Spatial variability of specific yield and vertical hydraulic conductivity in a highly permeable alluvial aquifer
Spatial variability of specific yield and vertical hydraulic conductivity in a highly permeable alluvial aquifer
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DOI：
10.1016/j.jhydrol.2010.05.017
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发表时间：
2010-07
影响因子：
6.4
通讯作者：
Xunhong Chen;Jinxi Song;Wenke Wang
中科院分区：
文献类型：
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作者：
Xunhong Chen;Jinxi Song;Wenke Wang
在过去的几十年里，从抽水试验数据中估计的无承压含水层的比产值低于预期一直是地下水界关注的问题。抽水时低于下降的地下水位的延迟产量被认为是造成比产量不确定性的主要原因。地下水位下降以上的排水过程以向下流动为主。因此，垂直导水率（Kv）一定会对排水过程产生影响。然而，还没有对Kvvariation进行仔细的检查。对syc的空间变异也没有很好的评价。本文研究了冲积含水层的比屈服率和垂直导水率的非均质性。利用60多个沉积物岩心进行了排水试验和渗透率试验，以确定比屈服和垂向水力导率。排水试验表明，可渗透岩心在2h内释放了50%以上的可排水水，大部分岩心在24h内释放了近100%的可排水水。因此，在渗透性含水层中，延迟屈服的明显影响不太可能持续超过24小时。Syand k都证明了一个和另一个沉积物岩心之间有很强的变化趋势，并且两个变量有一定的相关性。由于Kvis的非均质性和两个参数的相关性，在对不同的观测井进行抽运试验数据分析时，保持一定的kv值会给推导出的Syvalues带来误差。
Lower-than-expected specific yield values of an unconfined aquifer estimated from pumping test data have been a concern in the groundwater community over the last several decades. Delayed yield above the declining water table during pumping has been considered the primary cause of this uncertainty in the specific yield. The drainage process above the declining water table is a dominantly downward flow. Thus, the vertical hydraulic conductivity (Kv) must have an effect on the drainage process. However, careful examination of Kvvariation has not been done. The spatial variation of Syhas not been well evaluated either. This paper examines the heterogeneity of the specific yield and the vertical hydraulic conductivity of an alluvial aquifer. A drainage experiment and permeameter tests using more than 60 sediment cores were conducted to determine specific yield and the vertical hydraulic conductivity. Drainage experiments indicated that more than 50% of drainable water was released from the permeable sediment cores in less than 2h, and nearly 100% of drainable water was released from most of the cores within 24h. Thus, the appreciable effect of delayed yield in a permeable aquifer is unlikely to last longer than 24h. Both Syand Kvindicated a strong tendency of variation between one and another sediment core, and the two variables have some correlation. Because Kvis heterogeneous and the two parameters are correlated, holding a constant Kvvalue for different observation wells in the analysis of pumping test data can introduce errors to the derived Syvalues.