Dulce River Research Articles

Application of methods with a statistical approach to estimate minimum hydrological flows in the Dulce River (Argentina): Individual indices and flow regime

El caudal mínimo hidrológico es un parámetro de importancia para la gestión del recurso hídrico y su determinación se efectúa según un cuidado análisis que combina características físicas (profundidad, velocidad y sustrato); químicas (temperatura, oxígeno disuelto, pH,conductividad), y biológicas. Los métodos con enfoques estadísticos sonuna opción para considerar como primera aproximación en regionesdonde los datos de caudal son pocos debido a su falta de medición o porsu escaso periodo de cobertura. El Río Dulce es el principal tributario a la laguna Mar Chiquita, un importante ecosistema de gran escala ubicada entre las provincias de Córdoba y Santiago del Estero―región central de Argentina― y quedurante los últimos 20 años presentó una variación de superficie de 6 550a 2 500 km² entre los años 2003 y 2014. El objetivo principal fue aplicar en secciones de interés métodoshidrológicos con enfoque estadístico para analizar y aproximar los caudales mínimos necesarios del Río Dulce. Para ello se utilizaron seriesde caudal en periodos posteriores a la construcción de las principalesobras de regulación en la cuenca, a fin de considerar la variación delrégimen natural del río por la ejecución de las mismas. Estos novedososresultados de caudal mínimo hidrológico se presentan mediante un índicemínimo hidrológico anual, y por una variación mensual del caudal definidacomo régimen de caudales

Analysis of Some Physical-Chemical Indicators in Two Sections of the Cricovul Dulce River

Abstract In the present work, the main physical and chemical elements that define the water quality of the Cricovul Dulce river, within the Ialomita hydrographic basin, were monitored, a river that runs through the counties of Prahova and Dambovita. The central objective of this work was to analyze the physico-chemical indicators of the Cricovul Dulce river, of pH, temperature, oxygen, saturation, turbidity, BOD, COC-Cr level, in two sections, respectively upstream near the city of Moreni and within the radius of Baltita. After studying the mentioned parameters, the Cricovul Dulce river waters were classified into quality classes in the analyzed sections.

Application of methods with a statistical approach to estimate minimum hydrological flows in the Dulce River (Argentina): individual indices and flow regime

Application of methods with a statistical approach to estimate minimum hydrological flows in the Dulce River (Argentina): individual indices and flow regime

Functional diversity of benthic macroinvertebrates regarding hydrological and land use disturbances in a heavily impaired lowland river

This paper proposes the exploration functional diversity of benthic macroinvertebrates to evaluate their response to hydrological and land use stressors in a semi-arid lowland river. We aim to assess dominant functional traits and their sensitivity to environmental drivers, and how functional diversity respond to anthropogenic ecosystem impacts. Environment was evaluated through physical-chemical characterization of water, substrate and hydrological indices. For riparian condition assessment, we applied the QBR index for riparian forest quality and hemeroby index for level of anthropogenic intervention on the landscape. Links between environmental variables (R), taxa distribution (L) and trait composition (Q) were examined with RLQ and combined with fourth-corner analysis. The principal disturbance gradient was related to discharge regulation overlapping with land use represented by hemeroby index. There was also a gradient related to the hydrological regime which alternates seasonal floods with low flow periods. Traits related to reproductive and dispersal strategies were the most influenced by disturbance gradients, both natural and anthropogenic. Functional diversity decrease in sites subject to water abstraction and with higher hemeroby levels. Our findings have been promising in order to the application of functional diversity for biomonitoring in the Dulce River. Hemeroby enables the identification of trending changes between land uses, as well as to identify threat contexts. Furthermore, hemeroby could be useful in diagnostic stages to propose biomonitoring sites, by setting areas with different anthropogenic intervention on the ecosystem.

