The response of Carlos Botelho (Lobo, Broa) reservoir to the passage of cold fronts as reflected by physical, chemical, and biological variables

Abstract

This paper describes and discusses the impacts of the passage of cold fronts on the vertical structure of the Carlos Botelho (Lobo-Broa) Reservoir as demonstrated by changes in physical, chemical, and biological variables. The data were obtained with a continuous system measuring 9 variables in vertical profiles in the deepest point of the reservoir (12 m) coupled with climatological information and satellite images, during a 32-day period in July and August, 2003. During periods of incidence of cold fronts the reservoir presented vertical mixing. After the dissipation of the cold fronts a period of stability followed with thermal, chemical, and biological (chlorophyll-a) stratification. Climatological data obtained during the cold front passage showed lower air temperature, higher wind speed and lower solar radiation. The response of this reservoir can exemplify a generalized process in all shallow reservoirs in the Southeast Brazil and could have several implications for management, particularly in relation to the phytoplankton population dynamics and development of cyanobacterial blooms. Using this as a basis, a predictive model will be developed with the aim of advancing management strategies specially for the drinking water reservoirs of the Metropolitan Region of São Paulo.

Water quality changes in floodplain lakes due to the Amazon River flood pulse: Lago Grande de Curuaí (Pará)

“…In spite of the clear definition of the parameters used to assess water quality, this quality is easily affected by weather, solar radiation, hydrology, and human activities (Hooda et al, 2000;Tundisi et al, 2004;Whitehead et al, 2009). The dynamic nature of the aquatic systems makes it difficult to distinguish between natural variability and anthropogenic influences (Chipps et al, 2006).…”

Water residence time affecting phytoplankton blooms: study case in Ibitinga Reservoir (São Paulo, Brazil) using Landsat/TM images

“…Factors controlling phytoplankton growth other than HTR might have affected the development of extended and thick blooms. Among them, one can mention the decrease in Irradiance from January to June (Kirk, 2011), and in the frequency of frontal systems in the region (Tundisi et al, 2004).…”

The importance of protozoan bacterivory in a subtropical environment (Lobo-Broa Reservoir, SP, Brazil)

“…The reservoir has a maximum length of 8 km, volume of 22 x 10 6 m 3 and average depth of 3 m (Tundisi et al, 2004). The climate of the area is subtropical mesothermic -Cwa, according to Köppen, with a dry winter (from April to September) and wet summer (from October to March).…”

“…Due to the spatial heterogeneity, two sampling points (see Figure 1) were selected in this work: the point 1 (P1) is located near the dam and the point 2 (P2) is positioned near the mouth of the Itaqueri River. The samplings and the in situ grazing experiments were conducted bimonthly, at Tundisi et al, 2004). the water sub-surface (0.5m), during a year, which included three surveys in the dry season (May, July and September 2010) and three in the rainy season (November 2010, January and March 2011).…”