Groundwater In Catchments Research Articles

The importance of atmospheric base cation deposition for preventing soil acidification in the Athabasca Oil Sands Region of Canada

Industrial activities in the oil sands region of Alberta, Canada have resulted in greatly elevated emissions of SO2 and N (NOx and NH3) and there are concerns over possible widespread ecosystem acidification. Acid sensitive soils in the region are common and have very low base cation weathering rates: the median base cation weathering rate estimated for 63 sites using PROFILE was just 17mmolcm−2yr−1. Deposition of S and N in throughfall was approximately twice as high as deposition measured with open collectors and could be as high as 360mmolcm−2yr−1 within 20km of the main industrial center, although deposition declined logarithmically with distance from the industrial activities. Base cation deposition however, mostly exceeded the combined inputs of S and N in bulk deposition and throughfall, particularly during the summer months. The potential for soil acidification at a site close (<3km) to the largest mine was assessed using the dynamic ecosystem acidification model, MAGIC (Model of Acidification of Groundwater in Catchments). Despite very low base cation weathering rates (~6mmolcm−2yr−1) and high (~250mmolcm−2yr−1) acid (S+N) deposition at the site, soil base saturation and soil solution pH and molar Ca:Al ratio were predicted to increase in the future assuming acid and base cation deposition constant at current rates. This work shows that despite extremely low soil base cation weathering rates in the region, the risk of soil acidification is mitigated to a large extent by high base cation deposition, which in contrast to S emissions is derived from fugitive dust sources in the mines, and is poorly quantified for regional modeling studies.

Risk-based prioritization of ground water threatening point sources at catchment and regional scales

Contaminated sites threaten ground water resources all over the world. The available resources for investigation and remediation are limited compared to the scope of the problem, so prioritization is crucial to ensure that resources are allocated to the sites posing the greatest risk.A flexible framework has been developed to enable a systematic and transparent risk assessment and prioritization of contaminant point sources, considering the local, catchment, or regional scales (Danish EPA, 2011, 2012).The framework has been tested in several catchments in Denmark with different challenges and needs, and two of these are presented.Based on the lessons learned, the Danish EPA has prepared a handbook to guide the user through the steps in a risk-based prioritization (Danish EPA, 2012). It provides guidance on prioritization both in an administratively defined area such as a Danish Region, and within the bounds of a specified ground water catchment. The handbook presents several approaches in order to prevent the prioritization from foundering because of a lack of data or an inappropriate level of complexity. The developed prioritization tools, possible graphical presentation and use of the results are presented using the case studies as examples.The methodology was developed by a broad industry group including the Danish EPA, the Danish Regions, the Danish Nature Agency, the Technical University of Denmark, and consultants — and the framework has been widely accepted by the professional community in Denmark. The concepts are quite general and can be applied in other countries facing similar challenges.

Modelling pesticide transport in a shallow groundwater catchment using tritium and helium-3 data

Using tritium and helium-3 data for calibration, a 2-D transport model was set up to explain the occurrence of bentazone, dichlorprop, glyphosate, isoproturon, MCPA and metamitron in a small groundwater catchment in southern Sweden. The model was parameterised with site-specific degradation and sorption data to enable transport simulations. Local climatological data and a 21-year record of agricultural pesticide use within the study area were used as boundary conditions. Model output was evaluated against a 7-year long pesticide monitoring data-series from two monitoring wells within the study area. The model successfully predicts observed breakthrough of bentazone, dichlorprop, isoproturon and MCPA. However, it fails to simulate observed occurrences of glyphosate and metamitron. Glyphosate and metamitron exhibit relatively high sorption potential, and their occurrence is suggested to be the result of non-equilibrium preferential flow paths which the model cannot reproduce due the conceptualisation of the system as homogenous and isotropic. The results indicate a promising methodological approach applicable to groundwater contamination risk assessment, and demonstrate the potential for transport model calibration by means of tritium and helium-3 data. Main constraints of the study relate to the relatively simple system conceptualisation, indicating a need for further consideration of physical and chemical heterogeneity.