Sedimentological analysis and radioisotopic age of the Las Cañas Formation in Dulce river outcrops, Río Hondo, Santiago del Estero (Northwestern Argentina)

In northwestern Argentina (NWA), particularly at ~27° S, the best known Neogene depocenters are intermountain tectonic valleys located in the Sierras Pampeanas geological province. Conversely, basins located to the east from the Aconquija and Ambato ranges, toward the Chaco-Pampean Plain, have been scarcely studied due to the extensive vegetal coverage. In the last decade, despite some contributions were focused in these areas and reported valuable data concerning tectonic and lithological interpretations, chronostratigraphic data are scarce, even absent so far. Herein we present a sedimentological analysis and an 40Ar/39Ar age of the Dulce River outcrops related to the Neogene Guasayán Range deposits, at the transition between NW Sierras Pampeanas and Chaco-Pampean Plain basin (~27° S). The study area includes Neogene fossiliferous sediments of the Las Cañas Formation; particularly, we focused in a section located between Cañada de la Costa and Sotelo localities (Río Hondo Department, Santiago del Estero Province). The chronostratigraphic study allowed us to assign an early Pliocene age to the studied section of the unit; the first absolute dating obtained for this formation is 3.73 ± 0.07 Ma. The measured stratigraphic logs are ~540 m thick of relatively well-preserved light to reddish-brown clastic deposits. The paleoenvironmental analysis of partial stratigraphic sections suggests the presence of a braided sandy river with well-developed muddy floodplains. We identified two fossiliferous beds below the dated tuff bed, separated by a tuffaceous-sandstone deposit. The new chronostratigraphic datum indicates that the Guasayán Range began to rise during the late Pliocene. Based on the stratigraphy, absolute age, and geographical location of the studied area, a correlation among the Las Cañas Formation, India Muerta Formation (NW Sierras Pampeanas), and the Pozo del Tigre Member, Chaco Formation (Chaco-Pampean Plain) is suggested. This study represents a significant contribution in the context of the scarcely, isolated, and fossiliferous Neogene outcrops of the Tucumán Basin.

Efecto del muestreo de diferentes hábitats sobre la aplicación de índices bióticos basados en macroinvertebrados

El objetivo de este estudio fue evaluar el efecto del hábitat en la aplicación de índices bióticos (BI) basados en macroinvertebrados bentónicos. Se muestrearon dos hábitats, (macrófitas y sedimentos), en dos sitios del río Dulce (Cuenca Salí-Dulce, Argentina): S1 (27° 31’ 5.82” S, 64° 52’ 41.37” O) y S2 (27° 28’ 36.21” S, 64°49’ 30.30” O). El muestreo se realizó con caudal bajo, octubre/2015. Se midió pH, conductividad eléctrica (CE µS/cm), temperatura (T °C), sólidos suspendidos totales (SST mg/L), oxígeno disuelto (OD mg/L) y demanda biológica de oxígeno (DBO5 mg/L). Los macroinvertebrados se filtraron con red de nylon de 250 µm y se identificaron al nivel taxonómico requerido para la aplicación de los IB. Se analizaron riqueza taxonómica y diversidad. Se aplicaron tres IB: el IBMWP, el BMWP’ adaptado al río Salí y el IMRP desarrollado para la ecoregión Pampa de Argentina. También se aplicó el ASPT asociado con los BMWP’. Los parámetros físicos y químicos mostraron buena calidad del agua, con un pH promedio de 8,57; CE 773 µS/cm; T 19,5°C; SST 9,27 mg/L; OD 7,49 mg/L y DBO5 3,29 mg/L. Los taxones registrados fueron 34 y la diversidad fue mayor en las macrófitas que en los sedimentos. Los IB mostraron resultados diferentes según el hábitat donde se aplicaron. Las macrófitas contribuyeron con el doble de taxones a los IB, en comparación con los sedimentos. Los valores de ASPT correspondieron a calidad del agua impactada. El IMRP fue el más inclusivo en cantidad de taxones para el cálculo. La conclusión es que el tipo de hábitats influye en la aplicación de los IB.

Structure, distribution patterns and ecological responses to hydrological changes in benthic macroinvertebrate assemblages in a regulated semi-arid river: baseline for biomonitoring studies

Biological monitoring requires a comprehensive baseline of assemblage distribution patterns and their environmental drivers. In this study we evaluated benthic macroinvertebrates in a regulated river, located in a semi-arid region, which has a seasonal flood pulse and is affected by several anthropogenic pressures. Taxonomic and trophic structures of benthic macroinvertebrate assemblages were analysed in terms of their longitudinal distribution, hydrological regime and environmental factors, including the effects of hydromorphology, riparian land use and water abstraction. Most taxa were generalists and classified in the collector–gatherer functional feeding group. A large taxonomic replacement was associated with hydromorphological characteristics. Local environmental variables were critical for macroinvertebrate assemblages. There was significant temporal variability regarding seasonal flood pulse. Water abstraction for irrigation had a strong effect on assemblage structure. We suggest some challenges and issues for successful implementation of biomonitoring tools in the Dulce River, related primarily to high spatiotemporal variability.

