Stream Subbasins Research Articles

Biomass Model and Water Balance Application for Watershed Drought Analysis

The hydrological cycle is an important process for monitoring various functions of the landscape. However, changes from land use and natural events, such as drought, have caused several problems in watersheds, such as water scarcity episodes. Thus, the creation of tools for monitoring these events is important in environmental research. Therefore, the objective of this work is delimiting the potential biomass and elaborates the water balance of the Serra Azul stream sub-basin (MG) to analyze the influence of drought on the water storage of the hydrographic basin. The used methodology involved the calculation of the Vegetation Condition Index (VCI), application of the biomass model and evaluation of water balance. Furthermore, a regression analysis was performed between the analyzed data to verify the influence of the variation in biomass and water balance in the worsening of drought in the study region. The results indicated that variations in land use and the natural changes in the hydrological cycle contributed to the worsening of drought proving the effectiveness of biomass model associated to water balance and VCI data for monitoring drought.

EVALUATION OF VULNERABILITY TO SOIL LOSS IN THE ESPINHO STREAM SUB-BASIN, MUNICIPALITY OF MORRINHOS, CEARÁ, BRAZIL

The present work aims to identify the different degrees of vulnerability to soil loss in the Espinho stream sub-basin, municipality of Morrinhos, Ceará, Brazil. For this, it was used as a methodology the construction of a geographic database with the help of the QGIS software version 3.16-Hanover, from the criteria Geology (G), Slope (D), Pedology (S), Use and Coverage (U ) and Climate (C). Four classes of vulnerability to erosive processes were identified in the sub-basin. The results showed that the classes with predominance of pedogenetic processes accounted for 34% of the sub-basin area. The one whose processes represent balance between pedogenesis and morphogenesis was 64%. The class where morphogenetic processes prevail totaled 2% of the studied area.

Hydrochemical and environmental isotopes characteristic of groundwater and controlling factors for waters’ chemical composition in the iron–copper mine area of Elazığ, SE Turkey

Environmental context Predicting the hydrodynamic structure of water resources based on water chemistry and isotope results is important for understanding their transport and effects on the hydrogeological system. According to the results of this study, hydrogeological characteristics of ground and surface water resources in the Zeryan Stream sub-basin in the iron–copper mining area and their geochemical evolution are mainly controlled by the weathering of silicate and carbonate minerals, and ion exchange. Rationale and hypothesis Groundwater is generally the most important water resource in mine areas, and its circulation processes need to be studied in detail for rational resource exploitation. This work tested the hypothesis that the evolution of groundwater chemistry and recharge by using hydrogeochemical indicators and isotope tracers together are affected by the hydrogeochemical processes that may have taken place during the water-rock interactions in the Zeryan Stream Sub-basin, where the Iron-Copper mine is located. Methodology It used approaches such as hydrochemistry, Piper diagrams, saturation index, ionic ratios, and environmental isotopes to analyze groundwater origin and hydrochemical processes affecting water chemistry. Fifty-seven water samples were collected from 19 points during wet and dry periods. Results Results indicated that the dominance of cations and anions in the mine water follows the trend Mg2+ > Ca2+ > Na+ > K+ and SO42− > HCO3− > Cl−, and most of the water samples are Mg-Ca-HCO3-SO4, Mg-Ca-SO4-HCO3, and Ca-HCO3. Discussion Evaluation of analyzed groundwater chemical data showed that dissolution or precipitation of silicate minerals dominated in the hydrochemical evolution of groundwater, dissolution of carbonate minerals was a secondary process and to a lesser extent, ion exchange processes played a role. The δD and δ18O isotopic contents indicated that the water samples were controlled by local atmospheric precipitation, and affected by secondary evaporation during the recharge process. Tritium levels indicated some well waters are recharged from older groundwater resources from water-rock interaction and residence time. Findings The findings of this study were provided to decision-makers in order to design sustainable implications for groundwater utilization based on the sub-basin.

