INTEGRATED MANAGEMENT OF LANDBASED ACTIVITIES IN THE SÃO FRANCISCO BASIN PROJECT ANA/GEF/UNEP/OAS Subproject 4.7.B - Plan for a Piezometric Monitoring Network In the Basin of the Rio Verde Grande Executive Summary of the Final Report PLAN FOR A PIEZOMETRIC MONITORING NETWORK IN THE BASIN OF THE RIO VERDE GRANDE Belo Horizonte - MG INTEGRATED MANAGEMENT OF LANDBASED ACTIVITIES IN THE SÃO FRANCISCO BASIN PROJECT ANA/GEF/UNEP/OAS Subproject 4.7.B - Plan for a Piezometric Monitoring Network In the Basin of the Rio Verde Grande Executive Summary of the Final Report PLAN FOR A PIEZOMETRIC MONITORING NETWORK IN THE BASIN OF THE RIO VERDE GRANDE Subproject Coordination Fernando de Britto Dantas Agência Nacional de Águas - ANA Consultant Waldemir Barbosa da Cruz Contract CPR/OAS no 31631 September 2002 PLAN FOR A PIEZOMETRIC MONITORING NETWORK IN THE BASIN OF THE RIO VERDE GRANDE EXECUTIVE SUMMARY INTRODUCTION Activity 4.7.B, “Plan for a Piezometric Monitoring Network in the Basin of Rio Verde Grande”, belongs to Component IV (Formulation of the Integrated Management Program) of the Integrated Management of Land Based Activities in the São Francisco River Basin Project (GEF/ANA/OAS/UNEP). The Activity views the implementation of the necessary actions for proposing a piezometric monitoring network, which will provide subsidies and a deeper knowledge of the availability of groundwater resources in the Basin. The Basin of the Rio Verde Grande, a right-margin tributary of the São Francisco River, has approximately 31,000 km², being located in Northwestern Minas Gerais and Southwestern Bahia, as shown in the map in Figure 1. In this Sub-basin, there are important sources of groundwater, which have been exhaustively exploited for urban, irrigation and livestock supplies. In the past years, it has been noticed a significant increase in the drilling of high-yield wells, for farming activities. In some places, conflict of uses and over-exploitation has been identified, with interference among wells and excessive lowering of the water table. The first chapter of the Final Report contains a description of the methodology and of the activities carried out. Chapter 2 includes a review of the available documentation, including studies on a regional level, and current works in the Basin. Based on secondary data, Chapters 3 and 4 describe the physiographic characteristics of the surface water resources and hydrogeologic aspects of the Sub-basin. Chapters 5 and 6 present a preliminary definition of the used criteria for selecting control and monitoring points, culminating with the identification of the target areas, object of the field surveillance, carried out in the following step. At this stage, a data form was created for registering the control points and the necessary information for identification of suitable sites for implantation of the monitoring network, as indicated in Chapter 7. The proposal of the piezometric monitoring network plan, with objectives, basic procedures, number of selected points, equipment, data reception and other specifications are included in Chapter 8. The guidelines for the creation of an information system, including a complementary hydrologic data collection system, with emphasis on well discharge control, are presented on Chapter 9. The main conclusions, relating to identified problems and obtained results, are in Chapter 10. The presented recommendations include suggestions for completing the study, with the implementation of three projects, whose preliminary terms of reference are presented. i 1. IMPLEMENTED ACTIVITIES The initial stage of the work was carried out in the office, according to the following procedures: • Gathering and analyzing available documentation on physiographical, hydrological, geological and hydrogeological aspects of the area. • Hydrogeologic characterization: identification of aquifer systems, definition of the hydrogeologic model (recharge areas, flow conditions and discharge areas) of registered wells’ characteristics and yields, of conditions of use and groundwater quality; • Preliminary definition of selection criteria for control points. • Identification of target areas for directing field work and defining the network. • Preparing aquifer system’s map. • Preparing the 1st Partial Report (Main Hydrogeological Aspects of the Rio Verde Grande Basin), in July of 2002. The second stage consisted of a field reconnaissance, implemented from July 21st through August 2nd, 2002, when the wells in the previously selected areas were catalogued, viewing the identification of suitable sites for the monitoring. Results from this phase were presented in the 2nd Partial Report (August/2002). The following step consisted of the elaboration and final proposal of the Plan for a Piezometric Monitoring Network, containing objectives, used criteria, basic procedures and other specifications (3rd Partial Report). The last stage comprehended the implementation of activities aimed at the formulation of guidelines and recommendations for the information and complementary hydrologic data collection systems. Those systems must be integrated with the one to be developed by ANA, in the Basin. All results are presented in the 4th Partial Report (September/2002). 