Recently induced anoxia leading to the preservation of seasonal laminae in two NE-German lakes

The recent sediments of two lakes in the NE German lowland became seasonally laminated at different times. Anoxic bottom conditions resulted from a surplus of organic matter (OM), in the early stage indicated by irregularly laminated sediments comprising abundant iron-sulfide framboids. Their diagenetic formation predates the preservation of biochemical calcite varves. In the larger, deeper Lake Tiefer See near Klocksin, anoxia developed stepwise. A first anoxic pulse was contemporary with inflow narrowing by railway-dam construction and accumulation of OM. It was favored by a decrease of the intensity of lake circulation (turnover). Nutrients introduced from artificial fertilizer then increased the primary production (diatoms) to the point of OM surplus and seasonal laminae formation started 40 years later in 1924. In the smaller, shallower Lake Tiefer See in the Uckermark, a massive pulse of iron sulfide was centered around 1960, seven years after installation of piped field drainage into the lake. Anoxia developed rapidly with the nutrients drained from a fertilized groundwater catchment that is 10 times larger than the surface catchment, while surface erosion was reduced. Reducing bottom conditions became regular and the seasonal lamination was preserved after 1967. Morphological criteria to screen lakes for varved sediments should include reductions of natural lake inflow and catchment increase, such as by inflow of field drainage. Similar developments of increased nutrient input or intensity decrease of lake circulation may result from historical human activities but also from natural processes.

Effects of Climate, Land Management, and Sulfur Deposition on Soil Base Cation Supply in National Forests of the Southern Appalachian Mountains

Forest soils having low exchangeable calcium (Ca) and other nutrient base cation (BC) reserves may induce nutrient deficiencies in acid-sensitive plants and impact commercially important tree species. Past and future depletion of soil BC in response to acidic sulfur (S) deposition, forest management, and climate change alter the health and productivity of forest trees. This study used a process model (Model of Acidification of Groundwater in Catchments [MAGIC]) to address a number of questions related to soil BC status for a group of 65 streams and their watersheds in the southern Blue Ridge physiographic province of the southern Appalachian Mountains. Future S deposition to the study watersheds used for the Base Scenario was specified according to proposed reductions in S emissions at the time of this study, representing a reduction of 42 % of ambient S deposition by 2020. Twenty additional simulations were considered, reflecting four alternate S deposition scenarios (6 %, 58 %, 65 %, and 78 % reduction), and various changes in timber harvest, temperature, and precipitation. Base Scenario soil exchangeable Ca and % base saturation showed decreasing trends from 1860 to 2100. Changes in tree harvesting had the largest effect on stream sum of base cations (SBC) and soil BC supply. Each of the scenario projections indicated that median year 2100 soil exchangeable Ca will be at least 20 % lower than pre-industrial values. The simulations suggested that substantial mass loss of soil BC has already occurred since pre-industrial times. Nearly the same magnitude of BC loss is expected to occur over the next 145 years, even under relatively large additional future reductions in S deposition.

Neotectonic belts, remote sensing and groundwater potentials in the Eastern Cape Province, South Africa

The Eastern Cape Province is surrounded by three major neotectonic belts (south, east and north). Each one of these neotectonic belts has its own particularities. This study aims at characterizing and targeting potentially high yield aquifers in the neotectonic zones in the Eastern Cape Province. The methods used in this study include a comprehensive literature review, examination of digital elevation models and extraction of lineaments through remote sensing. The results indicate the following: 1) the eastern neotectonic belt has a higher density of lineaments oriented NW-SE, which makes it the second important neotectonic belt; these lineaments correlate with the normalized difference vegetation index indicative of a good circulation of groundwater; 2) the surface topography is not uniform, high elevations in the east are related to the uplift that took place in the Quaternary, most vector gradients are oriented E-W; 3) in the south the Eastern Cape great lineament oriented E-W is now considered a neotectonic domain because of many seismic epicenters that occur therein, its geomorphologic shape in a graben type form is a favourable structure for groundwater catchment. This project has given fundemental highlights to characterize the major and potential good yield aquifers in the Eastern Cape Province in south Africa. Key words: Neotectonics, groundwater, lineament, remote sensing, hot spring, uplift.