Temporal analysis of drought coverage in a watershed area using remote sensing spectral indexes

The development of several time series analysis programs using satellite images has provided many applications based on resources from geostatistics field. Currently, the use of statistical tests applied to vegetation indexes has enabled the analysis of different natural phenomena, such as drought events in watershed areas. The objective of this article is to provide a comparative analysis between NDVI and EVI vegetation index data made available by MOD13Q1 project of MODIS sensor for drought mapping using vegetation condition index (VCI) in the Serra Azul stream sub-basin, MG. The methodology adopted the Cox-Stuart statistical test for seasonality analysis and Pearson's linear correlation to verify the influence of different indexes on delimitation of drought in a watershed. The results indicated the NDVI vegetation index as more efficient than EVI in spatial characterization of studied watershed region, mainly in identification of seasonality. The VCI proved to be highly feasible for monitoring drought in study period between 2013 and 2018, allowing the effective delimitation of drought conditions in the Serra Azul stream sub-basin. In addition, the effectiveness of MODIS sensor data in characterizing drought events that affected the study area was proven.

Land use and occupation in the Fundaça Stream subbasin, Espírito Santo, Brazil

The objective of the research was to evaluate land use and occupation in the Fundaça Stream subbasin, state of Espírito Santo, Brazil, aiming at subsidizing improvements in environmental conservation and territorial planning. The procedures were performed in the ArcGIS® computer program. First, the study defined the limits of the subbasin, and then obtained the features of land use and occupation for the state of Espírito Santo from two mappings, from 2007 to 2008, and from 2012 to 2015. These features were edited, defining the classes of use and occupation only for the subbasin. They were identified, quantified, and mapped. There is a predominance of pasture, with percentages above 50 %, although this occupation decreased by 1.94 % between the periods studied. Coffee growing, the third predominant class, also decreased, which can be attributed to the preference for other activities, such as eucalyptus forestry. This showed strong growth, although with even lower percentages. Mishandling of those areas can cause environmental and economic damage. However, the areas of native vegetation represented a minimal rate, even with an increase, due to the decrease of vegetation in the early stage of regeneration. Macega (wild vegetation) coverage, besides being close to the native vegetation and which was predominantly fragmented, indicates problems with the use and occupation planning. The action of the local riverbasin committee and public managers, besides environmental education, and correct management of rural activities, are necessary actions.

Assessment of Soil loss Tolerance limit to Latosol, Argisol and Cambisolin the southern Minas Gerais state

Soil Loss Tolerance (T) reflects the maximum erosion rate that still allows a sustainable level of crop production. The T limit can be used to support the conservationist land-use planning and to propose erosion mitigation measures. In this context, we aim to determine the Soil Loss Tolerance limit to different soil classes located at the Coroado Stream Subbasin, southern Minas Gerais, Brazil. The soil classes of the subbasin area was classified as Dystrophic Red Latosols - LVd (90.0%), Eutrophic Red-Yellow Argisols - PVAe (5.4%), and Dystrophic Tb Haplic Cambisols - CXbd (1.9%). The following attributes were used to determine the T limits: texture, depth, density, permeability, and organic matter. To analyzing these parameters, we collect soil samples at 18 points distributed along the subbasin area. T values ranged from 4.75 to 7.40 Mg ha-1 year-1, with the lowest limit observed for CXbd (4.75 Mg ha-1 year-1). These results indicate that the Cambisol should be prioritized in the adoption of conservation practices to reduce water erosion and to maintain soil loss levels at acceptable rates. Latosols, Argisols, and Cambisols are the most common soils in the Brazilian territory. Thus, the results provided by the work can be used as a reference to monitoring the erosion process and evaluate the sustainability of agricultural activities in Brazil.

Capacidade de uso da terra da sub-bacia do Córrego Maria Comprida usando Sistemas de Informações Geográficas

Agriculture is fundamental for the development of humanity; however, it is necessary to adjust land use planning in order to reconcile agricultural activities with proper soil management practices, thus reducing the impact on the environment. The study aimed to evaluate the land use capacity of the Córrego Maria Comprida-MG sub-basin, located in the Caratinga and Rio Doce river basins. The support of the Geographic Information System (GIS) was used for the framing of the lands according to the system of the capacity of use. The Number of Exceeding Classes (NCE) was evaluated in order to identify conflicts between land use and current land use. It was verified that the sub-basin presents approximately 60% of its land in class VI of the capacity of use and that about half of the study area is being used above its capacity, occupied mainly by pastures. The results proved its importance for planning the rational use of land in the Maria Comprida stream sub-basin.

