Cape Town faces “Day Zero,” the date when the city could run out of water. The proximate cause is... more Cape Town faces “Day Zero,” the date when the city could run out of water. The proximate cause is a three-year drought, considered to be a roughly 1-in-400-year hydrological event. By end of February 2018, the Theewaterskloof dam fell to ~11%, highlighting the importance of obtaining water from diverse sources in adequate storage volumes for assurance of supply, especially in variable and less predictable climate. Development of the Cape Flats Aquifer as an emergency and long-term source was initiated in 2017. This combination of shortand long-term horizons necessitated adopting a ‘No Regrets’ and ‘Build Back Better’ approach, inherent in Disaster Risk Response and Reduction best practice. The integration of remote sensing mapping, GIS modelling, and geological (process) understanding informed the aquifer geometry and properties (product). This aquifer geometry and properties was innovatively combined with of landand air-borne geophysics, parallel exploration and production drilling...
FUNDING: South African National Research Foundation (grant no. 114696) To improve its resilience ... more FUNDING: South African National Research Foundation (grant no. 114696) To improve its resilience to increasing climatic uncertainty, the City of Cape Town (the City) aims to become a water sensitive city by 2040. To undertake this challenge, a means to measure progress is needed that quantifies the urban water systems at a scale that enables a whole-of-system approach to water management. Using an urban water metabolism framework, we (1) provide a first city-scale quantification of the urban water cycle integrating its natural and anthropogenic flows, and (2) assess alternative water sources (indicated in the New Water Programme) and whether they support the City towards becoming water sensitive. We employ a spatially explicit method with particular consideration to apply this analysis to other African or Global South cities. At the time of study, centralised potable water demand by the City amounted to 325 gigalitres per annum, 99% of which was supplied externally from surface stor...
When the Santo Andre coastal lagoon (SAL) is closed to the sea, and no surface runoff is generate... more When the Santo Andre coastal lagoon (SAL) is closed to the sea, and no surface runoff is generated, its water balance is mainly controlled by the hydraulic connection between the stream network discharging into the SAL and the top detritic layer of the multi-layer Sines aquifer system, allowing the classification of this lagoon as a groundwater dependent ecosystem (GDE). A monitoring plan has been implemented to continuously register stream flow discharges in order to estimate groundwater contributions to calibrate the developed numerical flow model of the top detritic Sines aquifer. Simultaneously, the monitoring network was also continuously recording the aquifer level variation, and manual measurement of the hydraulic head of several wells installed in the top detritic aquifer were also used for the numerical flow model calibration. This paper presents estimates of groundwater contributions to the SAL obtained through monitoring and modelling and stream flow estimates contributin...
The dynamics related to evolution of nitrate-contaminated groundwater are analyzed with focus on ... more The dynamics related to evolution of nitrate-contaminated groundwater are analyzed with focus on the impact of intrinsic aquifer properties, agricultural activities and restoration measures at Campina de Faro aquifer (M12), southern Portugal. Agricultural practices in the region developed in the 1970s and resulted in high abstraction rates, nitrate contamination and salinization. Despite the implementation of the European Union (EU) Nitrates Directive since 1997, nitrate levels still show increasing trends at some locations, constituting a threat to the chemical status of M12 and consequent nitrate discharge to Ria Formosa coastal lagoon. Simultaneously, groundwater levels are not dropping consistently, despite apparent overexploitation. A groundwater flow and mass transport model is developed for M12 to assess the evolution of nitrate under different scenarios. Model results reveal that M12 has a hydraulic connection with northernmost aquifers, a process not properly assessed so far. Results further show that nitrate contamination in the upper Plio-Quaternary layer of M12 is extremely persistent and mostly linked to unbalanced fertilizer application practices and irrigation return flows. The response of M12 to implementation of good agricultural practices in compliance with EU policies is slow, indicating that good qualitative status would be impossible to reach by the required EU deadlines. Integration of climate change scenarios into the transport model reveals that despite the implementation of restoration measures, there could be a retardation of the nitrate levels’ decrease in the upper aquifer as a result of enhanced evapoconcentration caused by lower recharge, higher water demands and incomplete mixing within the aquifer.