Life-cycle and freshwater withdrawal impact assessment of water supply technologies

Four alternative cases for water supply were environmentally evaluated and compared based on the standard environmental impact categories from the life-cycle assessment (LCA) methodology extended with a freshwater withdrawal category (FWI). The cases were designed for Copenhagen, a part of Denmark with high population density and relatively low available water resources. FWI was applied at local groundwater catchments based on data from the national implementation of the EU Water Framework Directive. The base case of the study was the current practice of groundwater abstraction from well fields situated near Copenhagen. The 4 cases studied were: Rain & stormwater harvesting from several blocks in the city; Today's groundwater abstraction with compensating actions applied in the affected freshwater environments to ensure sufficient water flow in water courses; Establishment of well fields further away from the city; And seawater desalination. The standard LCA showed that the Rain & stormwater harvesting case had the lowest overall environmental impact (81.9 μPET/m3) followed by the cases relying on groundwater abstraction (123.5–137.8 μPET/m3), and that desalination had a relatively small but still important increase in environmental impact (204.8 μPET/m3). Rain & stormwater harvesting and desalination had a markedly lower environmental impact compared to the base case, due to the reduced water hardness leading to e.g. a decrease in electricity consumption in households. For a relevant comparison, it is therefore essential to include the effects of water hardness when comparing the environmental impacts of water systems of different hardness. This study also emphasizes the necessity of including freshwater withdrawal respecting the relevant affected geographical scale, i.e. by focusing the assessment on the local groundwater catchments rather than on the regional catchments. Our work shows that freshwater withdrawal methods previously used on a regional level can also be applied to local groundwater catchments and integrated into the standard LCA as an impact category. When standard LCA is extended to include impacts of freshwater withdrawal, rain & stormwater and seawater (0.09–0.18 compared to 11.45–17.16 mPET/m3) were the resources resulting in least overall environmental impact.

Nitrogen and oxygen isotopes in nitrate in the groundwater and surface water discharge from two rural catchments: implications for nitrogen loading to coastal waters

In Prince Edward Island, Canada, widespread intensive potato production has contributed to elevated nitrate concentrations in groundwater and streams, and eutrophic or anoxic conditions occur regularly in several estuarine systems. In this research, the stable isotopes of nitrogen and oxygen in nitrate in intertidal groundwater discharge and stream water were used, in conjunction with water quality and quantity data and land use information, to better understand the characteristics of nitrate delivered to two small estuaries with contrasting land use in their contributory catchments. Most of the water samples collected during the two-year study had isotopic signatures that fell in the range expected for nitrate derived from ammonium-based fertilizers (26.5 % of the samples) or in the overlapping range formed between ammonium-based fertilizers and nitrate derived from soil (64 % of the samples). Overall, isotopic signatures spanned over relatively narrow ranges, and correlations with other water quality parameters, or catchment characteristics, were weak. Nitrate in groundwater discharge and surface water in the Trout River catchment exhibited significantly different isotopic signatures only for the nitrogen isotope, while in the McIntyre Creek catchment groundwater discharge and surface water had similar isotopic signatures. When the isotopic results for the waters from the two catchments were compared, the surface waters were found to be similar, while the isotopic signatures of nitrate in groundwater were distinct only for the nitrogen isotope. Denitrification in the two study catchments was not evident based on the isotopic results for nitrate; however, in the case of the Trout River catchment, where a small freshwater pond exists, an average nitrate load reduction of 14 % was inferred based on a comparison of nitrate loads entering and leaving the pond. Overall, it appears that natural attenuation processes, occurring either in the streams or groundwater flow systems, do not significantly reduce nitrate loading to these estuaries.

