Monitoring a flood event in a densely instrumented catchment, the Upper Eden, Cumbria, UK

Multi‐day rainfall events appear to be an important cause of recent flooding in the UK. Hydrological data from an extensive, nested hydrometric network in the unregulated, predominantly rural Upper Eden catchment in northern England are presented for one such flood event. These highlight antecedent catchment conditions and the propagation of the multi‐day flood event during February 2004. An assessment of flood response is provided over varying scales and land use between the upland Gais Gill catchment (1.1 km²) and the larger Upper Eden catchment (616 km²). Large spatial variations in rainfall totals are identified from a dense raingauge network during the flood event and are principally related to catchment elevation. High cumulative rainfall totals for the 6‐day event, particularly at upland sites appear to be the exceptional feature of the flood event with return periods in the order of 100 years at some upland gauges. Resultant patterns of flood attenuation and translation are quantified in different areas of the catchment, highlighting the flashy response of the headwater catchments and the attenuated downstream response in the lowland environment. The study forms part of the national Catchment Hydrology And Sustainable Management (CHASM) programme.     

Temporal variability of nitrate transport through hydrological response during flood events within a large agricultural catchment in south-west France

The temporal variability of nitrate transport was monitored continuously in a large agricultural catchment, the 1110 km² Save catchment in south-west France, from January 2007 to June 2009. The overall aim was to analyse the temporal transport of nitrate through hydrological response during flood events in the catchment. Nitrate loads and hysteresis were also analysed and the relationships between nitrate and hydro-climatological variables within flood events were determined. During the study period, 19 flood events were analysed using extensive datasets obtained by manual and automatic sampling. The maximum NO₃⁻ concentration during flood varied from 8.2 mg l⁻¹ to 41.1 mg l⁻¹ with flood discharge from 6.75 m³ s⁻¹ to 112.60 m³ s⁻¹. The annual NO₃⁻ loads in 2007 and 2008 amounted to 2514 t and 3047 t, respectively, with average specific yield of 2.5 t km⁻¹² yr⁻¹. The temporal transport of nitrate loads during different seasonal flood events varied from 12 t to 909 t. Nitrate transport during flood events amounted to 1600 t (64% of annual load; 16% of annual duration) in 2007 and 1872 t (62% of annual load; 20% of annual duration) in 2008. The level of peak discharge during flood events did not control peak nitrate concentrations, since similar nitrate peaks were produced by different peak discharges. Statistically strong correlations were found between nitrate transport and total precipitation, flood duration, peak discharge and total water yield. These four variables may be the main factors controlling nitrate export from the Save catchment. The relationship between nitrate and discharge (hysteresis patterns) investigated through flood events in this study was mainly dominated by anticlockwise behaviour.     

Effects of land use change on hydrological cycle from forest to upland field in a catchment,Japan

Understanding the effects of land use change on the hydrological cycle is very important for development of sustainable water resource in an upland field catchment. In this study, soil and hydrological properties in an upland field catchment, which was reclaimed partially from a forest catchment, were compared with another forest catchment. The soil properties of surface and subsurface layers were investigated in the two catchments. The soil was compacted and water-holding capacity of soil in the upland field catchment became smaller after the reclamation from forest to upland field, which decreased infiltration rate and water storage in the soil layers. We found that peak discharge and direct runoff in the upland field catchment increased compared with the forest catchment. Annual evapotranspiration from the upland field catchment tended to be lower due to the change in vegetation type and soil properties. Furthermore, a semi-distributed hydrological model was applied in the upland field catchment to understand the integrated effects of reclamation on the hydrological cycle. The model parameters, which were determined using a nonlinear optimization technique—the Shuffled Complex Evolution method (SCE), were compared between the two catchments. The Nash and Sutcliffe coefficient was used to evaluate the model performance. The simulated results indicated that evapotranspiration was decreased and change in discharge was more obvious in the surface layer. We considered that declined infiltration and water storage and increased peak discharge and direct runoff have a negative impact on water resources in the upland field catchment. This study will provide information for forest managers in planning and making decisions for land and water resource management.     

