Identification of groundwater recharge areas for improving regional

Identification of groundwater recharge areas for improving regional
water conservation: application example of water use funds in Brazil
N.W. Dias*, C.E. Anjos**, H.N. Diniz***, M.S. Targa****
*Professor, Graduate Program in Environmental Science, Universidade de Taubaté, Est. Dr. Jose Luiz
Cembranelli, 5000, Taubaté, SP, Brazil CEP 12081-010, Email [email protected]
**Director of MC Geologia e Meio Ambiente Ltda., Alameda Harvey C. Weeks, 14, S. 01, São José dos
Campos, SP, Brazil, CEP 12223-080, Email [email protected]
***Geologist, Geologic Institute of the State of São Paulo Secretary of the Environment, Av. Miguel Stéfano,
3.900, São Paulo, Brazil, CEP 04301-903, Email [email protected]
****Professor and Director, Graduate Program in Environmental Science, Universidade de Taubaté, Est. Dr.
Jose Luiz Cembranelli, 5000, Taubaté, SP, Brazil CEP 12081-010, Email [email protected]
Abstract: This article presents the results of a research project funded by the Paraiba do Sul
Hydrographic Basin Committee with funds obtained through charging water users in this basin.
The objective of this project is to develop a series of geospatial geologic information layers and a sequence
of hydrogeologic analysis to determine the location of groundwater recharge areas in the basin for future
conservation purposes. The results indicate eleven areas with most interaction among lineament
characteristics, fracture bundles, and higher fracture densities. These areas should be considered as having
higher percolation quality and infiltration capacity, therefore areas with higher potential for groundwater
recharge. The results also show that the sedimentary region is the most important groundwater recharge
area in the Paraiba do Sul river valley.
Keywords: Groundwater recharge; hydrogeology; water conservation.
INTRODUCTION
Brazil holds one of the world’s largest freshwater reserves, both surface and underground, which accounts
for approximately 12% of the planet’s available freshwater. In the last 50 years the country experienced fast
urban and population growths that were coupled with devastating impacts on water resources (notably in
the south and southeast regions). This degradation is mainly caused by pollution associated with untreated
sewage and industrial discharges, as well as land use and land cover changes. During the 1980s, the Federal
Government tried to cease this devastating process by creating new policies, laws and regulations. Most of
those top-down initiatives had little effect. The most important outcome of that period was the new
Constitution of 1988, which determined in its Articles 20 and 26 that water resources are a public good.
This article in Brazil’s Constitution closed any possibility of privatizing water resources in the country.
Another important initiative was the National Council of the Environment (CONAMA) resolution number
20 of 1986 that established a hierarchical classification of water bodies and a set of limiting concentrations
of water quality parameters. These water quality standards were revised in CONAMA’s resolution
357 released in 2005.
Even though these official top-down measures came accompanied with high hopes of government
officials, they caused little impact in terms of changing the way the Brazilian society and its leaders related
to the natural resources. As a result, water resource degradation continued its accelerating track well over
the 1990s. However, during that same decade Brazil initiated a wide process of decentralizing government
at all levels (federal, state, and local). Important effects were observed toward the end of last century on the
economy, environment, and society. One of those positive effects was the creation of Hydrographic Basin
Committees after that the National Water Resource Policy law came into effect in 1997. Paraiba do Sul
Hydrographic Basin Committee (CBH-PS) was the first established in the country and today is still viewed
as model to other committees recently created or still under development. The main characteristic of such
committees is its representation structure to motivate wide community participation. All of them should
have up to 40% of government representation, up to 40% of water users’ representation, and at least 20% of
civil society representation. The main tasks of these committees are to develop a Hydrographic Basin Plan
Water Practice & Technology Vol 3 No 3 © IWA Publishing 2008 doi: 10.2166/WPT.2008066
(usually valid for 3 years then renewed) and to manage a trust fund derived from moneys transferred from
the Federal Government and derived from charging water use in federal rivers. This water use charge
system became effective in 2002 primarily charging private and government water supply service
companies that utilize water from rivers that cross more than one state (those are considered federal rivers).
