DAMS CONSTRUCTION AND LOSS OF GEODIVERSITY IN THE
ARAGUARI RIVER BASIN. MG. BRASIL
Sílvio Carlos Rodrigues1
Thallita Isabela Silva2
Federal University of Uberlândia
Institute of Geography
Av. João Naves de Ávila, 2121. Bloco 1H, Sala 1H16, Campus Santa Mônica CEP: 38.408-100. Uberlândia
– MG.
¹silgel@ufu.br
²thallitaisabela@yahoo.com.br
ABSTRACT
The Araguari River is located in the central uplands of Brazilian and in the last forty
years these region suffered a huge change in the regional economy due to the
agricultural green revolution. The Araguari River is one of the main tributaries of
the Paraná River, the second biggest river in South America. This region has been
occupied since the middle of the 19th century. The main changes in the landscape
were the construction of four hydroelectric power plants on the valley, and now in
the first 200km of the valley, only 9km has the original features. These changes on the
river course and flow modify the landscape, with the submersion of many geosites
with different singularities, in special gorges and islands, also sections of the valley
and communities were affected. The concepts of Geodiversity, geoabundance and
georichness are used to understand and assess the loss of diversity in the Araguari
Valley. Twelve geosites with complex counterparts were found in the area and six of
them were completely transformed in single hydrological geosites due to the
submersion after the creation of two new lakes. The change in the landscapes creates
also new scenarios with interesting location, and thus creates new geosites. The main
changes found occurs in the diversity of complex geosites, that was reduce to 50% to
the original situation. The richness of geosites also was affected by the substitution of
complex geosites by single ones. The research reveals that 14.29% of the geodiversity
was lost after the change in the river course.
Key words: Geodiversity loss, Geoabundance, Georichness, Geosites, Araguari River,
Brazilian landscapes.
1. INTRODUCTION
Geodiversity is defined as a large range of geological and geomorphological phenomena
constituting the geological heritage and is fundamental to understand the geological
heritage of some regions and to coordinate its efficient geoconservation. The term
Geodiversity appears first in the decade of 1990 on articles from Tasmania and Australia.
(Sharples 1993; Dixon 1995; Kiernan 1996). The initial use of the term Geodiversity are
linked to holistic ideas of nature conservation, with major significance to the geological
1
elements, but forward development integrates other elements of human and physical
environment. (Duff, 1994; Eberhard, 1997; Serrano Cañadas and Ruiz Flaño; 2007,
Sharples, 1995). Geosite is the main term used in geodiversity studies and could be a
geological monument, a geological heritage site, or a geological heritage object. These
geological objects should be exposed on the landscape, and accessible for research and
visits. The classification of geosites necessitates of a large number of situations on the land
to be properly indicates as a site with geological interest, as for example, the area could not
be buried in the earth’s interior. Ruban (2010). Geodiversity gain or loss can be evaluated
with an accounting of increases or decreases in geosites type ranks linked to the damage of
them. Gray (2004), Gray (2008); Ruban, (2010). Despite a series of usage of the term
Geodiversity, Serrano Cañadas and Ruiz Flaño (2007) indicates that while the Biodiversity
concept has a clear definition, Geodiversity has an important conceptual weakness, and
that the concept is linked to others as Geoconservation,Geological Heritage and used in
legal figures as Geoparks and Geomorphosites.
According Ruban 21 types of geosites can be distinguished, namely paleontological,
stratigraphical, igneous, sedimentary, metamorphic, mineralogical, geothermal,
cosmogenic, radiogeological, geochemical, seismical, structural, palaeogeographical,
geocryological, geomorphological, hydrological and hydrogeological, engineering,
neotectonical, pedological and geohistorical. These geosites can appear as single or
complex counterparts depending on the singularities of the landscape. (Ruban, 2010)
In any given territory several types of geosites may occur on, and of course the entire
range of geosite types occurs on the planet. (Ruban 2010). Gray (2004, 2008) defines
geodiversity as the diversity of geomorphological, geological, and soil types with a
description of ‘‘their assemblages, relationships, properties, interpretations and systems’’
(Gray, 2004) On the other hand, Ruban (2010) discusses that Geodiversity is the
“numerical expression of geosite diversity”. Geodiversity loss could be generally welldefined as a decline in the number of geosite types. Geoabundance is defined as the total
quantity of geosites on a given territory and Georichness is a complex characteristic which
involves Geodiversity and Geoabundance. (Ruban, 2010).