Estimates of soil losses by the erosion potential method in tropical latosols

ABSTRACT Water erosion is one of the main problems faced in coffee cultivation, as it promotes environmental degradation and crop yield decrease. Erosion estimates support the planning of conservation management practices and allowing determining the rates of soil losses. Thus, the objective of this paper was to estimate the soil loss by water erosion using the Erosion Potential Method in a sub-basin predominantly covered by coffee cultivation and then to compare the results with the Soil Loss Tolerance limits. The study area is the Coroado Stream Sub-basin, located at Alfenas Municipality, south of Minas Gerais, Brazil. The sub-basin presented an Erosion Coefficient of 0.272, indicating a predominance of low-intensity erosion. The total soil loss estimate was 1,772.01 Mg year-1 with an estimated average of 1.74 Mg ha-1 year-1. Soil Loss Tolerance limits range from 4.75 to 7.26 Mg ha-1 year-1 and, according to the Erosion Potential Method, only 1.0% of the sub-basin presented losses above the limits. The areas with the highest slopes and bare soil concentrated the highest losses rates and should be prioritized in the adoption of mitigation measures. The Erosion Potential Method estimated soil losses in tropical edaphoclimatic conditions in a fast, efficiently and at low cost, supporting the adoption of conservation management practices.

Morphometric analysis of Suketi river basin, Himachal Himalaya, India

Suketi river basin is located in the Mandi district of Himachal Pradesh, India. It encompasses a central inter-montane valley and surrounding mountainous terrain in the Lower Himachal Himalaya. Morphometric analysis of the Suketi river basin was carried out to study its drainage characteristics and overall groundwater resource potential. The entire Suketi river basin has been divided into five sub-basins based on the catchment areas of Suketi trunk stream and its major tributaries. Quantitative assessment of each sub-basin was carried out for its linear, areal, and relief aspects. The analysis reveals that the drainage network of the entire Suketi river basin constitutes a 7th order basin. Out of five sub-basins, Kansa khad sub-basin (KKSB), Gangli khad sub-basin (GKSB) and Ratti khad sub-basin (RKSB) are 5th order sub-basins. The Dadour khad sub-basin (DKSB) is 6th order sub-basin, while Suketi trunk stream sub-basin (STSSB) is a 7th order sub-basin. The entire drainage basin area reflects late youth to early mature stage of development of the fluvial geomorphic cycle, which is dominated by rain and snow fed lower order streams. It has low stream frequency (Fs) and moderate drainage density (Dd) of 2.69 km/km 2. Bifurcation ratios (Rb) of various stream orders indicate that streams up to 3rd order are surging through highly dissected mountainous terrain, which facilitates high overland flow and less recharge into the sub-surface resulting in low groundwater potential in the zones of 1st, 2nd, and 3rd order streams of the Suketi river basin. The circulatory ratio (Rc) of 0.65 and elongation ratio (Re) of 0.80 show elongated nature of the Suketi river basin, while infiltration number (If) of 10.66 indicates dominance of relief features and low groundwater potential in the high altitude mountainous terrain. The asymmetry factor (Af) of Suketi river basin indicates that the palaeo-tectonic tilting, at drainage basin scale, was towards the downstream right side of the drainage basin. The slope map of Suketi river basin has been classified into three main zones, which delineate the runoff zone in the mountains, recharge zone in the transition zone between mountains and valley plane, and discharge zone in the plane areas of Balh valley.

