Hydrographic Regions Research Articles

Governança da água: comparação entre a região hidrográfica do centro de Portugal e a bacia hidrográfica do rio Apodi-Mossoró/RN no Brasil

Este trabalho objetiva comparar a forma de gestão dos recursos hídricos de Portugal e do Brasil. Para isso, a metodologia inclui: revisão sistemática de literatura, investigação documental sobre a legislação das águas e, estudo de campo sobre participação social na gestão das águas. Apurou-se avanço na legislação dos recursos hídricos e diferenças jurídicas em ambos os países. Estas distinções refletem diretamente na participação pública da gestão dos recursos hídricos, verificando-se que em Portugal os Conselhos de Região Hidrográfica são informativos e consultivos, enquanto no Brasil os Comitês de Bacia Hidrográfica são negociadores e deliberativos. Portanto, as referidas leis precisam de aperfeiçoamento para a sua efetivação com eficácia, com verificação dos seus aspectos positivos e negativos.

Monitoring the water quality Formoso river of the Amazon Region – Brazil using principal component analysis

The expansion of the agricultural frontier poses a major threat to the quality of water bodies and conservation and biodiversity of biomes. In the Tocantins-Araguaia, hydrographic region is located the largest irrigated flood type rice project in the world, and in the inter-harvest period, the area is still used for soybean production. Considering the great economic, environmental and social importance of the area, the objective of this study was to evaluate the water quality Considering the great economic, environmental and social importance of the area, the objective of this study was to evaluate the water quality of a river in the Amazon Region, Brazil, and to identify the critical pollution sites in the area of influence of the agricultural project. The monitoring occurred between April 2018 and February 2019, during periods of drought and drought. The water quality was evaluated based on the determination of 34 physical-chemical and 2 microbiological parameters. The comparison of the values obtained with the limits allowed by the legislation for class II waters pointed out samples with high total phosphorus values, which can lead to eutrophication phenomena, concentrations above the expected of metals such as Fe, Cu, and Mn and samples with low percentage of dissolved oxygen. The main component analysis (PCA) showed little variation along the river, i.e., homogeneity in the different points evaluated in the same collection; however, the comparison between collections with different seasonalities revealed quite divergent results, reinforcing that seasonal variations can aggravate the changes in the water quality of the river.

ANÁLISE MORFOMÉTRICA DO RELEVO DA REGIÃO HIDROGRÁFICA DA VÁRZEA – ALTO RIO URUGUAI (RS)

Este trabalho apresenta resultados relativos à análise e interpretação de dados morfométricos e observacionais da região hidrográfica do rio da Várzea – norte do Estado do Rio Grande do Sul –, no contexto da alta bacia do rio Uruguai. O objetivo foi avaliar se os índices morfométricos analisados são indicativos ou não de maturidade do relevo e de influência tectônica na região. A metodologia utilizada baseia-se em uma abordagem morfoestrutural por meio de análise de perfis longitudinais de canal e topográficos de varredura, de parâmetros morfométricos e de superfícies de isobase. Dentre os principais resultados apontados destacam-se: (i) curvas hipsométricas predominantemente convexas e representativas de uma morfologia que passa por ativa desnudação; (ii) uma onda erosiva remontante na direção sul da região hidrográfica que amplia a desnudação dos planaltos superiores (Planalto das Missões e dos Campos Gerais); (iii) a elaboração das escarpas erosivas, a incisão dos vales e a elaboração da superfície do Planalto Dissecado do rio Uruguai onde se concentram os maiores declives; (iv) na contraposição ao mapeamento geomorfológico da região constatou-se a coincidência das compressões de isolinhas (anomalias topográficas) com os limites entre os compartimentos planálticos da região. A morfogênese desse relevo é coerente com a atuação de fatores estruturais de caráter tectônico que fizeram com que houvesse um encaixamento do rio Uruguai produzindo uma onda erosiva remontante que se expressa na rede de drenagem.
 Palavras-chave: morfologia estrutural, perfil longitudinal de canal, dissecação fluvial

Daily rainfall estimates considering seasonality from a MODWT-ANN hybrid model

Abstract Analyses based on precipitation data may be limited by the quality of the data, the size of the available historical series and the efficiency of the adopted methodologies; these factors are especially limiting when conducting analyses at the daily scale. Thus, methodologies are sought to overcome these barriers. The objective of this work is to develop a hybrid model through the maximum overlap discrete wavelet transform (MODWT) to estimate daily rainfall in homogeneous regions of the Tocantins-Araguaia Hydrographic Region (TAHR) in the Amazon (Brazil). Data series from the Climate Prediction Center morphing (CMORPH) satellite products and rainfall data from the National Water Agency (ANA) were divided into seasonal periods (dry and rainy), which were adopted to train the model and for model forecasting. The results show that the hybrid model had a good performance when forecasting daily rainfall using both databases, indicated by the Nash–Sutcliffe efficiency coefficients (0.81–0.95), thus, the hybrid model is considered to be potentially useful for modelling daily rainfall.

