Water quality monitoring is used to determine the impact of human activities on the environment. We evaluated water quality in the Água Boa stream, located within the municipality of Dourados, State of Mato Grosso do Sul, Brazil, by analyzing physico-chemical, chemical, and microbiological parameters, as well as chlorophyll concentrations. Five sets of water samples were collected between December 2012 and November 2013 from three locations within the stream. The results showed the presence of Escherichia coli and antibiotic-resistant Pseudomonas spp. strains and high concentrations of organic matter (total dissolved solids), inorganic species (Mg, Ca, and Fe), and agrochemical residues (thiamethoxam). The main stream water contaminants are derived from urban, industrial, and agricultural activities within the watershed. Given the presence of contaminants, it is important that such findings are disseminated in order to highlight the risks that contact with this water may pose to human health. To preserve the environment and improve site conditions, people would need to participate by demanding that normative national and international standards be respected and that the situation be supervised by the competent governmental agencies; this would make it possible to reverse or minimize contamination problems within the Água Boa stream.

Stream water quality is controlled by the interaction of natural and anthropogenic factors over a range of temporal and spatial scales. Among these anthropogenic factors, land cover changes at catchment scale can affect stream water quality. This work aims to evaluate the influence of land use and seasonality on stream water quality in a representative tropical headwater catchment named as Córrego Água Limpa (Sao Paulo, Brasil), which is highly influenced by intensive agricultural activities and urban areas. Two systematic sampling approach campaigns were implemented with six sampling points along the stream of the headwater catchment to evaluate water quality during the rainy and dry seasons. Three replicates were collected at each sampling point in 2011. Electrical conductivity, nitrates, nitrites, sodium superoxide, Chemical Oxygen Demand (DQO), colour, turbidity, suspended solids, soluble solids and total solids were measured. Water quality parameters differed among sampling points, being lower at the headwater sampling point (0m above sea level), and then progressively higher until the last downstream sampling point (2500m above sea level). For the dry season, the mean discharge was 39.5ls⁻¹ (from April to September) whereas 113.0ls⁻¹ were averaged during the rainy season (from October to March). In addition, significant temporal and spatial differences were observed (P<0.05) for the fourteen parameters during the rainy and dry period. The study enhance significant relationships among land use and water quality and its temporal effect, showing seasonal differences between the land use and water quality connection, highlighting the importance of multiple spatial and temporal scales for understanding the impacts of human activities on catchment ecosystem services.

New explorations in the desert of northeastern Zacatecas, in central-northern Mexico, revealed dozens of archaeological and geoarchaeological sites. One of them, Ojo de Agua, contains the remains of a Pleistocene spring-fed hydrographic system located at the southeastern end of a large elongated endorheic basin. The locality yielded a particularly dark, highly organic stratigraphic layer commonly known in the Americas as Black Mat (BM), exposed on the natural profiles of a creek, but not associated with cultural materials. Several radiocarbon assessments confirmed the formation of the Ojo de Agua Black Mat during the Younger Dryas chronozone, with ten calibrated results clustering between 12,700–12,100 cal BP. This multi-proxy study confirmed the peculiarity of the deposit and found similarities and differences with other contexts of Younger Dryas age. The Ojo de Agua Black Mat (stratum C2) is far richer in charcoal specks than the related strata, but lacks phytoliths, diatoms or ostracods. No further biological remains were found in it, except for intrusive capillary roots. Clearly water-lain in a shallow pond, the stratum qualifies as a clayey silt with an acidic-to-neutral pH. Rich in heavy metals and with high contents of titanium, the Ojo de Agua Black Mat yielded significant indicators of intense wildfires during the Younger Dryas, but produced no carbon spherules or nanodiamonds supposedly linked to the impact theory.

