Proposal of Unidirectional Laminar Flow Model to Black Waters Lakes in Central Amazonian, Brazil: A Case Study

Abstract

This case study was conducted in Tupé lake a Ria black water lake in the Negro River basin, Central Amazonian, with historical data from 2001 to 2018. The aim was to propose a unidirectional laminar flow model, relating it to the limnological data, in special temperature and dissolved oxygen in the water column. Climatological, geomorphological and hydrological data as well as general environmental factors were included for the construction and study of the water circulation model. The Tupé lake (3º01'33.5 ”- 3º02'47.8” S; 60º14'57.5 ”- 60º16'1.2” W) is supplied in most of the time by waters coming from forest streams. As a result, the lake has specific properties of circulation and flow of nutrients, being considered a meromictic lake with permanent stratification. Although the statistical test suggests that there is no difference in the average density between the vertical layers of water, the observed pattern confirms exactly the opposite, reinforcing the existence of permanent stratification due to uneven mass densities between the epilimnion and hypolimnion. The continuous and almost permanent unidirectional laminar flow from the forest streams guarantees the state of non-conservation of energy at the bottom of the lake, with constant renewal and variation of this behavior. A laminar flow model was established for the lake, highlighting the partial circulation of water in the epilimnion. The condition of permanent stratification is not common to be observed. Thus, with these results, a model can be established to help identify this behavior in other Ria lakes in the Amazon region.