scholarly journals Conceptual and numerical modeling of the Guaraní Aquifer System

2012 ◽  
Vol 9 (8) ◽  
pp. 9885-9930
Author(s):  
L. Rodríguez ◽  
L. Vives ◽  
A. Gomez
Keyword(s):  
Hydraulic Conductivity ◽  
Water Balance ◽  
Groundwater Modeling ◽  
Regional Scale ◽  
Early Years ◽  
Scale Model ◽  
Aquifer System ◽  
Aquifer Storage ◽  
Guarani Aquifer ◽  
The Impact

Abstract. In large aquifers relevant for their considerable size, regional groundwater modeling remains challenging given geologic complexity and data scarcity in space and time. The Guaraní Aquifer System is the largest transboundary aquifer in South America. It contains an enormous volume of water, however, it is not well known being difficult to assess the impact of exploitation currently used to supply over 25 million inhabitants. This is a sensitive issue because the aquifer is shared by four countries. Moreover, an integrated groundwater model, and therefore, a global water balance were not available. In this work, a transient regional scale model for the entire aquifer based upon five simplified, equally plausible conceptual models represented by different hydraulic conductivity parametrizations, is used to analyze the flow system and water balance components. Combining an increasing number of hydraulic conductivity zones and an appropriate set of boundary conditions, the hypothesis of a continuous sedimentary unit yielded errors within the calibration target in a regional sense. The magnitude of the water budget terms resulted very similar for all parametrizations. Recharge and stream/aquifer fluxes were the dominant components representing, on average, 84.2% of total inflows and 61.4% of total outflows, respectively. However, leakage was small compared to stream discharges of main rivers. For instance, the simulated average leakage for the Uruguay river was 8 m3 s−1 while the observed absolute minimum discharge was 382 m3 s−1. Streams located in heavily pumped regions switched from a gaining condition on early years to a losing condition over time. Water is discharged through the aquifer boundaries, except at the eastern boundary. On average, pumping represented 16.2% of inflows while aquifer storage experienced a small overall increment. The model water balance indicates that the current rate of groundwater withdrawals does not exceed the rate of recharge on a regional sense.

scholarly journals Conceptual and numerical modeling approach of the Guarani Aquifer System

2013 ◽  
Vol 17 (1) ◽  
pp. 295-314 ◽  
Author(s):  
L. Rodríguez ◽  
L. Vives ◽  
A. Gomez
Keyword(s):  
Hydraulic Conductivity ◽  
Water Balance ◽  
Water Budget ◽  
Flow System ◽  
Regional Scale ◽  
Early Years ◽  
Scale Model ◽  
Aquifer System ◽  
Guarani Aquifer ◽  
The Impact

Abstract. In large aquifers, relevant for their considerable size, regional groundwater modeling remains challenging given geologic complexity and data scarcity in space and time. Yet, it may be conjectured that regional scale groundwater flow models can help in understanding the flow system functioning and the relative magnitude of water budget components, which are important for aquifer management. The Guaraní Aquifer System is the largest transboundary aquifer in South America. It contains an enormous volume of water; however, it is not well known, being difficult to assess the impact of exploitation currently used to supply over 25 million inhabitants. This is a sensitive issue because the aquifer is shared by four countries. Moreover, an integrated groundwater model, and therefore a global water balance, were not available. In this work, a transient regional scale model for the entire aquifer based upon five simplified, equally plausible conceptual models represented by different hydraulic conductivity parametrizations is used to analyze the flow system and water balance components. Combining an increasing number of hydraulic conductivity zones and an appropriate set of boundary conditions, the hypothesis of a continuous sedimentary unit yielded errors within the calibration target in a regional sense. The magnitude of the water budget terms resulted very similar for all parametrizations. Recharge and stream/aquifer fluxes were the dominant components representing, on average, 84.2% of total inflows and 61.4% of total outflows, respectively. However, leakage was small compared to stream discharges of main rivers. For instance, the simulated average leakage for the Uruguay River was 8 m3 s−1 while the observed absolute minimum discharge was 382 m3 s−1. Streams located in heavily pumped regions switched from a gaining condition in early years to a losing condition over time. Water is discharged through the aquifer boundaries, except at the eastern boundary. On average, pumping represented 16.2% of inflows while aquifer storage experienced a small overall increment. The model water balance indicates that the current rate of groundwater withdrawals does not exceed the rate of recharge in a regional sense.

