Sources of Ground Water Salinization in Parts of West Texas

Abstract
Determination of chemical constituent ratios allows distinction between two salinization mechanisms responsible for shallow saline ground water and vegetative-kill areas in parts of west Texas. Mixing of deep-basin (high Cl) salt water and shallow (low Cl) ground water results in saline waters with relatively low Ca/Cl, Mg/Cl, SO₄4/ Cl, Br/Cl, and NO₃/Cl ratios. In scattergrams of major chemical constituents vs. chloride, plots of these waters indicate trends with deep-basin brines as high Cl end members. Evaporation of ground water from a shallow water table, in contrast, results in saline water that has relatively high Ca/Cl, Mg/Cl, SO₄/Cl, and Br/CL ratios. Trends indicated by plots of this water type do not coincide with trends indicated by plots of sampled brines. Leaching of soil nitrate in areas with a shallow water table accounts for high NO₃ concentrations in shallow ground water.     

人工神经元网络方法对首都圈地区潜在震源区的划分

指标选取是人工神经元网络方法应用中最基础，最重要的五环，是判别工作成败的关键。但目前尚没有比较成熟的指标选取或指标显著性评价方法。因此，指标问题入往成了方法效果进一步提高的“瓶颈”问题。该问题在潜在震源区划分应用中也同样存在。     

Assessing Ground Water Development Potential Using Landsat Imagery

Seven villages in southeastern Kenya surround Mt. Kasigau and depend on the mountain's cloud forest for their water supply. Five of these villages have regularly experienced water shortages, and all village water supplies were contaminated with Escherichia coli bacteria. There is a need to economically find new sources of fresh ground water. Remote sensing offers a relatively quick and cost-effective way of identifying areas with high potential for ground water development. This study used spectral properties of features on Landsat remote sensing imagery to map linear features, soil types, surface moisture, and vegetation. Linear features represented geologic or geomorphologic features indicating either shallow ground water or areas of increased subsurface hydraulic conductivity. Regarding soil type, black soils were identified as potential indicators of shallow aquifers based on their relatively lower elevation and association with river valleys. A vegetation map was created using unsupervised classification, and three of the resulting vegetation classes were observed to be commonly associated with wet areas and/or ground water discharge. A wetness map, created using tasseled cap analysis, was used to identify all areas of high ground moisture, including those that corresponded to vegetated areas. The linear features, soil type, vegetation, and wetness maps were overlaid to produce a composite that highlighted areas with the highest potential for ground water development. Electrical resistivity surveys confirmed that areas highlighted by the composite image had relatively shallow depths to the water table. Some figures in this paper are available in color in the online version of the paper.     

A Discrete Point Sampler for Ground Water Monitoring Wells

A discrete point sampler has been developed that overcomes disadvantages inherent in several current small-volume samplers. It is designed to obtain ground water samples after a well has been purged with a pump. It consists of a sample chamber, two ports, and a stopcock for withdrawing sample aliquots. After lowering the sampler into a well, sampling is initiated by pulling on a line that sequentially removes the plugs in the lower and the upper level ports. The sample chamber fills from the bottom port and vents air from the top port. The device is suitable for sampling for volatile organic compounds in ground waters that are not subject to spontaneous bubble degassing. The upper port is sufficiently far above the lower port that none of the water that is sampled is exposed to the vented air. The sample chamber fills in such a way that the water that is taken from the chamber for analysis is not exposed to the headspace in the chamber.     

泉州地区地下水位观测资料初步分析

介绍了泉州地区地下流体网点分布的概况,对水位观测资料质量进行简单地分析。着重探讨水位观测资料的连续完整率、稳定性、动态特征及其观测资料的内在观测质量等,以获取泉州地区水位观测资料对于地震预报的利用价值。     

Potential Effects on Ground Water of a Hypothetical Surface Coal Mine in Indiana

The possible mine will remove a gently, less than 50 feet per mile, westerly dipping Springfield coal from an area covered by glacial till and some channel sands and gravel. The area is flat, with less than 20 feet of relief in a square mile. The channel sands and gravels, the till and the bedrock are capable of yielding ground water at 5 to 75,3 to 10, and 1 to 10 gallons per minute (gpm), respectively. The ground water in the drift and the shallow bedrock is calcium-bicarbonate type, contrasting with the sodium-bicarbonate type in the deep bedrock. The surface mine will feature selective handling of overburden. The probable hydrologic consequences of the mine will be 1) a short-term, areally limited dewatering, 2) an increase in dissolved solids, 3) a change in ground water chemistry in some areas to a calcium-bicarbonate sulfate water, 4) an increase in ground water storage, and 5) a new integrated surface water system. The proposed ground water monitoring system will include seven monitoring wells in the glacial material and one in the bedrock. The primary effort in ground water monitoring to the west of the mine will be to detect changes in the quality of the ground water, whereas to the east, changes in both quality and quantity will need to be monitored intensively.     

