Lower São Francisco River Basin
INTEGRATED MANAGEMENT OF LAND BASED ACTIVITIES IN THE SÃO FRANCISCO RIVER BASIN PROJECT GEF/ANA/OAS/UNEP
Activity 2.1 – Thematic Land Use Mapping of the Middle-Lower São Francisco Basin
Executive Summary of the Final Report DETERMINATION OF LAND USE IN THE MIDDLE- LOWER SÃO FRANCISCO RIVER BASIN
Companhia de Desenvolvimento dos Vales do São Francisco e do Parnaíba
Brasília - DF
INTEGRATED MANAGEMENT OF LAND BASED ACTIVITIES IN THE SÃO FRANCISCO RIVER BASIN PROJECT GEF/ANA/OAS/UNEP
Activity 2.1 – Thematic Land Use Mapping of the Middle-Lower São Francisco Basin
Executive Summary of the Final Report DETERMINATION OF LAND USE IN THE MIDDLE- LOWER SÃO FRANCISCO RIVER BASIN
Coordinator Rui Alcides de Carvalho Junqueira Companhia de Desenvolvimento dos Vales do São Francisco e do Parnaíba - CODEVASF
Consultants Carlos Alcebíades Barros Cavalcanti Francisco Javier Fernandez Fawaz Ileana Saraiva de Alencar Mota Verner Riebold
December 2000
DETERMINATION OF LAND USE IN THE MIDDLE-LOWER SÃO FRANCISCO RIVER BASIN
EXECUTIVE SUMMARY
INTRODUCTION
The Middle-Lower São Francisco extends itself from the City of Remanso to the City of Paulo Afonso, both in the State of Bahia. Land Use mapping in the Region was associated to several physical variables, such as topography, pedology, irrigation land classes, soil agricultural aptitudes, hydrologic regime of the São Francisco River and tributaries, demand and consumption of water, by sub-basin, etc.
The crossing of these variables produces essential information for the rational planning of political, technical and administrative actions viewing the sustainable development of the São Francisco River Basin, through the elaboration of the Integrated Management Plan of the São Francisco River Basin.
1. CHARACTERISTICS OF THE AREA
The Middle-Lower São Francisco Region is located between the 7º e 11º30´ South Parallels and the 37º e 43º West Meridians, occupying 126,770 km2 , which corresponds to around 19.8% of the São Francisco Basin. It covers 86 Municipalities, in the States of Alagoas, Bahia and Pernambuco.
According to the 2000 Demographic Census, 31% of the population in the Brazilian Northeastern Region live in urban centers. This is about the same proportion found in the Middle-Lower Region. Summation of urban and rural population in the Municipalities within the area is 2.431.000 inhabitants.
The Municipalities of Petrolina, in Pernambuco, and Juazeiro, in Bahia, are the most expressive development poles in the Middle-Lower São Francisco. CODEVASF built, until December of 2000, irrigation public districts, covering 49,000 ha, aiming at the development of a new agricultural technology in the region, proving to the private sector that irrigation and agro- industry were highly profitable economic activities. Today, those are the most remarkable activities in the Region, being responsible for improvements in the regional population’s life quality in the past years.
The Middle-Lower has significant water resources potential. Power generation, guaranteed by a complex of reservoirs and power plants built in the Region, by CHESF, was a determinant factor in the economic development of the Northeast, providing the basic conditions for the energy infrastructure, for consolidating irrigated agriculture and the agro-industry.
i Proper administration and optimization of governmental and private investments, already made or programmed for the Region, are essential conditions for consolidation and maintenance of the Middle-Lower São Francisco as the most important development pole in the Northeastern Semi- Arid.
2. CURRENT SITUATION OF THE LAND USE MAPPING IN THE MIDDLE-LOWER SÃO FRANCISCO
CODEVASF has already mapped land use in the São Francisco River Basin located within Minas Gerais, producing 84 sheets, in a 1:100,000 scale. Activity 2.1 is an extension of the work started by the Company, consisting in the mapping of the Middle-Lower Region, with additional 62 sheets, in the same scale.
Both Works follow the same methodology. However, the satellite images used for the Middle- Lower Region, according the list of orbits/points of the Landsat satellite shown in Figure 3, are more recent than those used by CODEVASF, from the 1994-1996 period.
3. METHODOLOGY
The work was carried out according to the following stages: • Definition of cartographic parameters; • Bibliographical survey; • Review and adjustments in the cartographic base; and • Preparation of the thematic maps.
3.1 DEFINITION OF CARTOGRAPHIC PARAMETERS
The adopted projection system was the Universal Transverse Mercator projection, the Córrego Alegre Horizontal Datum, the vertical datum from the marigraph at Imbituba (SC) and the 1924 international ellipsoid reference. The minimum dimension for the mapped polygons, representing the different classes of land use, according to the legenda, was 10 ha.
