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SECAO 2
ANTECEDENTES GEOGRAFICOS,
PANTANAL E HIDROVIA
Esta secao estabelece os antecedentes geograficos para este estudo.
Esta dividida em
quatro subsecoes:
1.A Bacia Hidrografica do Paraná-Paraguai
2.As Bacias Hidrograficas do Paraguai e Alto Paraguai
3.O Pantanal Matogrossense
4.O Projeto da Hidsrovia Paraná-Paraguai (Hidrovia).
Este estudo focaliza o impacto do projeto proposto da hidrovia
Paraná-Paraguai no
Pantanal Matogrossense, o qual se situa na bacia do Rio Paraguai, um
tributario impor
tante do sistema hidrografico Paraná-Paraguai. As fontes de referencia
para as informa
coes contidas nesta Secao estao listadas no Apendice 1. As figuras e
tabelas para todas
as Secoes estao incluidas nos Apendices 2 e 3, respectivamente.
2.1
A Bacia Hidrografica do Paraná-Paraguai
A bacia hidrografica do Paraná-Paraguai e a mais importante do
sistema do Prata em
termos de descarga (75 %) e area de drenagem (84 %) (Bonetto, 1975). O
sistema do
Rio da Prata e o segundo maior de America do Sul, depois do Amazonas.
A bacia do Paraná-Paraguai drena uma regiao extensa, compreendendo
2605 000
km2 no Brazil, Argentina, Paraguai e Bolivia. Como seu nome indica, e
composta de
dois rios principais: o Paraná e o Paraguai. O Paraná e o maior dos
dois, drenando
1510 000 km2 (58 %) da bacia. O rio Paraguai, drenado os 1095 000 km2
restantes, e
o tributario mais importante do rio Paraná.
A distribuicao geografica da bacia do rio Paraná re a seguinte: 59
% no Brasil, 37.4
% na Argentina e 3.6 % no Paraguai. A distribuicao geografica da bacia
do rio Paraguai
e: 33.3 % no Brasil, 33.3 % no Paraguai, 16.7 % na Argentina e 16.7 % na
Bolivia
(Anderson et al, 1993). A bacia hidrografica combinada dos rios ParanáParaguai drena
uma parte significativa desses quatro paises Sul Americanos (Figura 1).
O rio Parana
esta dividido em tres secoes distintas (Bonetto, 1975):
1.O Alto Paraná, das cabeceiras do rio Paraná nas vizinhancas de
Brasilia, ate a con
fluencia com o rio Paraguai.
2.O Medio Paraná, da confluencia com o rio Paraguai ate o porto de
Diamante,
perto de Santa Fé, Argentina, uma distancia de cerca de 700 km.
3.O Baixo Paraná, de Diamante ate o estuario do rio da Prata, uma
distancia de
aproximadamente 400 km.
2.2
As Bacias Hidrograficas do Paraguai e Alto Paraguai
As cabeceiras da bacia do rio Paraguai estao localizadas na serra
de Tapirapuã, nas
proximidades da Vila de Parecis, no estado de Mato Grosso (EDIBAP, 1979).
Depois
de escoar geralmente na direcao Sul por uma distancia de cerca de 2800
km, o rio
Paraguai alcanca o Paraná em Confluencia, ao norte das cidades Argentinas
de
Corrientes e Resistencia (Figura 1).
O rio Paraguai esta dividido em tres secoes (Anderson et al,
1993):
1.O Alto Paraguai, escoando a traves do Brasil, Bolivia e Paraguai, das
suas cabecei
ras ate a confluencia com o rio Apa, uma distancia de 1873 km.
2.O Medio Paraguai, escoando a traves de Paraguai e Argentina, da
confluencia com
o rio Apa ate a confluencia com o rio Tebicuary, uma distancia de 797 km.
3.O Baixo Paraguai, atravessando o Paraguai e Argentina, da confluencia
com o rio
Tebicuary ate a confluencia com o rio Paraná, uma distancia de 130 km.
Os rios Pilcomayo e Bermejo, tributarios do Medio e Baixo Paraguai,
respectiva
mente, descem dos Andes para o Oeste (Figura 1). Similarmente, os
tributarios orientais
do Medio e Baixo Paraguai escoam sobre relevo montanhoso. O restante da
bacia do
rio Paraguai compreende uma imensa planicie interior, com relevo
extremadamente
plano. Essa disposicao geomorfologica peculiar causou a existencia do
Pantanal Ma
togrossense, um extenso grupo de alagadicos localizado integralmente na
bacia do Alto
Paraguai (Tricart, 1982).