scholarly journals Evaluation of Evapotranspiration for Exorheic Catchments of China during the GRACE Era: From a Water Balance Perspective

2020 ◽  
Vol 12 (3) ◽  
pp. 511 ◽  
Author(s):  
Yulong Zhong ◽  
Min Zhong ◽  
Yuna Mao ◽  
Bing Ji
Keyword(s):  
Water Balance ◽  
Balance Equation ◽  
Land Surface ◽  
Regional Scale ◽  
Water Balance Equation ◽  
Direct Measurements ◽  
Terrestrial Water ◽  
Gravity Recovery ◽  
The Impact ◽  
Mean Square Errors

Evapotranspiration (ET) is usually difficult to estimate at the regional scale due to scarce direct measurements. This study uses the water balance equation to calculate the regional ET with observations of precipitation, runoff, and terrestrial water storage changes (TWSC) in nine exorheic catchments of China. We compared the regional ET estimates from a water balance perspective with and without considering TWSC (ETWB: ET estimates with considering TWSC, and ETPQ: ET estimates from precipitation minus runoff without considering TWSC). Results show that the regional annual ET ranges from 417.7 mm/yr to 831.5 mm/yr in the nine exorheic catchments based on the water balance equation. The impact of ignoring TWSC on calculating ET is notable, as the root mean square errors (RMSEs) of annual ET between ETWB and ETPQ range from 12.0–105.8 mm/yr (2.6–12.7% in corresponding annual ET) among the exorheic catchments. We also compared the estimated regional ET with other ET products. Different precipitation products are assessed to explain the inconsistency between different ET products and regional ET from a water balance perspective. The RMSEs between ET estimates from Gravity Recovery and Climate Experiment (GRACE) and ET from land surface models can be reduced if the deviation of precipitation forcing data is considered. ET estimates from Global Land Evaporation Amsterdam Model (GLEAM) can be improved by reducing the uncertainty of precipitation forcing data in three semiarid catchments. This study emphasizes the importance of considering TWSC when calculating the regional ET using a water balance equation and provides more accurate ET estimates to help improve modeled ET results.

scholarly journals Assessment of the Impact of the Spatial Extent of Land Subsidence and Aquifer System Drainage Induced by Underground Mining

2020 ◽  
Vol 12 (19) ◽  
pp. 7871
Author(s):  
Artur Guzy ◽  
Agnieszka A. Malinowska
Keyword(s):  
Land Subsidence ◽  
Indirect Effects ◽  
Underground Mining ◽  
Regional Scale ◽  
Spatial Extent ◽  
Direct Effects ◽  
Hydrogeological Model ◽  
Mining Operations ◽  
Aquifer System ◽  
The Impact

The environmental impact assessment of underground mining usually includes the direct effects of exploitation. These are damage to rock mass and land subsidence. Continuous dewatering of the aquifer system is, however, necessary to carry out underground mining operations. Consequently, the drainage of the aquifer system is observed at a regional scale. The spatial extent of the phenomenon is typically much wider than the direct impact of the exploitation. The research presented was, therefore, aimed at evaluating both the direct and the indirect effects of underground mining. Firstly, the spatial extent of land subsidence was determined based on the Knothe theory. Secondly, underground mining-induced drainage of the aquifers was modeled. The 3D finite-difference hydrogeological model was constructed based on the conventional groundwater flow theory. The values of model hydrogeological parameters were determined based on literature and empirical data. These data were also used for model calibration. Finally, the results of the calculations were compared successfully with the field data. The research results presented indicate that underground mining’s indirect effects cover a much larger area than direct effects. Thus, underground mining requires a broader environmental assessment. Our results can, therefore, pave the way for more efficient management of groundwater considering underground mining.

