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Coupling hydrogeophysics with hydrodynamic modelling to infer subsurface hydraulic architecture of an alluvial floodplain
Near Surface Geophysics ( IF 1.6 ) Pub Date : 2020-11-22 , DOI: 10.1002/nsg.12136
J. Michael Martin 1 , Mark E. Everett 1 , Peter S.K. Knappett 1
Affiliation  

This paper underscores the importance of spatially dense geophysical data sets for making informed decisions in water management strategies. Such decisions may require understanding how site‐specific subsurface architecture – especially hydraulic connectivity – impacts the response of a shallow aquifer to anthropogenic hydrologic disturbances (e.g. over‐pumping of a shallow aquifer). At a 0.2‐km2 alluvial floodplain site characterized by thick clay over fine sand to gravel and shale bedrock in the subtropical, sub‐humid belt of the Gulf Coast of the United States, we image an asymmetrically shaped, compartmentalized, sand‐dominated channel‐belt using electrical resistivity tomography and 31 time‐domain electromagnetic soundings probing to depths of ∼40 m and ∼90 m, respectively. Lithological interpretation and a hydrological model are developed based on the geophysical data and nearby sediment cores, where the resistivity of the groundwater is 9.1 Ωm. In a modelling scenario wherein the compartmentalized sand channel‐belt starts out dry (i.e. an over‐pumped shallow aquifer), we simulate 26 weeks of infiltration due to flooding of the surface. Preferential filling of the channel‐belt occurs through its sides rather than from above, generating a new understanding of the hydraulic connectivity around and into asymmetrically shaped, sand‐dominated channel‐belts. This insight can inform decisions about the optimal placement of shallow water wells in a heterogeneous alluvial floodplain aquifer system and also highlights the dangers of over‐pumping.

中文翻译:

将水文地球物理与水动力模型耦合以推断冲积洪泛区的地下水力结构

本文强调了空间密集的地球物理数据集对于在水管理策略中做出明智决策的重要性。此类决策可能需要了解特定地点的地下结构(尤其是水力连通性)如何影响浅层含水层对人为水文干扰(例如,浅层含水层的过度抽水)的响应。在美国海湾海岸亚热带,半湿润带的一块0.2 km2的冲积洪泛区,特征是在细砂到砾石和页岩基岩上有厚厚的黏土,我们成像了一个不对称形状,分隔的,以沙子为主的河道-利用电阻层析成像和31个时域电磁测深分别探测了约40m和90m的深度。根据地球物理数据和附近的沉积物岩心,开发了岩性解释和水文模型,其中地下水的电阻率为9.1Ωm。在模拟方案中,分隔的河道带开始变干(即,浅层含水层被过度抽水),我们模拟了由于地表淹没而导致的26周的渗透。通道带的优先填充是通过其侧面而不是从上方进行的,从而使人们对围绕非对称形状,以沙子为主的通道带的水力连通性有了新的认识。这种见解可以为关于在异质冲积洪泛平原含水层系统中最佳布置浅水井的决策提供依据,并且还可以突出说明过度抽水的危险。地下水的电阻率为9.1Ωm。在模拟方案中,分隔的河道带开始变干(即,浅层含水层被过度抽水),我们模拟了由于地表淹没而导致的26周的渗透。通道带的优先填充是通过其侧面而不是从上方进行的,从而使人们对围绕非对称形状,以沙子为主的通道带的水力连通性有了新的认识。这种见解可以为关于在异质冲积洪泛平原含水层系统中最佳布置浅水井的决策提供依据,并且还可以突出说明过度抽水的危险。地下水的电阻率为9.1Ωm。在模拟方案中,分隔的河道带开始变干(即,浅层含水层被过度抽水),我们模拟了由于地表淹没而导致的26周的渗透。通道带的优先填充是通过其侧面而不是从上方进行的,从而使人们对围绕非对称形状,以沙子为主的通道带的水力连通性有了新的认识。这种见解可以为关于在异质冲积洪泛平原含水层系统中最佳布置浅水井的决策提供依据,并且还可以突出说明过度抽水的危险。我们模拟了由于表面淹没而导致的26周渗透。通道带的优先填充是通过其侧面而不是从上方进行的,从而使人们对围绕非对称形状,以沙子为主的通道带的水力连通性有了新的认识。这种见解可以为关于在异质冲积洪泛平原含水层系统中最佳布置浅水井的决策提供依据,并且还可以突出说明过度抽水的危险。我们模拟了由于表面淹没而导致的26周渗透。通道带的优先填充是通过其侧面而不是从上方进行的,从而使人们对围绕非对称形状,以沙子为主的通道带的水力连通性有了新的认识。这种见解可以为关于在异质冲积洪泛平原含水层系统中最佳布置浅水井的决策提供依据,并且还可以突出说明过度抽水的危险。
更新日期:2020-11-22
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