Atmospheric NH3 and NO2 concentration and nitrogen deposition in an agricultural catchment of Eastern China

To assess the atmospheric environmental impacts of anthropogenic reactive nitrogen in the fast-developing Eastern China region, we measured atmospheric concentrations of nitrogen dioxide (NO₂) and ammonia (NH₃) as well as the wet deposition of inorganic nitrogen (NO₃⁻ and NH₄⁺) and dissolved organic nitrogen (DON) levels in a typical agricultural catchment in Jiangsu Province, China, from October 2007 to September 2008_. The annual average gaseous concentrations of NO₂ and NH₃ were 42.2 μg m⁻³ and 4.5 μg m⁻³ (0 °C, 760 mm Hg), respectively, whereas those of NO₃⁻, NH₄⁺, and DON in the rainwater within the study catchment were 1.3, 1.3, and 0.5 mg N L⁻¹, respectively. No clear difference in gaseous NO₂ concentrations and nitrogen concentrations in collected rainwater was found between the crop field and residential sites, but the average NH₃ concentration of 5.4 μg m⁻³ in residential sites was significantly higher than that in field sites (4.1 μg m⁻³). Total depositions were 40 kg N ha⁻¹ yr⁻¹ for crop field sites and 30 kg N ha⁻¹ yr⁻¹ for residential sites, in which dry depositions (NO₂ and NH₃) were 7.6 kg N ha⁻¹ yr⁻¹ for crop field sites and 1.9 kg N ha⁻¹ yr⁻¹ for residential sites. The DON in the rainwater accounted for 16% of the total wet nitrogen deposition. Oxidized N (NO₃⁻ in the precipitation and gaseous NO₂) was the dominant form of nitrogen deposition in the studied region, indicating that reactive forms of nitrogen created from urban areas contribute greatly to N deposition in the rural area evaluated in this study.     

液氮冻结技术在地铁端头井加固中的应用

液氮冻结具有系统简单、冻结速度快、温度低和冻土强度高等特点,在城市地下工程建设中得到广泛应用。为了对某一地铁端头井进行加固,保证盾构机进洞安全,利用液氮冻结技术进行加固。经现场温度实测与分析,冻结效果达到了设计要求。运用数值模拟软件对液氮冻结和常规盐水冻结效果进行模拟,结果表明,液氮冻结土体5d左右就基本交圈,而常规盐水冻结需要30d左右才可以交圈,充分显示了液氮冻结技术低温、快速等优点。     

Human‐influenced streamflow during extreme drought: identifying driving forces,modifiers, and impacts in an urbanized catchment in central Poland

This study investigates the response of the streamflow to an extremely hot and dry summer 2015 in the urbanized catchment of the Utrata River in central Poland. The objectives were to: reveal changes in the flow regime, assess anomalies in summer river flows, estimate the natural and wastewater effluent contribution and provide an ecological context for the in‐stream conditions. The mean annual flow rate in the period 1996–2015 increased by 0.61 m³/s as compared to 1951–1970. The mean annual wastewater inflow rate to the river in 2015 was approximately 0.770 m³/s, constituting 39% of the observed flow. Almost the entire period of August this contribution approached 100%. The optimum river water temperature threshold for warm‐water fish species was exceeded. Streamflow modifications are attributed to an increase of wastewater discharge, urban impact through an increase in imperviousness, and the variability of climatic driving forces.     

GIS的嘉陵江流域吸附态氮磷污染负荷研究

以美国通用土壤流失方程为基础,根据研究流域的特征和已有的研究成果确定方程中的因子算式,在地理信息系统GIS支持下,估算了各单元的土壤流失量,应用吸附态非点源污染负荷模型,对嘉陵江流域吸附态氮磷污染负荷进行了数值模拟与定量分析。结果表明:嘉陵江流域近年平均输沙模数为161.94 t/(km2.a),北碚出口吸附态氮磷污染负荷分别为29620.8 t/a和1391.96 t/a,吸附态氮磷流失较严重的地区主要分布在白龙江和西汉水流域,各土地利用类型吸附态氮磷流失模数大小顺序依次为:荒地>灌木>草地>农田>城镇>林地。     

Seasonal variation and impact factors of available phosphorus in typical paddy soils of Taihu Lake region,China

