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61.
Liu, Clark C.K. and John J. Dai, 2012. Seawater Intrusion and Sustainable Yield of Basal Aquifers. Journal of the American Water Resources Association (JAWRA) 48(5): 861‐870. DOI: 10.1111/j.1752‐1688.2012.00659.x Abstract: Basal aquifers, in which freshwater floats on top of saltwater, are the major freshwater supply for the Hawaiian Islands, as well as many other coastal regions around the world. Under unexploited or natural conditions, freshwater and the underlying seawater are separated by a relatively sharp interface located below mean sea level at a depth of about 40 times the hydraulic head. With forced draft, the hydraulic head of a basal aquifer would decline and the sharp interface would move up. It is a serious problem of seawater intrusion as huge amounts of freshwater storage is replaced by saltwater. Also, with forced draft, the sharp interface is replaced by a transition zone in which the salinity increases downward from freshwater to saltwater. As pumping continues, the transition zone expands. The desirable source‐water salinity in Hawaii is about 2% of the seawater salinity. Therefore, the transition zone expansion is another serious problem of seawater intrusion. In this study, a robust analytical groundwater flow and salinity transport model (RAM2) was developed. RAM2 has a simple mathematical structure and its model parameters can be determined satisfactorily with the available field monitoring data. The usefulness of RAM2 as a viable management tool for coastal ground water management is demonstrated by applying it to determine the sustainable yield of the Pearl Harbor aquifer, a principal water supply source in Hawaii. 相似文献
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Abstract: Apparent ground‐water ages as determined by the noble gas isotope 85Kr and the water isotope 3H are compared. Refined gas extraction methodology at the wellhead permits efficient collection of Kr for 85Kr isotope enrichment. 85Kr isochrones elucidate areas of much younger ground‐water ages than 3H. Declining 3H activities in the catchment prevent its correlation with the youngest measured 85Kr ages. Source water for most drinking water supplies in the Collyer River catchment is recharged within 40 years BP (2004). Mean‐age (τ) transport modeling suggests uncertainty of ground‐water ages is greatest in the central basin area. 相似文献
64.
Gary S. Johnson Bryce A. Contor Donna M. Cosgrove 《Journal of the American Water Resources Association》2008,44(1):27-36
Abstract: Water right transfers are one of the basic means of implementing changes in water use in the highly appropriated water resource systems of the western United States. Many of these systems are governed by the Prior Appropriation Doctrine, which was not originally intended for application to ground‐water pumping and the conjunctive management of ground water and surface water, and thus creates an administrative challenge. That challenge results from the fact that ground‐water pumping can affect all interconnected surface‐water bodies and the effects may be immeasurably small relative to surface water discharge and greatly attenuated in time. Although we may have the ability to calculate the effects of ground‐water pumping and transfers of pumping location on surface‐water bodies, mitigating for all the impacts of each individual transfer is sufficiently inefficient that it impedes the transfer process, frustrates water users, and consequently inhibits economic development. A more holistic approach to ground‐water right transfers, such as a ground‐water accounting or banking scheme, may adequately control transfer third‐party effects while reducing mitigation requirements on individual transfers. Acceptance of an accounting scheme can accelerate the transfer process, and possibly reduce the administrative burden. 相似文献
65.
根据内抽外压式集烟尘器专利研制了一个内抽外压式集尘器,并在井下进行实验。经过3种方法测试均收到预期的的效果,司机工作区达到了国家卫生要求,由于采用外筒压风,防止了瓦斯积聚避免瓦斯爆炸。应用离散颗粒模型模拟了内抽外压式集尘器内气相流场和粉尘颗粒的运动,该集尘器不仅把矿井巷道中细微可呼吸粉尘吸收到除尘器中,又能防止了瓦斯积聚。数值模拟与实验结果的一致性表明:把内抽外压式集尘器放置在掘进机前方,由于粉尘在气流的携带下运动使掘进机司机在矿井巷道中的工作环境得到改善,减少矿工患尘肺病的概率,开发了井下集尘的新工艺、新设备。 相似文献
66.
H. S. Lin H. D. Scott K. F. Steele H. I. Inyang 《Environmental monitoring and assessment》1999,58(2):151-172
Statistical methods and a Geographic Information System (GIS) were used to investigate potential indicators of ground water vulnerability to agricultural chemical contamination in a representative area of the Mississippi River alluvial aquifer. A total of 47 wells were sampled for analysis of nitrate, phosphorus, potassium, and 13 pesticides commonly-used in the area. Ten soil and hydrogeologic variables and five ground water vulnerability indices were examined to explain the variations of chemical concentrations. The results showed that no individual soil or hydrogeologic variables or their linear combinations could explain more than 25% of the variation of the chemical concentrations. A quadratic response surface model with the values of confining unit thickness, slope, soil permeability, depth to ground water, and recharge rate accounted for 62% of the variation of nitrate, 43% of P, and 83% of K, suggesting that the interactions among soil and hydrogeologic variables were significant. Observed trends of decreasing nitrate and P concentrations with increasing well depth and/or depth to ground water seemed to correlate with carbonate equilibrium in the aquifer and more reduced environment with depth. In view of uncertainties involved, it was recognized that the limitations associated with input data resolution used in GIS and the formulation of leaching indices limited their use for predicting ground water vulnerability. Misuse of pesticides could be another factor that would complicate the relationships between pesticide concentrations and the vulnerability indices. 相似文献
67.
船舶航行时螺旋桨产生的射流会对河道水流产生扰动,这种扰动是否能引起河床底泥的再悬浮需要更深入的论证分析。通过对比分析螺旋桨射流发展规律的研究成果,以湘江典型河段为研究对象,结合实船测量结果和此段河流地质资料,探讨了螺旋桨射流对湘江长株潭段河床底泥扰动的影响,并对此段河床底泥起动和悬浮条件进行了理论分析。结果表明:在周围环境流速较低的条件下,螺旋桨射流初始速度、河床水深及泥沙粒径是决定泥沙是否运动的主要因素。湘江长株潭河段已基本库区化,大部分河道平均水深远大于航道的标准水深2.8 m,河床泥沙平均粒径大于0.87 mm,其中细颗粒泥沙很少,由于螺旋桨射流断面平均流速小于泥沙起动流速,悬浮指标计算值远大于4,因此可以判断船舶正常航行在该段河流时底泥难以起动和再悬浮。 相似文献
68.
对强夯施工的现场进行了近距离的测量 ,得到了最大地动位移值随距离的变化特征 ,其衰减规律较好地符合负幂函数衰减规律 ,水平径向与垂直向的衰减指数分别为 1 495 3,0 4714。 相似文献
69.
Most of the mesoscale models use roughness parameters to characterise the ground and to compute the surface stress. As the experimental determinations of the urban roughness parameters are rare and not very reliable, a new methodology based on microscale numerical simulations is presented here and the first results from two-dimensional simulations with different roof shapes are analysed.Firstly, it appears that the roof shape has a large influence : large difference in the Reynolds stress profile and in the roughness sub-layer thickness, enhancement of the exchanges at the roof level by buildings with attic. It also appears that the fetch necessary to obtain a constant flux layer is unrealistic compared to the real spatial homogeneity of quarters in European cities. Consequently, a new parameterisation of the urban ground-induced friction is to be developed without reference to the constant flux layer theory. 相似文献
70.