Use of gaseous tracers (CFCs and SF6) and transit-time distribution spectrum to validate a shallow groundwater transport model

► Pertinent data for validation of catchment solute-transport models are lacking. ► Interests of gaseous tracers and spectrum of transit time distribution are analysed. ► Transit time distribution spectrum is a very relevant validation variable. Catchment-scale solute transport models constitute potentially powerful tools of water resources management for predicting the evolution of water quality in response to land use modifications. Validation of the models remains a crucial step in order to get reliable prediction. However, pertinent data for the validation step are lacking. When catchment solute transport models are applied to shallow groundwater catchments, catchment-scale model validation relies on the validation of the groundwater solute transport model. Here we studied the interests of two approaches for groundwater solute transport model validation: the use of (i) gaseous atmospheric tracers and (ii) of spectral properties of transit time distributions derived from tracer concentration time series of rainfall and stream base-flow. The Kervidy-Naizin catchment, a 5 km 2 catchment in Western France was chosen as case application. Three simulations with a shallow groundwater transport model were performed using three sets of effective porosity, respectively. We then investigated the ability of four gaseous tracers (CFC-11, CFC-12, CFC-113 and SF 6 ) and transit time distribution spectra to identify the most realistic simulations. The three simulations led to mean transit times that varied over a wide range of values, from 1.2 to 12.1 yr. Simulated groundwater mixing ratio differences for the three simulations did not exceed 5% for CFC-11, regardless of the groundwater location. The values of the SF 6 , CFC-12 and CFC-113 mixing ratio differences between the two simulations that contained the two shortest mean transit times were within expected measurement error of the tracer concentrations, regardless of the groundwater location. In contrast, the mixing ratio differences between the two simulations with the shortest mean transit times and the simulation containing the largest one exceeded 28% at all groundwater locations for SF 6 and 9% in groundwater discharging into the stream for CFC-12 and CFC-113. The spectra of the three simulated transit time distributions do not match the transit time distribution spectrum derived from chloride concentration time series. So these results show that transit time distribution spectrum, and in much less extend SF 6 , CFC-12 and CFC-113 mixing ratios are sensitive enough to effective porosity values to be used as validation variables in shallow groundwater transport modelling. Transit time distribution spectrum constitutes an integrative variable able to discriminate between shallow groundwater transport simulations leading to very close mean transit times. In the present work, the discrepancy between the simulated spectra and the spectrum derived from the chloride concentration may come from other catchment processes than groundwater transport process, or from a wrong modelling of the groundwater transport process. Globally, deriving reliable transit time distribution spectrum requires high-frequency and extensive time series of a conservative tracer measured in stream water and rainfall, which is not straightforward to collect. The low sensitivity of simulated CFC-11 tracer mixing ratios to simulated groundwater transit times, and thus to model parameters, constituted a shortcoming to use it as a validation variable of groundwater solute transport models.

Statistical screening for descriptive parameters for pesticide occurrence in a shallow groundwater catchment

Summary We have assessed the ability of a range of pesticide, site and climate parameters to discriminate between detected and non-detected pesticides as observed by long-term monitoring data of pesticide use and groundwater occurrence in a small catchment in southern Sweden. Of seventeen investigated parameters, six demonstrated such an ability: dosage applied, the Henry’s Law Constant (HLC), the octanol–water partitioning coefficient (log P ow ), the amount of precipitation the week before application, the amount of precipitation the month after application, and the substance degradation potential (DT 50 ). The apparent influence of the investigated parameters on pesticide occurrence in groundwater, and their apparent suitability as descriptive parameters in terms of assessment of related risks, is accordingly discussed. We conclude that knowledge of actual pesticide use appear fundamental for risk assessment of groundwater contamination potential. We further suggest that chemical property-parameters of specific pesticides, although clearly valuable, should be applied in groundwater contamination risk assessments with care. If site-specific values are unattainable, tabular values of log P ow , HLC and water solubility ( W s ) are demonstrated to exhibit a superior explanatory ability than those of substance adsorption potential ( K oc ) and DT 50 which, in the latter case, is shown to be able to lead to misleading conclusions on actual risks. The demonstrated explanatory ability of precipitation both before and after application suggests that relatively greater precipitation amounts occur in relation to application of non-detected substances. Increased dilution and run-off as well as decreased soil matrix retainment and decreased top-soil cracking are potential explanations although higher-resolution monitoring records are needed in order to confirm these hypotheses.

