Edmundo C. Drago

The Physical Dynamics of the River–Lake Floodplain System

The Parana River is the second largest river in South America in terms of catchment area (1.51 million km2), the second longest (4,400 km from the headwaters of Grande River in Brazil to the Rio de la Plata estuary), and the third in terms of discharge (about 470 km3 of freshwater carried to the sea annually). Within this fluvial hydrosystem, the segment of the Middle Parana encompasses 700 km upstream from the Paraguay outlet to the apex of the delta upstream from Rosario city (Santa Fe Province, Argentina) (Chap. 1, Fig. 1.5). Along its main channel, the Middle Parana has built a relatively wide fringing floodplain with a surface of ca. 20,000 km2. This floodplain resembles other large tropical and temperate floodplains in its amplitude and duration of flooding, and in many of its ecological characteristics. The annual phases of flood and drought and the complex hydrological connectivity between lotic and lentic waters are the major variables driving the lateral and longitudinal exchanges of sediments, organic matter and organisms at the riverscape scale. Moreover, the hydrology of the floodplain lakes, as well as the sedimentation- resuspension processes, the thermal behavior and the heat content variations are closely linked with the flood and drought phases. The aim of this chapter is to extend the knowledge on the hydro-sedimentological dynamics, as well as the thermal structures and mixing processes that occur in the river–floodplain lake systems of the Middle Parana during the annual connection and disconnection phases.

Bed Sediment Characteristics in the Paraná and Paraguay Rivers

ABSTRACT This paper presents a granulometric characterization of the Parana and Paraguay rivers bed sediments. Samples obtained along 2,900 km of the thalweg of those rivers form the basis of this study. The main results and other features of the study are as follows: a) the bed sediment of both rivers is composed mainly of medium to fine well-sorted sands, with sizes in the Parana slightly higher than those in the Paraguay river; b) the variations of mean diameters for both rivers are well correlated with the energy slopes. The correlation coefficient in the Paraguay river increases notably if the discharge and width/depth relationship variations along the channel are included in the regression; and, c) the origin of the transported sands could be related to the geologic characteristics of the Parana river basin. An explanation is also suggested for the different bed sediment texture found in the Parana de las Palmas and Parana Guazu rivers in the lower delta. The explanation is based on the geomorphic p...

Origin, Evolution, and Types of Floodplain Water Bodies

The interest from geomorphological and limnological standpoints is the analysis of the origin, evolution, morphometry, and abundance of floodplains lakes, which provides relevant information about the management of these wetland ecosystems. The Middle Parana River contains a heterogeneous mosaic of lotic and lentic water bodies with changing shapes and areas according to the variable dynamics of the fluvial processes and the short- and long-term evolution of the different portions of the river floodplain. Thus, floodplain lotic and lentic environments can be eroded, filled, or enlarged at each flood event. The field data obtained from more than 30 years of the last century to the beginning ones, and the interpretation and analysis of the morphological structure of the floodplain lakes were accomplished using aerial photographs scaled from 1:20,000 to 1:50,000, Landsat satellite images and topographic charts (Paira 2003; Paira and Drago 2006). The aerial photographs and satellite images used were taken during mean and low water stages of the Parana River. The aim of this chapter is to summarize a basin-wide characterization of the origin, shape, and morphological evolution of the floodplain lakes and its relationships with the aquatic and terrestrial vegetation and river dynamics.

Fluvial Sediments: Main Channel and Floodplain Interrelationships

The quantity and quality of sediments supplied to such a large and complex system as the middle Parana River, its differential transport through the drainage network, and the eventual sedimentation rates on the adjacent alluvial plain, are all variables that need to be known due to their crucial role on the type and survival of communities characterizing certain environments and on the possible interrelationships among them. Since the water transparency, the transfer of some nutrients and salts, the periodical renovation of alluvial plain surface soils, and the substratum features of lotic and lentic environments are all factors (processes) closely related to sediment, its pondering as a key variable for the state regulation of complex fluvial ecosystems has a sound justification.

Invasion process of Limnoperna fortunei (Bivalvia: Mytilidae): the case of Uruguay River and emissaries of the Esteros del Iberá Wetland, Argentina

Limnoperna fortunei (Dunker, 1857), during its invasion process in South America, has caused severe impacts both on natural environments altering native biodiversity, ecosystem structure and function-, and on man-made structures causing economic looses. Twenty-one samples were taken from the right bank of the Uruguay River, from tributaries of the Uruguay and Parana Rivers, the drainage of the Esteros del Ibera Wetland. Based on this fieldwork, the presence of larvae and adults of L. fortunei was determined. Also, through the comparison of environmental characteristic with the known tolerance limits for the species, the possibility of its establishment in environments not yet invaded was determined. Most of the sampling stations have features that allow the development of stable populations L. fortunei, including the rivers that drain the Esteros del Ibera, allowing access of this invasive species to this important wetland.

Thermal summer characteristics of lakes and ponds on Deception Island, Antarctica

During January and February 1981, water temperature measurements were made in lakes and ponds of Deception Island, Antarctica. The depth of these waterbodies varies between 0.88 m and 36 m, with maximum surface areas of over 290 000 m2. Some ponds freeze completely during winter, and the lakes are covered by ice for 9–10 months of each year. The maximum ice thickness measured in early summer (December), dit not exceed 0.5 m.Solar radiation and geothermal heating largely determine the thermal structure of these aquatic environments. The water temperature of tributary meltwater streams did not exceed 3 °C, but the littoral waters reached 9 °C. The bottom water temperatures of meromictic lakes 5 (Irízar) and 9, are 12.3 °C and 19.9 °C respectively. These deep waters are heated from geothermal sources and it is possible that some ponds may be also influenced by their proximity to hot soils. With the exception of the meromictic lakes, the aquatic environments studied here did not show a vertical stratification of temperature.It is not possible to establish a general thermal classification for the waterbodies of Deception Island. The interaction of the lacustrine morphology, solar radiation and vulcanism produce contrasting thermal features. Taking into account only the upper layers of meromictic lakes (mixolimnion), and emphasizing the fact of that some ponds freeze completely during winter, the waterbodies of Deception Island would be classified as ‘pleomictics’ (Paschaslki, 1964).