Analysis of the impact of hydraulic properties and climate change on estimations of borehole yields
Analysis of the impact of hydraulic properties and climate change on estimations of borehole yields
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DOI：
10.1016/j.jhydrol.2019.123998
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发表时间：
2019-10
影响因子：
6.4
通讯作者：
M. Ascott;M. Mansour;J. Bloomfield;K. Upton
中科院分区：
文献类型：
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作者：
M. Ascott;M. Mansour;J. Bloomfield;K. Upton
了解气候变化对裂隙含水层井眼出水量的影响对于未来的水资源规划和管理至关重要。尽管裂隙含水层的导水率随深度（VKD）的变化是一个众所周知的现象，但气候变化和VKD对钻孔产量估计的相对重要性却知之甚少。我们假设，VKD施加了一个显着的额外的控制钻孔产量在气候变化下，尚未考虑到产量评估。我们开发了一个简单的两层径向地下水流模型的理想化抽水井在英格兰东南部的裂缝白垩含水层，并应用11 VKD配置文件的基础上，一个简单的概念表示的渗透率随深度的变化在白垩。对于每个时间步，通过在前一个时间步计算的饱和深度上积分VKD剖面来计算透射率。对于每个VKD配置文件和由此产生的transmittance，我们应用了1962-2014年期间的20种气候情景和6种恒定的抽水率。然后，我们估计钻孔产量的基础上得出的最低抽水水平在关键干旱年（如1976年）。我们表明，含水层的水力特性更显着（p < 0.001）比气候变化（p > 0.1）在控制最低抽水地下水位时，抽取率<9000 m3/天，这两个是显着的抽取≥9000 m3/天。水力传导率是一个重要的控制气候钻孔产量，虽然响应是非线性相关的抽水水位-抽水率曲线是否相交的关键产量限制（如水泵进水口深度，主要流入层）。建议在今后评估气候变化条件下的钻孔产量时，应考虑导水率随深度的变化。所提出的方法是通用的，可以应用于不同的含水层垂直异质性存在，影响transmittance。
Understanding the impact of climate change on borehole yields from fractured aquifers is essential for future water resources planning and management. Although variation in hydraulic conductivity with depth (VKD) in fractured aquifers is a well-known phenomenon, the relative significance of climate change and VKD on borehole yield estimates is poorly understood. We hypothesize that VKD exerts a significant additional control on borehole yields under climate change that has not been considered in yield assessments to date. We developed a simple two-layered radial groundwater flow model of an idealised pumping borehole in the fractured Chalk aquifer of south-east England, and applied 11 VKD profiles based on a simple conceptual representation of variation in hydraulic conductivity with depth in the Chalk. For each time step, the transmissivity is calculated by integrating the VKD profile over the saturated depth calculated at the previous time step. For each VKD profile and resulting transmissivity, we applied 20 climate scenarios and six constant pumping rates for the period 1962–2014. We then estimated borehole yields based on the derived lowest pumping water levels during key drought years (e.g. 1976). We show that the hydraulic properties of the aquifer are more significant (p < 0.001) than changes in climate (p > 0.1) in controlling lowest pumping groundwater levels when abstraction rates are <9000 m3/day, and that both are significant when abstraction ≥9000 m3/day. Hydraulic conductivity is as significant a control as climate on borehole yields, although responses are non-linear associated with whether pumping water level-pumping rate curves intersect key yield constraints (e.g. pump intake depth, major inflow horizons). It is recommended that variations in hydraulic conductivity with depth are taken into consideration in future assessments of borehole yields under climate change. The approach presented is generic and can be applied across different aquifers where vertical heterogeneity is present and affects transmissivity.