3.2. BIBLIOGRAPHICAL SURVEYS
Surveys were carried out gathering information on the predominant economic activities and on the different physiognomic forms of vegetative covers in the Region. The works of the State Secretary of Water Resources of Pernambuco, entitled State Water Resources Plan of 1994, and a
document prepared in 1995 by CODEVASF`s Planning Directory, entitled “Brigida River Basin – A Proposal for Sustainable Development”, were consulted.
3.3. REVIEW AND ADJUSTMENTS TO THE CARTOGRAPHIC BASE
As a cartographical support to the land use mapping of the Middle-Lower São Francisco, ,CODEVASF provided 62 digital topographic sheets, obtained by digitalization of analogical sheets published by the Army’s Directory of Geographic Services and by the Brazilian Institute of Geography and Statistics (IBGE), in a 1:100,000 scale. This material turned out to be of non- homogeneous quality, requiring additional work not specified in the Terms of Reference, such as the adjustment of vectorial elements of the hydrographic network and updating of the main and secondary road systems, base don the digitalization of the Landsat images.
3.4. PREPARATION OF THE THEMATIC MAPS
Advanced remote sensing, digital cartography and geographic information system techniques widely adopted for elaboration of thematic land use maps base don satellite images were used.
In this case, the following remote sensing products were used: 12 scenes the Landsat 5 and 7 satellites, bands 3, 4 and 5, combined in R/4, G/5, B/3, 30 m spatial resolution, nine of them obtained in 1999 and remaining three in 1994, 1997 and 1998 (all of them prior to the drought periods in the Region). The supervised classification method was adopted, and the image processing software was the Envi, version 3.2.
4. MAPPING LEGENDA
Defining the legenda required different stages and was concluded only after field verification and correlation, during two trips made by the consultants, in March and September of 2000.
The chosen legenda represents the set of different land use classes and vegetative covers best fit to the actual soil occupation conditions in the Region. It is supported by field investigations by land or by helicopter. The objective was to select a set of classes which was more compatible with information collected in the field than with the results of a digital classification. Even though supervised, the latter emphasized distinct areas of spectral responses which would not necessarily correspond to distinct classes of land use.
Viewing easier searches and analyses in a computer environment, each class of land use or vegetative cover was associated to a numeric attribute designated by the term “class” or “gridcode”, correlated to their respective descriptive texts, as folllows:
Class Vegetative Cover area (km2) %of the Middle- Lower Region 1 Dense Caatinga 20,195.22 15.93 2 Dense degraded Caatinga 28,175.22 22.23 3 Open Caatinga 20,549.29 16.21 4 Open degraded Caatinga 19,175.24 15.13 5 Herbaceous coverture 210.74 0.17 22 Atlantic Forest fragments (highland swamps) 139.52 0.11 Land use and other covers 6 Riparian vegetation associated with small 1,074.55 0.85 irrigation 7 Deforested áreas 1,256.97 0.99 8 Pasture 242.30 0.19 9 Agriculture 1,359.57 1.07 10 Diversified agriculture, associated with native 25,683.59 20.26 vegetation, small scale deforestation, resting soils (rotation regime) and pasture 11 Irrigated áreas 1,461.75 1.15 12 Rock emergences 116.60 0.09 13 Rock emergence associated with native vegetation 263.04 0.21 and or nude soils 14 Water bodies 3,756.73 2.96 15 Mining áreas 18.74 0.01 16 Nude soils 173.03 0.14 17 Urban areas 498.83 0.39 18 Clouds and cloud shaded areas 340.19 0.27 19 Low productivity irrigated areas, associated to 1,167.13 0.92 poor soil management 20 Areas subjected to water level fluctuations 646.31 0.51 (margins of reservoirs) 21 Dry riverbeds 266.31 0.21 Total 126,770.93 100.00
5. DEMONSTRATIVE SIG PROJECT
Viewing the presentation of an embryo of an spatial consulting system, regarding the information produced by Activity 2.1, a digital product was created to allow the analysis of data relating them to the administrative divisions and to the hydrographic units defined by the Otto Pfafstetter Method, the “ottobasins”.
The presented product consists of a demonstrative Project of a GIS, in apr format (ArcView), obtained by the fusion of graphics and alphanumeric databanks related to land use, ottobasins and political-administrative division themes.
This demonstrative project was developed in an ArcView 3.2a environment, combining the 62 sheets in 1:100,000 scale, into a sole digital file in shape format, formed by a total of 30,126 polygons. The system allows spatial analysis among different classes of land use and of their location within the ottobasins and State/Munnicipal units.
Law 9,433/97, of January 8th, 1997, which instituted the National Water Resources Policy, defined the Basin as the territorial unit for implementation of the Policy and of the National Water Resources Management System.