But only those that utilize water from the main channel can be charged, since all of their tributaries are
considered state rivers state rivers and can only be regulated by state governments. As a result, in 2005, the
State of São Paulo passed its water use charge law that expanded the possibility of charging water use to all
rivers in the state as well as groundwater reserves. After creating a water user database during 2006, the
charging system started in 2007 in the Paraiba do Sul Hydrographic Basin. This basin committee already
established specific categories for funding allocation based on what determines the hydrographic basin
plan. Allocation of these funds is determined by an annual Request for Proposals reviewed and evaluated
by thematic sub-committees. In the first five years funding has been allocated to the following areas: local
government interventions (sewage collection and treatment), state government infra-structure expansion
(sewage treatment plants and riparian forest plantation), research and development (mapping, water quality
monitoring, hydrologic characterization), and environmental education.
Most people question issues associated with transparency and corruption in systems where
institutions that involve government officials, private company leaders, and community representatives, get
together to decide money expenditures. Reality shows that in the top-down environmental policy strategies
adopted by the government in the 1980s actual results were insignificant due to such evasive behaviors. The
reason for such bad performance was that empowerment remained in the hands of government officials, the
only individuals responsible for enforcing new rules through law suits, fees, and other instruments. The
more recent experiences, after the creation of hydrographic basin committees, has shown that once
empowerment gets shifted to the hands of a wider representative structure, transparency increases and
corruption decreases. In order to improve such system it would be recommended that more incentives
should be created to those that comply with the goals determined by the Committee via its Hydrographic
Basin Plan.
This article focuses on the results obtained from a project funded by the Paraiba do Sul
Hydrographic Basin Committee, called Identification of Groundwater Recharge Areas in the São Paulo
State’s Portion of Paraiba do Sul River Basin. This project was designed to implement a sequence of
hydrogeologic analysis derived from existing data and the interpretation of Landsat TM data.
Intensified industrial activities and urban population growth in the second half of the last century
caused increased water resource degradation. According to Coimbra et al. (2003), this degradation is the
result of one billion litters of non-treated sewage released daily to Paraiba do Sul River, since 90% of the
municipalities in this basin have no sewage treatment plants capable of reducing this organic load to the
river. On top of the urban load, there is also 150 tons of BOD (Biologic Oxygen Demand) released daily by
organic industrial discharges. Total organic load of the entire Paraiba do Sul River basin is estimated at 330
tons of BOD per day, 55% percent from urban and 45% from industrial discharge. As a result, the Paraiba
do Sul Hydrographic Basin Committee negotiated, in 2004, with all water managing organizations
responsible for determining the river flow, a minimum flow amount of 36 m3/s, since it was observed three
years earlier (during a dramatic drought) that flows below that level would reduce the river natural dilution
capacity of the organic load. The combination of surface water quality degradation and increased demand
for quality water sources by the industry and city water supply companies has put additional pressure on
groundwater reserves. Due to this fact, there was a need to identify and describe the most significant
groundwater recharge areas within the basin limits in order to develop more adequate plans for both
preservation and conservation of those critical areas.
A reasonable amount of existing records derived from hydrogeologic data obtained during well
perforation done by private companies and assembled by the Department of Water and Energy of the State
of São Paulo (DAEE) made possible to implement the methods utilized in this study. The method can be
briefly described as a geographic overlap of several layers of geospatial information produced from well
recorded hydrogeologic data and satellite derived geologic information obtained from visible and infrared
(Landsat TM) image interpretation.
The geologic context of this basin is reasonably well known, since there are several published
articles derived from previous field surveys and applied research. “The Middle Valley of Paraiba do Sul
River shows geologic and hydrogeologic important anomalies if compared to the rest of the State of São
Paulo. Taubaté basin, formed by neotectonic reactivations, is the main responsible for such characteristics.
2
These aquifers are heterogeneous and anisotropic. The hydro fluxes percolate in the direction of Paraiba do
Sul River main channel. In this area, the flow is interrupted by the hydrogeologic abrupt contrast in the
fractured border of the horst, causing accumulation and mixing of water. These characteristics are enhanced
by the potentiometric gradient of groundwater exploration” (Anjos et al., 2006).
