The interaction between a waterproof curtain and withdrawal wells (or simply, the wall-well effect) is a key factor in controlling the environmental effects that occur during the dewatering of foundation pits. A series of laboratory investigations was conducted to study the changes in groundwater level during dewatering. The influence of the buried depth of the waterproof curtain placed in a dewatering confined aquifer (D), and the filter length of the pumping well (L), is investigated. Based on the laboratory test results, numerical simulations are used to analyse the ground settlement. The relationship between the approximate hydraulic gradients on both sides of the wall (Δi), or the ground settlement outside the excavation (S), using ratio RD (D divided by the thickness of the confined aquifer) or ratio RL (L divided by the thickness of the confined aquifer), can be simulated using a Boltzmann curve. The value of Δi increases while S decreases with an increase in RD, whereas Δi decreases while S increases with an increase in RL. The value of the contraflexure point of the Boltzmann curve is regarded as the effective value of RD or RL. Based on a comprehensive consideration, RD is suggested to be equal to or larger than the effective value, and RL is suggested to be equal to or lesser than the effective value.

Registro de la presencia del sabalote Chanos chanos (Forsskål, 1775) (Gonorynchiformes: Chanidae) en el río Shatt al-Arab/ Arvand, Basora y las aguas marinas de Irak, con notas sobre su tolerancia al agua dulce En este estudio, se describen dos especímenes de sabalote Chanos chanos (LT 380 y 390 mm) en aguas marinas de Irak y otros cuatro del río Shatt al-Arab/Arvand en la ciudad de Abu alKhaseeb, al sur de Irak (LT 310-312,5 mm). Ambas localidades significan una extensión del rango de distribución para el sabalote y la de Abu al-Khaseeb representa la distancia máxima para que esta especie ascienda por el río. Se proporcionan y comparan datos morfométricos y merísticos con especímenes de otras partes del mundo. Se incide sobre la tolerancia en hábitats dulceacuícolas a 65 km del mar. | Abstract: In the present study, two specimens of the milkfish Chanos chanos (380 and 390 mm TL) are described from the marine waters of Iraq and another four specimens from the Shatt al-Arab River at Abu alKhaseeb City, south of Iraq (310-312.5 mm TL). Both localities represent a new range extension for the milkfish, but those from Shatt al-Arab River represent the maximum distance for this species to ascend. Morphometric and meristic data are provided and compared with other specimens of this species from other parts of the world. A note is given about the tolerance to freshwater habitats about 65 km away from the sea.

The mining industry, especially coal mining, may severely affect the spatial and temporal evolution of groundwater. To provide a potential model outlining the hydrogeochemical evolution of groundwater as influenced by coal mining, a multi-layer groundwater system in a coal mining area was investigated. A total of 76 groundwater samples were collected between 1964 and 2018 for hydrogeochemical analysis from boreholes, underground tunnels, and surface pits at Xinglongzhuang Coal Mine in China. Hierarchical cluster analysis and principal component analysis were used to classify four significant groundwater zones and two principal components. The results showed that mining may have caused the rock strata to sink, obstructing the path linking the Permian and lower Quaternary aquifers, and resulting in intensified ion exchange in the lower Quaternary aquifer. The concentrations of Na⁺ and Ca²⁺ in the groundwater from the lower Quaternary aquifer changed over the studied period (~54 years). The gradual increase of Na⁺ and decrease of Ca²⁺ concentration verified the action of cation exchange. The four main aquifers had relatively independent hydrogeochemistry, suggesting that the hydraulic conductivity of the natural faults is weak and the sealing properties of hydrogeological drill holes in the coal field are good. Analysis of 26 heavy metals in the mine drainage water showed that there is only minor pollution after the water has been simply treated. These data analysis methods and results could be useful in areas with long-term mining to interpret the evolution of groundwater and to promote groundwater quality management.

The temporal and spatial monitoring of groundwater levels is among the most widely used techniques for understanding groundwater reserves, which is essential for the management of regions with drought-related issues. Between 2010 and 2017, the Brazilian semi-arid region suffered a severe drought, presenting intensity and societal impacts undetected in decades. This research aimed to understand how Gravity Recovery and Climate Experiment (GRACE) data can be used as a tool for monitoring groundwater reserves in one of the most important aquifers in the Araripe Sedimentary Basin (Middle Aquifer System), located in a developing region with scarce amounts of data, and where 84,000,000 m³ of groundwater is abstracted annually through pumping. Groundwater storage (GWS) in-situ data were related to GWS estimates based on a combination of GRACE-based terrestrial water storage (TWS with both mascon and spherical harmonic solutions) and Global Land Data Assimilation System (GLDAS) soil moisture (CLM, MOS, NOAH and VIC models were evaluated). Results were analyzed with Nash-Sutcliffe (NS) and Pearson correlation coefficient metrics, and showed that the GWS GRACE-based estimate using the Community Land Model (CLM) land-surface model was more suitable for representing aquifer storage variations. Seven wells (58%) demonstrated a NS > 0.50 for both GWS GRACE-based solutions. In conclusion, GWS GRACE-based methodology has potential for monitoring the 1,394-km² outcrop area of the Middle Aquifer System.