2. AVAILABLE DOCUMENTATION – PREVIOUS WORKS The most relevant works in the Basin were analyzed, including those on a regional level and the ones specific to the area, carried out by CETEC/MG, COPASA, HIDROSISTEMAS/MG, CPRM, IGAM/MG and CODEVASF. The most remarkable of those were the “Methodology for Development of Watershed Environmental Management – Case Study of the Rio Verde Grande”, by CETC (1995), “Groundwater Resources Availability in the State of minas Gerais”, by COPASA/HIDROSISTEMAS (1995), “Water Resources Director Plan for the Tributary Basins of the São Francisco in Minas Gerais”, by SOAPA/RURALMINAS (1997); “Hydrogeologic Inventory and Study as Subsidies to the Water Resources Monitoring, Control and Management System of the Rio Verde Grande Basin”, by SEMAD/IGAM/FUNARBE (2000). ii 3. PHYSIOGRAPHIC CHARACTERISTICS OF THE SURFACE WATER RESOURCES Most of the Rio Verde Grande Basin is nested in a lower plains, in a zone denominated Sanfranciscan Depression”, with 500 to 600 meters of altitude, in Tertiary-Quarternary colluvial cover and pelitic and carbonatic metasediment domains of the Bambuí Group. Bordering this depression, there are relief forms associated to the “São Francisco Plateau”, with elevations between 700 and 1,000 meters, characterized by tablelands with well delineated eroded borders, developed over cretacic sandstones, of the Urucuia Formation. To East, taking the N-S direction, with maximum elevation of 1,300 m, the Espinhaço Sierra establishes the limits for the São Francisco, the Jequitinhonha and the Pardo Rivers Basins. The predominant climate, according to Köppen’s Classification, is the Aw, a humid and warm tropical climate with a well accentuated dry season, covering the most of the Basin. Also, the Cw, mesothermal with warm and rainy summers and dry winters with milder temperatures, is also characteristic of oriental border of the Espinhaço Sierra. The total annual rainfalls show significant variation, ranging from 630 to 1,700 mm, with an annual mean precipitation of 1.098 mm, in Montes Claros. These values are lowered towards the North, reaching 700 to 800 mm, in Monte Azul. The rainy season extends from October to March, when 90% of rainfalls occur, and the dry season from April to September. Temperatures are high, with annual mean of 23.5 ºC, with the lowest values (mean of 21 ºC), occurring in the months of June and July. The Rio Verde Grande enlarges from South to North, having as main tributaries the Gorutuba and the Verde Pequeno Rivers, to the right margin, and the Cana Brava, Suçuapara and Jacuí rivers on the left side. The available hydrologic data indicate a mean flow of 26.4 m³/s and a relatively low specific discharge with mean, maximum and minimum of 0.875, 6.83 and 0.32 l/s.km², respectively, for the station at Boca da Caatinga, with drainage area of 30,180 km². 4. HYDROGEOLOGICAL CHARACTERISTICS 4.1 GEOLOGY AND AQUIFER SYSTEMS It is worth highlighting the granular aquifer systems associated to the alluvial and Tertiary- Quarternary detritic deposits usually with restricted importance in the Sub-basin, and the sandstone aquifers of the Urucuia Formation, occurring in the Plateau zone. The main aquifers and with the highest yields are associated with the pelitic (slate and siltstones) and carbonatic (limestone) rocks, of the Bambuí Group, which is spread over 60% of the Sub-Basin’s area. Eastern of the 43º Meridian, fractured aquifers with low yields are predominant. They are in the domains of quartizitic, schistose and gneiss-granitic rocks of the Espinhaço Supergroup, of the Macaúbas Group and of the Pre-Cambrian Crystalline Basement (Figure 2). iii 4.2 CHARACTERISTICS OF WELLS The data regarding the catalogued tubular wells are from different sources and are stored in a databank with diversified structure and types of information, provided by DNOCS, CODEVASF, CERB/BA, CETEC/MG, COPASA/MG e IGAM. The most recent series are in IGAM’s and CPRM’s databases. The first one includes 3,717 wells, catalogued in 2000. The latter, still under way, covers the micro-region of Montes Claros. In a general way, a greater well density is found around urban centers and in areas around irrigation projects, concentrated in regions of high yield carstic aquifers. The Municipalities with greater concentration of wells are Montes Claros, Janaúba, Francisco Sá and Jaíba. Well depths range from 20 to 200 meters, most of them between 50 and 100 meters deep. 4.3 WELL YIELDS The higher yield wells, with discharges over 1.0 l/s/m, have greater incidence in the Municipalities of Montes Claros, Capitão Enéas, Francisco Sá, Janaúba, Verdelândia, Jaíba and Matias Cardoso, besides certain areas in Glaucilândia, São João da Ponte, Varzelândia, Porteirinha, Nova Porteirinha, Iuiú (BA) and Urandi (BA). Zones with lower yields, with discharges lower than 0.1 l/s/m, occur in the Lower Gorutuba and in the Eastern-Northeastern areas of the Rio Verde Pequeno.