O trecho Alto Paraguai e a secao mais a montante do rio Paraguai,
das suas cabecei
ras ate a confluencia com o rio Apa. Esse ultimo define a fronteira
entre o Brasil (ao
Norte) e Paraguai (ao Sul). A bacia do The Upper Paraguay river basin
contains the Pan
tanal of Mato Grosso and its headwaters, wholly within Brazilian
territory, and portions
of Eastern Bolivia and Northwestern Paraguay.
While the precise western
limits of the
basin are uncertain (the Bañados de Izogog, in Eastern Bolivia), the
northern and east
ern limits are delimited by mountain ranges, all within Brazil. To the
East, the basin is
limited by the Maracaju, Caiapó, and Saudade ranges; to the North by the
Parecis range,
and partly by the Azul range.
The basin lies between 14o and 23o S, and
53o and 60o
W (Fig. 2).
The Upper Paraguay river basin comprises 496 000 km2, in two
distinct regions
(DNOS, 1974):
1.The area to the left (west) of the Paraguay and Jauru rivers, wholly
within Brazilian
territory, encompassing 336 000 km2; half of this area is above the
altitude of 200
m.
2.The area to the right (east) of the Paraguay and Jauru rivers,
encompassing 160 000
km2, of which 145 000 km2 are in Bolivian and Paraguayan territory, and
the re
maining 15 000 km2 are in Brazil; 19 percent of this area (31 000 km2) is
above the
altitude of 200 m.
The principal tributaries of the Upper Paraguay river are (Fig. 2):
1.Sepotuba,
2.Cabaçal,
3.Jauru,
4.Cuiabá, and its tributaries São Lourenço and Piquiri-Itiquira,
5.Taquari, and
6.Miranda, and its tributary the Aquidauana.
Other tributaries, primarily intermittent, include the Negro,
Aquidabã, Branco, Tereré,
and Amonguijá. All these are left-bank tributaries, located wholly
within Brazil.
For reference purposes, Table 1 shows selected hydrographic
characteristics of the
Upper Paraguay river. Table 2 shows selected hydrologic data at gaging
stations along
the Upper Paraguay river (Fig. 3). Table 3 shows valley slopes along the
Upper Para
guay river and its major tributaries.
Table 1 shows that the Upper Paraguay river is quite sinuous,
particularly upstream of
Corumbá, where the sinuosity, i.e., the ratio of river length to valley
length, can be quite
high. For instance, the reach from 40 km downstream of Porto Conceição
to Refúgio
das Três Bocas, where the sinuosity is: 161 km/55 km = 2.92. The
influence of sinu
osity on proposed navigational improvements is analyzed in Section 4.1.1.
Table 2 shows that the difference between maximum and minimum
observed water
levels along the Upper Paraguay river is smallest at Descalvados (2.61
m), remaining
small (less than 3.5 m) for about 200 km downstream (at Porto Conceição
it is 3.28 m;
at Bela Vista do Norte it is 3.27 m).
This indicates the presence of
substantial channel
overflows in the Upper Paraguay river between Descalvados and Bela Vista
do Norte.
Table 3 shows that valley slopes in the Upper Paraguay river basin
decrease gradually,
from 15-50 cm/km close to the mountains to the north, east, and south, to
7-15 cm/km
along the major tributaries, and to 0.7-6.5 cm/km along the Upper
Paraguay river.
This reveals that the Upper Paraguay river constitutes a regional base
level for the flow
of its eastern tributaries.
2.3
The Pantanal of Mato Grosso
The Pantanal of Mato Grosso is a seasonally inundated depression
wholly contained
within the Upper Paraguay river basin, encompassing approximately 136 700
km2 (Pro
jeto RADAMBRASIL, 1982a&b). The Pantanal is geomorphologically and
hydrologi
cally positioned to attenuate and reduce the runoff from the basin.
Tricart (1982) has
stated that the mountains to the south of the Pantanal "strangle" the
valley of the Upper
Paraguay river close to the location where it exits Brazilian territory.
Significantly, this
geomorphic feature is referred to locally as Fecho dos Morros, literally,
"closing of the
hills." (Fig. 3). The Pantanal is a huge natural reservoir receiving
distributed inflows from
the Upper Paraguay river and its tributaries, and concentrating runoff at
the basin outlet,
the Apa river confluence, about 100 km downstream of Fecho dos Morros.
