Abstract
AbstractUnderstanding the hydrologic connectivity between kettle holes and shallow groundwater, particularly in reaction to the highly variable local meteorological conditions, is of paramount importance for tracing water in a hydro(geo)logically complex landscape and thus for integrated water resource management. This article is aimed at identifying the dominant hydrological processes affecting the kettle holes' water balance and their interactions with the shallow groundwater domain in the Uckermark region, located in the north‐east of Germany. For this reason, based on the stable isotopes of oxygen (δ18O) and hydrogen (δ2H), an isotopic mass balance model was employed to compute the evaporative loss of water from the kettle holes from February to August 2017. Results demonstrated that shallow groundwater inflow may play the pivotal role in the processes taking part in the hydrology of the kettle holes in the Uckermark region. Based on the calculated evaporation/inflow (E/I) ratios, most of the kettle holes (86.7%) were ascertained to have a partially open, flow‐through‐dominated system. Moreover, we identified an inverse correlation between E/I ratios and the altitudes of the kettle holes. The same holds for electrical conductivity (EC) and the altitudes of the kettle holes. In accordance with the findings obtained from this study, a conceptual model explaining the interaction between the shallow groundwater and the kettle holes of Uckermark was developed. The model exhibited that across the highest altitudes, the recharge kettle holes are dominant, where a lower ratio of E/I and a lower EC was detected. By contrast, the lowest topographical depressions represent the discharge kettle holes, where a higher ratio of E/I and EC could be identified. The kettle holes existing in between were categorized as flow‐through kettle holes through which the recharge takes place from one side and discharge from the other side.
Highlights
The Pleistocene landscapes of northern Europe, Asia, and America are composed of a multiplicity of interwoven freshwater ecosystems including wetlands, riparian zones, and lake systems (Brock, Yi, CloggWright, Edwards, & Wolfe, 2009; Patzig, Kalettka, Glemnitz, & Berger, 2012)
Results demonstrated that shallow groundwater inflow may play the pivotal role in the processes taking part in the hydrology of the kettle holes in the Uckermark region
We explore the possible connectivity of kettle holes to shallow groundwater based on the calculation of evaporative losses across the region via evaporation/inflow (E/I) ratios obtained from the isotopic mass balance model “Hydrocalculator.” Third, we investigate the topographical-driven connectivity among the kettle holes by analysing the relationships between E/I ratios and electrical conductivity of kettle holes with their respective landscape elevations
Summary
The Pleistocene landscapes of northern Europe, Asia, and America are composed of a multiplicity of interwoven freshwater ecosystems including wetlands, riparian zones, and lake systems (Brock, Yi, CloggWright, Edwards, & Wolfe, 2009; Patzig, Kalettka, Glemnitz, & Berger, 2012). In order to address the question of kettle hole hydrology and groundwater dependence, several tools are available including the installation of hydrometric devices for water level derivation coupled with modelling approaches These methods are locally highly useful, they suffer from high costs and limited spatial coverage often to a few specific sites. The challenge becomes even more formidable for the characterization and quantification of complex and sporadic interaction between seemingly isolated kettle holes and their adjacent shallow groundwater as a result of high dynamics of the effective transmission zone where the flux exchange takes place between the two domains (e.g., groundwater and kettle hole; Brannen, Spence, & Ireson, 2015) This quantification is important for water resource management and for maintaining the biodiversity of kettle holes in order to resolve conflicts related to water use and for restoring water ecosystems. We anticipate that our findings will be of use in future water management decisions to protect these wetlands, as farmers expand crop production in this region
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