Broad and fine-scale threats on threatened Brazilian freshwater fish: variability across hydrographic regions and taxonomic groups

Abstract: Anthropogenic environmental changes are the main cause of species extinction during the Holocene. Species have been exposed to major source of threats, such as habitat loss and fragmentation, pollution, introduced species, and harvesting, many of which are derived from specific anthropogenic activities, such as urbanization, agriculture, and damming (i.e. fine-scale threats). However, the importance of these threats on the species conservation status in a given region depends on the type of impacts they are exposed to and the susceptibility of species to these impacts. In this study, we used a database of threatened Brazilian freshwater fish species to test whether the major source of threats and the specific anthropogenic impacts to species vary across hydrographic regions and taxonomic groups. Our results showed that habitat loss is a ubiquitous major threat jeopardizing the conservation status of the Brazilian fish species. However, different fine-scale threats mediate this process across hydrographic regions and taxonomic groups. The combination of impacts from agriculture, deforestation, and urbanization affects most of the threatened species in the basins of the Northeast, South, and Southeast, including the species of the most threatened order, the Cyprinodontiformes. Damming is the main human activity affecting threatened species of Siluriformes, Characiformes, Gymnotiformes, and Cichliformes, especially in northern basins (Amazon and Tocantins-Araguaia). Therefore, we found that specific fine-scale threats influencing threatened species vary across hydrographic regions and taxonomic groups, probably due to geographic variability in the incidence of human activities and differential niche requirements and vulnerability of species to these activities.

New records of two cladoceran species (Branchiopoda: Anomopoda) from Northeastern Brazil: the importance of studies in temporary ponds

Abstract Temporary ponds are heterogeneous aquatic environments, in which hydrodynamics and richness of macrophytes may increase the diversity of zooplankton and other invertebrate communities. Cladocerans are common residents of these ecosystems, showing great variability of forms. During a faunistic survey in temporary ponds under the influence of riparian vegetation, in the Camucim Forest Protected Area, Pernambuco Endemism Center, Brazil, the cladocerans Moina dumonti Kotov, Elias-Gutierrez and Granado-Ramirez, 2005 and Chydorus nitidulus (Sars, 1901) were found. These are their first records in the Oriental Northeast Atlantic hydrographic region, and the second record of M. dumonti in Brazil. The present study raises Cladocera species richness in Pernambuco State to 73 and also 16 in the Pernambuco Endemism Center.

Zooplankton Biomass Depletion Event Reveals the Importance of Small Pelagic Fish Top-Down Control in the Western Mediterranean Coastal Waters

The influence of hydrochemistry and trophic conditions on the coastal zooplankton community’s biomass and metabolic activities was investigated along the Spanish Mediterranean coastal waters, from Algeciras Bay to Barcelona, from autumn 2011 to autumn 2012. Two hydrographic regions were differentiated: NW Alboran (ALB) and W Mediterranean (MED). Zooplankton metabolism was assessed from measurements of the electron transport system (ETS) and aminoacyl-tRNA synthetases (AARS) activities, as proxies for potential respiration and somatic growth, respectively. Zooplankton showed three to fivefold higher biomass in ALB than in MED during autumn 2011 and spring 2012. However, in autumn 2012, a drastic decrease in biomass standing stock was observed in ALB, with no significant differences between the two regions. This biomass depletion event was not associated with environmental variables, food availability or zooplankton metabolic rates, but coincided with a twofold peak of Sardina pilchardus landings in ALB. A reduced standing stock coupled with high zooplankton growth rates suggests mortality by predation as the main cause for the low zooplankton biomass typically observed in MED, and in ALB during autumn 2012.