Large portions of the Pantanal are flooded only during the annual
crest of the Upper
Paraguay river and its tributaries, and much nonflooded terra firma is
interspersed
throughout the region. The mixture of permanent swamp, seasonal swamp,
and non
flooded land, as well as the contiguity of the Pantanal to major South
American biomes
(the humid Amazon rainforest to the north and northwest, the subhumid
savannas of
Central Brazil to the east, the humid Atlantic forest to the southeast,
and the semiarid
scrub forest of neighboring Bolivia and Paraguay to the west and
southwest) have condi
tioned the richness and variety of its vegetation and climate (Prance and
Schaller, 1982).
In turn, the Pantanal ecosystems support a rich and diverse fauna,
including numerous
species of mammals, reptiles, fish, birds, butterflies, and other
invertebrates (Brown,
1986).
The name Pantanal of Mato Grosso tends to hide the fact that the
depression of the
Upper Paraguay basin consists of not one but several seasonally flooded
regions, quite
distinct from each other; thus, the Portuguese name Planícies e pantanais
Matogros
senses, which stands for "Plains and swamps of Mato Grosso."
The following pantanais were identified by Projeto RADAMBRASIL
(1982a&b) (Fig.
4): Corixo Grande-Jauru-Paraguay, (2) Cuiabá-Bento Gomes-Paraguaizinho,
(3) ItiquiraSão Lourenço-Cuiabá, (4) Paiaguás, (5) Taquari, (6) Jacadigo-Nabileque,
(7) MirandaAquidauana, (8) Negro, (9) Tarumã-Jibóia, (10) Aquibadã, (11) BrancoAmonguijá, and
(12) Apa.
Alternatively, Adámoli (1981) has classified the Pantanal of Mato
Grosso into ten pan
tanais: (1) Cáceres, (2) Poconé, (3) Barão de Melgaço, (4) Paiaguás, (5)
Nhecolândia, (6)
Aquidauana, (7) Paraguay, (8) Miranda, (9) Nabileque, and (10) Abobral.
The peculiar characteristics of the pantanais have led to the use
of regional terminol
ogy to describe its most salient geomorphic features, namely baías,
baixadas, barreiros,
salinas, córregos, capões, cordilheiras, vazantes, and corixos. A brief
description of
each follows.
·The baías are lowlying areas of circular, semicircular, or irregular
shape, which have
standing water, sometimes saline; their linear dimensions vary from tens
to hundreds
of meters.
·The baixadas are portions of the baías subject to seasonal inundation
(Silva, 1990).
·The barreiros are baías that have seasonal or periodic water (Valverde,
1972).
·The salinas are lakes with saline water; they are covered during the dry
season with
salt crusts, and are for the most part unconnected from the seasonally
flooded baías
(Silva and Pinto-Silva, 1989).
·The córregos are small watercourses (Carvalho, 1986).
·The capões are vegetated earthmounds, of various sizes, and
approximately circular
or elliptical in shape (Ponce and Cunha, 1993).
·The cordilheiras are slight terrain elevations located between the
baías, with mean
elevations about 2-3 m above the water level in the baías. While they
are normally
dry, they are subject to inundation during exceptional floods.
They
serve as high
areas for the location of cattle ranches, and as refuge for livestock
during extraordi
nary and exceptional floods.
·The vazantes are large depressions situated between the cordilheiras,
lacking a
clearly defined channel (Carvalho, 1986). During the flood season, these
depressions
drain intermittent streams, extending for several kilometers. However,
many vazantes
are perennial, revealing the presence of substantial amounts of
subsurface flow.
·The corixos, unlike the vazantes, are small permanent watercourses
connecting adja
cent baías with narrower and much deeper channels. When the corixo is
long and
has a well defined cross section, it is referred to as corixão (Carvalho,
1986).
The characteristics of the several pantanais that constitute the
Pantanal of Mato
Grosso are described by Projeto RADAMBRASIL (1982a&b) and Silva (1986).
The soils
and inundation patterns (flooding levels) of the Pantanal are described
by Projeto RA
DAMBRASIL (1982a&b) and Amaral Filho (1986).
2.4
The Paraná-Paraguay Waterway (Hidrovia) Project
The Paraná-Paraguay river basin system is an extensive region in
South America,
which lies within the countries of Argentina, Bolivia, Brazil, and
Paraguay. The neigh
boring Uruguay river drains portions of Argentina, Brazil, and Uruguay.
