Comparison of Mine Drainage/Karst Springs Discharge Recession Curves

Abstract

Gravitational dewatering of mine works-interconnected network of adits and shafts-in certain aspects of flow concentration resembles groundwater circulation in karstified rocks. To compare similarities and differences in these groundwater circulation types, hydrographs of mine waters discharging from eight adits in the past centuries excavated in crystalline, metamorphic and volcanic hard rocks of Slovakia were analysed. Discharges here were gauged on weekly bases in the periods counting several years or even several decades. After creation of discharge recessional master curves, flow component analyses revealed the presence of one or several exponential shapes of recession curves, while linear recessional mode was present only marginally or not at all. Gauging results and subsequently constructed master recession curves of 10 typical karstic springs located under the edges of karstic plateaus were compared to the previous set of results. Middle and Upper Triassic carbonates of the Slovensky Kras and Muranska planina plateaus (Slovakia) were in the past subject to intensive karstification processes, so that hydraulic behaviour of the analysed karstic springs shows typical intensive discharge response to recharge impulses, visible as steep peaks in hydrographs. Although discharges of all 10 karstic springs were gauged on daily bases, before recessional master curves creation and flow component analyses the time series were transformed to weekly data, to keep the results comparable. Contrary to the mine drains, both linear and exponential shapes of recession curves were found by flow component analyses of karstic springs. Although interconnected network of shafts and adits in mine works might be perhaps similar to conduits in karstic environment, the main difference between those two different groundwater circulation environments (karstified rocks vs. insoluble fractured solid rocks opened by mining activities) is the absence of epikarst layer in the second one. Comparison of the shapes of master recession curves here shows that the linear shapes of flow components should be linked to the influence of groundwater stored in the epikarst layer of karstified aquifers.