The objective of this research is to identify the location and geographic distribution of groundwater
recharge areas in the São Paulo portion of Paraiba do Sul River Valley. In order to achieve this broader
objective the following specific objectives were set: develop a physic characterization of the study area
based on visual interpretation of Landsat TM scenes; generate a morphostructural and a hydrogeologic
conditionings map of the area; generate a map of structural lineaments; generate a slope map of the area;
evaluate the hydrogeologic characteristics of the area based on existing well perforation records; and
integrate all results to identify the recharge areas located in the study area.
DATA AND METHODS
Image interpretation was performed in two Landsat TM scenes acquired on 28/SET/2000 with path/roll
coordinates 219/076 and 218/076. Altimetry data was obtained from the Shuttle Radar Topographic
Mission (SRTM) acquired in 2000 for the following quadrants: S23ºW45º, S23ºW46º, S24ºW45º,
S24ºW46º. Additional information was obtained from topographic maps (published by the Brazilian
Institute of Geography and Statistics – IBGE); existing geology, geomorphology, and hydrogeology charts;
and existing data reprocessed by the following software packages SPRING 4.1, ARCVIEW 3.2,
AUTOCAD MAP 2000, SURFER 8.0, VISUAL GROUNDWATER, and BALASC.
All data compiled from existing sources were adjusted to the study’s cartographic scale of
1:100,000. Additional existing data were added to the analysis including geologic data from Kurdkdjian
(1992) and IBGE (1986), geotechnical and geomorphologic from IPT (1981), and hydrogeologic from
DAEE (1979). The study area stream network layer was produced from several existing digital maps in the
1:50,000 scale, followed by a process to reconstitute stream channel connections and build the final
network for the entire basin.
An interdisciplinary procedure was implemented in the final stage of the research with the purpose
of identifying and characterizing the recharge areas. This procedure involved the selection of specific
information associated with the characteristics and dynamics of the physical environment, such as geology,
geomorphology, hydrology, and geotectonic. This information, once integrated and interpreted, led to the
identification and characterization of the different compartments and environments that encompass the area
of intervention and the adjacent areas. The study followed and interdisciplinary approach with both
analytical (diagnostic) and systemic (integration, prognostic, and synthesis) emphasis that sought to
perceive the dynamic that rises from the interdependence of the different components. Image interpretation
follow a logic and systematic analysis of the texture elements as described by Veneziani et al. (1982),
where metric and geometric relations are considered, along with the structuring degree and order of the
textural elements associated with relief and drainage, and analyzed by inductive and deductive processes
(Coelho Neto, 2003).
The detailed characterization of the study area for the aspects associated with geomorphology,
morphodynamic characteristics, regional geology, structural geology, hydrogeologic conditioning
morphostructures is available in Anjos et al. (2006).
RESULTS AND DISCUSSION
Fracture density map is presented in Figure 1. This map was produced from the tracing of fractures
identified in the drainage network map. This information was generated from GIS (Geographic Information
System) analysis on a 1:100,000 scale base map utilizing 25 km² areas for developing this analysis. This
map shows concentrated areas, or zones, with similar secondary relative porosity and groundwater
recharge/discharge potentials. Density value was calculated based on the number of fracture traces found in
a 5 x 5 km cell. The calculated value was then applied to central node of the sampled cell. Density
calculations and cell node attributed values were repeated for same size cells until the entire study area was
covered. Then a GIS interpolation analysis was performed with a total of 48,000 traces applying kriging.
Four relative fracture density classes were produced along with contour line generation. The analysis of
3
relative fracture density data was the basis for identifying the axes of maximum fracturing. Additional
refinement of this analysis was implemented by categorizing the fracture trace population into six tectonic
directions: N15º - 35ºW; N35º - 55ºW; N45º- 65ºE; N80ºW - N80ºE; N10ºE- N10ºW; and N15º- 35ºE.
