DESIGN BASIS FOR EVERGLADES STORMWATER TREATMENT AREAS1

ABSTRACT: The State of Florida (1994) has adopted a plan for addressing Everglades eutrophication problems by reducing anthropogenic phosphorus loads. The plan involves implementation of Best Management Practices in agricultural watersheds and construction of regional treatment marshes (Stormwater Treatment Areas or STA's). This paper describes the development, testing, and application of a mass-balance model for sizing STA's to achieve treatment objectives. The model is calibrated and tested against peat and water-column data collected in Water Conservation Area-2A (WCA-2A), where phosphorus dynamics and eutrophication impacts have been intensively studied. The 26-year-average rate of phosphorus accretion in peat is shown to be proportional to average water-column phosphorus concentration, with a proportionality constant of 10.2 m/yr (90 percent Confidence Interval = 8.9 to 11.6 m/yr). Spatial and temporal variations in marsh water-column data suggest that drought-induced recycling of phosphorus was important during periods of low stage in WCA-2A. Maintaining wet conditions will be important to promote phosphorus removal in STA's. Sensitivity analysis of STA performance is conducted over the range of uncertainty in model parameter estimates to assess the adequacy of the model as a basis for STA design.     

山东省水环境自动监测监控系统数据的应用设计和使用方法

山东省水环境自动监测监控子系统的主要功能是将全省水质自动站数据利用计算机网络、数据仓库等技术导入到环境监测数据仓库中，实现全省水环境自动监测的统一监控和监测信息的自动管理和发布。本文简单介绍了系统担制中心端监测数据统计应用部分的功能设计和实现方法。     

COMPARISON OF MODELS FOR ESTIMATING FLOOD QUANTILES IN NEW HAMPSHIRE AND VERMONT1

We develop and compare three regression models for estimating flood quantiles at ungaged stream reaches in New Hampshire and Vermont. These models emerge from systematic analysis and validation of relations between flood magnitude and six candidate predictors reflecting basin size, topography, and climate and channel size at 36 gaging stations with record lengths exceeding 20 years. Of the candidate predictors, bank full width is most highly correlated with flood magnitude and the best prediction equation is based on width. Thus channel geometry is closely related to the current hydrologic regime in spite of geologically recent glaciation and apparently non-alluvial bank materials. We also develop models that use information obtainable from maps or GIS. The best of these uses drainage area and drainage-basin elevation as predictors, but it is substantially less precise than the width-based relation. A third relation using only drainage area as a predictor is even less precise but may be useful for some purposes. No other single predictors or combinations yielded useful predictions, although some had been included in previously-established models for the region. Model comparison included examination of residuals generated by regression using one-at-a-time suppression of data points and comparison with precision obtainable with gaging records of varying lengths.     

COMPARING SAMPLING SCHEMES FOR MONITORING POLLUTANT EXPORT FROM A DAIRY PASTURE1

ABSTRACT: Dairy cow pastures and feeding areas around barns can be a significant source of nonpoint source pollutants to nearby streams. To help document the significance of these sources, nutrient export in streamfiow from a 56.7-ha, mostly agricultural, watershed located in southwestern North Carolina was monitored from August 1994 to January 1996. Total nitrogen and phosphorus export rates from the upper, predominantly pasture, part of the watershed were 18.0 and 1.4 kg/ha/yr, respectively, as measured by weekly grab sampling and 18.7 and 4.9 kg/halyr, respectively, as measured from storm event monitoring. Nitrogen and phosphorus export rates for the area between the monitoring sites, which included overgrazed cow holding and feeding areas and farm buildings, were 376 and 86 kgfhalyr, respectively, for grab sampling and 351 and 160 kg/ha/yr, respectively, for storm event monitoring. To estimate the amount of reduction from nonpoint source controls necessary to effect a significant reduction in pollutant loading, statistical analyses of the load data were conducted. The analyses for the five pollutants monitored showed that total suspended solids would require the greatest reduction (34.6 percent for weekly grab and 33.6 percent for storm) in loading after the implementation of controls for statistical significance. Nitrate plus nitrite was found to require the least reduction (12.6 percent for weekly grab). Pollutant export rates computed from weekly grab samples and storm event samples used separately were compared to corresponding export rates computed from combining grab and storm event samples to assess the differences in monitoring schemes.     

NONLINEAR MODELING AND PREDICTION OF A RIVER FLOW SYSTEM1

ABSTRACT: Model estimation and prediction of a river flow system are investigated using nonlinear system identification techniques. We demonstrate how the dynamics of the system, rainfall, and river flow can be modeled using NARMAX (Nonlinear Autoregressive Moving Average with eXogenuous input) models. The parameters of the model are estimated using an orthogonal least squares algorithm with intelligent structure detection. The identification of the nonlinear model is described to represent the relationship between local rainfall and river flow at Enoree station (inputs) and river flow at Whitmire (output) for a river flow system in South Carolina.     

Water Use by Thermoelectric Power Plants in the United States1

Abstract: Thermoelectric power generation is responsible for the largest annual volume of water withdrawals in the United States although it is only a distant third after irrigation and industrial sectors in consumptive use. The substantial water withdrawals by thermoelectric power plants can have significant impacts on local surface and ground water sources, especially in arid regions. However, there are few studies of the determinants of water use in thermoelectric generation. Analysis of thermoelectric water use data in existing steam thermoelectric power plants shows that there is wide variability in unitary thermoelectric water use (in cubic decimeters per 1 kWh) within and among different types of cooling systems. Multiple‐regression models of unit thermoelectric water use were developed to identify significant determinants of unit thermoelectric water use. The high variability of unit usage rates indicates that there is a significant potential for water conservation in existing thermoelectric power plants.     

山东省城市空气自动监测监控系统数据的应用设计和使用方法

山东省城市空气自动监测监控系统的主要功能是将全省城市自动监测站数据利用计算机网络、数据仓库等技术导入到环境监测数据仓库中，实现全省城市空气质量自动监测的统一监控和监测信息的自动管理和发布。本文简单介绍了系统控制中心端监测数据统计应用部分的功能设计和实现方法。     

A TAU-LIKE TEST FOR TREND IN THE PRESENCE OF MULTIPLE CENSORING POINTS1

ABSTRACT: A common problem arises in testing for trends in water quality when observations are reported as “less than detection limit.” If a single detection limit is used for the entire study, existing non-parametric statistical methods, modified for ties, are applicable. If, however, the detection limit varies during the course of the study, resulting in multiple detection limits, then the commonly used trend detection methods are not appropriate. A statistic similar to Kendall's tau, but based on expected ranks, is proposed. Monte Carlo simulations show that the normal approximation to the distribution of this statistic is quite good, even for small samples and a large proportion of censored observations. The statistic is also shown to have greater power than the ad-hoc method of treating all observations less than the target censored observation as tied.     

SELECTING TREND TESTS FOR WATER QUALITY SERIES WITH SERIAL CORRELATION AND MISSING VALUES1

ABSTRACT: The use of nonparametric tests for monotonic trend has flourished in recent years to support routine water quality data analyses. The validity of an assumption of independent, identically distributed error terms is an important concern in selecting the appropriate nonparametric test, as is the presence of missing values. Decision rules are needed for choosing between alternative tests and for deciding whether and how to pre-process data before trend testing. Several data pre-processing procedures in conjunction with the Mann-Kendall tau and the Seasonal Kendall test (with and without serial correlation correction) are evaluated using synthetic time series with generated serial correlation and missing data. A composite test (pre-testing for serial correlation followed by one of two trend tests) is evaluated and was found to perform satisfactorily.