A biogeochemical approach to evaluate the optimization and effectiveness of hypolimnetic withdrawal

Soila Silvonen, Juha Niemistö, Adrián Csibrán, Tom Jilbert, Péter Torma, Tamás Krámer, Leena Nurminen, Jukka Horppila

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Hypolimnetic withdrawal (HW) is a lake restoration method that is based on the removal of phosphorus (P) along with near-bottom water. While it has often proven to be effective, the method also sets challenges: it is about balancing between effective P removal and maintenance of the thermal stratification of the lake. The success of different HW projects has been reviewed in some studies retrospectively, but scientific literature still lacks studies that use detailed data on the lake biogeochemistry to scale and optimize the method in advance, and to predict the outcomes of the restoration measure. In the current study, we investigated the seasonal biogeochemistry, P stocks and thermal stratification of a eutrophic lake (Lake Kymijarvi/Myllypohja basin, southern Finland) to determine an optimal withdrawal rate, to assess its effects on stratification, and to evaluate the expected success of HW. We found that by adjusting HW with P diffusive fluxes from the sediment (diffusion-adjusted HW), it is possible to remove a notable part of the cycling P without causing major disturbances to the thermal stratification even in a relatively shallow lake. Our results show that HW can have great potential in lake restoration: diffusion-adjusted HW in our study lake could increase the annual P output by 35-46%, shifting the P budget of the lake to negative. We thus propose a novel approach to optimize HW on the basis of the diffusive flux of P from the sediment, with the goal of extracting P continuously at an equivalent rate to the diffusive flux. We finally discuss how this can be achieved more effectively with HW based on a closed-circuit system. (c) 2020 The Authors. Published by Elsevier B.V.

Original languageEnglish
Article number143202
JournalScience of the Total Environment
Volume755, Part 2
Number of pages14
ISSN0048-9697
DOIs
Publication statusPublished - 10 Feb 2021
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 1181 Ecology, evolutionary biology
  • 1172 Environmental sciences
  • Lake restoration
  • Phosphorus
  • Sediment
  • Eutrophication
  • Internal loading
  • Thermal stratification
  • ORGANIC-MATTER MINERALIZATION
  • LAKE-SEDIMENTS
  • PHOSPHORUS RELEASE
  • PORE-WATER
  • IRON
  • DIAGENESIS
  • MANGANESE
  • SULFUR

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