Relating wellfield drawdown and water quality to aquifer sustainability – A method for assessing safe groundwater abstraction

• Published in: Ecological indicators 2020-03, Vol.110, p.105782, Article 105782
• Main Authors: Gejl, R.N., Bjerg, P.L., Henriksen, H.J., Bitsch, K., Troldborg, L., Schullehner, J., Rasmussen, J., Rygaard, M.
• Format: Article
• Language: English
• Subjects: Environmental water requirements and flow requirements (EWR and EFR); EU Water Framework Directive; Groundwater impact assessment; Sustainable groundwater abstraction; Water utility management
• ISSN: 1470-160X; 1872-7034
• DOI: 10.1016/j.ecolind.2019.105782

[Display omitted] •Novel method to assess the impacts of groundwater abstraction on adverse water quantity and quality relations.•Estimating environmental groundwater requirements from impacts on the aquifer.•Securing sustainable groundwater quality by constraining drawdown.•Obtaining spatially differentiated environmental groundwater requirements.•Assisting in the planning of abstracting water in relative water-abundant areas. Planning for sustainable groundwater abstraction requires realistic and reliable assessments of groundwater drawdown in aquifers as well as impacted groundwater-dependent terrestrial and aquatic ecosystems. Present-day impact assessments allocate water for the environment and ecosystems in the form of environmental groundwater requirements (EGWRs). However, securing sustainable groundwater abstraction also requires stable groundwater quality for consumers and receptors (e.g. streams and groundwater-dependent ecosystems). We suggest dividing EGWR into two parts, namely EGWRflow, related to impacts on surface water, and EGWRwq, related to impacts on groundwater quality. We then propose a method for modelling maximum safe groundwater abstraction rates based on a relationship between water quality and piezometric heads. The method provides estimations of sustainable abstraction rates that secure stable water quality and maintain water security. Using hydrological modelling, we estimated spatially differentiated EGWRwq, for Zealand, Denmark, based on three different conditioned drawdowns of 3, 6 and 9 m. We found that depending on the boundaries and the different conditioned drawdowns EGWRwq poses a 2.5–83% share of the groundwater recharge. We found that a redistribution of water abstraction would make 27 million m3 available compared with actual abstraction, dependent on scale, while keeping within a conditioned drawdown of 3 m. Our results demonstrate how conditioned drawdown can be implemented with the objectives of evaluating actual abstraction and securing stable water quality, hence comprising a step towards more reliable and relevant groundwater impact assessments.