VULNERABILIDADE AMBIENTAL NA SUB-BACIA DO MÉDIO TAPAJÓS (AM-PA)

O estudo da erosão hídrica do solo na região hidrográfica do Tapajós destaca-se pela expansão das atividades antrópicas na integridade da bacia hidrográfica. Para atender este objetivo foram utilizados dados pluviométricos estimados (GPCC) e topográficos (Imagens SRTM), além da rede hidrográfica (ANA) e indicadores socioambientais (EMBRAPA, IBGE e MMA). No processamento do risco ambiental foi empregado o interpolador Kernel para a densidade de drenagem e de ocupação do território. Como resultado obteve-se que as áreas mais susceptíveis a erosão, correspondem as regiões mais a noroeste, além da borda leste da bacia, indicando uma vulnerabilidade crescente e que responde principalmente ao potencial de antropismo da região.

Rainfall and streamflow extreme events in the São Francisco hydrographic region

AbstractExtreme rainfall and streamflow events are becoming increasingly more relevant to discussions concerning potential climate changes on planet earth. In most cases, impacts related to the occurrence of such phenomena can be amplified due to the lack of planning and structure. In this context, the main objective of the study is to estimate the period and level of return of intense rainfall events in homogeneous subregions of the São Francisco hydrographic region, as well as to define which of these subregions are most vulnerable to the recurrence of these episodes. We used rainfall data from 105 rain gauges and streamflow data from 103 stream gauges comprising the years from 1988 to 2017. Through cluster analysis, four homogeneous rainfall subregions were defined and validated by the silhouette index, capable of identifying misallocated stations in the clustering process. A generalized Pareto distribution from the extreme value theory was used to calculate the period and level of return of intense rainfall events in each subregion. We then related the retrieved estimates with information about the drainage network, streamflow, land use and occupation, and socioeconomic and demographic factors in the watershed region. Results indicated the existence of subregions vulnerable to hydrological and geological processes intensified due to human activity and the recurrence of hydrometeorological phenomena. The scenarios found for the recurrence of intense rainfall events indicated the severity to which some subregions may be subjected, moreover, they reinforce the need for the development of public policies for the prevention and minimization of impacts.

Ecological impacts of an invasive top predator fish across South America

Peacock bass Cichla ocellaris is a piscivorous cichlid native from the Amazon and Orinoco river basins, which has been broadly introduced into tropical areas worldwide, leading to several adverse local effects. However, predictors of its invasibility and assessments of its ecological impacts over large spatial scales are still lacking. The importance of different environmental factors in explaining the relative abundance of peacock bass in 62 sites across South America (30 native and 32 invaded systems) was investigated. The impacts of peacock bass on fish assemblages were appraised, using years since introduction as a proxy of its cumulative impacts and modern statistical techniques, such as random forests, and negative binomial regression models. Random forests highlighted maximum depth, introduced status, and ecosystem type as the best predictors of the peacock bass relative abundance, which ranged 0.01–26.0%, increased with maximum depth, was highest in invaded reservoirs but decreased with depth in native riverine populations. Other factors such as climate or limnological features were less important in explaining C. ocellaris abundance, which did not vary markedly with years since introduction. Introduction year was not related to latitude but varied among hydrographic regions, indicating invasion pathways not linked to geographical proximity. Variation partitioning of different fish assemblage metrics showed that hydrographic region followed by limnological and reservoir features accounted for most explained variation, indicating a strong historical and local influence. Introduction time accounted for 5–8% of variation in species composition and diversity, independently of limnological features. Our results suggest that the ecological effects of introduced C. ocellaris on native fish fauna are likely but small compared to large geographical and environmental gradients. Although experiments and before-after designs are probably more sensitive in detecting the ecological impacts of invasive species, large-scale compilations of available data are more feasible and can provide invaluable information, especially for large-sized invaders that are often illegally introduced.

Water reuse potential for irrigation in Brazilian hydrographic regions

Abstract The present paper carried out an evaluation of the reuse potential of the Wastewater Treatment Plants (WWTPs) effluents for irrigation in the 12 Brazilian Hydrographic Regions (BHRs). For this purpose, initially, the WWTPs were categorized and the effluent flow rate was estimated. Category 1 represents secondary effluent with an efficiency of organic matter removal greater than 80%; Category 2 represents effluent that underwent some disinfection step; and effluents that perform less than the other categories were called ‘Uncategorized’. After that, the irrigation water demands for each BHRs were compiled, and finally, the production of water for reutilization was compared with the demand for irrigation. Thus, it was observed that all the sewage flow rates generated in Brazil classified in Categories 1 and 2 represent 9% of the total irrigation water demand in the country (1,078.71 m3/s) and it stands out that only 7% of the flows treated in Brazil undergo a tertiary treatment step.

