THE DEVELOPMENT OF CRYSTALLINE BASEMENT AQUIFERS IN A TROPICAL ENVIRONMENT
THE DEVELOPMENT OF CRYSTALLINE BASEMENT AQUIFERS IN A TROPICAL ENVIRONMENT
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DOI：
10.1144/gsl.qjeg.1987.020.04.02
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发表时间：
1987-01-01
期刊：
影响因子：
--
通讯作者：
ACWORTH, RI
中科院分区：
文献类型：
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作者：
ACWORTH, RI
化学风化作用是结晶基岩风化剖面发育的主要过程。在饱和的风化剖面下部，地下水是主要的化学试剂，地下水流的速度决定了风化反应的速度。在这种环境中寻找成功的钻孔地点还取决于找到地下水流速处于最佳位置。因此，通过评价地下水流动在化学风化过程中所起的作用，可以促进这种探索。控制通过风化系统单位横截面的地下水流量的主要因素是补给的可用性、风化物质的渗透性以及补给区和排泄区之间的水力坡度。在这三个方面，补给的重要性是显而易见的，因为这决定了地下水系统的投入。风化材料的渗透率是化学风化程度的函数，因此与地下水流经系统的历史有内在联系。剩下的自变量是水力坡度。这通常是在通常较薄的风化层中形成的，风化层与表面形态密切相关。因此，水力坡度是地下水流动路径上平均地表坡度的函数，因此与地表地貌有关。因此，地表地貌补给图成为一种有效的投影，在其上可以划分不同的地下水省，并提供了一种有用的手段来分类风化剖面内地下水的各种赋存状态。
Chemical weathering is the dominant process in the development of a weathering profile on crystalline basement rocks. In the saturated lower part of the weathering profile, groundwater is the principal chemical reagent and the rate of groundwater flow determines the rate of weathering reactions.The search for successful borehole sites in this environment also depends upon finding locations where the rate of groundwater flow is at an optimum. This search could therefore be facilitated by an appreciation of the part which groundwater flow plays in the chemical weathering process.The principal factors which control the quantity of groundwater flow through a unit cross sectional area of the weathering system are the availability of recharge, the permeability of the weathered material and the hydraulic gradient between the recharge and discharge areas. Of these three, the importance of recharge is clear as this determines the input to the groundwater system. The permeability of the weathered material is a function of the extent of chemical weathering and is therefore intrinsically linked to the history of groundwater flow through the system. The remaining independent variable is the hydraulic gradient. This is normally developed in what is generally a relatively thin weathered layer which closely follows the surface morphology. The hydraulic gradient is therefore a function of the average surface slope over the groundwater flow path and therefore related to the surface morphology.A plot of recharge against surface morphology therefore becomes a valid projection upon which the various groundwater provinces can be plotted and provides a useful means of classifying the various occurrences of groundwater within the weathered profile.