The territory of continental Portugal has a geologic history marked by the Hercynian orogeny, and to the north of this country the Hercynian large-scale tectonic structures are typically represented ...by long and deep NW-SE trending ductile shear zones and NNE-SSW trending fragile faults. These structures are elements of mineral and thermal water circuits that discharge as springs in more than one hundred locations. The purpose of this study is to investigate if these structures are also used by shallower non-mineral groundwater, integrated in a large-scale regional flow system. Using an original combination of water balance and recession flow models, it was possible to calculate catchment turnover times based solely on groundwater discharge rates and recession flow parameters. These times were then used to classify a group of 46 watersheds as closed or open basins, and among the later class to identify source and sink basins, based on innovative interpretations of relationships between turnover time and catchment area. By definition, source basins transfer groundwater to sink basins and altogether form a regional flow system. Using a Geographic Information System, it could be demonstrated the spatial association of open basins to the Hercynian ductile and fragile tectonic structures and hence to classify the basins as discharge cells of a regional flow system. Most of the studied watersheds are sub-basins of the Douro River basin, one of the largest regional catchments in the Iberian Peninsula, being located in its mouth area. Because the largest part of open basins is sink, which by definition tends to dominate in the mouth area of regional catchments, it is proposed as an extension of the studied area conceptual boundaries towards the Douro River basin headwaters, where the corresponding sources could be searched for.
A rainwater harvesting system (RHS) was designed for a waste treatment facility located near the town of Mirandela (northern Portugal), to be used in the washing of vehicles and other equipment, the ...cleaning of outside concrete or asphalt floors, and the watering of green areas. Water tank volumes representing 100% efficiency (Vr) were calculated by the Ripple method with different results depending on two consumption scenarios adopted for irrigation. The RHS design was based on a precipitation record spanning a rather long period (3 decades). The calculated storage capacities fulfilled the water demand even when prolonged droughts occurred during that timeframe. However, because the drought events have been rather scarce the Vr values were considered oversized and replaced by optimal volumes. Notwithstanding the new volumes were solely half of the original Vr values, the projected RHS efficiency remained very high (around 90%) while the probability of system failure (efficiency<100%) stayed very low (in the order of 5%). In both scenarios, the economic savings related to the optimization of Vr were noteworthy, while the investment's return periods decreased substantially from the original to the optimized solutions. A high efficiency with a low storage capacity is typical of low demanding applications of rainwater harvesting, where water availability (Vw) largely exceeds water demand (Cw), that is to say where demand fractions (Cw/Vw) are very low. Based on the results of a literature review covering an ample geographic distribution and describing a very large number of demand fraction scenarios, a Cw/Vw=0.8 was defined as the threshold to generally distinguish the low from the high demanding RHS applications.
•Defining a demand fraction threshold for low demanding RHS applications•Characterizing the efficiency of low demanding RHS•Forecasting the probability of failure in low demanding RHS•Designing a low demanding RHS in a region of temperate climate
► Neutralize redundancy between DRASTIC features using multivariate statistics. ► Automatically adjust DRASTIC feature weights to local settings. ► Validate a pioneering method of vulnerability ...mapping with pollution risk assessment.
An assessment of aquifer intrinsic vulnerability was conducted in the Sordo river basin, a small watershed located in the Northeast of Portugal that drains to a lake used as public resource of drinking water. The method adopted to calculate intrinsic vulnerability was the DRASTIC model, which hinges on a weighted addition of seven hydrogeologic features, but was combined with a pioneering approach for feature reduction and adjustment of feature weights to local settings, based on a multivariate statistical method. Basically, with the adopted statistical technique-Correspondence Analysis-one identified and minimized redundancy between DRASTIC features, allowing for the calculation of a composite index based on just three of them: topography, recharge and aquifer material. The combined algorithm was coined vector-DRASTIC and proved to describe more realistically intrinsic vulnerability than DRASTC. The proof resulted from a validation of DRASTIC and vector-DRASTIC by the results of a groundwater pollution risk assessment standing on the spatial distribution of land uses and nitrate concentrations in groundwater, referred to as NO3--DRASTIC method. Vector-DRASTIC and NO3--DRASTIC portray the Sordo river basin as an environment with a self-capability to neutralize contaminants, preventing its propagation downstream. This observation was confirmed by long-standing low nitrate concentrations in the lake water and constitutes additional validation of vector-DRASTIC results. Nevertheless, some general recommendations are proposed in regard to agriculture management practices for water quality protection, as part of an overall watershed approach.