Compiling geophysical and geological information into a 3-D model of the glacially-affected island of Föhr

Abstract. Within the scope of climatic change and associated sea level rise, coastal aquifers are endangered and are becoming more a focus of research to ensure the future water supply in coastal areas. For groundwater modelling a good understanding of the geological/hydrogeological situation and the aquifer behavior is necessary. In preparation of groundwater modelling and assessment of climate change impacts on coastal water resources, we setup a geological/hydrogeological model for the North Sea Island of Föhr. Data from different geophysical methods applied from the air, the surface and in boreholes contribute to the 3-D model, e.g. airborne electromagnetics (SkyTEM) for spatial mapping the resistivity of the entire island, seismic reflections for detailed cross-sections in the groundwater catchment area, and geophysical borehole logging for calibration of these measurements. An iterative and integrated evaluation of the results from the different geophysical methods contributes to reliable data as input for the 3-D model covering the whole island and not just the well fields. The complex subsurface structure of the island is revealed. The local waterworks use a freshwater body embedded in saline groundwater. Several glaciations reordered the youngest Tertiary and Quaternary sediments by glaciotectonic thrust faulting, as well as incision and refill of glacial valleys. Both subsurface structures have a strong impact on the distribution of freshwater-bearing aquifers. A digital geological 3-D model reproduces the hydrogeological structure of the island as a base for a groundwater model. In the course of the data interpretation, we deliver a basis for rock identification. We demonstrate that geophysical investigation provide petrophysical parameters and improve the understanding of the subsurface and the groundwater system. The main benefit of our work is that the successful combination of electromagnetic, seismic and borehole data reveals the complex geology of a glacially-affected island. A sound understanding of the subsurface structure and the compilation of a 3-D model is imperative and the basis for a groundwater flow model to predict climate change effects on future water resources.

Drought, groundwater storage and stream flow decline in southwestern Australia

In this study we examine the hydrological processes that underpin non‐stationarity in hydrological prediction. This is achieved by analysis of linkages between rainfall, groundwater storage, and runoff in Southwest Western Australia (SWWA), a region experiencing stream flow decline since the mid‐1970s. We find a close connection between rainfall and changes in catchment groundwater storage, with increases in storage in years with annual rainfall above a threshold (1050–1400 mm), and declines during low rainfall years. Where groundwater is in contact with the stream bed, runoff, as a proportion of rainfall, is highly correlated with groundwater storage. Recent drought years have reduced groundwater storage and runoff ratio. In the absence of replenishing wetter years, lower runoff ratios are subsequently maintained. Runoff from a given depth of annual rainfall is now far lower than that produced 15 years ago. In this way groundwater storage acts as the catchment's “memory”. This study highlights the importance of catchment groundwater storage that may be used to improve runoff prediction in a drying climate.

Target loads of atmospheric sulfur and nitrogen deposition for protection of acid sensitive aquatic resources in the Adirondack Mountains, New York

The dynamic watershed acid‐base chemistry model of acidification of groundwater in catchments (MAGIC) was used to calculate target loads (TLs) of atmospheric sulfur and nitrogen deposition expected to be protective of aquatic health in lakes in the Adirondack ecoregion of New York. The TLs were calculated for two future dates (2050 and 2100) and three levels of protection against lake acidification (acid neutralizing capacity (ANC) of 0, 20, and 50 μeq L−1). Regional sulfur and nitrogen deposition estimates were combined with TLs to calculate exceedances. Target load results, and associated exceedances, were extrapolated to the regional population of Adirondack lakes. About 30% of Adirondack lakes had simulated TL of sulfur deposition less than 50 meq m−2 yr to protect lake ANC to 50 μeq L−1. About 600 Adirondack lakes receive ambient sulfur deposition that is above this TL, in some cases by more than a factor of 2. Some critical criteria threshold values were simulated to be unobtainable in some lakes even if sulfur deposition was to be decreased to zero and held at zero until the specified endpoint year. We also summarize important lessons for the use of target loads in the management of acid‐impacted aquatic ecosystems, such as those in North America, Europe, and Asia.