scholarly journals Impact of Sedimentation on Water Seepage Capacity in Lake Nakuru, Kenya

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Parfait Iradukunda ◽  
Maurice O. Nyadawa
Keyword(s):  
Hydraulic Conductivity ◽  
Water Balance ◽  
Water Level ◽  
Sediment Sample ◽  
Permeability Coefficient ◽  
Lake Nakuru ◽  
Water Seepage ◽  
Average Ratio ◽  
The Impact ◽  
Maximum Permeability

Accumulation and deposition of sediments in waterbody affect the seepage capacity that could lead to improper water balance and results in the water level rise. This study analysed the influence of sedimentation on seepage capacity in Lake Nakuru and the impact of sediment characteristics to the water seepage and the flow rate formation at the lake bed level. The study was performed by sampling and analysing the sediment cores from two locations in the lake. The sediment hydraulic properties, i.e., moisture and porosity, particle sizes, and hydraulic conductivity, were determined using the oven-drying method, sieve analysis, hydrometer analysis, and falling head tests, respectively. The results showed that the lake sediment sample from location P1 had an average ratio of 39.38% for silty soil, 34.00% for clayey sediment, and 26.63% for fine-sand sediment particles with the maximum permeability coefficient of 3.37 ∗ 10 − 5  cm/s, while the one from location P2 had an average ratio of 63.17% for sand, 20.17% for fine particles, and 16.67% for gravels with the maximum permeability coefficient of 0.010793 cm/s. The hydraulic conductivity of sediment sample from location P1 and P2 increased along the core depth. This could lead to the rise of water level due to the decreases of water movement induced from the sediment cementation in the top layers under the waterbody. Sedimentation affects Lake Nakuru water volume and water balance; hence, there is a need to control the inflow of sediment resulting from anthropogenic activities in the watershed.

scholarly journals Determining a composite value for the saturated hydraulic conductivity in a recharge area of the Guarani Aquifer System, using pedotransfer functions

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Marcelo Eduardo Dias de Oliveira ◽  
Didier Gastmans ◽  
Marcelo Donadelli Sacchi ◽  
Rodrigo Esteves Rocha ◽  
Camila de Lima ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Field Measurements ◽  
Saturated Hydraulic Conductivity ◽  
Pedotransfer Functions ◽  
Essential Property ◽  
Sampling Point ◽  
Catchment Scale ◽  
Recharge Area ◽  
Aquifer System ◽  
Guarani Aquifer

ABSTRACT The saturated hydraulic conductivity (Ks) is an essential property for modeling water and contaminants movement into aquifers. However, Ks is extremely variable, even when considering nearby locations, which poses a challenge for modeling at catchment scales. Field measurements of Ks are most of the time expensive, time-consuming and labor-intensive. This study aimed to obtain, for modeling purposes, and using pedotransfer functions (PTFs), a composite value of Ks at a catchment scale, in a recharge area of the Guarani Aquifer System. Soil samples were taken across the study area, and the Ks for each sampling point were determined by several PTF methods. At the same locations, Ks field measurements were taken using a Guelph permeameter. Average values of Ks for all the sampling points calculated by PTFs were similar to the average value obtained by field measurements. The use of PTFs proved to be a faster and simpler method to efficiently determine the Ks value for the watershed and to capture the stochastic variation in terms of soil pore combination at the watershed scale.

scholarly journals Atmospheric ethanol in London and the potential impacts of future fuel formulations

2016 ◽  
Vol 189 ◽  
pp. 105-120 ◽  
Author(s):  
Rachel E. Dunmore ◽  
Lisa K. Whalley ◽  
Tomás Sherwen ◽  
Mathew J. Evans ◽  
Dwayne E. Heard ◽  
...  
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Road Transport ◽  
Emission Source ◽  
Chemical Mechanism ◽  
Scale Model ◽  
Chemical Transport Model ◽  
Regional Modelling ◽  
Primary Emissions ◽  
The Impact