•A model for the dimensioning and siting of a flood-detention system in a watershed.•1st module indicates a volume to retain and tracks the associated catchment area.•2nd identifies topographically ...suited locations for the retention basin using GIS.•3rd selects a optimal place based on pre-defined environmental objectives.•Scenarios of decentralization using multiple retention basins are addressed.
A straightforward approach in flood management is the attenuation of peak discharges through an appropriate detention system. In this study, a flexible framework model was developed to optimize the dimensioning and site selection of a flood mitigation system based on detention basins. The general workflow can be summarized by three separate but interrelated modules: (i) the hydrologic module, which back tracks the detention basin contributing area based on the application of engineering formulae to historical information on local river floods and associated hydrometric data; (ii) the geomorphologic module, implemented in a Geographic Information System, which indicates all the potential locations with adequate contributing area as required for the detention system, by analyzing the flow accumulation within the river basin; and (iii) the environmental module, which comprises the implementation of a multi-criteria decision analysis for the selection of best location(s) for the detention basin system, addressing three different objectives: to minimize diffuse pollution; to minimize point-source pollution; to optimize landscape integration (by minimizing the dam height). The framework model was applied to the flood-prone Vez River, which is the main tributary of the Lima River in Northwestern Portugal. Although the expectations as regards diffuse and point-source pollution are optimistic, results show that detention of the largest flood in this river could only be accomplished with one very large dam or a number of decentralized large dams. Decentralizing the detention system with multiple basins installed in various branches of the Vez River did not reduce the mean dam height, because the catchment is located in a region of craggy topography and high annual rainfall. An extensive reforestation of the basin headwaters would increase evapotranspiration reducing runoff. Eventually, this would expand the alternatives for flood mitigation, namely through the construction of sustainable flood detention basins.
•Evaluate environmental land use conflicts (LUC) in rural watersheds.•Investigate the ecological quality of surface water in LUC areas.•Characterize the structure of macroinvertebrate communities ...within LUC areas.•Assess the overall impact of LUC on the riverine ecosystem.•Propose measures of soil conservation and water protection to mitigate impacts of LUC.
Starting from a diagnosis of areas with different environmental land use conflicts located in various rural sub-basins of the River Sordo basin (northern Portugal), the present study analyzed the ecological quality of surface water in small mountain streams to establish a relationship between land use, water and aquatic biota. Environmental land use conflicts were set up on the basis of land use and land capability maps, coded as follows: 1 – agriculture, 2 – pasture, 3 – pasture/forest, and 4 – forest. Land capability was assessed by the ruggedness number methodology (RN). The difference between the codes of capability and use defines a conflict class, where a negative or null value means no conflict and a positive value means class i conflict. Within and without the conflict areas, ecological quality of surface water was evaluated by the metrics EPT taxa, IPtIN index, diversity of Shannon–Wiener and Evenness index. Macroinvertebrate communities are strongly correlated to conflict classes, because sites without (reference sites) or with minor physicochemical and hydromorphological degradation (Class 1) presented high diversity, evenness, EPT taxa and IPtIN index, while more impacted sites (Class 2) presented an ecological status not fulfilling the demands of the European Union Water Framework Directive (2000/60). The present study indicates a significant impact of land use on water quality which has straight influence on the distribution of biota, emphasizing the key role of riparian vegetation in the conservation of aquatic ecosystems. The highest impacts on macroinvertebrate assemblages were associated with changes in water quality parameters such as temperature, oxygen saturation (%), turbidity, total suspended solids (TSS), nitrates, phosphates and sulphates, conductivity and dissolved oxygen, as well as hydromorphological alterations driven by the total absence of riparian vegetation as a consequence of terrace building, agriculture and the resectioning/reinforcement of the banks associated with the culture of vine. Macroinvertebrates proved reliable to distinguish conflict classes and separate seasons. The main conservation measures required to improve the conflict areas in the short and medium term mainly include the adoption of agroforestry practices as these not only improve the quality of water and soil, maintaining land resources over a long period of use, but also brings many benefits to the landowner.