Modelling the hydrogeology and managed aquifer system of the Chalk across southern England

Abstract Six regional recharge and groundwater models have been recently developed of the Chalk and Upper Greensand from Dorset to Kent. Updated Chalk stratigraphy and mapping have improved understanding of geological structure and the development of preferential groundwater flow pathways along hardground horizons. Where shallow dipping folds bring these into the zone of active groundwater flow, extensive ‘underdrainage’ may result in marked differences between surface and groundwater catchments. Hardgrounds and marls are also associated with spring discharges, as are some faults and the clay formations that underlie or confine the aquifer system. Higher specific yield within the Upper Greensand helps support summer baseflow, as do local groundwater discharges from augmentation schemes, watercress and fish farm operations. The aquifer system has been successfully modelled using the ‘variable hydraulic conductivity with depth’ version of MODFLOW. Depths of secondary permeability development have been distributed according to ground and groundwater level data. Interfluve–valley contrasts overlie a base hydraulic conductivity set according to the formation saturated at the water table and enhanced by active hardgrounds. Local parameter overrides may also be needed. The Wessex Basin conceptual and numerical model is described before summarizing similarities and contrasts from the other five regional model areas.

Predicting groundwater response times and catchment impacts from land use change

Predicting groundwater response times and catchment impacts from land use change

Target loads of atmospheric sulfur deposition protect terrestrial resources in the Adirondack Mountains, New York against biological impacts caused by soil acidification

The model of acidification of groundwater in catchments (MAGIC) was used to simulate a matrix of target load (TL) values for use in protection and restoration of forest resources in the Adirondack Mountains of New York against soil acidification by acidic deposition. Modeling results were extrapolated to the population of 1,320 watersheds in the Adirondack Ecoregion that contain lakes expected to be >1 ha and >1 m deep and that have acid neutralizing capacity <200 μeq/L. Results of the TL simulations were combined with regional estimates of atmospheric sulfur deposition to calculate the extent to which ambient deposition exceeds the TL needed to achieve forest ecosystem protection. Modeling results were highly uncertain for estimating the TLs to protect against changes in soil solution chemistry. Although simulation uncertainty was generally lower for TL projections calculated to protect against changes in soil percent base saturation (% BS), TL modeling results based on soil chemistry were strongly dependent on selection of an appropriate % BS threshold. In order to more effectively model critical loads and TLs to protect and restore acid-sensitive terrestrial resources using a dynamic model such as MAGIC, additional information regarding dose/response relationships is needed to determine the % BS levels at which adverse impacts to sensitive plant species occur.

Using multivariate statistical methods to assess the groundwater quality in an arsenic-contaminated area of Southwestern Taiwan

Groundwater is a major water resource in Southwestern Taiwan; hence, long-term monitoring of water quality is essential. The study aims to assess the hydrochemical characteristics of water in the arsenic-contaminated aquifers of Choushui River alluvial fan and Chianan Plain, Taiwan using multivariate statistical methods, namely, factor analysis (FA), cluster analysis (CA), and discriminant analysis (DA). Factor analysis is applied to reveal the processes controlling the hydrochemistry of groundwater. Cluster analysis is applied to spatially categorize the collected water samples based on the water quality. Discriminant analysis is then applied to elucidate key parameters associated with the occurrence of elevated As concentration (>10 μg L(-1)) in groundwater. Major water types are characterized as Na-Ca-Cl and Na-Mg-Cl in the Choushui River alluvial fan and Chianan Plain, respectively. Inorganic species of arsenic (As), particularly As(III), prevail in these two groundwater catchments, and their levels are higher in the Chianan Plain than in the Choushui River alluvial fan. Through FA, three factors, namely, the degree of salination, As reduction, and iron (Fe) reduction, are determined and denoted irrespective of some differences between the factorial compositions. Spatial distribution patterns of factors As reduction and Fe reduction imply that the redox zonation is delineated by As- and Fe-dominance zones separately. The results of CA demonstrate that three main groups can be properly explained by the factors extracted via FA. Three- (Fe(2+), Fe(3+), and NH (4) (+) ) and four-parameters (Fe(2+), Fe(3+), NH (4) (+) , and Ca(2+)) derived from discriminant analysis for Choushui River alluvial fan and Chianan Plain are elucidated as key parameters affecting the distribution of As-contained groundwater. The analytical results indicate that the reductive dissolution of Fe minerals is prerequisite for the mobilization of As, whereas the shift of redox condition from Fe- to As-reducing leads to the accumulation of dissolved As in this area.