The Querença-Silves (QS) aquifer system is one of the most important natural groundwater reservoi... more The Querença-Silves (QS) aquifer system is one of the most important natural groundwater reservoirs in the Al-garve region of southern Portugal. With a surface area of 324 km2, this karst aquifer system is the main source of supply for irrigation as well as an important source of water for the urban supply. Due to the importance given to QS aquifer system by both governmental actors and end users, ongoing research during the last two decades at the University of Algarve has attempted to provide a better understanding of the hydrogeology and hydraulic behavior, which has resulted in the development of regional scale numerical models. The most recent hydrogeo-logical data has been acquired during the ongoing MARSOL project (MARSOL-GA-2013-619120) which aims to demonstrate that Managed Aquifer Recharge (MAR) is a sound, safe and sustainable strategy that can be applied with great confidence in finding solutions to water scarcity in Southern Europe. Within the scope of the project large...
ABSTRACT Geoelectrical and electromagnetic (time and frequency domains) hydrogeophysical methods ... more ABSTRACT Geoelectrical and electromagnetic (time and frequency domains) hydrogeophysical methods were applied and jointly interpreted together with auxiliary information such as regional piezometric maps, borehole lithological logs and offshore data. The objective was to retrieve the structure and geometry of the Albufeira-Ribeira de Quarteira coastal aquifer system (Algarve, Portugal) and to upgrade the current hydrogeological conceptual model. The results allowed for the detection of the freshwater–saltwater interface along the coastline and identification of the water-bearing layers and aquitards and their hydraulic relationships. An explanation for the location of the inter- and subtidal fresh groundwater discharge is also presented and a new modeling unit is proposed for groundwater flow modeling. Limitations of the used hydrogeophysical methods are indicated and recommendations are made for follow-up studies.
We applied geoelectrical and electromagnetic (time and frequency domains) hydrogeophysic methods ... more We applied geoelectrical and electromagnetic (time and frequency domains) hydrogeophysic methods to retrieve the structure of the Albufeira-Ribeira de Quarteira coastal aquifer (Algarve, Portugal) and to update the current hydrogeological conceptual model (HCM). The results allowed detecting the freshwater–saltwater interface along the coast line, identifying the water-bearing layers and aquitards and their hydraulic relationships, as well as explaining the location of the inter- and subtidal freshgroundwater discharge. These results will be integrated further works in a hydrogeophysics-based HCM that will support the setup of variable-density groundwater flow numerical model.
Cape Town faces “Day Zero,” the date when the city could run out of water. The proximate cause is... more Cape Town faces “Day Zero,” the date when the city could run out of water. The proximate cause is a three-year drought, considered to be a roughly 1-in-400-year hydrological event. By end of February 2018, the Theewaterskloof dam fell to ~11%, highlighting the importance of obtaining water from diverse sources in adequate storage volumes for assurance of supply, especially in variable and less predictable climate. Development of the Cape Flats Aquifer as an emergency and long-term source was initiated in 2017. This combination of shortand long-term horizons necessitated adopting a ‘No Regrets’ and ‘Build Back Better’ approach, inherent in Disaster Risk Response and Reduction best practice. The integration of remote sensing mapping, GIS modelling, and geological (process) understanding informed the aquifer geometry and properties (product). This aquifer geometry and properties was innovatively combined with of landand air-borne geophysics, parallel exploration and production drilling...
FUNDING: South African National Research Foundation (grant no. 114696) To improve its resilience ... more FUNDING: South African National Research Foundation (grant no. 114696) To improve its resilience to increasing climatic uncertainty, the City of Cape Town (the City) aims to become a water sensitive city by 2040. To undertake this challenge, a means to measure progress is needed that quantifies the urban water systems at a scale that enables a whole-of-system approach to water management. Using an urban water metabolism framework, we (1) provide a first city-scale quantification of the urban water cycle integrating its natural and anthropogenic flows, and (2) assess alternative water sources (indicated in the New Water Programme) and whether they support the City towards becoming water sensitive. We employ a spatially explicit method with particular consideration to apply this analysis to other African or Global South cities. At the time of study, centralised potable water demand by the City amounted to 325 gigalitres per annum, 99% of which was supplied externally from surface stor...