Flooded-area satellite monitoring within a Ramsar wetland Nature Reserve in Argentina

The protection and restoration of water-related ecosystems is one of the goals to be achieved by the United Nations’ 2030 Agenda for Sustainable Development. In this framework and requested by government Argentine institutions concerned with water, biodiversity and territorial management, this study analyzes the evolution of the flooded area within the Dulce River wetlands and Mar Chiquita Lake Nature Reserve (centered around 30.6°S, 62.6°W, 70 m above sea level) in Argentina since 2003, when the historical maximum extent was reached, until 2017. The Modified Normalized Difference Water Index (MNDWI) was calculated on atmospherically corrected NASA Landsat 5 Thematic Mapper (L5-TM) and Landsat 8 Operational Land Imager (L8-OLI) reflectance data over two-scene cloudless-sky mosaics to cover the whole Reserve. Mixed-water pixels constituted an important fraction of the total-water covered area, particularly during years of minimum water level in Mar Chiquita Lake. So, MNDWI values were analyzed along transects crossing two stable regional water bodies to determine precise thresholds for detection of non-water (MNDWI < −0.15 for L5-TM, MNDWI < −0.35 for L8-OLI), mixed-water (−0.15 < MNDWI < 0.4 for L5-TM, −0.35 < MNDWI < 0.5 for L8-OLI) and open-water (0.4 < MNDWI for L5-TM, 0.5 < MNDWI for L8-OLI) pixels. A higher spatial resolution image, SPOT5-HGR2, was used to validate the classification method. A confusion matrix was built which resulted in an overall accuracy of 99.2% and a Kappa coefficient of 0.98. In-situ Geo-referenced photographic registers were also taken simultaneously to a Landsat 8 overpass to confirm the classification thresholds. The analysis of simulated MNDWI response, by using the assumption of the linear mixture model, showed that mixed pixels should present from 9% to 76% of detectable open-water area. Maximum total flooded area extensions of about 3600 km2 by 2003–2005 and a minimum one of 2050 km2 by the end of 2011 were established, followed by a recent trend to the recovering with a total flooded area of about 3400 km2 in the period 2015–2017. Open-water covered area follows closely the behavior of in-situ water level measurements of Mar Chiquita Lake, showing a maximum in year 2003 and a minimum towards the end of 2013, in a significant linear relation from which a topographical slope of the terrain of about 0.012% is inferred that agrees with previous bathymetric studies. Results show the powerful complement between a reliable water satellite monitoring tool and locally-measured parameters in so dynamic wetland regions.

Evaluation of total phenol pollution in water of San Martin Canal from Santiago del Estero, Argentina.

Santiago del Estero is a province located in northwestern Argentina. The Dulce River is used for irrigation through a vast network of channels and ditches, including the San Martin Canal (SMC), which crosses the capital city of Santiago del Estero. This canal's water is used for drinking, as well as recreational use for the general population. However, this river has been seriously polluted for several decades. The present study focuses on the identification and the quantification of the water pollution levels of total phenols in the SMC according to the seasonal periods. Water samples from various areas of the canal in different months of the year, extending from December to September, were collected for analysis. Additionally, the concentration of total dissolved solids (TDS), chlorides, sulphates, nitrites and organic matter, as well as water hardness and alkalinity, were analysed in order to conduct a more complete study of the contamination of this area. The results showed a worrying total phenol concentration that exceeded the limit set by Argentine legislation for drinking water, as well as water for recreational use (5 μg/L). The total phenol (TP) concentration was directly determined by a molecular absorption spectroscopy method based on a new flow injection analysis system (FIA). Under the selected experimental conditions, the detection and quantification limits were 0.0490 and 0.1633 μg/mL, respectively. The developed method provides a number of improvements related to the speed of analysis, the restricted consumption of the reagents and sample volumes and the unnecessary sample treatment that contribute to environmentally friendly analytical chemistry. The results showed that TP make a significant contribution in the SMC pollution, especially during the months of April (400 ± 110 μg/L) and September (240 ± 20 μg/L). A high sulphate concentration that was higher than the limit allowed by the legislation was also found.