Taxonomic Catalog of the Brazilian Fauna: order Trichoptera (Insecta), diversity and distribution

Caddisflies are a highly diverse group of aquatic insects, particularly in the Neotropical region where there is a high number of endemic taxa. Based on taxonomic contributions published until August 2019, a total of 796 caddisfly species have been recorded from Brazil. Taxonomic data about Brazilian caddisflies are currently open access at the “Catálogo Taxonômico da Fauna do Brasil” website (CTFB), an on-line database with taxonomic information on the animal species occurring in Brazil. The order Trichoptera at CTFB includes a catalog of species recorded for the country, with synonymic lists, distribution throughout six biomes, 12 hydrographic regions, and 27 political states (including Federal District) from Brazil. The database is constantly updated to include newly published data. In this study, we reviewed the taxonomic effort on Brazilian caddisflies based on data currently in CTFB database. The accumulation curve of species described or recorded from the country, by year, shows a strong upward trend in last 25 years, indicating that it is possible that there are many more species to be described. Based on presence/absence of caddisfly species at three geographic levels (biomes, hydrographic regions, and states), second order Jackknife estimated at least 1,586 species occurring in Brazil (with hydrographic regions as unities), indicating we currently know about 50% of the Brazilian caddisfly fauna. Species distribution by Brazilian biomes reveals that the Atlantic Forest is the most diverse, with 490 species (298 endemic), followed by the Amazon Forest, with 255 species (101 endemic). Even though these numbers may be biased because there has been more intense collecting in these two biomes, the percentage of endemic caddisfly species in the Atlantic Forest is remarkable. Considering the distribution throughout hydrographic regions, clustering analyses (UPGMA) based on incidence data reveals two groups: northwestern basins and southeastern. Although these groups have weak bootstrap support and low similarity in species composition, this division of Brazilian caddisfly fauna could be related to Amazon-Atlantic Forest disjunction, with the South American dry diagonal acting as a potential barrier throughout evolutionary time.

Phytoplankton community dynamics in a coastal bay under upwelling influence (Central Chile)

Marine coastal areas have high social-economic relevance and ensuring the good quality of these areas has gained importance in the past decades due to the increase of anthropogenic pressures. Understanding the dynamics of these areas is crucial to support management decisions. In this context, phytoplankton communities are generally used as key indicators of environmental quality as they respond in short time-scales and are at the base of food webs. This work intends to improve our understanding on how phytoplankton communities respond to environmental conditions, particularly in upwelling areas. Seawater samples were collected from Algarrobo Bay, Central Chile, for both phytoplankton pigments and microscopy analysis. Data were analyzed in combination with physico-chemical parameters and two distinct hydrographic regions were identified for the study area: i) a region occupying most of the northern bay section, characterized by lower temperatures and dissolved oxygen (DO), higher concentration of nutrients and higher N:P, where a mixed community with diatoms, chrysophytes, cryptophytes, haptophytes and other small flagellates were observed; and ii) a central-southern section, with higher temperatures and DO, lower nutrients and lower N:P, where diatoms, in particular the centric diatom Chaetoceros Ehrenberg, 1844 sp. (~92.5% on average), dominated the phytoplankton assemblage. Other common but much less abundant diatom genus included Skeletonema Greville, 1865, Eucampia Ehrenberg, 1839, Dactyliosolen Castracane, 1886, Nitzschia Hassall, 1845, Cylindrotheca Rabenhorst, 1859 and Asterionellopsis Round, 1990. Apart from diatoms, the most abundant taxa belonged to flagellates, mainly chrysophytes (228.4 × 103 cells L−1 on average) and cryptophytes (213 × 103 cells L−1 on average). Overall, results suggest that the southern part of the Algarrobo Bay, with higher residence times and nutrient discharges, may act as an upwelling shadow area, where phytoplankton species can accumulate.