When the Santo Andre coastal lagoon (SAL) is closed to the sea, and no surface runoff is generate... more When the Santo Andre coastal lagoon (SAL) is closed to the sea, and no surface runoff is generated, its water balance is mainly controlled by the hydraulic connection between the stream network discharging into the SAL and the top detritic layer of the multi-layer Sines aquifer system, allowing the classification of this lagoon as a groundwater dependent ecosystem (GDE). A monitoring plan has been implemented to continuously register stream flow discharges in order to estimate groundwater contributions to calibrate the developed numerical flow model of the top detritic Sines aquifer. Simultaneously, the monitoring network was also continuously recording the aquifer level variation, and manual measurement of the hydraulic head of several wells installed in the top detritic aquifer were also used for the numerical flow model calibration. This paper presents estimates of groundwater contributions to the SAL obtained through monitoring and modelling and stream flow estimates contributin...
The dynamics related to evolution of nitrate-contaminated groundwater are analyzed with focus on ... more The dynamics related to evolution of nitrate-contaminated groundwater are analyzed with focus on the impact of intrinsic aquifer properties, agricultural activities and restoration measures at Campina de Faro aquifer (M12), southern Portugal. Agricultural practices in the region developed in the 1970s and resulted in high abstraction rates, nitrate contamination and salinization. Despite the implementation of the European Union (EU) Nitrates Directive since 1997, nitrate levels still show increasing trends at some locations, constituting a threat to the chemical status of M12 and consequent nitrate discharge to Ria Formosa coastal lagoon. Simultaneously, groundwater levels are not dropping consistently, despite apparent overexploitation. A groundwater flow and mass transport model is developed for M12 to assess the evolution of nitrate under different scenarios. Model results reveal that M12 has a hydraulic connection with northernmost aquifers, a process not properly assessed so far. Results further show that nitrate contamination in the upper Plio-Quaternary layer of M12 is extremely persistent and mostly linked to unbalanced fertilizer application practices and irrigation return flows. The response of M12 to implementation of good agricultural practices in compliance with EU policies is slow, indicating that good qualitative status would be impossible to reach by the required EU deadlines. Integration of climate change scenarios into the transport model reveals that despite the implementation of restoration measures, there could be a retardation of the nitrate levels’ decrease in the upper aquifer as a result of enhanced evapoconcentration caused by lower recharge, higher water demands and incomplete mixing within the aquifer.
The Querença-Silves (QS) aquifer system is one of the most important natural groundwater reservoi... more The Querença-Silves (QS) aquifer system is one of the most important natural groundwater reservoirs in the Al-garve region of southern Portugal. With a surface area of 324 km2, this karst aquifer system is the main source of supply for irrigation as well as an important source of water for the urban supply. Due to the importance given to QS aquifer system by both governmental actors and end users, ongoing research during the last two decades at the University of Algarve has attempted to provide a better understanding of the hydrogeology and hydraulic behavior, which has resulted in the development of regional scale numerical models. The most recent hydrogeo-logical data has been acquired during the ongoing MARSOL project (MARSOL-GA-2013-619120) which aims to demonstrate that Managed Aquifer Recharge (MAR) is a sound, safe and sustainable strategy that can be applied with great confidence in finding solutions to water scarcity in Southern Europe. Within the scope of the project large...
ABSTRACT Geoelectrical and electromagnetic (time and frequency domains) hydrogeophysical methods ... more ABSTRACT Geoelectrical and electromagnetic (time and frequency domains) hydrogeophysical methods were applied and jointly interpreted together with auxiliary information such as regional piezometric maps, borehole lithological logs and offshore data. The objective was to retrieve the structure and geometry of the Albufeira-Ribeira de Quarteira coastal aquifer system (Algarve, Portugal) and to upgrade the current hydrogeological conceptual model. The results allowed for the detection of the freshwater–saltwater interface along the coastline and identification of the water-bearing layers and aquitards and their hydraulic relationships. An explanation for the location of the inter- and subtidal fresh groundwater discharge is also presented and a new modeling unit is proposed for groundwater flow modeling. Limitations of the used hydrogeophysical methods are indicated and recommendations are made for follow-up studies.
