Key factors in vertical mixing processes in a reservoir bordering the Pantanal floodplain, Brazil

Figures & data

Fig. 1 Location and configuration of the Ponte de Pedra Reservoir and its drainage basin. Schematic representations of: (a) input channel; and (b) off-take.

Fig. 2 (a) Mean monthly air temperature, 2005–2011 (Site 31951; source: SINDA) and mean annual flow, 1970–2011 (Gauge site 01654000; source: Hidroweb/ANA); and (b) monthly variation in rainfall at Coxim, 2005–2011 (Gauge site 31951; source: SINDA/INPE).

Fig. 3 Seasonal variation in the vertical profile of physical and chemical variables in the Ponte de Pedra Reservoir (period 2005–2011).

Table 1 Seasonal pattern of vertical stratification (S) and homogeneity (H) in physical and chemical variables in the Ponte de Pedra Reservoir (2005–2011).

Variable	Winter	Spring	Summer	Autumn	Group
Water temp.	H	S	S	H	1
pH	H	S	S	H
DO	H	S	S	S	2
Turbidity	H	S	S	S
NO3ˉ	H	S	S	S
EC	H	H	S	S	3
NH4^+	H	H	S	S
Total P	H	H	S	S
Total solids	S	S	H	H	-

Fig. 4 Seasonal cycle of stratification and vertical mixing: (a) of vertical amplitudes of physical and chemical variables between seasonal periods; and (b) of physical and chemical variables between collection depths. Figures were constructed based on the results of the ANOSIM, which are also presented. Bold values indicate p < 0.05.

Fig. 5 Seasonal variation in: (a) hydraulic retention time and cumulative solar radiation; and (b) speed and direction components of wind in the northeast quadrant (where reservoir fetch is greatest), in the Ponte de Pedra Reservoir (2005–2011).

Fig. 6 Relative contribution (% explained) of wind (W), hydraulic retention time (HR) and accumulated solar radiation (SR), explaining the vertical mixing in physical and chemical variables in the Ponte de Pedra Reservoir. U: unexplained component. Main components (W, HR and SR) are testable. Bold values indicate significant difference (p < 0.05), zero means less than 0.5%.