Page 30 - GENERACION Y TRANSPORTE DE SEDIMENTOS

30 PEA BERMEJO

present conditions, the Upper Basin of the Ber- analysis and characterization of solid transport
mejo is not affected by the anthropic action in the mechanisms in the lower Bermejo River
areas of a higher amount of sediments produced
by any source. It was made to understand the water regime
This conclusion should be considered in the and fluviomorphological dynamics of the Lower
context of the influence of the sediments of the Bermejo River Basin, estimating the magnitude of
Bermejo in the Paraguay-Paraná-Río de la Plata sediment transport in relation to processes of ero-
system. However, the foregoing does not mean sion and deposits observed, as well as the frequen-
that specific local problems related to the pro- cies and magnitudes associated with overflows and
cesses of sediment production at any point of the flooding caused by river level raisings.
Basin cannot be solved through structural and/or A morphological and sediment description of the
non structural measures. According to any point river was performed based on field data collected
of view, such measures are able to meet any spe- and surveyed under the project, consisting of liquid
cific local objective. and solid flows, cross-sections of the river, bed ma-
Other topic of interest covered in the book is terial particle size and suspended sediment.
the process associated with the presence of res- It should be noted that the material carried by
ervoirs. Reservoirs on rivers with high sediment the river in this section, both at the bottom and in
transport rates have had drawbacks associated suspension, is very thin (mainly silt). We found a dif-
with silt-in processes at a faster rate than the one ference in grain size of riverbed depending on the
evaluated in the project. Such is the case of San state of the same, under flood situations, the lower
Jacinto Reservoir in Bolivia, and of several oth- Bermejo River behaves like a very fine sand river.
ers in the northwest of Argentina. The book also The silts found in a large quantity in the surface
raised the issue of modeling the sedimentation of sampling during low water, are deposited in the
reservoirs with simple numerical models, as well months following the high water period, and such
as modeling erosion processes downstream. Ap- silts give the final configuration to the sections.
plications are presented to the Rio Grande in Ju- By comparison of gauging at El Yacare and El
juy, and in planned dams in Las Pavas, Arrazayal Colorado stations, an important qualitative conclu-
and Cambarí. The possibility of construction of sion has been drawn about the hydrosedimento-
dams and reservoirs in the Upper Bermejo Basin logical operation of the river: large flows can gener-
for any use is associated with adequate manage- ate resuspension of the riverbed material, of such
ment of the sediments, which should be included magnitude that they are warned by the measure-
since the conception of the work. Policies of clean- ments. After the passage of peaks, sedimentation
ing operation of reservoirs, associated with their processes that, under ordinary flow conditions, re-
use, will enhance the life of the reservoir under store the approximate shape and dimension of the
environmentally acceptable conditions. cross section, occur.