There is growing global consumption of non-fossil fuels such as ethanol made from renewable biomass. Previous studies have shown that one of the main air quality disadvantages of using ethanol blended fuels is a significant increase in the production of acetaldehyde, an unregulated and toxic pollutant. Most studies on the impacts of ethanol blended gasoline have been carried out in the US and Brazil, with much less focus on the UK and Europe. We report time resolved measurements of ethanol in London during the winter and summer of 2012. In both seasons the mean mixing ratio of ethanol was around 5 ppb, with maximum values over 30 ppb, making ethanol currently the most abundant VOC in London air. We identify a road transport related source, with ‘rush-hour’ peaks observed. Ethanol is strongly correlated with other road transport-related emissions, such as small aromatics and light alkanes, and has no relationship to summer biogenic emissions. To determine the impact of road transport-related ethanol emission on secondary species (i.e. acetaldehyde and ozone), we use both a chemically detailed box model (incorporating the Master Chemical Mechanism, MCM) and a global and nested regional scale chemical transport model (GEOS-Chem), on various processing time scales. Using the MCM model, only 16% of the modelled acetaldehyde was formed from ethanol oxidation. However, the model significantly underpredicts the total levels of acetaldehyde, indicating a missing primary emission source, that appears to be traffic-related. Further support for a primary emission source comes from the regional scale model simulations, where the observed concentrations of ethanol and acetaldehyde can only be reconciled with the inclusion of large primary emissions. Although only constrained by one set of observations, the regional modelling suggests a European ethanol source similar in magnitude to that of ethane (∼60 Gg per year) and greater than that of acetaldehyde (∼10 Gg per year). The increased concentrations of ethanol and acetaldehyde from primary emissions impacts both radical and NOx cycling over Europe, resulting in significant regional impacts on NOy speciation and O3 concentrations, with potential changes to human exposure to air pollutants.

scholarly journals Cloud and aerosol radiative effects as key players for anthropogenic changes in atmospheric dynamics over southernWest Africa

2018 ◽  
Author(s):  
Konrad Deetz ◽  
Heike Vogel ◽  
Peter Knippertz ◽  
Bianca Adler ◽  
Jonathan Taylor ◽  
...  
Keyword(s):  
West Africa ◽  
Regional Scale ◽  
Atmospheric Dynamics ◽  
Atmospheric Pollutants ◽  
Scale Model ◽  
Model Framework ◽  
Local Pressure ◽  
Temporal Shift ◽  
Near Surface ◽  
The Impact

Abstract. Southern West Africa (SWA) undergoes rapid and significant socioeconomic changes associated with a massive increase in air pollution. Still, the impact of atmospheric pollutants, in particular that of aerosol particles, on weather and climate in this region is virtually unexplored. In this study, the regional-scale model framework COSMO-ART is applied to SWA for a summer monsoon process study on 2–3 July 2016 to assess the aerosol direct and indirect effect on clouds and the atmospheric dynamics. The modeling study is supported by observational data obtained during the extensive field campaign of the project DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) in June–July 2016. As indicated in previous studies, a coastal front is observed that develops during daytime and propagates inland in the evening (Atlantic Inflow). Increasing the aerosol amount in COSMO-ART leads to reduced propagation velocities with frontal displacements of 10–30 km and a weakening of the nocturnal low-level jet. This is related to a subtle balance of processes related to the decrease in near-surface heating: (1) flow deceleration due to reduced land-sea temperature contrast and thus local pressure gradient, (2) reduced turbulence favoring frontal advance inland and (3) delayed stratus-to-cumulus transition of 1–2 h via a later onset of the convective boundary layer. The spatial shift of the Atlantic Inflow and the temporal shift of the stratus-to-cumulus transition are synergized in a new conceptual model. We hypothesize a negative feedback of the stratus-to-cumulus transition on the Atlantic Inflow with increased aerosol. The results exhibit radiation as the key player governing the aerosol affects on SWA atmospheric dynamics via the aerosol direct effect and the Twomey effect, whereas impacts on precipitation are small.

scholarly journals Numerical simulations of aerosol radiative effects and their impact on clouds and atmospheric dynamics over southern West Africa

