为揭示河道型水库冬季溶解CH_4浓度的分布规律,于2020年1月在湖北宜昌黄柏河流域内西北口水库采用自主研发的新型快速水—气平衡装置(FaRAGE)连接便携式温室气体分析仪,开展了水体溶解CH4浓度的连续走航式监测及断面垂向监测.根据溶解CH4从库尾至库首的浓度变化可以将水库分为3段:距回水末端1 km内为快速降低段,溶解CH4浓度范围为0.117～0.233 μmol/L;1～6 km内为缓慢降低段,CH4浓度范围为0.055～0.117 μmol/L;6～13km范围内为浓度平稳段,CH4浓度范围为0.039～0.080 μmd/L.整体上,水库表层水体溶解CH_4浓度与表层水温、水深及距回水末端的距离呈显著负相关关系(r=-0.77、-0.89、-0.81;P0.01),与叶绿素a浓度、溶解氧浓度呈显著正相关性(r=0.95、0.97;P0.01).基于当月平均风速,采用薄边界层法估算了上述3段区域的DH_4扩散通量,分别为(0.023±0.004)、(0.012±0.003)、(0.007±0.001) mg/(m~2·h).西北口水库在冬季表现为向大气释放CH_4的"源",且由于溶解CH_4浓度分布不均而表现出较强的空间差异性.     

Morphological records of storm floods exemplified by the impact of the 1872 Baltic storm on a sandy spit system in south‐eastern Denmark

Beach‐ridge systems are important geo‐archives providing evidence for past wave climate including catastrophic storm flood events. This study investigates the morphological impacts of the 1872 Baltic storm flood on a beach‐ridge system (sandy spit) in south‐eastern Denmark and evaluates the frequency of extreme storm flood events in the area over a longer time perspective. This paper combines field studies of morphology and sedimentary deposits, studies of historical maps, digital terrain model, ground‐penetrating radar profiles, and luminescence dating. Sea water reached 2.8 m above mean sea level (amsl) during peak inundation and, based on studies of the morphological impacts of the 1872 storm flood, the event can be divided into four phases. Phase 1: increasing mean water levels and wave activity at the beach brought sediments from the beach (intertidal bars and normal berm) higher up in the profile and led to the formation of a storm‐berm. Phase 2: water levels further increased and sediment in the upper part of the profile continued to build up the storm‐berm. Phase 3: water levels now reached the top of the dune ridge and were well above the storm‐berm level. Sea water was breaching the dune ridge at several sites and wash‐over fans were generated until a level where the mean water level had dropped too much. Phase 4: the non‐vegetated wash‐over fans functioned as pathways for aeolian sand transport and relatively high dunes were formed in particular along the margins of the fan where aeolian sand was trapped by existing vegetation. The studied beach‐ridge system records about 4500 years of accumulation; the storm flood sediments described are unique suggesting that the 1872 Baltic storm flood event was an extreme event. Thus studies of beach‐ridge systems form a new source for understanding storm surge risk. Copyright © 2013 John Wiley & Sons, Ltd.     

地震台站噪声水平定量评估及其在气枪源探测中的应用

对福建气枪源探测实验中所接入315个实时传输台站分1~10 Hz、0.1~1 Hz、10~60 s 3个频段进行台网噪声水平评估研究。统计240个小时的背景噪声记录,得到各台站的噪声水平MODE线,再利用本文提出的全球新高低噪声模型线与MODE线所占面积比来量化台网噪声水平,根据不同色标将台网噪声水平划分为十个等级进行评估,评选出优质台站。进一步研究背景噪声对气枪激发效果的影响,验证了台站接收能力与背景噪声密切相关,分析了不同台基（固定、加密、流动、海底）环境噪声水平的影响,得出环境噪声水平由低到高分别为固定台、加密台、流动台、海底台。通过台网噪声评估能有效提高气枪震源信号的检测能力,也为优质台站重点维护提供重要参考。     

A 24 h investigation of the hydrogeochemistry of baseflow and stormwater in an urban area impacted by mining: Butte,Montana

