For the correct distribution of vegetation in an area, it is essential to manage accurate information on the variables that condition information. Most likely, the parameter that determines further the type of vegetation that can grow in one place is the amount of water available to plants. In this sense, and leaving aside the formations linked to watercourses, lakes, etc., the main source of this resource is the rain. Thus, the study of the distribution of vegetation in any territory is closely related to the analysis of rainfall it receives. To know the amount of rainwater that receives a zone always uses data provided by meteorological stations located in the same. The data collected by these stations are applied to a hypothetical, uniform and flat surface. This information is accurate enough when the scale at which it works is small (1: 100,000, 1: 50,000), but when it requires greater detail, especially in arid areas where the vegetation structure is open and the soil directly receives much of the rainfall, soil conditions exist that determine the distribution of rainwater and therefore access to this resource plants.Two of these variables, perhaps the most important are the inclination and the presence of rocky outcrops or stoniness on the floor. In short, our job is to propose different mathematical models that allow to know the actual amount of water available to plants, we call A. This value is obtained from rainfall data (P), relating to the sloping terrain and the percentage of it occupied by rocks (af). The relationship  between precipitation and tilt gives us a value we call the real precipitation (P'), which is lower the greater the inclination, since the amount of rainfall should be distributed over a larger area. The amount of rocky outcrop increases runoff, accumulating water in the earthy areas between the rocks, so a higher percentage of stoniness in soil involves an accumulation of water in the surrounding soil. Thus a model that allows both better explain the distribution of vegetation in arid areas and on large scales (: 25.000 or higher 1) is provided.To test the model and test its usefulness, it has made a study of it in different localities in arid areas of the island of Gran Canaria, one of the Canary Islands. On this island 14 towns located in arid environments, with precipitation always less than 200 mm/m2 were chosen. Among these locations, with similar climatic conditions, there is a very important plant diversity. Most are occupied by a crasicaule very open scrub dominated by Euphorbia balsamífera, called tabaibal de tabaiba dulce, typical of the most barren areas of the Canary Islands, and considered the potential of its arid and hyper-arid vegetation areas. But other situations are occupied by a lush vegetation: the cardonal, almost totally enclosed high scrub, dominated by Euphorbia canariensis, the cardón; and even formations characterized by the presence of a undertree thicket where different woody species such as Olea cerasiformis, wild olive, Juniperus turbinata subsp. canariensis, the sabina, and even the Canary Island pine, Pinus canariensis. These same plant formations appear as potential in areas with higher rainfall, so its presence in these arid areas should be related to some variable affecting the distribution of water resources.For each of these locations was made calculating the amount of water available to plants, obtaining results that meet the alleged contradiction to find different types of vegetation, with different water requirements in the same climatic zone. Thus it is improving the proposed model provides when it comes to study how vegetation is distributed in arid and territories detail scale is checked. It is clear that as we decrease the scale of the study of the distribution of vegetation in any territory, it is essential to increase the parameters analyzed, especially if it comes to analyzing the situation of vegetation in arid, where the structure of vegetation and seasonality of rainfall make the characteristics of the substrate affect significantly to the presence of vegetation way. Given the scarcity of water resources in these ecosystems, any aspect influencing the availability of water for plants will be of great importance for understanding distribution. | Para conocer la correcta distribución de la vegetación en un territorio, es fundamental manejar información precisa sobre las variables que la condicionan. Muy probablemente, el parámetro que condiciona en mayor medida el tipo de vegetación que puede crecer en un lugar es la cantidad de agua de que disponen las plantas. En este sentido, y dejando a un lado las formaciones ligadas a cursos de agua, lagos, etc., el principal origen de este recurso es la lluvia. De esta manera, el estudio de la distribución de la vegetación en cualquier territorio está muy relacionado con el análisis de las precipitaciones que recibe. Para conocer la cantidad de agua de lluvia que recibe una zona se recurre siempre a los datos aportados por las estaciones meteorológicas situadas en la misma. Los datos recogidos por estas estaciones se aplican a una superficie hipotética, homogénea y plana. Esta información es suficientemente precisa cuando la escala a la que se trabaja es pequeña (1:100.000; 1:50.000), pero cuando se precisa de un mayor detalle, sobre todo en territorios áridos, donde la estructura de la vegetación es abierta y el suelo recibe directamente gran parte de la precipitación, existen condiciones del terreno que condicionan el reparto del agua de lluvia y por tanto el acceso de las plantas a este recurso. Dos de estas variables, quizá las más importantes son la inclinación y la presencia de afloramientos rocosos o de pedregosidad en el suelo.En definitiva, nuestro trabajo consiste en proponer diferentes modelos matemáticos que posibiliten conocer la cantidad real de agua de que disponen las plantas, que denominamos A. Este valor se obtiene a partir de los datos pluviométricos (P), relacionándolos con la inclinación del terreno y el porcentaje del mismo ocupado por rocas (af). La relación entre la precipitación y la inclinación nos proporciona un valor que denominamos precipitación real (P´), que es menor cuanto mayor es la inclinación, ya que la cantidad de agua caída debe repartirse en una superficie mayor. La cantidad de afloramiento rocoso aumenta la escorrentía, acumulando agua en las zonas terrosas situadas entre las rocas, por lo que un mayor porcentaje de pedregosidad en el suelo conlleva una acumulación de agua en el suelo que lo rodea. De esta manera se proporciona un modelo que permite tanto explicar mejor la distribución de la vegetación en zonas áridas y a escalas grandes (1:25.000 o mayores).Para contrastar el modelo y comprobar su utilidad, se ha realizado un estudio del mismo en diferentes localidades situadas en territorios áridos de la isla de Gran Canaria, una de las Islas Canarias. En esta isla se escogieron 14 localidades situadas en ambientes áridos, con precipitaciones siempre inferiores a 200 mm/m2. Entre estas localidades, de condiciones climáticas similares, existe una diversidad vegetal muy importante. La mayor parte están ocupadas por un matorral crasicaule muy abierto dominado por Euphorbia balsamifera, denominado tabaibal de tabaiba dulce, propio de las zonas más desérticas del Archipiélago Canario, y considerado la vegetación potencial de sus zonas áridas e hiperáridas. Pero otras situaciones están ocupadas por una vegetación más exuberante: el cardonal, matorral alto casi totalmente cerrado, dominado por Euphorbia canariensis, el cardón; e incluso por formaciones caracterizadas por la presencia de un matorral subarbóreo donde están presentes diferentes especies leñosas como Olea cerasiformis, el acebuche, Juniperus turbinata subsp. canariensis, la sabina, e incluso el pino canario, Pinus canariensis. Estas mismas formaciones vegetales aparecen como potenciales en lugares con mayor precipitación, por lo que su presencia en estas zonas áridas debe estar relacionado con alguna variable que afecte a la distribución del recurso hídrico.Para cada una de estas localidades se ha realizado el cálculo de la cantidad de agua disponible para las plantas, obteniéndose unos resultados que resuelven la presunta contradicción de encontrar diferentes tipos de vegetación, con requerimientos hídricos diferentes, en una misma zona climática. De esta manera se comprueba la mejora que el modelo propuesto ofrece cuando se trata de estudiar cómo se reparte la vegetación en territorios áridos y a escala de detalle. Queda claro que, a medida que disminuimos la escala del estudio de la distribución de la vegetación en cualquier territorio, es imprescindible aumentar los parámetros analizados, más aún si se trata de analizar la situación de las formaciones vegetales de zonas áridas, donde la estructura de la vegetación y la temporalidad de las precipitaciones hacen que las características del sustrato afecten de manera importante a la presencia de la vegetación. Dada la escasez del recurso hídrico en estos ecosistemas, cualquier aspecto que influya en la disponibilidad del recurso para las plantas será de gran importancia para comprender su distribución.