VDFST-CFP (variable-density flow and solute transport–conduit flow process) is a density-dependent discrete-continuum numerical model for simulating seawater intrusion in a dual-permeability coastal karst aquifer. A previous study (Xu and Hu 2017) simulates variable-density flow only in a single conduit, and studies the parameter sensitivities only in the horizontal case (2D domain as horizontal section) by the VDFST-CFP model. This paper focuses on the density-dependent vertical case (2D domain as vertical section) with two major improvements: 1) when implementing double-conduit networks in the domain, simulated intruded plumes in the porous medium are extended in the double-conduit scenario, compared to the single-conduit system; 2) by quantifying micro-textures on the conduit wall by the Goudar-Sonnad equation and considering macro-structures as local head loss. Sensitivity analysis shows that medium hydraulic conductivity, conduit diameter and effective porosity are important parameters for simulating seawater intrusion in the discrete-continuum system. On the other hand, rougher micro-structures and additional macro-structure components on the conduit wall would reduce the distance of seawater intrusion to the conduit system, but, rarely affect salinity distribution in the matrix. Compared to the equivalent mean roughness height, the new method (with more detailed description of structure) simulates seawater intrusion slightly landward in the conduit system. The macro-structure measured by local head loss is more reasonable but needs further study on conduit flow. Xu and Hu (2017) Development of a discrete-continuum VDFST-CFP numerical model for simulating seawater intrusion to a coastal karst aquifer with a conduit system. Water Resources Research: 53, 688-711.

Las subcuencas del río Maravilla-Chiz y Quebrada Honda, localizadas en la región oriental del área metropolitana de Costa Rica, tienen una superficie aproximada de 46,8 km2, donde la principal actividad económica es la producción tanto agrícola como pecuaria y su población se abastece de fuentes de agua subterránea. El objetivo de la investigación fue determinar la amenaza de contaminación del agua subterránea, mediante la evaluación del estado de las áreas de protección en manantiales de público. Para eso, se tomaron en cuenta las fuentes potenciales de contaminación puntuales, lineales y difusas, así como se clasificaron, según la metodología POSH, por sus siglas en inglés (Pollutant Origin Surcharge Hydraulically). El área protegida correspondió a un radio de 200 m alrededor de las nacientes (Ley 276, Costa Rica). Los resultados identificaron que un 7 % del área presentó fuentes difusas con un potencial generador de carga contaminante elevado, debido a las grandes cantidades de plaguicidas aplicados en hortalizas y verduras, mientras que un 55 % presentó un potencial moderado, en parcelas de caña, café y ocupación urbana carente de alcantarillado sanitario. De las fuentes puntuales encontradas, la mitad se clasificó con potencial elevado y 46 % con moderado. De los 252 km lineales, correspondientes a ríos, red vial y poliducto, 89 % fue de potencial moderado, 10 % elevado y 1 % reducido. Finalmente, se constató la invasión de fuentes lineales y difusas en las áreas de protección de los manantiales; por ello, al gobierno local se le recomienda establecer un procedimiento legal para atender el problema. | The sub-basins of the Maravilla-Chiz and Quebrada Honda Rivers have an approximate area of 46.8 km2 and are located in the eastern part of the Costa Rican metropolitan area, where agricultural and livestock productions are the main economic activity. The sub-basins supply the populations nearby with groundwater sources. The objective of the paper was to determine the possible groundwater contamination by assessing the state of the protection areas of springs used for public water supply. For such purposes, potential point, line, and diffuse sources of contamination were considered and classified according to the POSH (Pollutant Origin and its Surcharge Hydraulically) method. The protected area corresponded to a 200 m radius around the headwaters (Costa Rican Law 276). Results identified that 7% of the area showed diffuse sources of high potential generating pollutant load, due to the large quantities of pesticides used in greens and vegetables, while 55% presented a moderate potential in plots of sugarcane, coffee, and urban areas with no sanitary sewer. Half of the point sources found were classified as a high potential and 46% as moderate. Of the 252 line-kilometers corresponding to rivers, road network, and pipeline, 89% was classified as moderate potential, 10% as high, and 1% as reduced. Finally, the invasion of line and diffuse sources in the spring protection areas was confirmed; therefore, the local government is recommended to start a legal procedure to address the problem. | As sub-bacias do rio Maravilha-Chiz e Quebrada Honda Rio, localizadas na região oriental da área metropolitana da Costa Rica, possui uma superfície de aproximadamente 46,8 km2, onde a principal atividade econômica é a produção tanto agricultura quanto pecuária, e sua população é abastecida pelas fontes de água subterrânea. O objetivo da pesquisa foi determinar a ameaça de contaminação da água subterrânea, através da avaliação do estado das áreas de proteção em nascentes de abastecimento público. Para tanto, foram consideradas as fontes potenciais de contaminação pontuais, lineares e difusas, como também classificadas de acordo com a metodologia POSH (Pollutant Origin Surcharge Hydraulically). A área protegida correspondeu a um raio de 200 m ao redor das nascentes (Lei 276, Costa Rica). Os resultados identificaram que 7% da área apresentou fontes difusas com um potencial gerador de alta carga de poluição devido às grandes quantidades de pesticidas aplicados em legumes e verduras, enquanto 55% apresentou um potencial moderado, em parcelas de cana, café e ocupação urbana carente de esgoto sanitário. Das fontes pontuais encontradas, metade foi classificada com alto potencial e 46% com moderada. Dos 252 km lineares, correspondentes a rios, rede viária e oleoduto, 89% foram de potencial moderado, 10% alto e 1% reduzido. Por fim, confirmou-se a invasão de fontes lineares e difusas nas áreas de proteção das nascentes; portanto, recomenda-se que o governo local que estabeleça um procedimento legal para resolver o problema. | Universidad Nacional, Costa Rica | Escuela de Ciencias Biológicas