Changes in water quality during a storm event were continuously monitored over a 24 h period at a single location along an urban stormwater drain in Butte, Montana. The Butte Metro Storm Drain (MSD) collects groundwater baseflow and stormwater draining Butte Hill, a densely populated site that has been severely impacted by 130 years of mining, milling, and smelting of copper‐rich, polymetallic mineral deposits. On the afternoon of 26 June 2002, a heavy thunderstorm caused streamflow in the MSD to increase 100‐fold, from 0·2 ft³ s⁻¹ to more than 20 ft³ s⁻¹. Hourly discharge and water quality data were collected before, during, and following the storm. The most significant finding was that the calculated loads (grams per hour) of both dissolved and particulate copper passing down the MSD increased more than 100‐fold in the first hour following the storm, and remained elevated over baseline conditions for the remainder of the study period. Other metals, such as zinc, cadmium, and manganese, showed a decrease in load from pre‐storm to post‐storm conditions. In addition to the large flush of copper, loads of soluble phosphorus increased during the storm, whereas dissolved oxygen dropped to low levels (<2 mg l⁻¹). These results show that infrequent storm events in Butte have the potential to generate large volumes of runoff that exceed Montana water quality standards for acute exposure of aquatic life to copper, as well as depressed levels of dissolved oxygen. This study has important implications to ongoing reclamation activities in the upper Clark Fork Superfund site, particularly with respect to management of storm flow, and may be applicable to other watersheds impacted by mining activities. Copyright © 2005 John Wiley & Sons, Ltd.     

Evaluation of a wind erosion model in a desert area of northern Asia by eddy covariance

For the first time, vertical fluxes of mineral dust measured by Eddy Covariance in two desert sites of Northern Asia have been used to test the performances of a wind erosion model in the field. Soil parameters required by the model were obtained through field and laboratory determinations. Model predictions and direct measurements have been compared. The main finding was that the direction of the horizontal wind relative to the orientation of nebkhas played a crucial role in determining the emission of particles in one of the investigated sites. Being unable to simulate such interaction, the model generally overestimated the actual emission. It provided, instead, reliable predictions (r² = 0·87) when the wind direction was suitable in detaching loose erodible elements placed on nebkhas thanks to their normal orientation. Copyright © 2009 John Wiley & Sons, Ltd.     

Impact of urbanization on suspended sediment and organic matter fluxes from small catchments in Tahiti

This study provides an initial characterization of pollution associated with storm runoff in Tahiti. A thousand floodwater samples were collected from three representative catchments and subsequently analysed. The main pollution parameters chosen were total suspended sediment (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total nitrogen (TN) and Total Phosphorus (TP). First, organic pollution appeared to be related closely to sediment, thus TSS could be used as a global indicator. Next, regression models between an event's TSS load and its hydrological characteristics were used to obtain annual load estimates. Great interannual variability was found to be strongly influenced by the few major floods that occur during the rainy season. Our results also emphasize the importance of the impact of urbanization on solid catchment exportation: from 60 TSS t/km²/year in a natural forested catchment, fluxes reached more than 700 TSS t/km²/year during preparatory urbanization earthworks before stabilizing at 140 TSS t/km²/year in a consolidated urbanized area. Clearly, runoff effects need to be taken into consideration for effective urban planning and for the preservation of the coastal environment in Tahiti. Copyright © 2002 John Wiley & Sons, Ltd.     

Modeling of environmental influence in structural health assessment for reinforced concrete buildings

One branch of structural health monitoring (SHM) utilizes dynamic response measurements to assess the structural integrity of civil infrastructures. In particular,modal frequency is a widely adopted indicator for structural damage since its square is proportional to structural stiffness. However,it has been demonstrated in various SHM projects that this indicator is substantially affected by fluctuating environmental conditions. In order to provide reliable and consistent information on the health status of the monitored structures,it is necessary to develop a method to filter this interference. This study attempts to model and quantify the environmental influence on the modal frequencies of reinforced concrete buildings. Daily structural response measurements of a twenty-two story reinforced concrete building were collected and analyzed over a one-year period. The Bayesian spectral density approach was utilized to identify the modal frequencies of this building and it was clearly seen that the temperature and humidity fluctuation induced notable variations. A mathematical model was developed to quantify the environmental effects and model complexity was taken into consideration. Based on a Timoshenko beam model,the full model class was constructed and other reduced-order model class candidates were obtained. Then,the Bayesian modal class selection approach was employed to select the one with the most suitable complexity. The proposed model successfully characterizes the environmental influence on the modal frequencies. Furthermore,the estimated uncertainty of the model parameters allows for assessment of the reliability of the prediction. This study not only improves the understanding about the monitored structure,but also establishes a systematic approach for reliable health assessment of reinforced concrete buildings.