Complex dynamics of water quality mixing in a warm mono-mictic reservoir

Roohollah Noori, Elmira Ansari, Rabin Bhattarai, Qiuhong Tang, Saber Aradpour, Mohsen Maghrebi, Ali Torabi Haghighi, Lars Bengtsson, Bjørn Kløve

Research output: Contribution to journalArticlepeer-review


Cycling of water quality constituents in lakes is affected by thermal stratification and homo-thermal conditions and other factors such as oligotrophication, eutrophication, and microbial activities. In addition, hydrological variability can cause greater differences in water residence time and cycling of constituents in man-made lakes (reservoirs) than in natural lakes. Thus, investigations are needed on vertical mixing of constituents in new impounded reservoirs, especially those constructed to supply domestic water. In this study, sampling campaigns were conducted in the Sabalan reservoir, Iran, to investigate vertical changes in constituent concentrations during the year in periods with thermal stratification and homo-thermal conditions. The results revealed incomplete mixing of constituents, even during cold months when the reservoir was homo-thermal. These conditions interacted to create a bottom-up regulated reservoir with sediment that released settled pollutants, impairing water quality in the Sabalan reservoir during both thermal stratification and homo-thermal conditions. Analysis of total nitrogen and total phosphorus concentrations revealed that the reservoir was eutrophic. External pollution loads, internal cycling of pollutants diffusing out from bottom sediments, reductions in inflow to the reservoir, and reservoir operations regulated vertical mixing and concentrations of constituents in the Sabalan reservoir throughout the year.

Original languageEnglish (US)
Article number146097
JournalScience of the Total Environment
StatePublished - Jul 10 2021


  • Homo-thermal condition
  • Incomplete mixing
  • Nutrients
  • Oxycline
  • Thermal stratification

ASJC Scopus subject areas

  • Pollution
  • Waste Management and Disposal
  • Environmental Engineering
  • Environmental Chemistry


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