Assessing disruption of longitudinal connectivity on macroinvertebrate assemblages in a semiarid lowland river

Abstract Aim: Our aim in this study was evaluate the effects of flow regulation for irrigation on the macroinvertebrate assemblages in a semiarid river. Methods We sampled two reaches in Dulce River; one placed upstream a weir that diverts flow into a network of irrigation channels and the other downstream that weir, in the assessment of the fluvial discontinuity. We assess the differences among reaches and sites, environmental variables, invertebrate density, richness and Shannon-Wiener index applying non-parametric analyses of variance Kruskal Wallis. The similarity percentage analysis (SIMPER) was used to identify which species contributed to the dissimilarities on macroinvertebrate assemblage structure. Canonical Correspondence Analysis (CCA) was performed with the total set of samples to explore macroinvertebrate distribution in reaches and associations of the assemblages with habitat variables. Results The density, richness and Shannon index values did not show differences between the reaches located upstream and downstream. Beta diversity (Whittaker) was 0.72 among upstream sites, 0.56 among downstream sites and higher species turnover (0.73) was obtained between both reaches. The Canonical Correspondence Analysis explained 46.71% of the variance differentiating upstream sites explained by higher values of organic matter of bottom sediments and discharge, high density of Nais communis, Bothrioneurum americanum, Pelomus, Stephensoniana trivandrana, Pristina menoni, P. jenkinae, P.longidentata, P. americana, Dero obtusa, Endotribelos, Heleobia and Turbellaria. The downstream sites were associated to coarser substratum and higher density of Lopescladius, Polypedilum, Cricotopus, Thienamaniella, Cryptochironomus, Baetidae, Nematoda and Corbicula fluminea. Conclusions The low-flow disturbance had effects on the composition of the benthic invertebrate assemblages, but attributes (such as density and richness) showed a lower variability probably because of taxa replacement.

Origin and Evolution of the Salinas Grandes and Salina De Ambargasta, Argentina

The Salinas Grandes and Salina de Ambargasta, on the eastern side of the Sierras Pampeanas in Argentina, constitute an 18,000 km2 tectonic depression. The eastward advance of the tectonic deformation is evident in the topographic elevations that intercept the Llanura Chaqueña. The interpretation of the tectonic processes that create the Salinas Grandes and Salina de Ambargasta are primarily due to the observation of morphotectonic macro indicators and structural field data. These geoforms allow us to interpret the horizontal deformation that has produced the right side displacement of parallel shears within a dextral releasing bend and restraining bend setting. This process occurred within a transtensional-transpressional setting, which produced a depression closure where lakes formed, the formation of Alto de Mancilla, deviation of rivers, the rotation and displacement of ranges and the transformation of lakes into salt flats. These processes are active and are shown by the hydro transference area where the Dulce River discharges into the Salado River, resulting in a considerable decrease of water flow into the Laguna Mar Chiquita.

Long-Term Waterbird Fluctuations in Mar Chiquita Lake, Central Argentina

Bird surveys were carried out from 1973 to 2010 in Mar Chiquita, an extensive saline lake and associated Dulce River marshes in central Argentina. The wetland has had marked fluctuations in water level and salinity over the past four decades. At the beginning of the 1970s, Mar Chiquita experienced a large drop in level and there were no waterbirds on the Segundo River mouth. By 1974 the lake had recovered its level and the Segundo River estuary had formed, harboring large concentrations of local waterbirds and Nearctic shorebirds. From mid-1977, a rise in water level led to the disappearance of the Segundo River estuary and by 2003 the lake area had expanded by about 3.5 times and covered half of the Dulce River marshes. Consequently, the wetland, especially the river estuaries, became less important for local waterbirds and Nearctic shorebirds. Since 2003 Mar Chiquita has fallen 4 m, beaches have formed and salinity has increased, but currently there are no Nearctic shorebird concentrations. For the site to recover its importance for birds, Mar Chiquita should continue dropping and salinity continue increasing.

The Geological and Morphological Structural Control in the Cricovul Dulce River Basin

The Geological and Morphological Structural Control in the Cricovul Dulce River Basin

The Mar Chiquita Lake: An indicator of intraplate deformation in the central plain of Argentina