Since the decade of 1960 major Brazilian rivers courses were affected by construction of
dams to multi-purposes, in special hydroelectric power plants. Most of these rivers flows
in the foothills landscape and some of then creates canyon sites, as the Parana River in the
location of Sete Quedas, or the Canyon of the São Francisco River in the northeast of the
country. The creation of giants’ dams and reservoirs causes loss of Geodiversity with the
suppression of geosites as waterfalls, paleontological sites, archaeological sites, caves and
others, and social troubles as the remotion of cities and people from his lands. In the
southeast part of Brazil, the major rivers was totally affected by dams and in the 2000
decade a new movement initiates over the medium size rivers, the construction of medium
size dams.
Middle-Lower Araguari River drains part of the Triangulo Mineiro region, their channel
includes a sequence of riffs and pools, creating a series of interesting points of natural
beautiful scenarios. The river cross a canyon landscape and, and other particularities are
considered geosites. Types of geosites can be described in the Araguari River Basin area as
river and stream sections, cliffs, meandered channel, outcrop rocks, waterfalls, roads,
2
railroad and canal cuttings, artificial dams, static geomorphological exposures, active
geomorphological exposures, fossil or other geological deposits, mine dumps, and some
others.
An overview of landscapes in the Araguari Basin and Geodiversity richness, and loss of
Geodiversity due to construction of hydroelectric power plants are the main purpose of this
paper.
2. STUDY AREA
The Araguari River is located in Central Brazil and is one of the main tributaries of the
Paraná River, the second biggest river in South America. (Figure.1). This region has been
occupied since the middle of the 19th century, but only in the last four decades of the 20th
century the vegetation has been replaced for agricultural and pasture fields that have since
then accelerated landscapes transformation, urbanization processes accelerates and the
needs for infrastructure increases quickly.
Figure 1 – Location of the study area.
The Araguari River Basin comprises 21.856Km2. It starts in the high flat surface of the
Canastra Range, at 1,400 meters above sea level following westwards according to a
regional trend. (Ferreira, 2001). Geology comprises Middle Pre-Cambrian schists and
quartzites, sometimes covered by Mesozoic sandstone at high and middle course of the
river. In the lower Araguari basin Cretaceous sandstones intercalate with basalt layers that
are the main lithologies. Close to the valley floor Lower Pre-Cambrian granites and
gneisses are found. Cenozoic sediments cover the Mesozoic sandstone and some terraces
are sculptured on basalt. (Rodrigues, 2002; Vrieling et al., 2008).
The Lower/medium Araguari River occupies three geomorphological systems (Figure 2).
In the Sedimentary Basin two landforms are developed over sedimentary and volcanic
rocks creating a flat plateau and a system of low hills. The main morphological feature of
this system is a planation surface. The Araguari Canyon is present where the river carved
all sedimentary and basaltic layers and reached Pre-Cambrian gneiss and schist in the
valleys bottom. The landform in this area is a complex of deep and steepest hills.
The vegetation cover consists mainly of pastures. Many pastures are degraded, which
implies a high fraction of weeds and shrubs, and a relatively limited vegetative ground
cover. Scattered trees and shrubs occur to different extents within the pastures. Sometimes
degraded pastures are renovated, which implies cutting and burning of present weeds,
3
shrubs, and trees resulting in a bare soil for several months. There is a gradual transition
from pastures to shrubland and woodland. Gallery forest occurs along the main drainage
lines.
Figure 2 – Landforms Units of Araguari River Lower/Mediun Basin.
According to Köpper classification the predominant climate in the study area is the Cw,
half-humid tropical type, with average temperature of 23°C, that it is characterized for
presenting, six dry months and with mild temperatures (winter - April to September) and
the others six months, hot and rainy (summer - October to March) and presents annual
pluviometric average between 1300 and 1700mm. (Vrieling et al., 2007).
3. MATERIAL AND METHODS
The use of satellite images is essential for mapping geosites of a given region or river
basin. The basic topomorphological map should be georeferenced and contain the
boundary of the basin, drainage, roads and contour lines.
a) Satellite images: LANDSAT 1 14/07/1973 (resolution 80x80 meters), Landsat 5,
26/05/1984 and 19/05/1993 (resolution 30x30 meters), Landsat 5, 01/05/2004
(resolution 30x30 meters), Landsat 5 04/29/2009 (resolution 30x30 meters) with
the purpose of conducting the supervised classification, with the analysis of
spectral bands;
b) b) Topomorphological sheets on a scale of 1: 25.000 (1984) in order to collect
samples;
c) Aerial orthophotos acquired on 2002, MI-2451-4-NO e MI-2451-4-SO (about 2-m
resolution);
d) SRTM data (resolution 90m);
e) GPS Trimble.