The recharge areas and groundwater flow map was produced from the interpretation of preliminary
maps, such as the map of hydrogeologic conditionings generated from the analysis of both drainage map
and structural lineament map. The map was designed based on the identification of symmetric relations
between consequent and obsequent drainage channels and the delineation of structural contour lines without
known level in the study area. A second map was generated to illustrate groundwater flow by following the
technique described by Veneziani et al. (1993). In this technique the association between flexural folding
and distensive movements can provide information about the distribution of groundwater along the
structural heights and lows indicating some aspects of the groundwater flow behavior in a specific region.
The final map is presented in Figure 2.
Based on this map a relative synthesis of morphostructural recharge areas was developed. The
result was the identification of the main recharge areas (divergent discordant flow), discharge areas
(convergent discordant flow), and concordant (unidirectional flow). A total of 16 recharge areas were
identified through this procedure. These areas are elongated portions of the area with main direction
oriented toward NE, parallel to the structuring of the area and to the elongated lithostructural units.
Figure 1: Density fracture map shown in density intervals. And map showing the location of the study area
(bottom right corner).
4
Figure 2: Map showing the location of recharge areas and groundwater flow patterns.
Hydrogeologic analysis of perforated wells’ records was divided in two sub-regions of the study
area due to the spatial concentration of wells in the southwestern portion of the area. A total of 368 wells
data located in the Taubaté sedimentary basin were used for this analysis. Potentiometric level was obtained
by the difference between the well level and the water table. The water table of all wells recorded at local
municipality offices were interpolated using Surfer 8.0. An equal-potential contour line map (Figure 3) was
generated for the entire study area taking into account differences of sampling densities in both
compartments. The map shown in Figure 3 demonstrates that groundwater flow tends to converge toward
Paraiba do Sul main channel from the surrounding higher elevation areas (Mantiqueira Mountain Chain in
the north and Jambeiro and Quebracangalha Mountain Chains in the south). The average groundwater level
at Paraiba do Sul river valley municipalities of São José dos Campos, Jacareí, and Caçapava is
approximately 540 m. In the municipality of Lorena (northeastern portion downstream) the average level is
510 m.
The analysis of equal-potential contour lines shows that the river channel presents water table
below the river’s base level. This finding indicates that the river influences groundwater recharge by
providing surface water to the aquifer when the river water level is higher than the aquifer surface level
and, where the river bed is made of permeable material. These results are similar to the findings of DAEE
(1977) and reinforce the theory that when the river is an influent agent in groundwater recharge in most of
its course near the municipality of São José dos Campos as well as near Lorena in the northeastern portion
of the study area. Influent rivers such as Paraiba do Sul are common in semi-arid regions; therefore this
behavior is not expected in the southeastern region of Brazil. This behavior indicates that groundwater
pumping through deep tubular wells in operation in the Paraiba do Sul river valley, since the 1930s, may be
inducing groundwater recharge from surface watercourses that infiltrate water in their beds and further
percolates supplying additional water to the sedimentary aquifer.
5
Figure 3: Potentiometric map of the study area showing groundwater levels in relationship to Paraiba do
Sul river level.
In other portions of the study area, such as near the municipalities of Taubaté and Tremembé, the
equal-potential contour lines show higher base level values, indicating that the river receives water from the
aquifer. This is a more common behavior in humid climates, such as in the southeastern region of Brazil.
The areas of high fracture density were analyzed in terms of their general density and specific
directions (identifying axes of maximum fracturing). They were then correlated to Riedel (1929)
deformation model that defines bundles of fracturing. The correlation of areas with high fracture densities
and the frequency of fracture bundles allowed describing the 16 previously selected recharge areas in terms
of their hydrogeologic potential. A total of 11 areas were identified as having high density. These areas
were further divided by the number of fracture bundles existing in each area. A weighting scale using
weights 1, 2, and 3 was adopted for classifying each area. The areas with most interaction among lineament
characteristics (lineament density and crossings), fracture bundles, and higher fracture densities, should be
considered as areas with higher percolation quality and infiltration capacity, therefore areas with higher
potential for groundwater recharge. Figure 4 shows the result of this final analysis.
6
Figure 4: Map showing the final recharge areas selected as priority areas for future conservation initiatives.