Artificial Neural Network and Fuzzy Inference System Models for Forecasting Suspended Sediment and Turbidity in Basins at Different Scales

The monitoring of hydro-sedimentological processes is important for environmental control but depends on resources that are not always available. The estimation of sedimentological variables with mathematical models is often limited by the scarcity of data for a single basin. This research experiments with the simulation of suspended sediment concentration (SSC) and turbidity (T) using a regional model, with data from agricultural basins of different scales within the same hydrographic region, using hourly precipitation as one of the predictive variables, aggregated through the exponentially weighted moving average (EWMA) of past rainfall, in artificial neural network (ANN) and fuzzy inference system (FIS) models. The data monitoring was performed from January 2013 to February 2020 in four watersheds within the same region in southern Brazil, with areas ranging from 1.3 to 524.3 km2. For the turbidity estimation, the FIS model, which also made use of the discharge (Q) and area (A) of each basin as inputs, performed best, with a Nash-Sutcliffe efficiency (NS) of 0.860 for the verification samples. Several FIS and ANN models performed very well for SSC prediction (with NSs ranging from 0.950 to 0.977) due to the EWMA variable, including an FIS model that uses only this variable (NS 0.952). The results allow us to conclude that it is possible, with few data for the individual basin and a regional empirical model, to estimate SSC and turbidity, provided the aggregation of hourly precipitation by the EWMA, as long as the basins have similar physical and climatic characteristics.

Hoverfly (Diptera: Syrphidae) assemblage of an oak-hornbeam in the Merlino Wood Natural Reserve and implications for its conservation.

Merlino Wood is a typical oak–hornbeam forest in the Po Plain hydrographic region. It is one of the few remaining lowland forests in Northern Italy and is a Regional Natural Reserve and a Site of Community Interest (code IT1160010). This is the first survey on hoverflies in the study area and they act as bioindicators to assess habitat conservation. Sampling was performed with three Malaise traps and an entomological net. A total of 61 species of Syrphidae were recorded between March and October 2019. Three of the species observed are considered to be under threat in Europe, three species have been recorded for the first time in Piedmont and Heringia latitarsis (Egger, 1865) has been recorded for the first time in Northern Italy. The Syrph the Net analysis has been used to assess habitat conservation. It shows good preservation of xylosaprophagous species, while the conservation conditions of other larval trophic categories are poor.

Analysis and spatial distribution of schistosomiasis mansoni in a historically endemic area of northeastern Brazil.

To perform a descriptive analysis of the activities of the Schistosomiasis Control Program, as well as the spatial distribution of the condition in the state of Alagoas, Brazil, for the period from 2007 to 2016. Descriptive ecological study. Data from positive human cases and operational data were collected in the Information System of the Schistosomiasis Control Program, and data for spatial analysis were collected on the website of the Brazilian Institute of Geography and Statistics. An analysis of spatial autocorrelation (Moran statistics) was performed, where a spatial pattern was established, which showed the Q1 and Q2 patterns to be the most important, and Q3 and Q4 representing transition areas. In the years under study, at least 85% (n=60/70) of the municipalities carried out the activities recommended by the PCE (Schistosomiasis Control Program). Alagoas presented an average positivity rate of 7.1%, which is very high compared to the prevalence of 3.3% at the last national schistosomiasis survey conducted between 2010 and 2015. Moran's statistics showed 22/70 municipalities forming a Q1 cluster, of high/high pattern, and 32/70 municipalities forming a Q2 cluster, of low/low pattern, with the others in a transition area. Moran Map data, however, showed only 7/70 municipalities in the endemic area with a spatial autocorrelation, with these municipalities having the Mundau River as a common element. Schistosomiasis mansoni is of great importance for public health in Alagoas and that the use of spatial analysis can identify priority areas for preventive and control measures against schistosomiasis mansoni.

Biased research generates large gaps on invertebrate biota knowledge in Brazilian freshwater ecosystems

Research biases are common and constant issues in biological research, with major consequences for biodiversity conservation. Freshwaters represent one of the most threatened ecosystems worldwide, but knowledge of freshwater biota is unevenly distributed due to bias toward marine and terrestrial groups. Therefore, detecting biases and associated knowledge gaps is crucial to steer future research effort and to guide applicable conservation policies for freshwater ecosystems. In this study, we investigated the existence of biases and gaps in knowledge about the biodiversity of invertebrate fauna (zooplankton, mollusks and freshwater crabs) in the hydrographic regions of Brazil. We searched for all studies published in this country on zooplankton, mollusks and freshwater crabs, in the Web of Science database. Subsequently, the number of papers was classified by taxonomic group and hydrographic region to detect research biases. Each report within a paper between a given taxonomic group and a hydrographic region was termed as a case. We also recorded human population density for each hydrographic region. Among the taxonomic groups, zooplankton was the most studied taxon, followed by mollusks and crabs, and it was also dominant across the hydrographic regions. The hydrographic region of Paraná comprised the largest number of cases for the three invertebrate groups. We detected a disproportionately low increase of number of cases in relation to human population density in the hydrographic regions. The identification of the major gaps reported here limits our ability to draw scenarios for the conservation of hydrographic regions and their megadiverse biota in Brazil.