Fieldwork was done from May 2004 till April 2006, and included an assessment of land
use characteristics and the execution of a field survey. A total of 199 locations throughout
the area were visited during the survey, for which the following characteristics were
4
recorded: co-ordinates (GPS), outcrop rocks, waterfalls, gorges, slope inclination,
buildings, bridges, roads, and interesting sites. Furthermore, several points were taken by
the GPS on road intersections for georeferencing purposes.
According to Ruban (2010) geosites could be leveled by importance in terms of local,
regional, national or global level due to their intrinsic singularity. As the geosites of course
are not equal over the word and the use of logarithmic scale to determine the score of a
geosite is more suitable for the reason that the significance of geosites with regional and
national ranks varies and attracts the attention of distinctive groups. Some of them as
unique, and others, examples of a repetitive condition on landscape. (Table 1).
Table 01 - Geosite ranks and their scores adapted from Ruban, (2010).
Rank
Limits of geosite importance
Local
Regional
National
Important for countries, districts, etc
Important for states, provinces, etc.
Important for countries
Suggested Logarithmic scale
0.001
0.01
0.1
Geodiversity quantification was performed using the Ruban (2010) approach, which
permits quantify the geodiversity, geoabundance and georichness of a given region. Table
(02). By definition Geodiversity here is the total quantity of geosites types occurring in a
given region, in this case the Medium-Lower Araguari River Basin.
Table 02 – Methodological approach to evaluate Geodiversity loss. (adapted from Ruban,
2010)
Concept
Geodiversity 1
Description
Total quantity of geosites types occurring
on a given territory
Mathematical expression
Gd1 = T
Geodiversity 2
Sum of maximum rank scores of each
particular type of geosites within a given
territory
Gd2 = rt1 + rt2 +----+ rti
Geodiversity 3
Total quantity of complex geosites divided
by Total quantity of geosites (in %)
Gd3 =
Geoabundance 1
Total quantity of geosites on a given
territory
Ga1 = N
Geoabundance 2
Sum of rank scores of geosites
Ga2 = rn1 + rn2 +----+ rni
Georichness 1
Quantity of geosites; where each type is
represented (fully or as a counterpart):
Gr1 = n1 + n2 +----+ ni
Georichness 1
Sum of the quantities of geosites of each
type weighed with the maximum rank
scores of the types:
Gr2 = (n1x rt1) (n2 x rt2) +......+ (ni
x rti)
Geodiversity loss 1
Actual Geodiversity 1 divided by
Geodiversity 1 before loss (in%)
Geodiversity loss 2
Actual Geodiversity 2 divided by original
Geodiversity (in%)
*100%
For Geodiversity (T = total quantity of geosite types; rt is a maximum rank score of each particular type of geosites;1….i is a
total range of types represented regionally; nc is a total quantity of complex geosites; N is a total quantity of geosites on a
given territory). For Geoabundance (N is a total quantity of geosites; rni is a rank score of geosite, 1…j is a total range of
geosites represented regionaly). For Georichness (n is a quantity of geosites, where each type is represented, rti is a
maximum rank score of each particular type of geosite; 1…i is a total range of types represented regionally.). For
5
Geodiversity loss (GD1ac is an actual geodiversity, CD1or is an original Geodiversity existed before the anthropogenic
influence (both are calculated with Eq. (1)), GD2ac is an actual geodiversity (calculated with Eq. (2)), GD2or is the original
geodiversity, rtior is a maximum rank score of each particular type of geosites within a given territory before the
anthropogenic influence).
4. RESULTS AND DISCUSSION
The research carried on the Araguari lower-medium valley found 12 geosites, with
complex phenomena and at least local interest, regional or national interest. (Figure 3 and
Table 3). The area was used by population in spontaneous visitation and the practice of
rafting, hiking, rappel, and fishing or only to enjoy the landscapes are common on these
places. Also scientific interest exists in the area in function of the singularity of the
landscape and the presence and exposure of a different geological rocks and minerals.
Figure 3 – Location of geosites.
As a river environment the main geosites are linked to it is hydrological type, as the PauFurado Gorge, Cantinho Gorge, Sabe-Tudo Island, Machado Island, Marinbondo Valley,
Fundão Valley and Pindaiba Valley. (Figura 4). Population and life style of some localities
are linked to the Araguari River, and also are important scenarios as Olhos d’Água, Tenda
dos Morenos, Alto São João and Cruzeiro dos Peixotos.