新地震区划图潜在震源区划分的主要技术特色

简要介绍了新地震区划图潜在震源区划分方案的形成过程,重点分析了潜在震源区三级划分、东西部地区潜在震源区划分技术途径的差异、不同级别活动块体边界带对高震级潜在震源区划分的控制作用、发震构造模型及其在潜在震源区划分中的应用等主要技术特色.共划分出29个地震带、77个地震构造区和1199个潜在震源区.与中国地震动参数区划图(2001)中综合方案相比,东西部地区潜在震源区的个数都有较大的增加,其中东部地区体现在震级上限6.0、6.5和7.0级的中强潜在震源区个数的明显增加,与划分工作中加强了该地区中强地震发震构造的判识研究相关;而西部地区体现在震级上限7.5和8.0级的高震级潜在震源区个数的大幅度增加,与划分工作中注重了活动块体边界带高震级潜在震源区划分,以及强调应用发震构造模型指导潜在震源区划分的技术特色相协调.     

Theory and Method for Identifying Well Water Level Anomalies in a Groundwater Overdraft Area

The overexploitation of underground water leads to the continuous drawdown of groundwater levels, change of water quality and dry-up in dynamic water level observation wells. Due to land subsidence, the well pipes uplift and the observation piping systems are damaged. These environmental geology problems can present serious difficulties for the identification of earthquake anomalies by groundwater level observation. Basied on hydrogeological theories and methods, the paper analyzes the relations of the water balance state of aquifers with stress-strain conditions and the water level regime, and then discusses preliminarily the theory and method for identifying well water level anomalies in a groundwater overdraft area. The result shows that we can accurately judge the nature of the anomaly according to the diffusion character of the drawdown funnel in the well area in combination with the aforementioned theory and method and multi-year variation patterns obtained from existing data. The results of the research are helpful for distinguishing the influence of single centralized water pumping from the long-term overdraft of water on the water level, correctly recognizing water level anomalies in the groundwater overdraft area and increasing the level of earthquake analysis and prediction.     

The Ground Water Recharge and Pollution Potential of Dry Wells in Pima County, Arizona

This paper summarizes a study to estimate the potential for dry-well drainage of urban runoff to recharge and pollute ground water in Tucson, Arizona. We selected three candidate dry wells for study. At each site we collected samples of runoff, dry-well sediment, vadose-zone sediment, perched ground water, and ground water. Water content data from vadose-zone samples suggest that dry-well drainage has created a transmission zone for water movement at each site. Volatile organic compounds, while undetected in runoff samples, were present in dry-well sediment, perched ground water at one site, and ground water at two sites. The concentrations of volatile organics (toluene and ethylbenzene) in the water samples were less than the corresponding EPA human health criteria. Pesticides were detected only in runoff and dry-well sediment. Lead and chromium occurred in runoff samples at concentrations above drinking water standards. Nickel, chromium, and zinc concentrations were elevated in vadose-zone samples at the commercial site. Of the metals, only manganese, detected at the residential site, exceeded Secondary Drinking Water Standards in ground water. It is concluded that the three dry wells examined during this study are currently not a major source of ground water pollution.     

Linear Amplification of Horizontal Strong Ground Motion in Zagreb (Croatia) for a Realistic Range of Scaled Point Sources

— The linear amplification of the larger horizontal component of strong ground motion along a selected profile in the city of Zagreb is estimated by examining the synthetic waveforms corresponding to a suite of 16 realistically chosen scaled point sources. The accelerograms, computed for the average bedrock model by modal summation, are propagated through local laterally heterogeneous anelastic models by the finite-difference algorithm. The ratio of peak ground acceleration (PGA) and of the response spectra (RS), obtained by using local and bedrock models, define the PGA and RS amplification AMP(PGA) and AMP(RS), respectively. Even variations of the order of commonly observed uncertainties of only dip and rake angles of the causative fault show that both AMP(PGA) and AMP(RS) vary at some sites by more than a factor of two. It follows that, especially for strongly laterally heterogeneous structures, local effects must be determined for each of the relevant sources considering all associated uncertainties as completely as possible. Such a conclusion certainly holds for the case of the microzonation of Zagreb, where the local geology is quite complex, and the seismicity is not confined to a single seismic source zone.     

Sources of Nitrate in Ground Water in a Sewered Housing Development, Central Long Island, New York

Nitrate concentrations in ground water on Long Island, New York, have increased markedly in the last 30 years. A significant amount of this increase has been attributed to lawn and garden fertilizers in addition to cesspool and septic-tank discharges. The increase in nitrate concentration is of particular concern in the central and eastern part of the island, where ground water is the sole source of drinking water. Ground-water samples were collected from 14 wells screened near the water table in the sewered Twelve Pines housing development constructed in Medford, Suffolk County, in 1970. Samples were collected during 1972–79 and analyzed for total ammonium, organic nitrogen, and nitrate. Statistical analyses indicate that concentrations of nitrate-nitrogen in water from 10 of the wells increased significantly during 1972–79; those in water from the other four wells did not. Nitrogen loads were estimated to be 2,300 kg/yr from fertilizers, less than 80 kg/yr from irrigation water, 200 kg/yr from animals, and less than 670 kg/yr from precipitation. Leakage from sewers was considered negligible. Nitrate-nitrogen isotope ratios also suggest that the greatest source of nitrogen is from cultivation sources (either mineralized soil nitrogen or fertilizers) rather than human or animal wastes.