Chemical and isotopic tracers indicating groundwater/surface-water interaction within a boreal lake catchment in Finland

Rautio, Anne; Korkka-Niemi, Kirsti

Chemical and isotopic tracers indicating groundwater/surface-water interaction within a boreal lake catchment in Finland | Traceurs chimiques et isotopiques en tant qu’indicateurs des interactions eau souterraine/eau de surface dans le bassin versant d’un lac boréal de Finlande Trazadores químicos e isotópicos indicadores de la interacción agua subterránea/agua superficial dentro de una cuenca de un lago boreal en Finlandia 揭示芬兰一个北方湖汇水区地下水/地表水相互作用的化学和同位素示踪剂 Traçadores químicos e isotópicos que indicam a interação águas subterrâneas/águas superficiais dentro da bacia hidrográfica de um lago boreal na Finlândia

2015

Rautio, Anne | Korkka-Niemi, Kirsti

Stable isotopes (δ¹⁸O, δD), dissolved silica (DSi) concentration and major ion composition were used to indicate groundwater/surface-water interaction between the aquifers, the rivers and a lake in the high-latitude Lake Pyhäjärvi catchment in Finland. Significant differences were recorded in water chemistry between the groundwater and surface waters, especially in the stable isotope composition and DSi concentrations, which could thus be used as tracers. The baseline data on isotopic patterns and hydrogeochemistry in the hydrological cycle were provided by a 1-year monitoring survey in this snow-type catchment area. The proportions of groundwater in the rivers, the lake inshore area and in a groundwater abstraction plant were calculated using stable isotopes and DSi. Two inflowing rivers had distinct differences in their water chemistry. DSi has potential as a tracer in the river environment, whereas stable isotopes were more applicable in the lake environment. Locally, near the shoreline, the effect of discharging groundwater on the lake-water quality could clearly be observed. Furthermore, infiltration of the lake water into the aquifer could be observed near the pumping wells onshore. This infiltration presents a potential risk for the water quality of water supply (intake) wells. Frequent sampling is needed as part of the evaluation of the level of groundwater/surface-water interaction in snow-type catchments in order to estimate the magnitude of seasonal variation. In groundwater/surface-water interaction studies, spring thaw and high-precipitation events could be problematic, in terms of both sampling and interpreting results.

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