Figura 4 – Samples of Geosites on the Araguari Valley.
6
The installation of two dams of the Amador Aguiar Complex Energy Power Plants in 2005
that ended up changing the hydrography to 53,10 km² creating two lakes and increasing
the area of the river almost five times. The geosites located at the river bottom, as the
gorges and islands were totally flooded and a lake landscape replaces it. We consider the
lake, in function of the beautiful landscape created after the area was completely stabilized
as a new geosite, with hydrological and local interest.
Table 3 – Geosites of Araguari River Basin (see fig.3 for location) specified for a
designation of local (000.1), regional (0.01) or national (0.1) importance.
Geosites
Funil Gorge
Pau-Furado gorge
Pindaiba
Marimbondo
Valley
Fundão section
Olhos d`Água
Cantinho Gorge
Sabe-tudo Island
Machado Island
Cruzeiro dos
Peixotos Locality
Tenda dos
Morenos Locality
Alto São João
Locality
Geosite type (rank score
for each counterpart is
given in parentheses)
Complex. counterparts:
Hydrological
( 0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Metamorphic
(0.001)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Metamorphic
(0.01)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Stratigraphical
(0.01)
Complex counterparts:
Hydrological
( 0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Stratigraphical
(0.01)
Complex. counterparts:
Hydrological
( 0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Engineering
(0.001)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.1)
Geomorphological
(0.1)
Sedimentary
(0.01)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Stratigraphical
(0.01)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Rank Score
of Geosites
before dams
construction
Geosite type after dam
construction (rank score for
each counterpart is given in
parentheses)
Single counterparts:
0.1
Hydrological
0.1
Single counterparts:
Hydrological
0,01
0,01
0,01
0,1
0,1
0.1
0.1
0.1
0,01
0.01
0.01
0.01
0.001
0.001
(0.001)
Single counterparts:
Hydrological
0.001
(0.001)
Single counterparts:
Hydrological
0.001
( 0.001)
Complex counterparts:
Hydrological
( 0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Stratigraphical
(0.01)
Complex. counterparts:
Hydrological
( 0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Engineering
(0.001)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Single counterparts:
Hydrological
0.001
( 0.001)
Single counterparts:
Hydrological
0.01
( 0.001)
Rank Score
of Geosites
after dams
construction
0.001
(0.001)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.1)
Geomorphological
(0.1)
Sedimentary
(0.01)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
Stratigraphical
(0.01)
Complex counterparts:
Hydrological
(0.1)
Geohistorical
(0.01)
Geomorphological
(0.1)
0.1
0.1
0.01
7
The evaluation of geodiversity, geoabundance and georichness indexes were calculated
and are presented in the Table 4.
Table 4 – Indexes of geodiversity, geoabundance, georichness and geodiversity loss for
Araguari River Medium/Lower Course.
Concept
Geodiversity 1
Geodiversity 2
Geodiversity 3
Geoabundance 1
Geoabundance 2
Georichness 1
Georichness 1
Geodiversity loss 1
(Actual Geodiversity 1 divided by
Geodiversity 1 before loss (in%))
Geodiversity loss 2
(Actual Geodiversity 2 divided by original
Geodiversity 2(in%))
Results before dams
construction
Results after dams construction
(ACTUAL geodiversity)
7
0,332
100%
12
0.75
43
3.661
6
0.323
50%
12
0.57
28
3.631
14,29
2,71
The results show us that the changes in the environment with the creation of two lakes,
replacing the natural river course cause the reduction of 14.29% of the total types of
geosites (Geodiversity 1), with the complete elimination of the metamorphic geosite type,
because the outcrops are located just few meters near the river course and was totally
recovery by the lake. So, the uniqueness of this situation just disappears on the landscape.
Geodiversity 2, which indicates the weight score of the total geosite suffers a small
decrease using this methodology because the equation uses the higher level of rank score
for each type of geosites and the hydrological type, which suffers the most important
impact sustains one locality with the higher level, so in the equation the reduction in
importance of the hydrological geosite type creates a small decrease in the value. The
index Geodiversity 3 was the most affected by the dams’ construction, because it indicates
the reduction of complex geosites. The lakes creations eliminates complex landscapes,
with complex elements and replace it by the lake landscape, so the complexity level of
geotypes was dropped at 50% in the area, and this indicates an homogeneous landscape.
