Positive and negative impacts of five Austrian gravel pit lakes on groundwater quality

Author(s)

Christian Müllegger, Tom Battin, Andreas Weilhartner, Thilo Hofmann

Abstract

Groundwater-fed gravel pit lakes (GPLs) affect the biological, organic, and inorganic parameters of inflowing

groundwater through combined effects of bank filtration at the inflow, reactions within the lake, and bank

filtration at the outflow. GPLs result from wet dredging for sand and gravel and may conflict with groundwater

protection programs by removing the protective soil cover and exposing groundwater to the atmosphere.

We have investigated the impact on groundwater of five GPLs with different sizes, ages, and mean residence

times, and all having low post-excavation anthropogenic usage. The results revealed highly active biological

systems within the lake water, in which primary producers significantly reduced inflowing nitrate concentrations.

Decalcification also occurred in lake water, reducing water hardness, which could be beneficial for

waterworks in hard groundwater areas. Downgradient groundwater nitrate and calcium concentrations were

found to be stable, with only minor seasonal variations. Biological degradation of organic material and organic

micropollutants was also observed in the GPLs. For young GPLs adequate sediment deposits may not yet have

formed and degradation processes at the outflow may consequently not yet be well established. However, our

results showed that within 5 years from the cessation of excavation a protective sediment layer is established

that is sufficient to prevent the export of dissolved organic carbon to downgradient groundwater.

GPLs can improve groundwater quality in anthropogenically (e.g., pesticides and nitrate) or geologically

(e.g., hardness) challenging situations. However, post-excavation usage of GPLs is often dominated by human

activities such as recreational activities, water sports, or fish farming. These activities will affect lake and groundwater

quality and the risks involved are difficult to predict and monitor and can lead to overall negative impacts

on groundwater quality.

Organisation(s)

External organisation(s)

WasserCluster Lunz

Journal

Science of the Total Environment

Volume

443

Pages

14-23

No. of pages

10

ISSN

0048-9697

Publication date

2013

Peer reviewed

Yes

Austrian Fields of Science 2012

105303 Hydrogeology, 105302 Hydrochemistry, 104002 Analytical chemistry, 104023 Environmental chemistry, 105904 Environmental research

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