Phosphorus loss from soil can play an important role in eutrophication of aquatic bodies. The seasonal variation of available phosphorus in soil profiles of three major paddy soils (Bai soil, Huangni soil and Wushan soil) during wheat and rice growth seasons was studied in the Taihu Lake region of China. The results were as follows: the available phosphorus contents differed in the three paddy soils. Available phosphorus content in Bai soil was the lowest in these soils. The available phosphorus content decreases rapidly with depth from the soil surface and reach the minimum value at approximately 45 cm before increasing slightly near the groundwater. The contents of available phosphorus were higher in February (tillering and shooting period of wheat) and in September (full heading time of rice) than in other months. The total phosphorus content strongly affects available phosphorus content in the studied soils. During the period of wheat cultivation, they show a typical power function relationship with correlation coefficient r = 0.6492** (n = 13), a significant positive linear correlation. In addition, available phosphorus content has a remarkable positive linear correlation with organic matter content, r = 0.9111** (n = 13), and a remarkable negative linear correlation with pH value, r = ?0.5945* (n = 13). In Wushan soil, there is a negative linear correlation between clay content and available phosphorus content, r = ?0.9289* (n = 4). Therefore, total phosphorus content, organic matter content and pH value are major impact factors on available phosphorus content in these soils.     

Quantitative assessment of groundwater vulnerability using index system and transport simulation, Huangshuihe catchment, China

Groundwater vulnerability assessment has been an increasingly important environment management tool. The existing vulnerability assessment approaches are mostly index systems which have significant disadvantages. There need to be some quantitative studies on vulnerability indicators based on objective physical process study. In this study, we tried to do vulnerability assessment in Huangshuihe catchment in Shandong province of China using both contaminant transport simulations and index system approach. Transit time of 75% of hypothetical injected contaminant concentration was considered as the vulnerability indicator. First, we collected the field data of the Huangshuihe catchment and the catchment was divided into 34 sub areas that can each be treated as a transport sub model. Next, we constructed a Hydrus1D transport model of Huangshuihe catchment. Different sub areas had different input values. Thirdly, we used Monte-Carlo simulation to improve the collected data and did vulnerability assessment using the statistics of the contaminant transit time as a vulnerability indicator. Finally, to compare with the assessment result by transport simulation, we applied two index systems to Huangshuihe catchment. The first was DRASTIC system, and the other was a system we tentatively constructed examining the relationships between the transit time and the input parameters by simply changing the input values. The result of comparisons between the two index systems and transport simulation approach suggested partial validation to DRASTIC, and the construction of the new tentative index system was an attempt of building up index approaches based on physical process simulation.     

Nitrogen characteristics in sediments of Xiangxi Bay,China Three‐Gorge Reservoir

Spatial and temporal distribution characteristics of total nitrogen and ammonium nitrogen in the sediments, pore water and overlying water of Xiangxi Bay in China Three‐Gorge Reservoir were investigated. In surveys, the sampling was undertaken from six sites of Xiangxi Bay on three dates: 29 March 2009, 28 March 2010 and 17 August 2010. Mean values of total nitrogen and ammonium nitrogen contents in the sediments and pore water of Xiangxi Bay all increased with time, especially in summer. There were intimate relationships between internal nitrogen loading and water ecosystem. Correlation coefficients R were 0.7408 (between total nitrogen in pore water and total nitrogen in sediments) and 0.7483 (between total nitrogen in sediments and chlorophyll‐a in surface water), respectively. Total nitrogen concentration differences between pore water and overlying water were all positive and had good correlation with chlorophyll‐a concentration of Xiangxi Bay. The release of nitrogen in sediments had an important impact on phytoplankton growth in Xiangxi Bay.     

A history evaluation modelling and forecastation of water quality in shallow lake

The frequent outbreaks of water eutrophication in Gehu Lake are regarded as one of the most troublesome environmental issues in Southeast China. Based on the water's potential capacity to accept pollutant loads, a catchment‐scale environmental management system was established to ensure inflows of clean water into Taihu Lake. Considering the complexity of the hydrological regimes operating within the river‐network plain, the capacities of the water environment for loads of COD and nutrients were estimated using the Water Quality Analysis Simulation Program, Version 7.3 (WASP 7.3) model. The calibration and the verification of this model were based on water quality measurements during the period 2009–2010. The variables of water quality that were examined are COD, NH₄‐N, TN and TP. The simulated distributions of the COD, NH₄‐N, TN and TP in the water column agree with the observations, but it indicates that more measurements are needed to verify the predictability of the simulations. The simulation results show that the average relative error is small, and the change trend of each indicator is consistent. The results have shown that the WASP model can be used to evaluate the future water quality changes in case that the pollution continues with the same rate. The work presented in this paper is expected to be a theoretical basis in exploring the degradation mechanism for self‐purification capacity of water bodies and in designing and constructing of Gehu Lake ecosystem restoration goals.     