Breeding and seasonal occurrence of the Orinoco Goose (Neochen jubata) in Brazil

The Orinoco Goose (Neochen jubata) is a “Near Threatened” species occurring extensively in South America. The objective of this study was to examine the breeding and seasonal occurrence of the species in Brazil. A search for adults and young was done by consulting the WikiAves database of photographs. Families with young were obtained by citizens in 11 municipalities within the Cerrado and Amazonia. In general, breeding birds were associated with rivers, been encountered swimming, or walking at sandy beaches. The Tocantins-Araguaia hydrographic region (TAHR) harbored most records with breeding evidence in the Cerrado, while families with young were recorded along the Guapore and Purus rivers in Amazonia. Families had 1–2 adults and 2–11 young. Differences between the mean brood sizes of downy young and juveniles were not significant. On the other hand, the mean number of young accompanied by two adults was significantly higher than that been cared by only one adult. In both the Cerrado and Amazonia, young were detected during the dry season and beginning of the rainy season, when the water level of rivers is low. Pium, Aruana, and Caseara are important breeding sites, while Sao Miguel do Araguaia and Lagoa da Confusao appear to be major non-breeding sites. The seasonal occurrence of records suggests that N. jubata might migrate within the TAHR. The species can breed successfully in central and northern Cerrado, where Parque Estadual do Cantao appears to be an important conservation unit for this species. Education of locals and strict protection are suggested as major actions for its conservation in Brazil.

ANÁLISE MULTIVARIADA E TENDÊNCIA DA PRECIPITAÇÃO PLUVIOMÉTRICA NA REGIÃO HIDROGRÁFICA DO RECÔNCAVO SUL (BA)

O objetivo desta pesquisa foi analisar a variabilidade espacial e temporal das precipitações pluviométricas, no âmbito da região hidrográfica do Recôncavo Sul, a partir de técnicas de tendência e da análise multivariada. Essa região localiza-se no leste do estado da Bahia, com uma área de, aproximadamente, 16.990 km². Em posse da série histórica de dados pluviométricos entre 1985 e 2010, os dados anuais completos foram organizados e analisados temporalmente através da estatística descritiva básica. Em seguida, identificou-se a possibilidade de existência de tendências na série histórica, aplicando os testes de Mann-Kendall e da Regressão Linear, ambos para o nível de significância de 5%. Por fim, para esses anos, foi realizada uma análise multivariada, onde, por meio da análise de agrupamentos, utilizando a Técnica de Cluster, foram formados grupos pluviométricos similares, que configuram as zonas homogêneas, em função da precipitação mensal. O município com a maior precipitação média foi Valença e o ano foi 1985, enquanto as médias precipitadas mais baixas foram observadas no município de Milagres e o ano foi o de 1993. Em ambos métodos de análise de tendência, o resultado foi o mesmo: apenas o município de Nilo Peçanha tem uma tendência significativa de queda da precipitação. A análise de agrupamentos resultou na divisão da área do Recôncavo Sul em três grupos homogêneos e um grupo anômalo, formado por dois municípios.

Water demand prospects for irrigation in the São Francisco River: Brazilian public policy

Abstract This study analyzed how irrigation expansion in the São Francisco Hydrographic Region (SFRH) could affect water availability in four physiographic regions: Upper, Middle, sub-Middle, and Lower SFRH. The Brazilian National Water Resources Plan (PNRH) is the main policy for water resources in Brazil. The PNRH, however, did not evaluate how the expansion of the irrigated area could affect water demand. We use a detailed computable general equilibrium model (CGE), applicable to Brazil, to simulate expansion scenarios in irrigated areas for 2025 and 2035, according to the Water Resources Plan for the São Francisco River (SFP). Simulations were carried out for areas deemed potentially suitable for irrigation. The Climatic Water Balance (CWB) was estimated for the SFRH to compare water supply and water demand. Results suggest that cities located in the Upper and Middle São Francisco Regions would present greater irrigation potential due to water availability and proximity to large irrigated areas. The comparative result of the CWB and the CGE model shows water availability problems in the states of Alagoas and Pernambuco, in particular, cities located in the São Francisco Lower Region.