Abstract
Karst aquifers produce the world’s largest springs and supply the water resources to about a quarter of the global population while being influenced by high-intensity human activities. Knowledge about spring discharge hydrographs driven by the effects of artificial regulation is essential to develop practical strategies for the management of karst groundwater. Based on hydrogeological conditions of the karst aquifer in Jinan, a two-dimensional laboratory tank was constructed, and a corresponding numerical simulation model was developed to explore how artificial regulation drives spring hydrographs in northern China. The results showed that the spring hydrographs were significantly changed under the effects of artificial regulation. The recession coefficient increased with pumping and decreased with increasing injection rates. The late sub-recession of spring discharge did not obey the exponential recession under the influence of injection. Pumping and injection in conduit zones showed more obvious effects on the recession coefficient in the late sub-recession curves. Groundwater exchange between conduits and fissure zones differed totally for different artificial regulation modes. With continuing rainfall, the flow fields were gradually controlled by rainfall. There was a time lag in the flow fields caused by rainfall. Under the stress of exploitation at different positions, stagnation points appeared at different locations in fissure zones, and locations of stagnation points were highly dependent on the positions of pumping wells. These findings are essential for better management of karst groundwater and karst spring protection.
Highlights
Karst regions cover 7–12% of the earth’s continental area [1], and approximately 20–25% of the global population depends mainly on groundwater obtained from karst aquifers [2]
Based on the field hydrogeological conditions, this paper provided a two-dimensional sketch of of the conceptual model proposed for the Jinan karst aquifer system
The lab-scale tank model and the the corresponding numerical simulation model were established to investigate spring hydrographs corresponding numerical simulation model were established to investigate spring hydrographs in in the karst aquifer affected by artificial regulation
Summary
Karst regions cover 7–12% of the earth’s continental area [1], and approximately 20–25% of the global population depends mainly on groundwater obtained from karst aquifers [2]. In some areas of the world, karst water contributes approximately 50% to regional freshwater supplies, such as in Austria, the Dinaric region (Europe), and some regions of China [1,3]. Often geologically complex and hydraulically connected over long distances, are created and developed by groundwater flows with great temporal and spatial hydrodynamic variability. These aquifers consist of double or triple porosity structures that cause mixed flow nature and varying conduit permeability [8,9,10,11]. Double or triple porosity structures play an important role in the hydrograph of a karst spring. The recession of spring hydrographs always can be divided into the early non-exponential recession and late exponential recession [17]
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