We applied geoelectrical and electromagnetic (time and frequency domains) hydrogeophysic methods ... more We applied geoelectrical and electromagnetic (time and frequency domains) hydrogeophysic methods to retrieve the structure of the Albufeira-Ribeira de Quarteira coastal aquifer (Algarve, Portugal) and to update the current hydrogeological conceptual model (HCM). The results allowed detecting the freshwater–saltwater interface along the coast line, identifying the water-bearing layers and aquitards and their hydraulic relationships, as well as explaining the location of the inter- and subtidal freshgroundwater discharge. These results will be integrated further works in a hydrogeophysics-based HCM that will support the setup of variable-density groundwater flow numerical model.
The Albufeira-Ribeira de Quarteira aquifer system on the south coast of Portugal is an important ... more The Albufeira-Ribeira de Quarteira aquifer system on the south coast of Portugal is an important source of groundwater for agriculture and tourism, as well as contributing to significant freshwater discharge along the coast in the form of inter- and sub-tidal springs, and maintaining groundwater dependent ecosystems along the Quarteira stream. During the last period of heavy abstraction in the late 1990s, water quality deteriorated significantly. This has alerted to a need to better understand the system, both in terms of quantifying available freshwater and the behavior of the fresh/saltwater interface. Towards this end, a variable density model that accurately represents the complex 3D geologic structure of the aquifer system is under development. The configuration and extent of the aquifer system is still subject to a certain amount of uncertainty. In an initial phase, several hypotheses of the system’s structure are tested with a numerical 2D profile model to simplify 3D model development. Results support a conceptual model that includes a connection between the various layers of the aquifer system and confirms the potential for an extensive freshwater lens several km offshore.
The Albufeira-Ribeira de Quarteira (ARQ) aquifer system on the south coast of Portugal is an impo... more The Albufeira-Ribeira de Quarteira (ARQ) aquifer system on the south coast of Portugal is an important source of groundwater for agriculture and tourism, as well as contributing to significant freshwater discharge along the coast in the form of inter- and sub-tidal springs, and maintaining groundwater dependent ecosystems along the Quarteira stream. During the last period of heavy abstraction in the late 1990s, water quality deteriorated significantly. This has alerted to a need to better understand the system, both in terms of quantifying available freshwater and the behaviour of the fresh/saltwater interface. Towards this end, a variable density model that accurately represents the 3D geologic structure, geometry, boundary conditions and material characteristics of the aquifer system was developed. Until recently, the configuration and extent of the aquifer system has been subject to a certain amount of uncertainty. Thus, we applied geoelectrical and electromagnetic (time and frequency domain) geophysical methods to update the current hydrogeological conceptual model. Results helped to detect the fresh/saltwater interface along the coastline, identify the water-bearing layers and aquitards and provided information on their hydraulic relationships, as well as explain the location of submarine groundwater discharge. In an initial phase, we developed a 2D vertical model in order to test several hypotheses of the system’s structure to simplify the 3D model development. A sensitivity analysis to a range of hydraulic conductivity and recharge values, allowed us to discount several hypotheses as inadequate to representing observed values of hydraulic head and location of the fresh/saltwater interface. Along with the interpretation of existing borehole logs, we are currently applying this data to create a 3D representation of geologic layers that make up the aquifer system, as well as define initial conditions for the fresh/saltwater interface configuration. In a future step, we aim to study the theoretical and practical potentialities and limitations of different approaches to simulating variable-density groundwater flow and their impact on coastal aquifer management. This expands on previous work, in which we have analyzed the importance of hydraulic, climatic and groundwater extraction factors that affect estimates of sustainable groundwater development.
