Karst aquifers consist of complex networks of conduits in which groundwater flows and recharge/discharge processes are generally more dynamic than in other types of aquifers. Due to their intrinsic heterogeneity and anisotropy, monitoring, quantifying, and analysing natural responses of karst springs is an efficient tool. Unlike Cenozoic and Mesozoic rocks, in Neoproterozoic karst systems, groundwater circulates and stores generally in dissolution features known as tertiary porosity, as the rock's primary porosity is recrystallized, considered negligible. This article studies the hydrodynamics of a karst portion of the São Miguel River basin, southwest of the state of Minas Gerais, Brazil. The region is predominantly composed of Neoproterozoic carbonate rocks, dating from about 570 to 540 million years ago. During a hydrological year (2019–2020), three karst springs (S1, S2, and S3) were daily monitored through their natural responses (variations of electrical conductivity, EC, temperature, T, and discharge, Q) to rainfall episodes. The data were interpreted based on the analysis of spring hydrographs, time series, recession curves (seasonal and intra‐annual), and statistics of EC, T, and Q variations. The results show the three springs generally exhibit quick flow, typically karstic, in the case of hydrosystems with a well‐structured and functional underground drainage network. The time series indicate the hydrosystem drained by S1 presents slower circulation and a lower degree of linearity, resulting from the higher sinuosity of the system, while the hydrosystems of S2 and S3 have similar behaviours, of quick water circulations immediately after a rainy episode. The degrees of karstification classify S1 and S2 as complex and extensive karst systems consisting of several subsystems, and S3 as a system in which the conduit network is more developed at the upper epiphreatic zone than near the outlet.

中文翻译：

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新元古代动态喀斯特泉水对降雨事件的自然响应，巴西米纳斯吉拉斯州圣米格尔流域

岩溶含水层由复杂的管道网络组成，其中地下水流动和补给/排放过程通常比其他类型的含水层更具动态性。由于其固有的异质性和各向异性，监测、量化和分析岩溶泉水的自然响应是一种有效的工具。与新生代和中生代岩石不同，在新元古代喀斯特系统中，地下水通常以称为三次孔隙度的溶解特征循环和储存，因为岩石的原生孔隙度被重结晶，被认为可以忽略不计。本文研究了巴西米纳斯吉拉斯州西南部圣米格尔河流域喀斯特部分的流体动力学。该地区主要由新元古代碳酸盐岩组成，距今约 570 至 5.4 亿年前。在一个水文年（2019-2020）期间，每天通过对降雨事件的自然响应（电导率 EC、温度 T 和流量 Q 的变化）监测三个喀斯特泉水（S1、S2 和 S3）。这些数据是根据春季水位线、时间序列、衰退曲线（季节性和年内）以及 EC、T 和 Q 变化的统计数据进行解释的。结果表明，在具有结构良好且功能齐全的地下排水网络的水文系统中，这三个泉水通常表现出快速流动，典型的岩溶现象。时间序列表明，S1 排水的水系统表现出较慢的循环和较低的线性度，这是由于系统的曲折性较高，而 S2 和 S3 的水系统具有类似的行为，即在雨季后立即出现快速的水循环。根据岩溶作用程度，S1和S2为由多个子系统组成的复杂而广泛的岩溶系统，S3为上表流带管道网络较出口附近更为发育的系统。