Flowing fluid electrical conductivity (FFEC) logging is a hydrogeologic testing method that is usually conducted in an existing borehole. However, for the 2,500-m deep COSC-1 borehole, drilled at Åre, central Sweden, it was done within the drilling period during a scheduled 1-day break, thus having a negligible impact on the drilling schedule, yet providing important information on depths of hydraulically conductive zones and their transmissivities and salinities. This paper presents a reanalysis of this set of data together with a new FFEC logging data set obtained soon after drilling was completed, also over a period of 1 day, but with a different pumping rate and water-level drawdown. Their joint analysis not only results in better estimates of transmissivity and salinity in the conducting fractures intercepted by the borehole, but also yields the hydraulic head values of these fractures, an important piece of information for the understanding of hydraulic structure of the subsurface. Two additional FFEC logging tests were done about 1 year later, and are used to confirm and refine this analysis. Results show that from 250 to 2,000 m depths, there are seven distinct hydraulically conductive zones with different hydraulic heads and low transmissivity values. For the final test, conducted with a much smaller water-level drawdown, inflow ceased from some of the conductive zones, confirming that their hydraulic heads are below the hydraulic head measured in the wellbore under non-pumped conditions. The challenges accompanying 1-day FFEC logging are summarized, along with lessons learned in addressing them.