The confluence
of these two rivers is near the city of Nueva Palmira, Uruguay (Fig. 1).
The ParanáParaguay and Uruguay rivers are the major tributaries of the La Plata
basin system.
The Paraná-Paraguay basin is home to a population of almost 20
million people. For
centuries, this river system has been used as a waterway for
transportation. In February
1995, the IDB and the UNDP commissioned an 18-month series of engineering
and en
vironmental impact studies to evaluate potential navigational
improvements to the exist
ing waterway. This study includes the possibility of extensive
engineering works to render
3442 km of the river navigable for ocean-going vessels, from Nueva
Palmira to Cáceres,
Brazil. Since the port of Cáceres is located upstream of the Pantanal of
Mato
Grosso, the short- and long-term impacts of the proposed navigational im
provements on the Pantanal should be clearly established prior to project
implementation.
The project is commonly referred to as the Hidrovia project, since
"Hidrovia" means
waterway in both Spanish and Portuguese. The stated purposes of the
Hidrovia project
are to enhance current river transport via improvements to existing port,
channel, and
navigation facilities and to construct a year-round navigable waterway
along the 3442
km. These efforts are being planned in two stages:
Phase 1 (Module A): Short-term intervention
This phase entails the improvement in navigational aids and the
required river engi
neering, including dredging and related works, along 80 percent of the
proposed pro
ject's length.
The affected region extends from the downstream port of
Nueva Palmira,
upstream to the port of Corumbá/Ladario, in Brazil, and neighboring
Puerto Quijarro, in
Bolivia.
Phase 2 (Module B): Medium- and long-term intervention
This phase entails the improvement in navigational aids and the
required river engi
neering, including dredging, channel modification, and other major river
interventions,
along the entire length of the proposed project (3442 km), from Nueva
Palmira to
Cáceres.
The executive agency for the Hidrovia project is the Comité
Intergubernamental de
la Hidrovia (CIH) (Intergovernmental Committee of the Waterway),
established in 1989
by the Ministers of Public Works and Transport of Argentina, Bolivia,
Brazil, Paraguay,
and Uruguay. The headquarters of the CIH is in Buenos Aires, Argentina.
To date, the only comprehensive document with enough detail on the
Hidrovia pro
ject is the Internave report, commissioned by the extinct Empresa de
Portos do Brasil
(PORTOBRAS), and completed in 1990 by the Brazilian company of the same
name
(INTERNAVE, 1990). This report is basically an economic feasibility study
of the Hidro
via project. As such, it uses projections of economic benefits to
justify the costs involved
in project implementation.
The Internave report has been criticized for its overly optimistic
projections of benefits
(CEBRAC/ICV/WWF, 1994). The IDB has formally rejected the Internave
study and
will use the Phase 2 feasibility study, currently under execution, to
recalculate cost and
benefits (Lammers et al, 1994).
However, the physical descriptions
contained in the
Internave report, which include channel straightening, dredging, blasting
of rock out
crops and other structural interventions in the river, some of them
irreversible, have re
mained the cause for significant concern among diverse segments of the
local, national
and international communities. These include environmental
organizations, nongovern
mental organizations (NGO's), professional associations, and universities
and scientific re
search institutions in Brazil, the American continent, and the rest of
the world.
Channel straightening by realignment and cutoffs, dredging, and
blasting of rocky sills
are being considered to improve navigational conditions along the
waterway. In particu
lar, the Terms of Reference of the Phase 2 (Module B-1) engineering
study, under
Section 1--Purpose, states the following task (No. 4), among seven others
(IDB, 1995,
p. 2):
The extent of these interventions and their possible impact on the
hydrologic regime of
the Pantanal of Mato Grosso will be better known by the second half of
1996, once the
ongoing studies are completed. The IDB has asserted that it may not fund
the Hidrovia
project through the Pantanal if serious environmental impacts are
anticipated (Lammers
et al, 1994). Thus, the present study is a contribution to the proper
assessment and
evaluation of these impacts.
The Internave report lists the various geographic locations along
the Hidrovia project,
starting from the port of Buenos Aires (Km 0), progressing upstream to
the port of
Cáceres (Km 3 442). For reference purposes, an abstracted list of
locations relevant to
this study is shown in Table 4. Minor discrepancies between river
distances in Tables 1
and 4 reflect the different sources for these tables: DNOS (1974) and
INTERNAVE
(1990).
_ _ _