November 11, 2024

PhD in Geology

Alexandre Oliveira Tavares , Ana Castilho Ramos Lopes e Pedro Alexandre Dinis

Surface water monitoring plays a pivotal role in identify sources of pollution, guiding sustainable practices and preserving aquatic ecosystems. This works aims at research the effectiveness of surface water monitoring in identifying land use and land cover changes and environmental pressures, assessing the impacts of land use and occupation changes, identifying drivers of surface water indicators, and formulating responses to these challenges. The Mondego River Basin located in central Portugal, characterized by diverse geology, land use, and significantly impacted by the 2017 wildfires and the 2021/2022 drought, was selected as the study area. The research hypotheses were examined through extensive monitoring and analysis, leading to practical recommendations.
Systematic surface water monitoring revealed significant water quality indicators associated with environmental pressures. These included increases in water turbidity, and aluminum (Al) and iron (Fe) concentrations associated with land cover changes and increased soil erosion following the wildfires. There were also inputs of ions (e. g. NO3, SO4, Mn) associated with byproducts of combustion during the fires. Land use conversion from fire-affected areas to agricultural areas was also reflected in surface water indicators, such as increased concentrations of NO3 and arsenic (As). These indicators are particularly noticeable during periods of higher precipitation, which demonstrated the role of precipitation in the mobilization of contaminants following land use and cover changes.
Long-term monitoring has proven particularly supportive in identifying the impacts of land use changes on surface water quality. By constructing geochemical baselines using historical data from the same locations, it is possible to establish a comparison threshold for currently monitored data and assess the impacts on surface water.
Using data from surface water monitoring parameters as dependent variables, and precipitation data and geographical data of the catchments as independent variables, it was possible to identify that the extent of the impact from wildfires is more significant when the fires affect developed areas compared to forested areas, highlighting the resilience of ecosystems. Precipitation erosion and transport capacity are higher after land cover changes due to wildfires, even compared to the first flush following a prolonged hydrological drought.
The results of this study indicate that surface water monitoring allows for the attribution of responses to issues regarding the relationship between land use and occupation changes and surface water quality. The responses operations range from measures for soil preservation following wildfires, to maintenance of surface water quality by rehabilitation of the surrounding ecosystems, and recommendations for agricultural restoration following the wildfires. Additionally, community engagement and stakeholder involvement should also contribute to improve surface water quality in these contexts.

Keywords: Surface water monitoring; Land use and occupation change; Wildfires; Drought; DPSIR