Two case studies were carried out in central Norway in order to assess the performance of bank filtration systems in cold-climate fluvial aquifers relying on recharge from humic-rich surface waters with moderate microbial contamination. Three municipal wells and two surface-water sources at operative bank filtration systems were monitored for naturally occurring bacteriophages, fecal indicators, natural organic matter (NOM) and physico-chemical water quality parameters during a 4-month period. Aquifer passage effectively reduced the microorganism and NOM concentrations at both study sites. Bacteriophages were detected in 13 of 16 (81%) surface-water samples and in 4 of 24 (17%) well-water samples, and underwent 3 ± 0.3 log₁₀ reduction after 50–80-m filtration and 20–30 days of subsurface passage. NOM reductions (color: 74–97%; dissolved organic carbon: 54–80%; very hydrophobic acids: 70%) were similar to those achieved by conventional water-treatment processes and no further treatment was needed. Both groundwater dilution and sediment filtration contributed to the hygienic water quality improvements, but sediment filtration appeared to be the most important process with regard to microbial and NOM reductions. A strengths-weaknesses-opportunities-threats analysis showed that bank filtration technology has a high potential as a pretreatment method for the provision of hygienically safe drinking water in Norway.

Past discussions around water-resources management and development in the River Nile basin disregard groundwater resources from the equation. There is an increasing interest around factoring the groundwater resources as an integral part of the Nile Basin water resources. This is hampered by knowledge gap regarding the groundwater resources dynamics (recharge, storage, flow, quality, surface-water/groundwater interaction) at basin scale. This report provides a comprehensive analysis of the state of surface-water/groundwater interaction from the headwater to the Nile Delta region. Piezometric and isotopic (δ¹⁸O, δ²H) evidence reveal that the Nile changes from a gaining stream in the headwater regions to mostly a loosing stream in the arid lowlands of Sudan and Egypt. Specific zones of Nile water leakage to the adjacent aquifers is mapped using the two sources of evidence. Up to 50% of the surface-water flow in the equatorial region of the Nile comes from groundwater as base flow. The evidence also shows that the natural direction and rate of surface-water/groundwater interaction is largely perturbed by human activities (diversion, dam construction) particularly downstream of the Aswan High Dam in Egypt. The decrease in discharge of the Nile River along its course is attributed to leakage to the aquifers as well as to evaporative water loss from the river channel. The surface-water/groundwater interaction occurring along the Nile River and its sensitivity to infrastructure development calls for management strategies that account groundwater as an integral part of the Nile Basin resources.

The classical aquitard-drainage model COMPAC has been modified to simulate the compaction process of a heterogeneous aquitard consisting of multiple sub-units (Multi-COMPAC). By coupling Multi-COMPAC with the parameter estimation code PEST++, the vertical hydraulic conductivity (K ᵥ) and elastic (S ₛₖₑ) and inelastic (S ₛₖₚ) skeletal specific-storage values of each sub-unit can be estimated using observed long-term multi-extensometer and groundwater level data. The approach was first tested through a synthetic case with known parameters. Results of the synthetic case revealed that it was possible to accurately estimate the three parameters for each sub-unit. Next, the methodology was applied to a field site located in Changzhou city, China. Based on the detailed stratigraphic information and extensometer data, the aquitard of interest was subdivided into three sub-units. Parameters K ᵥ, S ₛₖₑ and S ₛₖₚ of each sub-unit were estimated simultaneously and then were compared with laboratory results and with bulk values and geologic data from previous studies, demonstrating the reliability of parameter estimates. Estimated S ₛₖₚ values ranged within the magnitude of 10⁻⁴ m⁻¹, while K ᵥ ranged over 10⁻¹⁰–10⁻⁸ m/s, suggesting moderately high heterogeneity of the aquitard. However, the elastic deformation of the third sub-unit, consisting of soft plastic silty clay, is masked by delayed drainage, and the inverse procedure leads to large uncertainty in the S ₛₖₑ estimate for this sub-unit.