The abundance of geosites suffers also a reduction, not at the numbers of geosites
locations, as indicates Geoabundance 1 index, but at the weight of rank scores of the
geosites types caused by the reduction of locations with complex geosites (Geoabundance
2), and the starting of new single geosites due to the lake creation and the low level of
importance of this kind of new situation. The Georichness 1 index decrease substantially
from 43 to 28. This indicates that the dam construction involves geodiversity and
geoabundance decrease, because also counterparts as geosites types decreases. So the
richness of the geodiversity decreases with the impossibility of access to the complex
geosites.
8
5. CONCLUSION
This study aimed to identify and characterize the Geodiversity change and loss after the
construction of dams in the Basin of the Middle/Lower Rio Araguari. It is believed that
this goal has been reached.
The main information elaborated by the study was:
1 – In last 4 decades the natural flow condition of the Araguari River was replaced from
lotic to lentic condition.
2 – Construction of hydroelectric power plants and dam, changes the natural river channel
into a sequence of lakes in at least 200 km, from the mouth to the middle/upper course,
causing loss of geodiversity;
3 – Geodiversity was affected by decrease of 50% geosites with complex counterparts as
indicates the Geodiversity3 index;
4 – As consequence of changes some geosites disappear and no access to the population is
possible now.
5 – The new landscape was created (the artificial lakes) and so new hydrological geosites
could be accessed;
6 – Federal laws and political strategies affect the regional development and environmental
behavior, creating a path to geodiversity loss and degradation and/or re-organization of
geosystems.
Acknowledgments
The authors thank FAPEMIG for the resources available for the accomplishment of this
research. Proc. FAPEMIG CRA 7783/07.
REFERENCES
Dixon G, 1995. Aspects of Geoconservation in Tasmania: A Preliminary Review of
Significant Earth Features. Report to the Australian Heritage Commission, Occasional
Paper no. 32. Hobart, Tasmania: Parks and Wildlife Service.
Duff K, 1994. Natural Areas: an holistic approach to conservation based on geology. In
Geological and Landscape Conservation (O’Halloran, D. et al., eds.). London, 121-126.
Eberhard R, 1997. Pattern and process: towards a regional approach to national state
assessment of geodiversity. Technical series 2, Australian Heritage Commission &
Environment Forest Taskforce, Environment Australia, Canberra.
Ferreira IL, 2001. Mapeamento Geomorfológico do Triângulo Mineiro e Alto Paranaíba.
Relatório Final Iniciação Científica — FAPEMIG / UFU, Instituto de Geografia.
Universidade Federal de Uberlândia. Uberlândia.
Gray M, 2004. Geodiversity: Valuing and Conserving Abiotic Nature. J. Wiley,
Chichester, 434 pp.
9
Gray M, 2008. Geodiversity: developing the paradigm. Proceedings of the Geologists’
Association 119, 287–298.
Kiernan K, 1996. The Conservation of Glacial Landforms. Hobart, Tasmania: Forest
Practices Unit.
Rodrigues SC, 2002. Impacts of human activity on landscapes in Central Brasil. A case
study in the araguari watershed. Geograph Res 40:167–178. DOI: 10.1111/14678470.00172
Ruban DA, 2010. Quantification of geodiversity and its loss Proceedings of the
Geologists' Association, 121 (3), pp. 326-333. doi:10.1016/j.physletb.2003.10.071
Serrano Cañadas E. and Ruiz Flaño P. (2007) Geodiversity: Concept, Assessment and
Territorial Application. The Case of Tiermes-Caracena (Soria). Boletín de la A.G.E. N.º
45, págs. 389-393.
Sharples C, 1993. A Methodology for the Identification of Significant Landforms and
Geological Sites for Geoconservation Purposes. Hobart, Tasmania: Forestry Commission.
Sharples C 1995. Geoconservation in forest management: principles and procedures.
Taskforests, 7, 37-50.
Vrieling A, Rodrigues SC, Bartholomeus H, Sterk G, 2007. Automatic identification of
erosion gullies with ASTER imagery in the Brazilian Cerrados. Int J Remote Sens
28:2723–2728. http://dx.doi.org/10.1080/01431160600857469
Vrieling A, Jong SM, Sterk G, Rodrigues SC, 2008. Timing of erosion and satellite data: a
multi-resolution approach to soil erosion risk mapping. Int J Appl Earth Obs Geoinf
10:267–281 http://dx.doi.org/10.1016/j.jag.2007.10.009
10