Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455, USA.
Ground Water. 2011 May-Jun;49(3):324-35. doi: 10.1111/j.1745-6584.2010.00737.x.
Thermal patterns of karst springs and cave streams provide potentially useful information concerning aquifer geometry and recharge. Temperature monitoring at 25 springs and cave streams in southeastern Minnesota has shown four distinct thermal patterns. These patterns can be divided into two types: those produced by flow paths with ineffective heat exchange, such as conduits, and those produced by flow paths with effective heat exchange, such as small fractures and pore space. Thermally ineffective patterns result when water flows through the aquifer before it can equilibrate to the rock temperature. Thermally ineffective patterns can be either event-scale, as produced by rainfall or snowmelt events, or seasonal scale, as produced by input from a perennial surface stream. Thermally effective patterns result when water equilibrates to rock temperature, and the patterns displayed depend on whether the aquifer temperature is changing over time. Shallow aquifers with seasonally varying temperatures display a phase-shifted seasonal signal, whereas deeper aquifers with constant temperatures display a stable temperature pattern. An individual aquifer may display more than one of these patterns. Since karst aquifers typically contain both thermally effective and ineffective routes, we argue that the thermal response is strongly influenced by recharge mode.
喀斯特泉和洞穴溪流的热模式为含水层几何形状和补给提供了潜在有用的信息。明尼苏达州东南部 25 个泉和洞穴溪流的温度监测显示出四种不同的热模式。这些模式可以分为两种类型：一种是由热交换无效的流动路径产生的，如管道；另一种是由热交换有效的流动路径产生的，如小裂缝和孔隙空间。当水在与岩石温度达到平衡之前流经含水层时，就会产生热无效模式。热无效模式可以是事件规模的，如由降雨或融雪事件产生的，也可以是季节性规模的，如由常年地表溪流的输入产生的。当水与岩石温度达到平衡时，就会产生热有效模式，并且所显示的模式取决于含水层温度是否随时间变化。温度随季节变化的浅层含水层显示出相位偏移的季节性信号，而温度恒定的深层含水层则显示出稳定的温度模式。单个含水层可能显示出多种这些模式。由于喀斯特含水层通常包含热有效和无效的路径，我们认为热响应强烈受到补给模式的影响。