Presence of pesticides in surface water from four sub-basins in Argentina

Argentina has 31 million hectares given over to agriculture comprising 2.2% of the world’s total area under cultivation (Stock Exchange of Rosario, Argentina). Despite the intensity of this agricultural activity, data on pesticide pollution in surface water are rather scarce. In this sense, the aim of this work is to determine the presence of pesticides in surface water of four agricultural sub-basins of Argentine. An environmental monitoring was carried out to determine the impact of twenty-nine pesticides used in agricultural activities on the surface water quality of agricultural areas within the San Vicente, Azul, Buenos Aires southeast and Mista stream sub-basins.The samples were analyzed by solid-phase extraction (SPE) using OASIS HLB 60mg cartridges and ultra-high-pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC/MSMS) that provided good analytical quality parameters.The southeast of Buenos Aires was the site with the highest frequency of pesticides detection, followed by Azul and San Vicente microbasins. The most detected pesticides, considering all surface water samples, were atrazine, tebuconazole and diethyltoluamide with maximum concentration levels of 1.4, 0.035, and 0.701μgL−1, respectively. The results obtained for all basins studied show the presence of residual pesticides in surface waters according the different agricultural activities developed.

Environmental adaptation of the source of the subbasin of Rico Stream, Monte Alto - SP, Brazil

The aim of this study was to define the photographic patterns that represent the use and occupation of the landcover of the "spring" of the Rico Stream subbasin, located at Monte Alto, state of São Paulo (SP), Brazil, for environmental adaptation regarding the Brazilian Forest Law. The mapping was performed using remote sensing techniques and visual interpretation of the World View image, followed by the digitalization of the net of drainage and vegetation (natural and agricultural) at the AutoCad software with documents and field work. The study area has 2141.53 ha and the results demonstrated that the main crop is sugarcane with 546.34 ha, followed by 251.22 ha of pastures, 191.71 ha of perennial crops, 57.31 ha of Eucalyptus and 49.52 ha of onion, confirming the advance of sugarcane culture in the region. The region has 375.04 ha of areas of permanent preservation (APPs), and of this area it was found that only 72.17 ha (19.24%) has arboreal vegetation or natural forest, and 302.87 ha of these areas need to be enriched and reforested with native vegetation from the region, according to the current legislation. The data of the area enable future proposals of models for environmental adaptation to the microbasin according to the current environmental legislation.

Effects of the “Conversion of Cropland to Forest and Grassland Program” on the Water Budget of the Jinghe River Catchment in China

In 1999 China adopted the "Conversion of Cropland to Forest and Grassland Program" (CCFGP), a nationwide ecological recovery program, to minimize wide-scale soil erosion and vegetation degradation in China, as well as to improve water budgeting results. In the 10 yr since implementation, the CCFGP has resulted in the recovery and reforestation of >100,000 km of cropland and bare land, though the quantitative effect of this program on catchment water budget is not entirely clear. Therefore, we used the Soil and Water Assessment Tool to evaluate and quantify the effects of the CCFGP on the water budget of the Jinghe River catchment, a tributary of the Yellow River covering the central region of the Loess Plateau. Our results indicated that precipitation had dropped by 12.0% from the 1970s (611.6 mm) to the 2000s (538 mm) and that there was a corresponding 25.2% decrease in humidity index from 0.48 to 0.36. Before the CCFGP's implementation, forest and grassland had been decreasing, while bare land, cropland, and shrub land had been increasing. After the implementation of the CCFGP, the opposite trend was observed. Moreover, streamflow increased by about 15 and 20% for the upstream and middle stream subbasins, respectively, while soil water content also showed an obvious increase. Over the same period, evapotranspiration decreased by 5.2 and 13.5 mm and runoff decreased by 37.5 and 38.6% in the two subbasins. The same trends were obtained in the downstream subbasin, where changes were even greater. As a result of the reduced runoff and evapotranspiration, utilization of water resources was more efficient and ecological environment was improved under the CCFGP policy. Our results indicate the CCFGP resulted in a favorable ecological impact and should therefore be maintained.