Modelling tools are necessary for quantitative assessment of groundwater-dependent systems such as interacting groundwater aquifers and lakes. Numerical groundwater models supplemented by stream and lake submodels are the best available tools for testing the conceptual relation of surface water to groundwater, for identifying gaps in the amount and quality of data, and for better understanding the sustainability of a groundwater-lake system in the presence of stresses. Models are of particular interest when applied to an infrequently studied geological context that is subject to specific vulnerabilities and patterns of interaction. Volcanic lakes are one setting where flow models serve to extend current conceptual and practical understanding. In this study, a groundwater/surface-water flow model is presented for the flow-through Bracciano deep caldera lake located near Rome, Italy. The steady-state model quantifies and tests the existing conceptual understanding of the system by taking account of all sources and sinks, and by calibration of key parameters to head and flow data. A transient version of the model demonstrates the response of the system to dry and wet years and to anthropogenic stresses. Although precipitation is the dominant source of water overall for the lake, a major finding of this study is that the groundwater inflow to the lake can buffer fluctuations in lake-water level and reduce lake-level declines, especially during shorter periods of dry conditions.

The widely used groundwater flow model MODFLOW offers a range of software packages to simulate the interaction between streams and groundwater in aquifer systems. However, these existing packages lack a general method to address the chaotic simulation sequences of stream segments and require these segments to be ordered by modelers as input to the code. Therefore, it is challenging to simulate a stream network divided into a large number of segments such as a canal irrigation system. In this study, the Streamflow Automatic Routing (SAR) package was developed, and an effective method is proposed to automatically determine the segment simulation sequence. The stream segment order in the SAR input file is arbitrary, which allows modifications of the stream network by removing segments directly and adding segments at the end of the segment group. This mainly includes two processes: scanning all the outlet channels of the water system and calling the recursive algorithm for each outlet channel of the water system. The SAR package was tested using a hypothetical stream–aquifer system and applied to a complex flow field in Aiding Lake of Turpan Basin, China. In the results, a close fitting between the simulation and observations shows that the SAR package precisely simulated the exchange flux between the steams and aquifer. The SAR package can significantly improve the efficiency of simulations in a complex stream network, and it can be widely used as a subroutine package of MODFLOW in agricultural irrigation areas where rivers and canals are interlaced.

Understanding the response of groundwater levels in alluvial and sedimentary basin aquifers to climatic variability and human water-resource developments is a key step in many hydrogeological investigations. This study presents an analysis of groundwater response to climate variability from 2000 to 2012 in the Queensland part of the sedimentary Clarence-Moreton Basin, Australia. It contributes to the baseline hydrogeological understanding by identifying the primary groundwater flow pattern, water-level response to climate extremes, and the resulting dynamics of surface-water/groundwater interaction. Groundwater-level measurements from thousands of bores over several decades were analysed using Kriging and nonparametric trend analysis, together with a newly developed three-dimensional geological model. Groundwater-level contours suggest that groundwater flow in the shallow aquifers shows local variations in the close vicinity of streams, notwithstanding general conformance with topographic relief. The trend analysis reveals that climate variability can be quickly reflected in the shallow aquifers of the Clarence-Moreton Basin although the alluvial aquifers have a quicker rainfall response than the sedimentary bedrock formations. The Lockyer Valley alluvium represents the most sensitively responding alluvium in the area, with the highest declining (−0.7 m/year) and ascending (2.1 m/year) Sen’s slope rates during and after the drought period, respectively. Different surface-water/groundwater interaction characteristics were observed in different catchments by studying groundwater-level fluctuations along hydrogeologic cross-sections. The findings of this study lay a foundation for future water-resource management in the study area.

A simple method is proposed to visualize the magnitude of groundwater withdrawals from wells relative to user-defined water-resource metrics. The map is solely an illustration of the withdrawal magnitudes, spatially centered on wells—it is not capture zones or source areas contributing recharge to wells. Common practice is to scale the size (area) of withdrawal well symbols proportional to pumping rate. Symbols are drawn large enough to be visible, but not so large that they overlap excessively. In contrast to such graphics-based symbol sizes, the proposed method uses a depth-rate index (length per time) to visualize the well withdrawal rates by volumetrically consistent areas, called “footprints”. The area of each individual well’s footprint is the withdrawal rate divided by the depth-rate index. For example, the groundwater recharge rate could be used as a depth-rate index to show how large withdrawals are relative to that recharge. To account for the interference of nearby wells, composite footprints are computed by iterative nearest-neighbor distribution of excess withdrawals on a computational and display grid having uniform square cells. The map shows circular footprints at individual isolated wells and merged footprint areas where wells’ individual footprints overlap. Examples are presented for depth-rate indexes corresponding to recharge, to spatially variable stream baseflow (normalized by basin area), and to the average rate of water-table decline (scaled by specific yield). These depth-rate indexes are water-resource metrics, and the footprints visualize the magnitude of withdrawals relative to these metrics.