The Mar Chiquita saline lake is located in the lowest part of one of the largest endorreic saline basins of South America. With a surface area of 6000–6500 km 2, the lake is located in a tectonic depression with an asymmetric cross section. The Sierras Pampeanas foothills, (with altitudes near 1500 m) are to the west and a 100-m topographic high (San Guillermo high) is to the east whose western border is bounded by a buried Middle Pleistocene fault (the Tostado-Selva Fault). The main tributary of the lake is the Dulce River, which flows from north to south. The southward flow of the river was impeded by an obstacle that closed the Dulce Valley, generating the Mar Chiquita Lake. The megafans of the Primero, Segundo, and Tercero Rivers deposited a large amount of sediment against the faulted border of the San Guillermo high, generating an obstacle that impeded the normal flow of the rivers and diverted the Dulce and the Salado Rivers to their present positions. Precise data concerning the age of the impounding of Mar Chiquita does not exist, but lacustrine conditions are undoubtedly younger than the uplift of the San Guillermo high, which occurred in the Middle Pleistocene. The well-preserved dry valley of the Dulce River, located southward of Mar Chiquita, is still visible in satellite images and confirms the youth of the impounding. The observations introduced in this paper allow us to understand the origin of a significant feature of the central plains of South America. The generation of Mar Chiquita Lake and upstream wetlands produced a pronounced environmental change in the arid Chaco-Pampeana Plain, which favored human life by introducing changes in vegetation and fauna.

Development and validation of a Biotic Index for evaluation of environmental quality in the central region of Argentina

The Suquia River (Cordoba, Argentina) has become an important issue because it flows into Mar Chiquita Lake, one of the largest saline lakes in the world. This water body, together with the expansive swamps of the Dulce River on the northern shore and the mouth of Suquia and Xanaes River, is considered one of the most important wetlands in Argentina in terms of biodiversity in a range of freshwater to very saline environments. Nevertheless, the presence of densely populated urban settlements and the increasing environmental impact due to anthropogenic activities characterize the central and lower sections of Suquia River Basin. Fishes are particularly affected and change their distribution and abundance as a consequence of the environmental deterioration. We collected information on fish fauna to develop and validate a Biotic Index to assess degradation of the Suquia River Basin. We classified fish species according to their sensitiveness or tolerance to environmental degradation, based on their distribution and abundance variations along a water quality gradient in order to design a Biotic Index for Suquia River Basin. The set of metrics used in the Biotic Index calculation was conformed by: the abundance of Astyanax eigenmanniorum, Rineloricaria catamarcensis, Gambusia affinis and Cnesterodon decemmacultus, the proportion of sensitive species richness, and the proportion of tolerant species richness. They clearly distinguished between the impaired and referenced sites. We demonstrated that it is possible to use fish as indicators of water quality in Cordoba Province (central part of Argentina) in order to carry out rapid and relatively inexpensive monitoring and conservation programs. The application of this Biotic Index showed that fish assemblages reflect the watershed conditions and are sensitive to changes in water quality across the environmental gradient.

Groundwater arsenic in the Chaco-Pampean Plain, Argentina: case study from Robles county, Santiago del Estero Province

In large parts of rural Argentina people depend on groundwater whose As content exceeds the Argentine drinking water standards (0.05 mg l −1). The most affected areas are located in the Chaco-Pampean Plain, where aquifers comprise Tertiary loess deposits (in the Pampean Plain) and Tertiary and Quaternary fluvial and aeolian sediments (in the Chaco Plain). Robles county is located in the alluvial cone of the Dulce River consisting of loess (aeolian), and gravel, silt, sand and clay (alluvial) deposits. In the shallow aquifers, more than 48% of the 63 studied wells show As at toxic levels (maximum 4.8 mg l −1), while in the deep groundwater the concentration is below 0.05 mg l −1. The pH of the shallow groundwaters range between 6.5 and 9 and generally have high electrical conductivity with mean values of 2072 and 1693 μS/cm −1 in the years 1998 and 1999, respectively. Arsenic concentrations are high in the alkaline Na–HCO 3 type groundwaters, where As correlates positively with Na + and HCO 3 −. Moreover, As correlates positively with Mo, U, and V, while a negative correlation was observed with Ca 2+ and Mg 2+. The potential sources of groundwater As are: (i) layers of volcanic ash with 90% of rhyolitic glass; (ii) volcanic glass dispersed in the sediments; and (iii) clastic sediments of metamorphic and igneous origin. Great lateral variability in the concentration of groundwater As is caused by several hydrogeological and hydrogeochemical factors.

The first fish fauna from the Salado river (Central Argentina, South America) with additions to the Dulce river and limnological comments

L'ichthyologie de la province de Santiago del Estero est evaluee a l'aide de l'etude d'echantillons de 13 stations sur les rivieres Salado et Dulce, fournissant en meme temps des informations limnologiques