Page 28 - GENERACION Y TRANSPORTE DE SEDIMENTOS

28 PEA BERMEJO

Grande de Jujuy, the latter being the river passing erosion processes as landslides, and upon the lack
through Quebrada de Humahuaca. of baseline data to quantify it, methodologies and
While the Upper Basin is a mountainous area models were developed in order to predict orders
with streams and clearly defined watersheds as of magnitude of sediment production, properly val-
well as easily eroded steep slopes, the Middle and idated by contrast with solid flows and analysis of
Lower Basins of the Rio Bermejo develop in lowland reservoir bathymetry.
areas (Chaco plain), without precise limits. In these The Gavrilovic method was selected for calcu-
sections, the river has virtually no tributaries, but lating sediment production by slow processes in
is longitudinally accompanied by numerous aban- mountain river basins. This method estimates the
doned or ephemeral river beds. amount of material produced by surface erosion in
The high levels of sediment generation and trans- a watershed, which is transported to the section
portation, and the resulting restrictions to water of river defining such watershed. It is an empirical
use, were key in the definition of the strategic areas method that can assess both the volume of sedi-
and actions of the Strategic Action Program for the ment produced by erosion and transported to the
Binational Basin of the Bermejo River (SAP Bermejo), closing section of the basin as the product of the
executed during 2001-2009 by the Binational Com- average annual production of sediment by surface
mission for the Development of the Upper Bermejo erosion and the retention coefficient sediment.
and Grande de Tarija River Basins. An important as- The good response of the Gavrilovic method
pect of these actions was the implementation of a for estimating sediment production in different
basin-wide hydrosediment information network, mountain areas of South America, and particularly
allowing for the measuring of parameters of inter- in Northwest Argentina and Patagonia could be
est for the study of the processes observed in the proved. It also allows making predictive analysis for
Basin, including liquid level, solid and liquid river different scenarios of the variables involved (veg-
flows, and precipitation. Similarly, several structural etation, rainfall, climate change.)
and non-structural measures for sediment control On the processes of landslides in the Upper
were implemented, with highly succesful rates at Bermejo Basin (very difficult to quantify), a map
the local level, and important studies conducted to of susceptibility to the generation of such phe-
expand the knowledge base on this issue, the results nomena was produced, coming to the conclusion
of which are being presented in this publication. that Upper Basin regions most susceptible to
these processes are the headwaters of the riv-
Production of sediments in the Upper Bermejo ers Pescado and Iruya and the tributaries of the
River Basin Rio Grande in Jujuy in the area of Quebrada de
Humahuaca. In these areas, processes of dense
Given the importance of sediment production or hyper-concentrated flows are frequently ob-
in the Upper Basin, whether generated by surface served. This issue was dealt with due to its impor-