Therefore, the water resources plans must be elaborated for the basins, in the State and in the Country, which turns mandatory the definition of a classification and codification system for the basins in Brazil. With this purpose, it is expected the implementation of a georeferenced, spatial and tabulated digital base of codified basins, according to the Otto Pfafstetter Method. This technique, known as ottobasins, is based on the topology of the network and in the drainage area, and has been adopted by the Secretary of Water Resources of the Ministry of the Environment.
To illustrate how practical the developed system is, the following examples are presented:
5.1 EXAMPLE 1
Prepares a chart of statistical associated data, showing the total irrigated area in the Municipalities of Petrolina, in Pernambuco, and Juazeiro, in Bahia.
5.2 EXEMPLE 2
Shows the results of consultation on the area occupied with the class 10 land use (diversified agriculture, associated with native vegetation, small scale deforestation, resting soils and pasture), in the Terra Nova creek Basin, in Pernambuco.
5.3 EXEMPLE 3
Refines the outcomes of Example 2, separating the area with class 10 in the Terra Nova creek Basin located in the Municipality of Salgueiro, in Pernambuco.
6. PRESENTATION OF RESULTS
The results of the land use mapping in the Middle-Lower São Francisco are available in analogical and digital formats. The analogical products consist of LaserJet plotted hardcopies of all sheets in the thematic mapping object of Activity 2.1. The digital files are contained in a CD- ROM (shp, prt and apr ArcView formats) related to the implemented work.
8. CONCLUSIONS
The Middle-Lower São Francisco Region is spread over a 126,770 km2 territory, on the States of Alagoas, Bahia and Pernambuco. Approximately 69.5% of that area (88,094 km2) is covered by caatinga in different stages of preservation. It should be noticed that 32% of the mapped area (40,744 km2) is occupied by dense and open caatinga, corresponding to sectors not yet altered by man’s actions or with interventions so small that were not detected in the satellite images.
The degraded dense and degraded open caatinga occupy 37.3% (47,350 km2) of the total area. The activities contributing the most for the degradation are coal and fence post productions.
Around 2,568,000 ha (25,683.59 km2 ), equivalent to 20% of the Middle-Lower São Francisco, constitute the class identified as gridcode 10, characterized as areas under continuous changes, mostly due to anthropic factors. This class includes distinct groups of land use and vegetative covers, forming mosaics of small dimensions, occupied by subsistence agriculture, fragments of native vegetation, deforested areas, prepared and/or resting soils and pasture. Given the difficulty of cartographically representing individually each one of those occurrences, due to limitations in the used scale (1:100,000), they were grouped in a same class.
Irrigated areas, identified as gridcode 11, cover 146,000 ha, corresponding to 11.5% of the total. Public irrigation districts and private properties of all sizes, and in different technological stages, regarding irrigated agriculture, are all included here.
Desertification on the Middle-Lower São Francisco was object of an specific study, contracted with Professor Carlos Hiroto Saito, of the University of Brasília, simultaneously with the land use mapping. In spite of the great expectation regarding the process, no areas affected by the phenomenon were identified (at least none was visible in the adopted scale).
10. RECOMMENDATIONS It is recommended that the land use and soil occupation mappings mãe for the Upper and and Middle –Lower São Francisco be extended to the remaining physiographic areas (Middle and Lower Regions), in order to support the Integrated Management of Land Based Activities in the São Francisco River Basin Project.
A proposal was presented (Appendix 3) focused on the mapping of land use and soil occupation in the lower São Francisco, in a 5-month period, at a cost of US$71,700, from the GEF, and US$200,000, as a counterpart of the Federal Government. The work will be carried out by a tem similar to the one involved in that of the Middle-Lower São Francisco, under CODEVASF’s orientation.
For a better evaluation of the spatial changes occurring in the Middle-Lower São Francisco, it is recommended a periodic land use mapping, which will allow the efficient monitoring of the area. Through multi-temporal analyses, realized with images of the same orbit/point, for different dates, it is possible to detect trends and growth vectors for variables such as deforestation, urban and agricultural areas, anthropic activities, etc. It is the consultants’ opinion that the mappings should be repeated at 5 to 10 years intervals.
Another recommendation refers to the consolidation of the results obtained by the 27 Activities constituting the GEF São Francisco Project, in a computational environment, with the access capability made possible by the technology of the Geographic Information System (GIS).
Geographic information are increasingly a more important component in the great decision making process, both in the public sector and in the private initiative. The quality of this information represents the basic integrating element among the distinct components of a GIS.
In the case of the Middle-Lower São Francisco, the cartographic material used, provided by CODVASF, presents some technical flaws, already mentioned throughout this Report. They must be corrected, to avoid compromising the georeferencing of the collected or produced information. With this purpose, it is suggested a careful review of the digitalization of the mapping sheets (in 1:100,000 scale), covering the São Francisco River Basin.