•Identify anthropogenic impacts on mineral weathering using Correspondence Analysis.•Illustrate the impact of nitrification of N-fertilizers on mineral weathering.•Role of nitrification of ...N-fertilizers on development of dedolomitization reactions.
Correspondence Analysis was adopted as tool for investigating the statistical structure of hydrochemical and weathering datasets of groundwater samples, with the main purpose of identifying impacts on mineral weathering caused by anthropogenic activities, namely fertilizing of farmlands. The hydrochemical dataset comprised measured concentrations of major inorganic compounds dissolved in groundwater, namely bicarbonate, silica (usually by-products of chemical weathering), chloride, sulphate and nitrate (typically atmospheric plus anthropogenic inputs). The weathering dataset consisted of calculated mass transfers of minerals being dissolved in loess sediments of a region located in SW Hungary (Szigetvár area), namely Na-plagioclase, calcite and dolomite, and of pollution-related concentrations of sodium, magnesium and calcium. A first run of Correspondence Analysis described groundwater composition in the study area as a system of triple influence, where spots of domestic effluents-dominated chemistries are surrounded by areas with agriculture-dominated chemistries, both imprinted over large regions of weathering dominated chemistries. A second run revealed that nitrification of N-fertilizers is promoting mineral weathering by the nitric acid reaction (anthropogenic pathway), in concurrence with the retreating of weathering by carbonic acid (natural pathway). It also indicated that dolomite and calcite are being players in a dedolomitization process driven by dissolution of gypsum fertilizers and nitrification of N-fertilizers.
Sustainability is a utopia of societies, that could be achieved by a harmonious balance between socio-economic development and environmental protection, including the sustainable exploitation of ...natural resources. The present Special Issue addresses a multiplicity of realities that confirm a deviation from this utopia in the real world, as well as the concerns of researchers. These scholars point to measures that could help lead the damaged environment to a better status. The studies were focused on sustainable use of soils and water, as well as on land use or occupation changes that can negatively affect the quality of those resources. Some other studies attempt to assess (un)sustainability in specific regions through holistic approaches, like the land carrying capacity, the green gross domestic product or the eco-security models. Overall, the special issue provides a panoramic view of competing interests for land and the consequences for the environment derived therefrom.
•Assessing plagioclase weathering rates at the spring watershed scale.•Considering rock structure in the assessment of the reacting surface area.•Bridging solid-state and solute-flux rates through ...change in hydraulic diffusivity.
Springs emerging within massifs of crystalline rocks were monitored for discharge rate (Q), and the Q values combined with geomorphic and hydrographic parameters in a hydrologic model to calculate hydraulic conductivity (K) and effective porosity (ne) of the spring watersheds. The spring waters, several borehole waters and rain water were analyzed for major dissolved compounds, strontium and isotopes (δ18O, δ2H, δ13C and 87Sr/86Sr). With a shift to less negative values, δ18O and δ2H were fitted by a line approximately parallel to the GMWL, but no significant dependence on altitude was found. The δ18O and δ2H values correlate better with those of precipitation amount. The 87Sr/86Sr ratios in drilled well waters correlate positively with the depth of water circulation reported in the borehole logs. The corresponding regression equations were used to extrapolate the depth of hydraulic circuits within the spring watersheds. The previous data, together with groundwater travel times calculated by a water balance model, and with reactions of granite/metassediment plagioclase and biotite precipitating halloysite, gibbsite and vermiculite, were assembled in a mass balance model to calculate solute-flux weathering rates of plagioclase (WPl). The WPl’s were described as a function of D∝K/ne, where D is the hydraulic diffusivity. The discrepancies between the WPl values and solid-state rates, based on the differences between elemental, isotopic and mineral compositions measured in present-day regoliths and in the assumed protolith, were assigned to a decrease in D over time, from values in the protolith to values in the weathered aquifer.
