WATER QUALITY SAMPLING SCHEMES FOR VARIABLE FLOW CANALS AT REMOTE SITES1

ABSTRACT: Growing interest in water quality has resulted in the development of monitoring networks and intensive sampling for various constituents. Common purposes are regulatory, source and sink understanding, and trend observations. Water quality monitoring involves monitoring system design; sampling site instrumentation; and sampling, analysis, quality control, and assurance. Sampling is a process to gather information with the least cost and least error. Various water quality sampling schemes have been applied for different sampling objectives and time frames. In this study, a flow proportional composite sampling scheme is applied to variable flow remote canals where the flow rate is not known a priori. In this scheme, historical weekly flow data are analyzed to develop high flow and low flow sampling trigger volumes for auto‐samplers. The median flow is used to estimate low flow sampling trigger volume and the five percent exceedence probability flow is used for high flow sampling trigger volume. A computer simulation of high resolution sampling is used to demonstrate the comparative bias in load estimation and operational cost among four sampling schemes. Weekly flow proportional composite auto‐sampling resulted in the least bias in load estimation with competitive operational cost compared to daily grab, weekly grab sampling and time proportional auto‐sampling.     

黄磷厂废渣作水泥混合材的研究

本文较系统地研究了影响黄磷渣作水泥混合材的因素；推荐了提高黄磷渣作水泥混合材的掺量必须控制的条件；按推荐的控制条件，黄磷渣作水泥混合材的掺量可高达４０％以上。     

APPLICATION OF MODERN ORGANIZATIONAL CONCEPTS TO A LARGE WATER RESOURCE STUDY1

ABSTRACT: Modem management concepts were used to increase the efficiency and productivity of a large and complex water resource study conducted on two Delaware River components of the National Wild and Scenic Rivers System. The study analyzed the hydraulics of a 120 mile reach of the river using Rhodamine WT dye injected under medium-flow, low-flow steady-state, and low-flow-surge wave flow conditions. The study benefited from a decentralized management structure that used informal teams to attain quality control objectives, to overcome study difficulties, to secure substantial interagency cooperation, and to maximize limited financial and staffing resources.     

地震发生时间对人员伤亡影响的概率

本文用泊松分布表示家庭人数的概率分布,并假定在闲暇时间段人在室内的概率服从均匀分布,根据人在一天中的活动建立了不同时间段人在室内的概率公式。用一天中不同时间段人在室内的概率表示地震发生时间对人员伤亡的影响。     

UNIT HYDROGRAPHS FOR DEVELOPING DESIGN FLOOD HYDROGRAPHS1

ABSTRACT: In Illinois, a procedure has been developed to derive unit hydrographs for generating 100-year and probable maximum flood hydrographs, on the basis of 11 parameters that define the hydrograph shape very well. Regional regressions of these parameters with basin factors show very high correlation. Thus satisfactory values of parameters can be determined for ungaged areas or those with a few years' record. The nonlinearity in unit hydrographs derived from usual floods is largely attributed to mixing within-channel and overbank-flow flood events. To minimize the effects of nonlinearity and to derive unit hydrographa suitable for calculating spillway design floods, use of the proposed method of developing such hydrographs is recommended.     

PERIODIC AUTOREGRESSIVE-MOVING AVERAGE (PARMA) MODELING WITH APPLICATIONS TO WATER RESOURCES1

Results involving correlation properties and parameter estimation for autoregressive-moving average models with periodic parameters are presented. A multivariate representation of the PARMA model is used to derive parameter space restrictions and difference equations for the periodic autocorrelations. Close approximation to the likelihood function for Gaussian PARMA processes results in efficient maximum-likelihood estimation procedures. Terms in the Fourier expansion of the parameters are sequentially included, and a selection criterion is given for determining the optimal number of harmonics to be included. Application of the techniques is demonstrated through analysis of a monthly streamflow time series.     

SOME SIMPLE MODELS FOR DISCRETE VARIATE TIME SERIES1

ABSTRACT: Simple models are presented for use in the modeling and generation of sequences of dependent discrete random variables. The models are essentially Markov Chains, but are structurally autoregressions, and so depend on only a few parameters. The marginal distribution is an intrinsic component in the specification of each model, and the Poisson, Geometric, Negative Binomial and Binomial distributions are considered. Details are also given for the introduction of time-dependence into the means of the sequences so that seaonality can be treated simply.     

APPROACHES TO MULTIVARIATE MODELING OF WATER RESOURCES TIME SERIES1

ABSTRACT: Alternative approaches suggested for modeling multiseries of water resources systems are reviewed and compared. Most approaches fall within the general framework of multivariate ARMA models. Formal modeling procedures suggest a three-stage iterative process, namely: model identification, parameter estimation and diagnostic checks. Although a number of statistical tools are already available to follow such modeling process, in general, it is not an easy task, especially if high order vector ARMA models are used. However, simpler ARMA models such as the contemporaneous and the transfer-function models may be sufficient for most applications in water resources. Two examples of modeling bivariate and trivariate streamflow series are included. Alternative modeling procedures are used and compared by using data generation techniques. The results obtained suggest that low order models, as well as contemporaneous ARMA models, reproduce quite well the main statistical characteristics of the time series analyzed. It is assumed that the same conclusions apply for most water resources time series.     

西南地区的大气灾害及其时空变化规律

本地区为季风型、山地型和中纬多灾型的混合型多灾区，有七类３２种大气灾害、五类２８种大气灾链。在本区，受灾的面积和人口、死人、经济损失和灾种之最，皆推大气灾害，尤以旱灾类最重，其次是暴雨类。从主导的灾害类型、类、种的角度，将本地区划分成２大区、９区、１２亚区和５小区。近５００年来，大旱、大涝平均每２２．２年发生一次。     

非线性时序法在城市大气污染预测中的应用

建立城市大气污染预测模型是治理城市大气污染的重要工作。在简述时间序列方法基本原理的基础上，分析了系数为变量的自回归滑动平均（ARMA）模型、截断ARMA模型，和残差为自回归综合滑动平均（ARIMA）的半参数方法等城市大气污染预测模型。以法国某城市为例，分别采用AR模型和系数为变量的AR模型对大气污染进行了预测。通过比较预测结果可知，基于非线性时间序列方法的城市大气污染预测模型可以提高预测精度，降低预测误差。