Noble Gas Studies of Groundwater Recharge and Residence Time in Semi-Arid Region: Contrasting the Western Mojave River Basin with Central Australia and the Kalahari Desert

0001133希尔顿在这项提案中，我们将对三个经过充分研究的半干旱地区的一系列地下水进行惰性气体研究。 目标有两个：首先，我们计划评估4 He累积法的潜力，以准确估计地下水在100年代至50万年的时间范围内的停留时间。 该方法将涉及与一些不同的地下水测年技术（氚、14 C和36 Cl）进行相互校准，并将整个数据库纳入先前为各个流域开发的地下水流动模型。 一个重要的特点将是确定的性质的“地壳他通量”和它的量化在三个研究领域，特别是作为一个，西莫哈韦河流域，位于构造活动地壳，而其他两个，澳大利亚中部和博茨瓦纳，躺在稳定的地壳平台。 我们将集中精力推导这三个地区的长期古补给率--这是对当前资源管理策略至关重要的参数--但其他水力量（例如，第二个目的是利用惰性气体丰度（Ne、Ar、Kr和NH3的浓度）来推算补给时的温度和环境条件。 在每一个研究领域，我们将选择沃茨，4 He和其他技术的日期，专注于末次冰期。 通过惰性气体与稳定同位素d18 O和d2 H之间的关系，我们计划确定（古）温度变化和其他局部效应（例如，地下水位上升）。通过与各地区地质调查局的同事合作（美国，澳大利亚和博茨瓦纳），我们将有前所未有的机会获得广泛的地球化学和地球物理数据的研究区域，后勤支持，新的样品收集，培训机会，国家的最先进的地下水软件，以及本地化的专业知识，对现实世界的资源和地下水管理问题。

0001133HiltonIn this proposal, we will conduct a noble gas study of a series of groundwaters from three well-studied semi-arid regions. The aims are twofold: first, we plan to assess the potential of the 4He accumulation method to accurately estimate groundwater residence times over a range of ages from 100s to 500,000 years. The approach will involve inter-calibration with a number of different groundwater dating techniques (tritium, 14C and 36Cl, and integration of the total database into previouslydeveloped groundwater flow models for the individual basins. An important feature will be ascertaining the nature of the 'crustal He flux' and its quantification in the three studied areas, particularly as one, the West Mojave River Basin, is situated on tectonically active crust while the other two, Central Australia and Botswanna, lie on stable cratonic platforms. We will concentrate on deriving long-term, paleo-recharge rates for the three regions-a parameter of vital importance to current resource management strategies-but other hydraulic quantities (e.g., aquifer permeability can be also assessed using the 4He technique.The second aim is to utilize the noble gas abundances (concentrations of Ne, Ar, Kr and Xe) to derive both temperatures and environmental conditions at the time of recharge. In each of the studied areas, we will select waters, dated by 4He and other techniques, to focus on the last glacial period. Through the relationship between noble gases and stable isotopes d18O and d2H, we plan to determine (paleo) temperature variations and other localized effects (e.g., rising water tables) characteristic of past recharge regions.Through collaboration with colleagues from the Geological Surveys of the respective regions (U.S., Australia and Botswanna), we will have unprecedented access to a wide range of geochemical and geophysical data on the regions of study, logistical support for new sample collection, training opportunities on state-of-the-art groundwater software, and localized expertise on real-world resource and groundwater management issues.