Hard-rock catchments are considered to be source of valuable water resources for water supply to inhabitants and ecosystems. The present work aims to develop a groundwater vulnerability approach in the Caldas da Cavaca hydromineral system (Aguiar da Beira, Central Portugal) in order to improve the hydrogeological conceptual site model. Different types of information were overlaid, generating several thematic maps to achieve an integrated framework of key sectors in the study site. Thus, a multi-technical approach was used, encompassing field and laboratory techniques, whereby different types of data were collected from fields such as geology, hydrogeology, applied geomorphology and geophysics and hydrogeomechanics, with the fundamental aim of applying the so-called DISCO index method. All of these techniques were successfully performed and an intrinsic groundwater vulnerability to contamination assessment, based on the multicriteria methodology of GOD-S, DRASTIC-Fm, SINTACS, SI and DISCO indexes, was delineated. Geographic Information Systems (GIS) provided the basis on which to organize and integrate the databases and to produce all the thematic maps. This multi-technical approach highlights the importance of groundwater vulnerability to contamination mapping as a tool to support hydrogeological conceptualization, contributing to improving the decision-making process regarding water resources management and sustainability.
The occurrence of groundwater in urban hard rock areas is mostly controlled by secondary permeability caused by the fracturing degree and weathering grade. Vulnerability GIS-mapping, monitoring, and infiltration/recharge of water resources, and the delineation of the environmental protective background are key issues in evaluating, planning, managing, and decision-making for urban water systems. A small-scale urban area in Penafiel City was used as a case study. Historical and current scenarios were compared using hydrogeological GIS-based modelling. Water sources and potential contamination sources were mapped around the study area. Groundwater is mainly acidic, with a low mineralization and a Cl-Na to Cl-SO4-Na or Cl-Ca to Cl-SO4-Ca hydrogeochemical facies. Considering potential contamination sources, the moderate and the moderate-high classes dominate the area. The combined approach of the vulnerability indexes suggests that most of the area has a low to moderate vulnerability to contamination. The Infiltration Potential Index in urban areas (IPI-urban) indicates the prevalence of a low to moderate infiltration. Groundwater recharge evaluation indicates values < 2.3 mm/year and <60 mm/year for summer and winter scenarios, respectively. Finally, the investigation addresses insights for decision-makers for the appropriate planning and sustainable management of groundwater resources in small-scale urban areas.
Assessing groundwater vulnerability to contamination is vital worldwide, particularly in sustainable water resources management. That is mainly a concern in fractured media in urban areas due to a large diversity of contaminant sources and the complexity of recharge pathways. Thus, groundwater vulnerability assessment is essential to delineate groundwater protection zones around springs or wellheads. Furthermore, it considers the groundwater system’s heterogeneity and the surrounding hydrogeological conditions, as well as provides suitable solutions to protect the resource and mitigate potential hazards. DISCO-URBAN index focused on urban areas was applied to evaluate the intrinsic vulnerability in fractured media in the surroundings of Penafiel city (NW Portugal). The analytic hierarchy process (AHP) was used to determine the weight of each evaluation factor. Furthermore, multi-criteria indexes were applied: GOD‐S, DRASTIC‐Fm, SI DISCO and DISCO-URBAN. Low to moderate vulnerability classes dominate in the combined approach of the vulnerability indexes. However, very high vulnerability classes occur in DISCO and DISCO-URBAN, corroborated by the water-enriched nitrates. Therefore, the DISCO-URBAN method highlights a better delineation of groundwater safeguard zones. In fact, the DISCO-URBAN index is reliable in urban areas to be integrated as a tool to develop local site hydrogeological investigations related to springs safeguard zones.
Fractured media hydrosystems sources are valuable worldwide for irrigation, water supply, and industrial purposes. Mapping and evaluating intrinsic groundwater vulnerability is a balanced integrative methodology to describe the potential groundwater contamination or pollution. The Geographical Information System (GIS) overlay mapping technique and multi-parametric methodology are largely employed to evaluate vulnerability in groundwater systems. However, the DRASTIC index methodology is often used for regional approaches and is the most recognised for groundwater vulnerability assessment for general purposes. Therefore, several adaptations were proposed, such as the DRASTIC‐Fm methodology focused on fractured rock media. This study proposes an updated multi-parametric DRASTIC-Fm-URBAN methodology’s concept, importance, and applicability, which supports the potential groundwater vulnerability on fractured media assessment for urban areas. This approach is more accurate, particularly on regional to local scales. The analytic hierarchy process (AHP) was applied to define the weight of each assessment parameter. In addition, the index DISCO-URBAN, SI and GODS were used in the historic springs of the Porto and Vila Nova de Gaia riverside urban area. In fact, coupling DRASTIC-Fm-URBAN and DISCO-URBAN vulnerability indexes are reliable approaches to be included as a tool to develop a robust hydrogeological conceptual site model for urban areas.
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