The drinking water supply to Vila Pouca de Aguiar municipality in North Portugal is based on high quality groundwater, namely on nearly one hundred artesian springs and fifty boreholes. The ...groundwater resources are plentiful on a municipal level, but evidence some deficits at the sub-municipal (village) level, especially during the dry period (July- August) that coincides with the return of many emigrants for holiday time. The deficits affect mostly the municipal capital (Vila Pouca de Aguiar) and a neighboring village (Pedras Salgadas), which populations nearly double or even triple during that period. The estimated annual deficits approach 55,000 m³/yr in those villages. If the anticipated increase in consumption/habitant and decrease in annual rainfall become reality in the next two decades, then the deficits may raise to approximately 90,000 m³/yr. To balance the water supply system, this study proposes its transition towards a conjunctive water management based on surface water stored in small dams and groundwater. A hydrologic modeling involving small forested catchments (< 15 km²) elected the Cabouço watershed as most suited basin to store stream water, because surface water availability is large (2.4 Mm³/yr) and forest cover is dominant (84.8%). Estimated nutrient loads are also compatible with drinking water supply.
► Develop a weathering model that incorporates rock structure in the rate equation. ► Conceive a weathering model especially designed for fracture artesian springs. ► Create a model that integrates ...topography, hydrology, rock structure and weathering.
Weathering rate models designed for watersheds combine chemical data of discharging waters with morphologic and hydrologic parameters of the catchments. At the spring watershed scale, evaluation of morphologic parameters is subjective due to difficulties in conceiving the catchment geometry. Besides, when springs emerge from crystalline massifs, rock structure must be accounted in formulas describing the area of minerals exposed to the percolating fluids, for a realistic evaluation of the rates. These particular features are not included in the available approaches and for that reason a new model was developed, coined THROW model. This is a lumped approach that integrates (T)opography, (H)ydrology, (RO)ck structure and (W)eathering in a single algorithm. The study area comprises several stream watersheds and spring sites of the Vouga River basin (northern Portugal), shaped on granites. Firstly, the THROW model couples a terrain modeling analysis with hydrologic models based on discharge rates, to determine hydraulic conductivities (K), effective porosities (ne) and annual recharges (Vr) at the stream watershed scale. Subsequently, these parameters are used in a water balance model to estimate concomitant groundwater travel times (t). The mean K (4.7±3.2)×10−7ms−1 and ne (2.0±1.3)×10−2 values are adopted as proxies for the spring watersheds and a firm regression equation is defined between time and stream watershed area (A). Secondly, two more runs of terrain modeling analysis are executed to extrapolate morphologic parameters for the spring watersheds. The first run hinges on scaling properties of the drainage networks, known as Horton laws, and is used to scale watershed areas across stream orders (i). The scaling function is described by another regression equation. The second run evaluates the order of a spring watershed, defined as equivalent order (ieq) and equated to the mean order of the surrounding stream watersheds. Having calculated the ieq, spring watershed areas and travel times were downscaled using the regression equations (A<10km2 and t=1.4–2.8year). Standing on the physical and hydrologic parameters of the spring watersheds, the THROW model finally calculates plagioclase weathering rates in the vicinity of the spring sites. The SiB model (Pacheco and Van der Weijden, 1996) was used before to estimate the contribution of plagioclase dissolution to the chemical composition of these springs (Van der Weijden and Pacheco, 2006). The chemical data were now coupled with K, ne and t in a rate equation to estimate chemical weathering rates of plagioclase in the basin. In the THROW model, the rate equation describes the exposed surface area as a function of fracture spacings, openings and porosities (Pacheco and Alencoão, 2006). The calculated rates (WPl=(2.5±1.2)×10−14molm−2s−1) are consistent with previous reports and with results of experimental kinetic models. The SiB results predict formation of halloysite and gibbsite along the flow path, which were indeed close to equilibrium with the dissolved Al and Si activities.
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