1,720,993 research outputs found
Limitations of GALDIT to map seawater intrusion vulnerability in a highly touristic coastal area
Full text linkCoastal aquifers are susceptible to seawater intrusion, especially touristic areas where the overexploitation combined with the agricultural use of groundwater represent a severe issue for water management. GALDIT methodology was applied as a management tool to identify and prevent salinization of the aquifer. GALDIT methodology needs six input parameters: groundwater occurrence (G), aquifer hydraulic conductivity (A), groundwater head above sea level (L), distance from the shore (D), impact of the existing status of seawater intrusion (I), and thickness of the aquifer (T). Then a contour map is created using three degree of vulnerability: high, medium and low. The higher vulnerability zone ranges from 40 to 550 m towards the mainland with the rest of the aquifer characterized by medium vulnerability. The main problem affecting the selected field site is the large water requirement during the summer period due to the touristic activities, but the correct use of surplus water collected in the winter can overcome this problem. This study demonstrates that further investigation on groundwater hydrochemistry and on water demand trends from the different activities impacting the field site should be implemented, in order to guarantee environmental and touristic development sustainability
Assessment of intrinsic vulnerability using DRASTIC model and GIS in Kiti aquifer, Cyprus
No full textApproximately 70% of the population of the earth lives in coastal areas and the majority of these people depend on coastal aquifers for freshwater. For this reason the coastal aquifers are vulnerable to pollution and are now recognized as a crucial arena for future progress towards sustainability in world. This paper deals with the assessment of groundwater vulnerability of Kiti aquifer, South Cyprus. The Kiti aquifer, covering an area of about of 30 Km2, is situated in the southern part of Cyprus with a mean elevation of 20 m above sea level. The area is characterized by semi-arid climatic conditions. The groundwater resources are related to the Pleistocene coastal plain and the recent Tremithos river valley deposits. The concept of the groundwater vulnerability is based on the assumption that the physical environment may provide some degree of protection to groundwater against human activities. The DRASTIC method is applied to evaluate aquifer vulnerability. The method was developed by the United State Environmental Protection Agency (EPA), as a technique for assessing groundwater pollution potential, and is based on seven (7) parameters: Depth (D), Recharge (R), Aquifer media (A), Soil media (S), Topography (T), Impact of the vadose zone media (I), hydraulic Conductivity of the aquifer (C). Determination of the DRASTIC index (DI) involves multiplying each parameter weight by its site rating and summing the total. Based on DI values a groundwater vulnerability map was illustrated, using a Geographical Information System (GIS). The highest vulnerability values in the Kiti area, covering a large part, are associated with shallow aquifers without great depth of the vadose zone. The results provide important information and the vulnerability map could be used from local authorities and decision makers who are responsible for groundwater resources management and protection zoning.Published13-24N/A or not JCRope
A hybrid GIS and AHP approach for modelling actual and future forest fire risk under climate change accounting water resources attenuation role
Full text linkForest wildfires usually occur due to natural processes such as lightning and volcanic eruptions, but at the same time they are also an eect of uncontrolled and illegal anthropogenic activities. Dierent factors can influence forest wildfires, like the type of vegetation, morphology, climate, and proximity to human activities. A precise evaluation of forest fire issues and of the countermeasures needed to limit their impact could be satisfactory especially when forest fire risk (FFR) mapping is available. Here, we proposed an FFR evaluation methodology based on Geographic Information System (GIS) and the analytic hierarchy process (AHP). The study area is the Campania region (Southern Italy) that, for the last 30 years, has been aected by numerous wildfires. The proposed methodology analyzed 12 factors, and AHP was used for weight assignment, oering a new approach to some parameters. The method divided the study area into five risk classes, from very low to very high. Validation with fire alerts showed a good correlation between observed and predicted fires (0.79 R2). Analyzing the climate projections, a future FFR for 2040 was also assessed. The proposed methodology represents a reliable screening tool to identify areas under forest fire risk, and can help authorities to direct preventive actions
Simulating Future Groundwater Recharge in Coastal and Inland Catchments
No full textGroundwater is a primary source of drinking water in the Mediterranean, however, climate variability in conjunction with mismanagement renders it vulnerable to depletion. Spatiotemporal studies of groundwater recharge are the basis to develop strategies against this phenomenon. In this study, groundwater recharge was spatiotemporally quantified using the Soil and Water Assessment Tool (SWAT) in one coastal and one inland hydrological basin in Greece. A double calibration/validation (CV) procedure using streamflow data and MODIS ET was conducted for the inland basin of Mouriki, whereas only ET values were used in the coastal basin of Anthemountas. Calibration and simulation recharge were accurate in both sites according to statistical indicators and previous studies. In Mouriki basin, mean recharge and runoff were estimated as 16% and 9%, respectively. In Anthemountas basin recharge to the shallow aquifer and surface runoff were estimated as 12% and 16%, respectively. According to the predicted RCP 4.5 and 8.5 scenarios, significant variations in groundwater recharge are predicted in the coastal zone for the period 2020–2040 with average annual recharges decreasing by 30% (RCP 4.5) and 25% (RCP 8.5). Variations in groundwater recharge in the inland catchment of Mouriki were insignificant for the simulated period. Anthemountas basin was characterized by higher runoff rates. Groundwater management in coastal aquifers should include detailed monitoring of hydrological parameters, reinforced groundwater recharge during winter and reduced groundwater abstraction during summer depending on the spatiotemporal distribution of groundwater recharge