Groundwater vulnerability maps can be combined with pollution hazards to assess risks of groundwater pollution. However, groundwater vulnerability maps are generally difficult to interpret because they differ according to the factors considered and the way they are combined. Here, starting from process-based concepts and criteria, a robust definition for groundwater vulnerability to pollution is discussed. A methodology is developed based on processes governing the fate of pollutants at the land surface (i.e. runoff and infiltration) and below ground (i.e. pollutant transport in the subsurface). Groundwater vulnerability is evaluated based on combination of the land surface hazard and the subsurface attenuation capacity. Land surface hazard is defined to consider direct and lateral infiltration capacity of pollutants, regardless of any subsurface attenuation capacity, which refers to any process that leads to pollutant mass reduction from the infiltration location to the water table. The concept of subsurface attenuation capacity is adapted to the case of groundwater intrinsic vulnerability assessment, considering three process-based vulnerability coefficients, which are the pollutant minimum travel time from the hazard location to the water table, the pollution duration at the water table, and the maximum concentration of pollutant discharging into the groundwater. The concepts are illustrated by applying the developed method (named APSÛ) for intrinsic groundwater vulnerability assessment in the Néblon catchment, a karstified limestone/sandstone aquifer system in Belgium. The APSÛ method results are discussed and the perspectives for generalizing the method to groundwater-specific vulnerability and risk mapping are presented.

The Sustainable Groundwater Management Act (SGMA) enacted in California (USA) outlines legal standards to regulate groundwater management. A key requirement of SGMA is local-scale adaptive management, which requires evaluation of measurable objectives defined by local water users. The objective of this study is to illustrate a groundwater sustainability framework using performance indicators and groundwater-level elevation records that may be used to quantify objective management strategy outcomes. Application of the framework to groundwater basins in the Central Valley identified spatial variability in groundwater-basin sustainability indices, attributed to complex interactions between climate and groundwater use. Further, a temporal assessment of performance indicators documented the utility of the framework to evaluate the performance of adaptive management implementations. The proposed framework can be used to inform management decisions and identify future intervention management strategies.

A procedure is presented for valuation of information analysis (VOIA) to determine the need for additional information when assessing the effect of several design alternatives to manage future disturbances in hydrogeological systems. When planning for groundwater extraction and drawdown in areas where risks—such as land subsidence, wells running dry and drainage of streams and wetlands—are present, the need for risk-reducing safety measures must be carefully evaluated and managed. The heterogeneity of the subsurface calls for an assessment of trade-offs between the benefits of additional information to reduce the risk of erroneous decisions and the cost of collecting this information. A method is suggested that combines existing procedures for inverse probabilistic groundwater modelling with a novel method for VOIA. The method results in (1) a prior analysis where uncertainties regarding the efficiency of safety measures are estimated, and (2) a pre-posterior analysis, where the benefits of expected uncertainty reduction deriving from additional information are compared with the costs for obtaining this information. In comparison with existing approaches for VOIA, the method can assess multiple design alternatives, use hydrogeological parameters as proxies for failure, and produce spatially distributed VOIA maps. The method is demonstrated for a case study of a planned tunnel in Stockholm, Sweden, where additional investigations produce a low number of benefits as a result of low failure rates for the studied alternatives and a cause-effect chain where the resulting failure probability is more dependent on interactions within the whole system rather than on specific features.