REGIONAL MANAGEMENT OF DEPLETED AQUIFERS1

ABSTRACT: Aquifers with pressure head seriously reduced by overdrafting are referred to as depleted. In coastal areas they may be invaded by saltwater. An obvious remedy is to reduce the rate of withdrawal to the permanently available dependable yield. This is being done now in two areas for New Jersey, under the authority of the State's Water Supply Management Act; but it has not previously been accomplished on a regional scale. The dependable yield was estimated by means of detailed hydrogeological modeling. “Water Supply Critical Areas” were delimited on the basis of piezometric pressure, drawn down 30 feet below sea level. Within the depleted area, water withdrawals must be reduced by a fixed ratio (35 to 50 percent) below the amount withdrawn during 1983. This reduction is effective as soon as al alternative source of water can be made available, usually from a surface source. Special arrangements are made whereby ground water users unconnected to the alternative source of supply can pay to withdrawn their full needs from the depleted aquifers, the money being used to purchase additional water from the new surface water source, in return for which some other user will reduce his ground water withdrawal below his reduced allocation.     

Geostatistical analysis as applied to two environmental radiometric time series

This article details the results of an investigation into the application of geostatistical data analysis to two environmentalradiometric time series. The data series employed consist of ⁹⁹Tc values for seaweed (Fucus vesiculosus) and seawater samples taken as part of a marine monitoring program conducted on the coast of northern Norway by the Norwegian Radiation Protection Authority. Geostatistical methods were selected in order to provide information on values of the variables at unsampled times and to investigate the temporalcorrelation exhibited by the data sets. This information is ofuse in the optimisation of future sampling schemes and for providing information on the temporal behaviour of the variablesin question that may not be obtained during a cursory analysis.The results indicate a high degree of temporal correlation withinthe data sets, the correlation for the seawater and seaweed databeing modelled with an exponential and linear function,respectively. The semi-variogram for the seawater data indicatesa temporal range of correlation of approximately 395 days with noapparent random component to the overall variance structure and was described best by an exponential function. The temporal structure of the seaweed data was best modelled by a linear function with a small nugget component. Evidence of drift was present in both semi-variograms. Interpolation of the data setsusing the fitted models and a simple kriging procedure were compared, using a cross-validation procedure, with simple linearinterpolation. Results of this exercise indicate that, for theseawater data, the kriging procedure outperformed the simpleinterpolation with respect to error distribution andcorrelation of estimates with actual values. Using theunbounded linear model with the seaweed data produced estimatesthat were only marginally better than those produced by thesimple interpolation.     

NH4NO3-Pd(NO3)2联合基体改进剂石墨炉法测海水中痕量镉

用NH4NO3-Pd(NO3)联合基体改进剂,石墨炉法直接测海水中痕量镉.通过不同条件的实验,确定了最佳的分析条件;并通过对实际样品平行性和加标回收率的测定,验证了方法的精密度和准确度.建立了空白实验,在0.19～5.0μg/L线性范围内,镉的最低检出限为0.19μg/L.实验结果表明,该方法快速方便,提高了分析效率,准确度高,精密度好.     

海水热扩散研究进展与新问题分析

从实际的工程背景出发，较为详细地介绍了国内外关于热扩散问题的研究进展。还针对海水源热泵系统应用分析了当前研究存在的不足，指出了今后在该问题方面的研究方向。     

深圳妈湾排海工程非设计条件下海水入侵与冲洗研究

本文从微观的角度，分析了排海工程扩散管内海水入侵与冲洗的临界水力特点，并通过理论分析和物理模型试验的相互验证，得出了上述临界水力条件的判别关系式，提出了判别方法，并由此得到了深圳妈湾排海工程防止海水入侵的临界排放流量和出现海水入侵后的最小冲洗流量，为排海工程在非设计条件下的运行管理提供了依据。     

脱硫海水恢复试验研究

阐述了影响脱硫海水恢复的因素，着重介绍了稀释比、稀释方式、曝气时间、曝气速率等因素对海水恢复的影响试验，试验结果对脱硫海水恢复系统的优化设计具有一定的参考价值。     

Model Development and Calibration of a Saltwater Intrusion Model in Southern California1

Abstract: A nine‐layered confined‐unconfined flow and transport model is developed for the Alamitos saltwater intrusion barrier in Southern California. The conceptual model is based on the geological structure of the coastal aquifer system. The key parameters in the flow and transport models are calibrated using a two‐phase procedure which matches the types of data available for calibration. Because of the abundance of point measurements of hydraulic conductivity, the heterogeneous and random hydraulic conductivity field for each of the five aquifers is estimated by the geostatiscal method of natural‐neighbor‐kriging in Phase 1. In Phase 2, the longitudinal and transverse dispersivities in the transport model are estimated by a traditional inverse procedure that minimizes the least‐squares error for concentration (LSE‐CON). The minimum LSE‐CON is achieved near 15.2 and 1.52 m for the longitudinal and transverse dispersivities, respectively. Additional simulations with increasing transport parameter complexity did not yield significant improvements in LSE‐CON. Also, tracking least‐squares error for head while parametrically varying the transport parameters revealed there is a negligible interaction between predicted head and transport parameters.     

渤海湾燃煤电厂脱硫工艺选择

海水脱硫方案因其具有运行费用低等优点受到青睐.近几年,随着电力的快速发展,渤海湾出现了三十多座发电厂,竞相采用海水脱硫方案.而渤海湾属于半封闭的海湾,湾内海水与外海海水交换周期至少长达200年,区域的海流最大流速仅为外海的50%,扩散条件不太理想,污染物的长期累积情况很难确定.那么在渤海湾海域建设的滨海电厂采用海水脱硫是否可行呢?分析研究认为不宜在渤海湾选择海水脱硫工艺.     

在线浓缩-流动注射分光光度法测定海水中痕量的镉

本文针对海水中镉含量低、海水基体干扰严重等特点，建立了在线浓缩一流动注射分光光度法测定海水中痕量镉的新方法。优化了Cd（Ⅱ）的显色条件、浓缩条件和解吸条件，在最佳检测条件下，Cd（Ⅱ）的检出限为0．02μg/L，线性范围为0．05～2μg/L，相对标准偏差RSD为2.74％（n=g，Ccd（Ⅱ）=1μg／L）。将该方法应用于实际海水中Cd（Ⅱ）的测定。结果满意。     

The utilization of brackish water, protecting the quality of the upper fresh water layer in coastal aquifers

Increasing salinity is one of the most significant and widespread forms of groundwater pollution in coastal areas. This paper presents the causes and impacts of saline water intrusion in coastal areas. Various causes of salt water intrusion, and approaches for the determination of its extent and various measures to control the salt water intrusion are described. An aquifer performance test (APT) approach is presented to identify the extent of existing salt water intrusion in the study area located in the southwest coastal region of Gujarat State (India). A resistivity based experimental technique is used to identify the quality of the groundwater available at different depths. A methodology is presented to assess the extent of available fresh and saline groundwater and to find out the limit up to which lower saline groundwater can be withdrawn for industrial purposes without affecting the upper fresh water layer which can be made available for domestic purposes.