A catalog of Bacillariophyceae for the rivers of NW of Spain is made for the first time. It includes a re-examination of the taxa reported in previous publications, taxa cited during the last years of the rivers of the Galicia-Costa Hydrographic Demarcation, and a revision of the taxonomy, in line with the systematic and nomenclature changes, which have occurred mainly in recent years. The epilethic diatoms of the river basins of Galicia-Costa were sampled during the years 2005, 2006, and 2007, in May-June and September. The study was carried out in 41 localities distributed along 31 rivers, samples were taken in upstream and downstream sections. Diatom communities were compared in all upstream sections of these rivers draining from siliceous substrates. We identified 141 taxa of diatoms from the coast of Galicia. In this paper we present 15 new citations for Galicia, two for Spain and three for the Iberian Peninsula, in addition to a new species recently described. The dominant taxa are: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, and Navicula minima. Achnanthes subhudsonis was the most abundant species during the spring and summer months. The remaining species showed no relevant changes regardless of the time of year. The results indicate that the river diatoms of Galicia are an important component of the diversity of the ecosystem. | Se realiza por primera vez un catálogo de Bacillariophyceae para los ríos del NW de España. Se incluyen un nuevo examen de los táxones recogidos en publicaciones anteriores, datos de táxones citados durante los últimos años de los ríos de la demarcación hidrográfica de Galicia-Costa y una revisión de la taxonomía, en consonancia con los cambios sistemáticos y nomenclaturales, que se han producido sobre todo durante los últimos años. Se estudiaron las diatomeas epilíticas de las cuencas de los ríos de Galicia-Costa entre los años 2005, 2006 y 2007, durante dos temporadas diferentes: mayo-junio y septiembre. El estudio se llevó a cabo en 41 localidades distribuidas a lo largo de 31 ríos, donde se tomaron muestras en tramos aguas arriba y aguas abajo. Las comunidades de diatomeas de estos ríos que drenan de sustratos silíceos fueron comparadas en todos los tramos de aguas arriba. Se identificaron 141 táxones de diatomeas de la costa de Galicia. En este trabajo presentamos 15 nuevas citas para Galicia, dos para España y tres para la Península Ibérica, además de una nueva especie recientemente descrita. Los táxones dominantes son: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, y Navicula minima. Achnanthes subhudsonis fue la especie más abundante durante los meses de primavera y verano. Las especies restantes no mostraron cambios pertinentes independientemente de la época del año. Los resultados indican que las diatomeas de los ríos de Galicia son un componente importante de la diversidad del ecosistema.

In coastal-zone fields with a high groundwater level and sufficient rainfall, freshwater lenses are formed on top of saline or brackish groundwater. The fresh and the saline water meet at shallow depth, where a transition zone is found. This study investigates the mixing zone that is characterized by this salinity change, as well as by cation exchange processes, and which is forced by seepage and by rainfall which varies as a function of time. The processes are first investigated for a one-dimensional (1D) stream tube perpendicular to the interface concerning salt and major cation composition changes. The complex sequence of changes is explained with basic cation exchange theory. It is also possible to show that the sequence of changes is maintained when a two-dimensional field is considered where the upward saline seepage flows to drains. This illustrates that for cation exchange, the horizontal component (dominant for flow of water) has a small impact on the chemical changes in the vertical direction. The flow’s horizontal orientation, parallel to the interface, leads to changes in concentration that are insignificant compared with those that are found perpendicular to the interface, and are accounted for in the 1D flow tube. Near the drains, differences with the 1D considerations are visible, especially in the longer term, exceeding 100 years. The simulations are compared with field data from the Netherlands which reveal similar patterns.