Over-exploited groundwater is expected to remain the predominant source of domestic water in suburban areas of Hanoi, Vietnam. In order to evaluate the effect on groundwater recharge, of decreasing surface-water bodies and land-use change caused by urbanization, the relevant groundwater systems and recharge pathways must be characterized in detail. To this end, water levels and water quality were monitored for 3 years regarding groundwater and adjacent surface-water bodies, at two typical suburban sites in Hanoi. Stable isotope (δ¹⁸O, δD of water) analysis and hydrochemical analysis showed that the water from both aquifers and aquitards, including the groundwater obtained from both the monitoring wells and the neighboring household tubewells, was largely derived from evaporation-affected surface-water bodies (e.g., ponds, irrigated farmlands) rather than from rivers. The water-level monitoring results suggested distinct local-scale flow systems for both a Holocene unconfined aquifer (HUA) and Pleistocene confined aquifer (PCA). That is, in the case of the HUA, lateral recharge through the aquifer from neighboring ponds and/or irrigated farmlands appeared to be dominant, rather than recharge by vertical rainwater infiltration. In the case of the PCA, recharge by the above-lying HUA, through areas where the aquitard separating the two aquifers was relatively thin or nonexistent, was suggested. As the decrease in the local surface-water bodies will likely reduce the groundwater recharge, maintaining and enhancing this recharge (through preservation of the surface-water bodies) is considered as essential for the sustainable use of groundwater in the area.

The groundwater abstracted at a well field near the Yamuna River in Central Delhi, India, has elevated ammonium (NH₄ ⁺) concentrations up to 35 mg/L and arsenic (As) concentrations up to 0.146 mg/L, constituting a problem with the provision of safe drinking and irrigation water. Infiltrating sewage-contaminated river water is the primary source of the NH₄ ⁺ contamination in the aquifer, leading to reducing conditions which probably trigger the release of geogenic As. These conclusions are based on the evaluation of six 8–27-m deep drillings, and 13 surface-water and 69 groundwater samples collected during seven field campaigns (2012–2013). Results indicate that losing stream conditions prevail and the river water infiltrates into the shallow floodplain aquifer (up to 16 m thickness), which consists of a 1–2-m thick layer of calcareous nodules (locally known as kankar) overlain by medium sand. Because of its higher hydraulic conductivity (3.7 × 10⁻³ m/s, as opposed to 3.5 × 10⁻⁴ m/s in the sand), the kankar layer serves as the main pathway for the infiltrating water. However, the NH₄ ⁺ plume front advances more rapidly in the sand layer because of its significantly lower cation exchange capacity. Elevated As concentrations were only observed within the NH₄ ⁺ plume indicating a causal connection with the infiltrating reducing river water.

Wells along two regional flow paths were sampled to characterize changes in water quality and the vulnerability to contamination of the Memphis aquifer across a range of hydrologic and land-use conditions in the southeastern United States. The flow paths begin in the aquifer outcrop area and end at public supply wells in the confined parts of the aquifer at Memphis, Tennessee. Age-date tracer (e.g. SF₆, ³H, ¹⁴C) data indicate that a component of young water is present in the aquifer at most locations along both flow paths, which is consistent with previous studies at Memphis that documented leakage of shallow water into the Memphis aquifer locally where the overlying confining unit is thin or absent. Mixtures of young and old water were most prevalent where long-term pumping for public supply has lowered groundwater levels and induced downward movement of young water. The occurrence of nitrate, chloride and synthetic organic compounds was correlated to the fraction of young water along the flow paths. Oxic conditions persisted for 10 km or more down dip of the confining unit, and the presence of young water in confined parts of the aquifer suggest that contaminants such as nitrate-N have the potential for transport. Long-term monitoring data for one of the flow-path wells screened in the confined part of the aquifer suggest that the vulnerability of the aquifer as indicated by the fraction of young water is increasing over time.

Groundwater quality is often evaluated using microbial indicators. This study examines data from 12 international groundwater studies (conducted 1992–2013) of 718 public drinking-water systems located in a range of hydrogeological settings. Focus was on testing the value of indicator organisms for identifying virus-contaminated wells. One or more indicators and viruses were present in 37 and 15% of 2,273 samples and 44 and 27% of 746 wells, respectively. Escherichia coli (E. coli) and somatic coliphage are 7–9 times more likely to be associated with culturable virus-positive samples when the indicator is present versus when it is absent, while F-specific and somatic coliphages are 8–9 times more likely to be associated with culturable virus-positive wells. However, single indicators are only marginally associated with viruses detected by molecular methods, and all microbial indicators have low sensitivity and positive predictive values for virus occurrence, whether by culturable or molecular assays, i.e., indicators are often absent when viruses are present and the indicators have a high false-positive rate. Wells were divided into three susceptibility subsets based on presence of (1) total coliform bacteria or (2) multiple indicators, or (3) location of wells in karst, fractured bedrock, or gravel/cobble settings. Better associations of some indicators with viruses were observed for (1) and (3). Findings indicate the best indicators are E. coli or somatic coliphage, although both indicators may underestimate virus occurrence. Repeat sampling for indicators improves evaluation of the potential for viral contamination in a well.