Predicting runoff-induced pesticide input in agricultural sub-catchment surface waters: linking catchment variables and contamination

An urgent need exists for applicable methods to predict areas at risk of pesticide contamination within agricultural catchments. As such, an attempt was made to predict and validate contamination in nine separate sub-catchments of the Lourens River, South Africa, through use of a geographic information system (GIS)-based runoff model, which incorporates geographical catchment variables and physicochemical characteristics of applied pesticides. We compared the results of the prediction with measured contamination in water and suspended sediment samples collected during runoff conditions in tributaries discharging these sub-catchments. The most common insecticides applied and detected in the catchment over a 3-year sampling period were azinphos-methyl (AZP), chlorpyrifos (CPF) and endosulfan (END). AZP was predominantly found in water samples, while CPF and END were detected at higher levels in the suspended particle samples. We found positive (p<0.002) correlations between the predicted average loss and the concentrations of the three insecticides both in water and suspended sediments (r between 0.87 and 0.94). Two sites in the sub-catchment were identified as posing the greatest risk to the Lourens River mainstream. It is assumed that lack of buffer strips, presence of erosion rills and high slopes are the main variables responsible for the high contamination at these sites. We conclude that this approach to predict runoff-related surface water contamination may serve as a powerful tool for risk assessment and management in South African orchard areas.     

Nitrogen pollution and source identification in the Haicheng River basin in Northeast China

A survey was conducted in the Haicheng River near Liaodong Bay to analyze the characteristics and sources of the in-stream nitrogen pollution throughout the year 2010. The results indicated that the total nitrogen (TN) concentrations in the river water all exceeded the GB3838-2002 standard for Class V guideline of 2.0 mg/l at all sampling sites during the sampling seasons. Ammoniacal nitrogen (NH₃-N) dominated TN during the spring season, while nitrate nitrogen (NO₃-N) dominated during the summer and autumn seasons. Different forms of nitrogen had significant seasonal variations (p < 0.01 or p < 0.05). Only NH₃-N and NO₃-N displayed distinct spatial differences at p < 0.05 and p < 0.001, respectively. Most forms of nitrogen were interrelated with physicochemical parameters during different seasons, displaying nitrification and denitrification processes that occurred in the river rather than seasonal biological demand. Based on the nitrogen parameters, the 30 sampling sites were divided into three clusters, by which the pollution sources from chemical nitrogen fertilizers, animal wastes, domestic sewage, and industrial wastewater were identified. Generally, the Haicheng River basin provided about 700 tons of the annual TN flux, contributing to the eutrophication of the Liaodong Bay and Bohai Sea.     

Investigation of typical residential block typologies and their impact on pedestrian-level microclimate in summers in Nanjing,China

The morphology of urban residential blocks in China, which is strictly affected by regulations, can potentially improve or deteriorate microclimates. This paper first proposes a framework for identifying typical residential block typologies using Nanjing as an example. A thorough investigation, consisting of 114 samples, was conducted, and 18 typical residential block typologies were summarized. Second, 3D non-isothermal numerical simulations were performed on the hottest days of summer using the ENVI-met. The effect of morphological indices on the microclimate at the pedestrian level was explored using statistical methods and a novel graphic method named m-SpaceMate. The results revealed a strong correlation between the urban heat island intensity (UHII), mean radiation temperature, and universal thermal climate index (UTCI) and floor area ratio (FAR), as well as between wind velocity (U) and building coverage ratio (BCR). A significant increase in FAR (by approximately 1.0) can result in a low UTCI that was driven by MRT and shading conditions. Six-floor blocks, with FAR between 1.8 and 2.1, had a better overall thermal environment (except for lower U) than that of 11-floor blocks. When considering a similar BCR, blocks with slab-type buildings tended to have a U that was higher by approximately 30%.     