Using linked surface–groundwater catchment modelling to assess protection options for environmental assets threatened by dryland salinity in southern-eastern Australia

Dryland salinity threatens many high-value assets in Australia. Assessing the technical feasibility of intervention requires consideration of spatial and temporal dimensions of land management and associated surface–groundwater interactions. This paper presents results regarding the practicability of protecting assets in a 371,000-ha agriculturally dominated catchment in south-eastern Australia using a physically-based catchment model, the Catchment Analysis Tool (CAT). The model links surface land management and hydrology at the paddock scale (daily time step growth and water use, crop rotations and management) with a fully distributed groundwater model enabling the assessment of agronomic versus engineering options for landscape asset protection. Scenarios assessing management options and costs of planting of perennial vegetation or engineering through groundwater pumping are outlined. The impacts of scenarios are reported under future climatic conditions as well as for the ‘steady state’ response. The study demonstrates a linked surface–groundwater modelling approach to estimate groundwater capture zones, response times to equilibrium under current and climate change conditions, as well as groundwater abstraction volumes required to protect landscape features. These factors are important considerations for evidence-based decision making about protecting assets from dryland salinity.

Target loads of atmospheric sulfur deposition for the protection and recovery of acid-sensitive streams in the Southern Blue Ridge Province

An important tool in the evaluation of acidification damage to aquatic and terrestrial ecosystems is the critical load (CL), which represents the steady-state level of acidic deposition below which ecological damage would not be expected to occur, according to current scientific understanding. A deposition load intended to be protective of a specified resource condition at a particular point in time is generally called a target load (TL). The CL or TL for protection of aquatic biota is generally based on maintaining surface water acid neutralizing capacity (ANC) at an acceptable level. This study included calibration and application of the watershed model MAGIC (Model of Acidification of Groundwater in Catchments) to estimate the target sulfur (S) deposition load for the protection of aquatic resources at several future points in time in 66 generally acid-sensitive watersheds in the southern Blue Ridge province of North Carolina and two adjoining states. Potential future change in nitrogen leaching is not considered. Estimated TLs for S deposition ranged from zero (ecological objective not attainable by the specified point in time) to values many times greater than current S deposition depending on the selected site, ANC endpoint, and evaluation year. For some sites, one or more of the selected target ANC critical levels (0, 20, 50, 100μeq/L) could not be achieved by the year 2100 even if S deposition was reduced to zero and maintained at that level throughout the simulation. Many of these highly sensitive streams were simulated by the model to have had preindustrial ANC below some of these target values. For other sites, the watershed soils contained sufficiently large buffering capacity that even very high sustained levels of atmospheric S deposition would not reduce stream ANC below common damage thresholds.

Effects of crystalline massif tectonics on groundwater origin and catchment size of a large spring area in Zieleniec, Sudety Mountains, southwestern Poland

The recharge mechanism of a very large spring area in the town of Zieleniec in the Orlickie Mountains (part of the Sudety mountain chain) in southwestern Poland, was investigated and characterized. The spring area is located on a steep mountain slope at a high elevation, next to the continental water divide. It is estimated that at least 90% of the spring discharge comes from outside its topographic drainage basin. The study area has been strongly affected by tectonic episodes of different ages. Thus, there is a high density of fractures in the crystalline massif, which determines the water content of the area and the occurrence of large springs. The low variability in discharge of the Zieleniec spring area indicates the presence of a strong and stable component source of recharge. It has also been shown that gravitational drainage of solid-rock blocks and small fissures is also an important recharge component. The stable recharge component is associated with deep-water circulation from the Bĕla River drainage basin in the Czech Republic, flowing beneath the continental divide. Water flows in conformity with a high hydraulic head gradient through deep, open, NW–SE-oriented fissures.