EFFICIENTLY REDUCING NONPOINT PHOSPHORUS LOADS TO LAKES AND RESERVOIRS1

ABSTRACT: Several problems that make it difficult to deal with water pollution from cropland are identified. The most immediate need is for a rational framework for determining where conservation programs can make an impact on eutrophication problems in reservoirs draining rural watersheds. This includes estimating the level of control that would be required for each local farm situation and the economic impacts for the planning area. A modeling approach is suggested for a planning area in Southeastern Pennsylvania.     

基于Matlab软件自动化求取参数的HEC-RAS模型构建

水质模型是水环境模拟的重要工具,近年来越来越多的应用于水环境预测与管理中,但平原河网水质模拟一直是个难点.本研究采用HEC-RAS模型开展湖州市长兴城区平原河网水动力和水质模拟.模型的水质模块率定采用Matlab软件自动化求取参数,代替常规试错法求参率定,减少了人工干预,提高了模型率定效率.HEC-RAS模型在平原河网地区水动力模拟结果较好,水质模拟结果基本符合要求,证明了HEC-RAS模型在平原河网应用的可行性,但模型的精度通常受水系概化、水文状况、污染源信息等因素影响,对于信息比较充分的短时段水质模拟其精度相对较好.     

Evaluating the Applicability of a Two‐dimensional Flow Model of a Highly Heterogeneous Domain to Flow and Environmental Management

Two‐dimensional simulation of highly heterogeneous domains, especially those with disparate length scales, roughness conditions, and geometries, often leads to challenges such as long computation times and numerical instability. Simulation of challenging domains is often needed to guide flood management and environmental regulation agencies in operation and potential domain modifications. This work evaluates the ability of a two‐dimensional unsteady hydrodynamic model to represent long‐duration transient flows over a domain with highly heterogeneous roughness, geometric characteristics, and length scales through bed roughness representation. The domain includes 13 km of Cache Creek and the 14.5 km² Cache Creek Settling Basin, which traps both sediment and mercury. Calibration under different bed roughness methods, validation, and modeling results of bathymetric modification scenarios are presented. The modeling approach's performance supports its application as a tool for management of similar domains, such as settling basins, leveed floodplains, and reservoirs. Accurate representation of flow dynamics can also inform environmental management that involves transport of sediments, nutrients, and heavy metals. This study found that a two‐dimensional unsteady flow model can accurately represent long‐duration transient flow in a large settling basin with highly heterogeneous characteristics without parsing of the domain or flow events simulated.     

基于SAE-ARP958环天线校准技术研究

目的介绍基于SAE-ARP958环天线校准技术,研究提高该校准精确性的方法,为精确监测电磁环境提供保障。方法研制一套基于SAE-ARP958环天线的校准装置,提出采用直径分别为30,10,4 cm的三个发射环天线作为磁场发生装置的校准方案,并利用对比测试的方法对校准方案进行优化。结果优化后的校准方案能够实现环天线的精确校准。结论基于SAE-ARP958环天线校准方法具有不受待校环尺寸限制的优点,而且精确性高,值得向具有较多不同尺寸的环天线用户推广。     

HYDROLOGIC SIMULATION OF THE LITTLE WASHITA RIVER EXPERIMENTAL WATERSHED USING SWAT1

ABSTRACT: Precipitation and streamflow data from three nested subwatersheds within the Little Washita River Experimental Watershed (LWREW) in southwestern Oklahoma were used to evaluate the capabilities of the Soil and Water Assessment Tool (SWAT) to predict streamflow under varying climatic conditions. Eight years of precipitation and streamflow data were used to calibrate parameters in the model, and 15 years of data were used for model validation. SWAT was calibrated on the smallest and largest sub‐watersheds for a wetter than average period of record. The model was then validated on a third subwatershed for a range in climatic conditions that included dry, average, and wet periods. Calibration of the model involved a multistep approach. A preliminary calibration was conducted to estimate model parameters so that measured versus simulated yearly and monthly runoff were in agreement for the respective calibration periods. Model parameters were then fine tuned based on a visual inspection of daily hydrographs and flow frequency curves. Calibration on a daily basis resulted in higher baseflows and lower peak runoff rates than were obtained in the preliminary calibration. Test results show that once the model was calibrated for wet climatic conditions, it did a good job in predicting streamflow responses over wet, average, and dry climatic conditions selected for model validation. Monthly coefficients of efficiencies were 0.65, 0.86, and 0.45 for the dry, average, and wet validation periods, respectively. Results of this investigation indicate that once calibrated, SWAT is capable of providing adequate simulations for hydrologic investigations related to the impact of climate variations on water resources of the LWREW.     

试论酸度计在pH测定中的定位问题

本文阐述了酸度计在测定ｐＨ时温度补偿的原理,分析了错误定位的原因,指出了正确的定位方法     

TUD模型在内蒙古地区某污水处理厂适用性研究

TUD模型应用于内蒙古呼和浩特市某污水处理厂运行实践模拟预测。首先利用TUD模型及其缺省参数进行初步模拟试预测,发现模拟预测出水COD、PO34-、SS与实际检测数据基本吻合,但对氮的预测略有偏差。采用标准参数校正方法,对模型中氮的个别组分参数（iNSF、iNXS）和硝化细菌半饱和动力学参数（KNH4）进行修正,即,i...     

Aqualab水质自动监测系统的维护与校准

介绍Aqualab水质自动监测系统的维护过程和校准步骤,通过正确的维护与校准,可以保证仪器的正常运转,保证监测数据的公正性和可靠性。     

彩色CCD成像法测量光污染

光环境是城市人居条件的一项重要内容,光污染的监测主要是针对光环境。将色彩校正的方法应用于彩色CCD测量光环境亮度分布,并结合计算机图像处理技术,对不同的颜色转换矩阵进行实验分析,使得亮度计算值和实测值很好地吻合,得出图像RGB三刺激值与目标亮度的函数关系式。通过实验,对相机测量值与亮度计实测值进行对比,分析镜头渐晕现象...     

Modeling agricultural non-point source pollution in a high-precipitation coastal area of China

Non-point source （NPS） pollution simulation in the high-precipitation coastal areas of China is difficult because varying annual typhoon incidence leads to highly contrasting rainfall patterns in dry years and wet years. An IMPULSE （Integrated Model of Non-point Sources Pollution Processes） based NPS model of the Changtan Reservoir watershed, which is a typical high-precipitation coastal area in China, was established based on the analysis of point and NPS pollution data, a digital elevation model, and data on land-use, soil, meteorology, economy, and agricultural management practice. Pre-processed pre-rain- fall soil moisture levels were introduced during the simulation to model the effects of typhoons on hydrology. Rainfall events were simulated sequentially through the year and the model was calibrated and verified using hydrological and water quality data. Accuracy of the simulated rainfall runoff and water quality in the Changtan watershed was found to be acceptable. The study showed that the NPS modeling system could be applied to the simulation and prediction ofNPS loadings in the Changtan Reservoir watershed.