Trophic structure of a fish community in Bananal stream subbasin in Brasília National Park, Cerrado biome (Brazilian Savanna), DF

The aim of this study was to determine the trophic structure of the fish community in the Bananal stream subbasin, which belongs to a well-preserved Cerrado area (Brazilian Savanna) in Brasília National Park, Brazil. We also evaluated the influence of environmental variations in the diet of fish species. Four samples were taken in each 30 m long established transect, two in the rainy season and two in the dry season. A total of 1,050 stomachs of the 13 most abundant species were analyzed. A total of 36 food items were consumed, where 24 were autochthonous, 8 allochthonous, and 4 of undetermined origin. Non-metric multidimensional scaling (NMDS) analysis, in addition to the results of frequency of occurrence and abundance charts, was used to determine four groups of feeding guilds: detritivores, omnivores (tending toward herbivory and invertivory), invertivores and piscivores. Around 69% of the volume of resources consumed was allochthonous, which proves the importance of the resources provided by riparian vegetation. The contribution of autochthonous and allochthonous items in the diet differed due to seasonality for Aspidoras fuscoguttatus, Astyanax sp., Characidium xanthopterum, Hyphessobrycon balbus, Kolpotocheirodon theloura, Moenkhausia sp., Phalloceros harpagos, and Rivulus pictus. Despite the Cerrado climate characteristics, there was no significant influence of season on the fish diet. The absence of seasonal variation and the predominance of allochthonous items in the fish diet are probably associated with the presence of riparian vegetation, which acts as a transition area in the Cerrado biome and provides resources for the aquatic fauna. This work shows the importance of studies in non-disturbed areas considered here as a source of information concerning the biology of fish species and as a guide for direct conservation policies on the management of aquatic resources, recovery of damaged areas and determination of priority areas for conservation.

Composição e configuração da paisagem da sub-bacia do arroio jacaré, Vale do Taquari, RS, com ênfase nas áreas de florestas

A conversão de áreas com cobertura florestal contínua por fragmentos florestais vem contribuindo para a diminuição da diversidade biológica, em função da perda de micro-habitats únicos, mudanças nos padrões de dispersão e migração, isolamento de habitats e erosão do solo. A solução desses problemas está intimamente vinculada ao planejamento e manutenção de bacias hidrográficas. A sub-bacia do Arroio Jacaré, localizada no Vale do Taquari, RS, compreende uma área de 538,98 km², onde estão parcial ou totalmente inseridos nove municípios. Essa bacia se encontra em uma região de ecótono entre as formações vegetais do tipo Floresta Estacional Decidual (FED) e Floresta Ombrófila Mista - Mata de Araucária (FOM). Foram elaboradas e analisadas informações relacionadas às características estruturais das classes de mata na região (FED, FOM e vegetação secundária), utilizando-se imagem do satélite Landsat 7 ETM+, referente à passagem 04/02/2002 e software de Sistemas de Informações Geográficas (SIG) Idrisi, 3.2, software de Ecologia de Paisagem Fragstats 3.3. Os resultados indicaram que a região apresenta aproximadamente 50% de suas matas nativas conservadas ou em estágio de regeneração, porém de forma altamente fragmentada, com 87,82% dos fragmentos menores que 1 ha. Considerando um efeito de borda de 50 m, em torno de 40% dos fragmentos ainda apresentam área nuclear.

Landslide Hazard Evaluation: The Landslide Hazard Curves

This paper presents an innovative, practical methodology to establish priorities for slope monitoring and the planning of stabilization works in large hilly areas. The study is based on the analysis of geological and geomorphological maps, identification of catchment areas, and the division of catchment areas into primary (with main stream) and secondary (without main stream) sub-basins. Attention was focused on secondary sub-basins and their characteristics: lithology; an ad hoc parameter \iq (related to the average rainfall, the size of the basin, and the width of the toe section), and the average slope inclination \ii. The technique presented enables the “landslide hazard curve,” unique for a given formation in homogenous areas with similar rainfall conditions and seismicity, to be drawn in a chart which features \iq and \ii. All the ascertained and assumed unstable areas represented in the chart are located above the landslide hazard curve. The study was carried out scientifically by taking into account engineering aspects (geological, geomorphological, hydrological, and geotechnical), which influence slope stability. Groundwater levels, important in mapping out landslide prone areas, were considered in the study by means of the parameter \iq.