A novel hybrid method of specific vulnerability to anthropogenic pollution using multivariate statistical and regression analyses
No full textGroundwater resources are the main supply of freshwater for human activities. However, in the last fifty years aquifers have become more susceptible to chemical pollution due to human activities. The concept of groundwater vulnerability constitutes a worldwide accepted tool for water protection and planning. However, the existing methods and modified versions do not account for all the hydrogeochemical processes that drive anthropogenic pollution. The hydrogeochemical processes occurring within an aquifer can be determined using multivariate statistical analysis. In this study a specific vulnerability method named SVAP (Specific Vulnerability to Anthropogenic Pollution) is proposed. The index is based on seven quantitative parameters: depth to groundwater, recharge, nitrate losses, hydraulic resistance of the vadose zone, aquifer thickness, hydraulic conductivity of the aquifer, and slope. Weights of anthropogenic factors were determined by factor analysis and used to validate the SVAP methodology. The parameters’ classification was selected according to the highest Pearson's correlation coefficient with factor weights and then grouped via a linear combination. The new index was applied in two watersheds: the Florina basin (Greece) and the Garigliano River basin (Italy), both of which possess complex hydrogeochemical regimes. The main hydrogeochemical processes acting in the study areas were identified via factor analysis, which revealed that the anthropogenic pollution in both sites was due mainly to chemical fertilizers and manure. Verification of the SVAP method produced correlation coefficients with nitrate concentrations of 0.75 and 0.62 in Florina and Garigliano, respectively. The proposed SVAP method is more reliable and flexible than standard vulnerability assessment methods and can be easily adapted for complex aquifers
The importance of incorporating denitrification in the assessment of groundwater vulnerability
Full text linkHuman activities are deeply connected with groundwater reservoirs, so protecting them from pollution has become a priority in many regions of the world. Nitrate is considered the main groundwater pollutant since it is directly linked to many human activities. Agricultural activities and domestic wastewater have been identified as the main sources of nitrate in groundwater. Nevertheless, there are some natural processes that can mitigate nitrate pollution. Together with dilution processes, the degradation of nitrate through denitrification has been acknowledge as a process that can potentially reduce nitrogen loads, in both deep and shallow aquifers. Usually these processes were not properly quantified in vulnerability assessment methods, until the introduction of LOS indices. In this study, the application of the LOS indices on 4 agricultural areas is discussed, highlighting how the LOS indices can identify portions of the landscape with higher potential denitrification and how they directly enhance the groundwater vulnerability assessment. Previous studies have shown that LOS indices are a valuable tool for proper vulnerability assessment to nitrate, however they need to be coupled with other parameters that also describe nitrate behavior in groundwater. The SINTACS-SVN and DRASTIC-PA methods that include the LOS indices, were applied for the first time in the Epanomi coastal area to evaluate the reliably of the assessment and, despite the different classes range and the weights applied, similar groundwater vulnerability assessment maps were obtained. The nitrate vulnerability maps were comparable with the observed nitrate concentrations and were found to be highly comparable with original LOS maps. Nevertheless, it should be kept in mind that vulnerability methods are only screening tools and groundwater quality observations are pivotal information for environmental management
Formulation of Shannon entropy model averaging for groundwater level prediction using artificial intelligence models
No full textA two-level modeling strategy is formulated to predict groundwater levels (GWL) within a portion of Lake Urmia’s aquifer in NW Iran during 14 years (2001–2015), which both aquifer and lake suffer significant water decline. At Level 1, three artificial intelligence (AI) models were trained and tested, which comprise artificial neural network (ANN), Sugeno fuzzy logic (SFL), and neuro-fuzzy (NF). At Level 2, a novel formulation was employed, referred to as the Shannon entropy model averaging (EMA). This formulation combines the results at Level 1 by calculating the weights of Level 1 models based on an innovative approach, which incorporates performance, stability, and parsimony criteria. The results indicate that the models at Level 1 are fit-for-purpose and can capture the water table decline in GWL, but EMA improves RMSE by 5% in the testing phase. Although EMA does not significantly increase the performance of the models, the results of the homoscedastic test in models’ residuals indicate that EMA increases the reliability of prediction owing to the homoscedastic residuals with the highest p value compared to Level 1 models. The p values as per Breusch–Pagan and White tests are 0.88 and 1, respectively, which indicates further information does not remain in the EMA residual. The EMA formulation can be applied to other water resource management problems
Coastal zones between anvil and hammer: a glance to the future
No full textCoastal systems, from both the environmental and social standpoint, are complex systems that respond to inputs arising from spatial and temporal scales larger than those outlined by their local boundaries. The impact of human activities is not expected to decrease in the future and the globalization of "driving factors" poses serious questions about the solution of the prob-lems of coastal zones. The thoughts that are proposed concern only some of the pressing is-sues that must be addressed: the complexity of the systems must be dealt with by widening the spatial and temporal scales of investigation, considering the delays of systems in respond-ing to past and present inputs, and by building together hypothesis of adaptive management with long-view. In particular, we address issues concerning current methodological approaches used in the hydrogeology of the coastal areas, the promising adaptive management, the retoxi-fication by heavy metal at the land-sea interface and the possible comebacks of coastal groundwater to climate change and anthropogenic pressure in terms of "critical transitions "
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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