The Almádena-Odeáxere aquifer system with 63.5 km2 (AO) is located in Algarve (south Portugal) an... more The Almádena-Odeáxere aquifer system with 63.5 km2 (AO) is located in Algarve (south Portugal) and is hydraulically connected to several surface water bodies. The most significant of which are linked to the aquifer systems main discharge areas: (1) along the mouth of the Bensafrim stream and (2) at the “Boca do Rio”. These two areas are effluent reaches of rivers in hydraulic connection with the AO and feed wetlands associated with diffuse discharge of groundwater. Therefore, the exploitation of groundwater associated with AO affect the baseflow in these sensitive groundwater dependent ecosystems. In order to study the hydrodynamics of the AO
The AO was the main source of public water supply to the cities of Lagos and Vila do Bispo until the last decade of the last century. Recently this origin of water for the urban water supply of these cities was substituted for surface water from the dams of the region. However, problems with this single-source strategy brought to light during the drought of 2004-05 have started a move towards a water management approach integrating surface and ground water as sources of supply. It is therefore fundamental to comprehend the impacts that the exploitation of these subterranean resources could have on the aquifers and other systems which depend on them.
In order to investigate the quantitative relations of the datasets available for the historical data of aquifer extractions in municipal water wells and the state variables resulting from the monitoring of the AO (piezometric measurements and stream discharges) a regional finite element model was implemented. In a first phase of this work the model was calibrated using inverse modelling tools and integrating the previously available information regarding the aquifer system geometry, boundary conditions, geological cartography and relevant hydrological historical data. Considering its current state of development it is now possible to proceed with the validation of the model, not only to assess its accuracy but also to contribute to an analysis of the impact of the various extraction scenarios to which this aquifer system has been exposed over the last two decades. Therefore, the simulated scenarios in this period allow the analysis of the changes of the regional schemes of water resources management, not only in the exploitation of the AO in terms of regional scale hydrogeologic dynamics but also at the scale of the AO local discharge areas and the associated relations between groundwater and surface water.
Unlike the classically, exclusively hydro-geologic, approach to these issues, this analysis intends to also contribute to the interpretation of the stream-aquifer interactions, as well as the environmental implications resulting from the alteration of the regional flow pattern on the aquifer systems discharge zones. It is hoped that this study will allow for the identification of extraction regimes which do not adversely influence the functioning of the aforementioned natural systems, thus permitting a safer and more accurate management of this underground resource, and by doing so, contribute to demonstrating the usefulness of such models as tools in water resource management.
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Papers by Rui Hugman
The AO was the main source of public water supply to the cities of Lagos and Vila do Bispo until the last decade of the last century. Recently this origin of water for the urban water supply of these cities was substituted for surface water from the dams of the region. However, problems with this single-source strategy brought to light during the drought of 2004-05 have started a move towards a water management approach integrating surface and ground water as sources of supply. It is therefore fundamental to comprehend the impacts that the exploitation of these subterranean resources could have on the aquifers and other systems which depend on them.
In order to investigate the quantitative relations of the datasets available for the historical data of aquifer extractions in municipal water wells and the state variables resulting from the monitoring of the AO (piezometric measurements and stream discharges) a regional finite element model was implemented. In a first phase of this work the model was calibrated using inverse modelling tools and integrating the previously available information regarding the aquifer system geometry, boundary conditions, geological cartography and relevant hydrological historical data. Considering its current state of development it is now possible to proceed with the validation of the model, not only to assess its accuracy but also to contribute to an analysis of the impact of the various extraction scenarios to which this aquifer system has been exposed over the last two decades. Therefore, the simulated scenarios in this period allow the analysis of the changes of the regional schemes of water resources management, not only in the exploitation of the AO in terms of regional scale hydrogeologic dynamics but also at the scale of the AO local discharge areas and the associated relations between groundwater and surface water.
Unlike the classically, exclusively hydro-geologic, approach to these issues, this analysis intends to also contribute to the interpretation of the stream-aquifer interactions, as well as the environmental implications resulting from the alteration of the regional flow pattern on the aquifer systems discharge zones. It is hoped that this study will allow for the identification of extraction regimes which do not adversely influence the functioning of the aforementioned natural systems, thus permitting a safer and more accurate management of this underground resource, and by doing so, contribute to demonstrating the usefulness of such models as tools in water resource management.