Exposure duration in overheating assessments: a retrofit modelling study

ABSTRACT

A new indicator of overheating risk is introduced that more comprehensively represents heat stress and the way thermal environment is experienced. This indicator is compared with the industry standard overheating assessment approach (CIBSE TM52). This is demonstrated using an energy retrofit simulation case study of a typical London, UK terraced dwelling under different climate scenarios. Overheating was evaluated first according to TM52, then via an assessment of continuously overheated intervals (COIs) that account for the duration where adaptive limits are continuously exceeded. Results for the case study show that, first, extent of overheating can vary greatly based on climate uncertainties. Second, insulation retrofit only contributes to substantial overheating when the space lacks proper ventilation or protection from solar radiation. Nevertheless, overheating cannot be avoided completely under future climate scenarios even with appropriate passive cooling. More importantly, the results show that overheated hours tend to occur consecutively. This implies that violations of TM52 criterion 1 (which currently applies only at the seasonal scale) can occur at the monthly/weekly resolutions. This ‘buried’ information can be revealed via the COI approach to more comprehensively capture how an overheating situation unfolds in a manner more relevant to heat stress and occupants’ thermal experience.     

Thermal modelling of an industrial building with solar reflective coatings on external surfaces: case studies in China and Australia

Most industrial buildings rely almost entirely on air-conditioning systems to provide thermal comfort to staff and customers who use the premises. As an alternative to this active approach, passive strategy is recommended to either fulfil this task or to help reduce energy consumption of air-conditioning systems already installed. Applying solar reflective coatings on external surfaces of the building, a key passive strategy, appears to offer an effective solution to reduce solar heat, especially during the summer, penetrating through the building fabric. This article discusses a study that uses computer thermal modelling to investigate the effectiveness of this strategy and to explore its contribution to operational energy savings. Detailed mathematical modelling in accordance with thermodynamic and heat transfer theories through the building fabric is illustrated and solutions to the mathematical problems are presented. The study consists of a comparison between two scenarios (normal coating and reflective coating) in three locations in China and one in Australia. The application of solar reflective coatings on external surfaces of the building produces energy savings for all the four locations and is found to be more beneficial in hot climates where there is a considerable need to reduce summer solar gains.     

Realization, test and modelling of honeycomb wallboards containing a Phase Change Material

The present paper deals with the thermal study of honeycomb panels for short-term heat storage. Using honeycomb panels filled with Phase Change Materials (PCMs) allowed us to fulfil two criteria: enhancement of thermal conductivity and containment to avoid possible leaks. Paraffin whose thermal properties have been measured has been chosen as PCM. The response of the PCM panel to temperature variations was studied with a specific test bench. Temperature and flux measurements clearly showed a significant thermal inertia increase compared to samples filled with air and water. Modelling and numerical simulation have been carried out and validated with the experimental results.     

扩散火焰在聚甲基丙烯酸甲酯(PMMA)上蔓延研究:理论、试验和数值模拟

对PMMA进行数字模拟和试验，对描述自然边界层扩散火焰理论的假设进行评价。我们把流动特性（二维边界层）和表面热平衡作为评价的关键假设。试验、数字模拟和理论模型证实了对质量传递数值定义的假设是正确的，但研究也表明，有必要对流动特性进行三维模拟。     

粉砂地层盾构近距离侧穿已有建筑的控制技术

依托穗莞深城际轨道太平隧道工程,在其侧穿一多层房屋时,采用控制地层损失与旋喷桩加固土体相结合的方式,很好地保护了现有房屋的安全与正常使用状态。通过分析隧道穿越过程中房屋的实测变形规律,并进行有限元数值分析,比较了有无旋喷桩和地层损失率对土体垂直位移、房屋角点沉降、房屋整体倾斜、土体深层水平位移的变化规律。分析结果表明,设置旋喷桩和控制地层损失均能有效减小沉降和土体位移,但控制地层损失的效果远比设置旋喷桩要明显。随着地层损失的增大,土体水平位移曲线由“勺”型渐变至S型,最大水平位移位置逐渐上移且位于隧道的上边界附近。