FINAL REMARKS
The analysis implemented in this research, based on the convergence of evidence and on the integration of
information derived from different spatial correlations, generated results that permit identify areas that
show attributes highly associated with recharge and discharge properties in the Paraiba do Sul river valley
in the State of São Paulo. The correlation between recharge areas and high fracture density identified
portions of the study area with higher potential to be considered groundwater recharge areas.
The methods utilized presented opposite results for the two main regions, crystalline rocks and
sedimentary rocks. In the crystalline rock region the method adopted (interpretation of remote sensing data)
showed a better performance in terms of generating significant information about structural and tectonic
geology and the physical characterization (relief, drainage, and slope attributes) of the study area leading to
a straight forward identification of recharge and discharge areas. However, determining the hydrodynamic
behavior in this region was limited due to the fast spatial variation of geologic and structural parameters
and characteristics. This variation did not allow the determination of significant hydrogeologic correlations
at a regional scale.
In the sedimentary rock region there is a low dependency of groundwater recharge to fracture
systems due to the predominance of more homogeneous units with large lateral extent. This
characterization, however, is optimized by the analysis of deep well records. The results indicate that the
sedimentary rock region is the most important groundwater recharge area in the Paraiba do Sul river valley.
Funding for this research was provided by the Paraiba do Sul Hydrographic Basin Committee in a
competitive Request for Proposals released in 2003. This RFP was one of the first funded by money
transferred by the Federal Government from revenues obtained from water use charging fees. The results
obtained by this project will be used to support water resource management decisions made by the
Committee as well as support a series of community activities, especially in environmental education. This
project illustrates how funds are been spent by this newly developed hydrographic basin management
system supported by a high level of community participation and leading to a more transparent and wiser
use of public funding for water resource conservation in Brazil.
7
References
Anjos, C.E. e Diniz, H.N. 2006. Caracterização de Áreas de Recarga com Análise Integrada de Dados Orbitais TM
Landsat e Dados Hidrogeológicos: Região do Médio Vale do Rio Paraíba do Sul, Estado de São Paulo. MC
Geologia e Meio Ambiente Ltda., São José dos Campos,160 p.
Coelho Netto, A.L., 2003. Evolução de cabeceiras de drenagem no médio Vale do Rio Paraíba do Sul (SP/RJ): a
Formação e o crescimento da Rede de Canais sob Controle Estrutural. Revista Brasileira de Geomorfologia, 2:
69-100.
Coimbra, R. M.; Freitas, M. A. V., 2003. O estado das águas na bacia do rio Paraíba do Sul. Electronic document:
http://www.mma.gov.br/port/srh/acervo.
DAEE – Departamento de Águas e Energia Elétrica, 1977. Estudo de águas subterrâneas: Região Administrativa 3 –
S.J. dos Campos e faixa litorânea. Enco/DAEE, São Paulo, v.1, 112 p (texto).
IBGE - Instituto Brasileiro de Geografia e Estatística, 1986. Levantamentos de Recursos Naturais. Vol. 26.
IPT – Instituto de Pesquisas Tecnológicas do Estado de São Paulo, 1981. Mapa geomorfológico do estado de São
Paulo. São Paulo: IPT, 94p. (IPT. Monografias 5 – nº 1183).
Kurkdjian, M. L. N. O; Valério Filho, M; Veneziani , P; Pereira, M. N.; Florenzano, T. G.; Anjos, C. E.; Ohana, T.;
Donzeli, P.L.; Abdon, M. N.; Sausen,T. M.; Pinto, S.A .F.; Bertoldo, M. A.; Blanco, J. G.; Czordas, S. M., 1992.
Macrozoneamento da Região do Vale do Paraíba e Litoral Norte do estado de São Paulo. São José dos Campos,
176 p. (INPE- 5381-prp/165).
Riedel, W. , 1929. Zur mechanik geologischer bucherscheinungen. Central bl. f. Blatt F. Min. Geol. Und. Pal.,
8: 354-368.
Veneziani , P.; Anjos, C.E., 1982. Metodologia de interpretação de dados de sensoriamento remoto e aplicações em
geologia. São José dos Campos: INPE, 54p.
8