2018 ◽  
Vol 18 (13) ◽  
pp. 9767-9788 ◽  
Author(s):  
Konrad Deetz ◽  
Heike Vogel ◽  
Peter Knippertz ◽  
Bianca Adler ◽  
Jonathan Taylor ◽  
...  
Keyword(s):  
West Africa ◽  
Regional Scale ◽  
Atmospheric Dynamics ◽  
Atmospheric Pollutants ◽  
Scale Model ◽  
Model Framework ◽  
Local Pressure ◽  
Temporal Shift ◽  
Near Surface ◽  
The Impact

Abstract. Southern West Africa (SWA) is undergoing rapid and significant socioeconomic changes associated with a massive increase in air pollution. Still, the impact of atmospheric pollutants, in particular that of aerosol particles, on weather and climate in this region is virtually unexplored. In this study, the regional-scale model framework COSMO-ART is applied to SWA for a summer monsoon process study on 2–3 July 2016 to assess the aerosol direct and indirect effect on clouds and atmospheric dynamics. The modeling study is supported by observational data obtained during the extensive field campaign of the project DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) in June–July 2016. As indicated in previous studies, a coastal front is observed that develops during daytime and propagates inland in the evening (Atlantic inflow). Increasing the aerosol amount in COSMO-ART leads to reduced propagation velocities with frontal displacements of 10–30 km and a weakening of the nocturnal low-level jet. This is related to a subtle balance of processes related to the decrease in near-surface heating: (1) flow deceleration due to reduced land–sea temperature contrast and thus local pressure gradient, (2) reduced turbulence favoring frontal advance inland and (3) delayed stratus-to-cumulus transition of 1–2 h via a later onset of the convective boundary layer. The spatial shift of the Atlantic inflow and the temporal shift of the stratus-to-cumulus transition are synergized in a new conceptual model. We hypothesize a negative feedback of the stratus-to-cumulus transition on the Atlantic inflow with increased aerosol. The results exhibit radiation as the key player governing the aerosol affects on SWA atmospheric dynamics via the aerosol direct effect and the Twomey effect, whereas impacts on precipitation are small.

scholarly journals Assessment of Three Common Methods for Estimating Terrestrial Water Storage Change with Three Reanalysis Datasets

2020 ◽  
Vol 33 (2) ◽  
pp. 511-525 ◽  
Author(s):  
Shanshan Deng ◽  
Suxia Liu ◽  
Xingguo Mo
Keyword(s):  
Water Balance ◽  
Hydrological Cycle ◽  
Regional Scale ◽  
Water Storage ◽  
Balance Method ◽  
Terrestrial Water Storage ◽  
Water Balance Method ◽  
Terrestrial Water ◽  
The Impact ◽  
Storage Change

AbstractTerrestrial water storage change (TWSC) plays a crucial role in the hydrological cycle and climate system. To date, methods including 1) the terrestrial water balance method (PER), 2) the combined atmospheric and terrestrial water balance method (AT), and 3) the summation method (SS) have been developed to estimate TWSC, but the accuracy of these methods has not been systematically compared. This paper compares the spatial and temporal differences of the TWSC estimates by the three methods comprehensively with the GRACE data during the 2002–13 period. To avoid the impact of different inputs in the comparison, three advanced reanalysis datasets are used, namely 1) the National Centers for Environmental Prediction (NCEP)–Department of Energy (DOE) Reanalysis II (NCEP R2), 2) the ECMWF interim reanalysis (ERA-Interim), and 3) the Japanese 55-Year Reanalysis (JRA-55). The results show that all estimates with PER and AT considerably overestimate the long-term mean on a regional scale because the data assimilation in the reanalysis opens the water budget. The difficulty of atmospheric observation and simulation in arid and polar tundra regions is the documented reason for the failure of the AT method to represent the TWSC phase over 30% of the region found in this study. Although the SS result exhibited the best overall agreement with GRACE, the amplitude of TWSC based on SS differed substantially from that of GRACE and the similarity coefficient of the global distribution between the SS-derived estimate and GRACE is still not high. More detailed considerations of groundwater and human activities, for example, irrigation and reservoir impoundments, can help SS to achieve a higher accuracy.

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