scholarly journals Regional Aquifer Vulnerability and Pollution Sensitivity Analysis of Drastic Application to Dahomey Basin of Nigeria

2020 ◽  
Vol 17 (7) ◽  
pp. 2609
Author(s):  
Saheed Adeyinka Oke
Keyword(s):  
Sensitivity Analysis ◽  
Vadose Zone ◽  
Shallow Groundwater ◽  
Aquifer Vulnerability ◽  
Single Parameter ◽  
Southwestern Nigeria ◽  
Groundwater Vulnerability Mapping ◽  
Dahomey Basin ◽  
Vulnerability Map ◽  
The Impact

Shallow groundwater vulnerability mapping of the southwestern Nigeria sedimentary basin was assessed in this study with the aim of developing a regional-based vulnerability map for the area based on assessing the intrinsic ability of the aquifer overlying beds to filter and degrade migrating pollutant. The mapping includes using the established seven parameter-based DRASTIC vulnerability methodology. Furthermore, the developed vulnerability map was subjected to sensitivity analysis as a validation approach. This approach includes single-parameter sensitivity, map removal sensitivity, and DRASTIC parameter correlation analysis. Of the Dahomey Basin, 21% was classified as high-vulnerability and at risk of pollution, 61% as moderate vulnerability, and 18% as low vulnerability. Low vulnerability areas of the basin are characterised by thick vadose zones, low precipitation, compacted soils, high slopes, and high depth to groundwater. High-vulnerability areas which are prone to pollution are regions closer to the coast with flat slopes and frequent precipitation. Sensitivity of the vulnerability map show the greatest impact with the removal of topography, soil media, and depth to groundwater and least impact with the removal of the vadose zone. Due to the subjectivity of the DRASTIC method, the most important single parameter affecting the rating system of the Dahomey Basin DRASTIC map is the impact of the vadose zone, followed by the net recharge and hydraulic conductivity. The DRASTIC vulnerability map can be useful in planning and siting activities that generate pollutants (e.g., landfill, soak away, automobile workshops, and petrochemical industries) which pollute the environment, groundwater, and eventually impact the environmental health of the Dahomey Basin’s inhabitants.

Aquifer vulnerability to pollution of Oum El-Bouaghi region in North East of Algeria

2017 ◽  
Vol 28 (3) ◽  
pp. 384-399
Author(s):  
Nadjet Zair ◽  
Salah Chaab ◽  
Catherine Bertrand
Keyword(s):  
Sensitivity Analysis ◽  
Vadose Zone ◽  
Vulnerability Assessment ◽  
Design Methodology ◽  
Aquifer Vulnerability ◽  
Parameter Sensitivity Analysis ◽  
Content Type ◽  
North East ◽  
The Impact

Purpose The purpose of this paper is to assess the vulnerability of the aquifer using two models of analysis (DRASTIC and GOD) that were applied in practice in the regions of Bir Chouhada, Souk Naamane and Ouled Zouai in the district of Oum El-Bouaghi. Design/methodology/approach This study aims to determine the most adequate methods to ensure the protection of the Bir Chouhada, Souk Naamane and Ouled Zouai aquifer from pollution using vulnerability assessment. The application of the DRASTIC and GOD models made this evaluation possible. Findings The analysis of the both maps of vulnerability, resulting from the application of the two methods (DRASTIC and GOD), has revealed several classes of vulnerability that are no-, low-, medium- and high-vulnerable area. High DRASTIC vulnerability values vary between 145 and 178, and those of GOD vary between 0.07 and 0.57. It is observed that vulnerability increases from the center toward the eastern part of the plain; this is confirmed by the repartition of nitrate contents. The impact of the hydraulic conductivity on vulnerability to pollution is more significant than those of the vadose zone and the aquifer media. This is well observed when considering the single-parameter sensitivity analysis. Originality/value The text deepens the understanding of the vulnerability assessment and quality of the aquifer and the groundwater. The present study can be used for the assessment and the management of groundwater.

Groundwater Vulnerability Mapping in Urbanized Hydrological System Using Modified Drastic Model and Sensitivity Analysis

2018 ◽  
Vol 24 (3) ◽  
pp. 293-304 ◽  
Author(s):  
Ismail Chenini ◽  
Adel Zghibi ◽  
Mohamed Haythem Msaddek ◽  
Mahmoud Dlala
Keyword(s):  
Land Use ◽  
Vadose Zone ◽  
Vulnerability Assessment ◽  
Groundwater Vulnerability ◽  
Vulnerability Index ◽  
Drastic Model ◽  
Groundwater Vulnerability Mapping ◽  
Groundwater Vulnerability Assessment ◽  
Modified Drastic ◽  
The Impact

Abstract The groundwater vulnerability assessment is normally applied to rural watersheds. However, urbanization modifies the hydrogeological processes. A modified DRASTIC model was adopted to establish a groundwater vulnerability map in an urbanized watershed. The modified DRASTIC model incorporated a land-use map, and net recharge was calculated taking into account the specificity of the urban hydrogeological system. The application of the proposed approach to the Mannouba watershed demonstrates that the groundwater vulnerability indexes range from 80 to 165. The study's results shows that 30 percent of the Mannouba watershed area has a high vulnerability index, 45 percent of the area has a medium index, and 25 percent of the study area has a low vulnerability index. To specify the effect of each DRASTIC factor on the calculated vulnerability index, sensitivity analyses were performed. Land use, topography, and soil media have an important theoretical weight greater than the effective weight. The impact of the vadose zone factor has the most important effective weight and affects the vulnerability index. The sensitivity assessment explored the variation in vulnerability after thematic layer removal. In this analysis, the removal of hydraulic conductivity and impact of vadose zone modified the vulnerability index. Groundwater vulnerability assessment in urbanized watersheds is difficult and has to consider the impact of urbanization in the hydrogeological parameters.

Influence of the shape of inter-horizon boundary and size of soil tongues on preferential flow under shallow groundwater conditions: A simulation study

2011 ◽  
Vol 91 (2) ◽  
pp. 211-221 ◽  
Author(s):  
Priyantha B. Kulasekera ◽  
Gary W. Parkin
Keyword(s):  
Solute Transport ◽  
Vadose Zone ◽  
Simulation Study ◽  
Soil Profile ◽  
Preferential Flow ◽  
Shallow Groundwater ◽  
Soil Horizon ◽  
Tongue Length ◽  
The Impact ◽  
Water And Solute Transport

Kulasekera, P. B. and Parkin, G. W. 2011. Influence of the shape of inter-horizon boundary and size of soil tongues on preferential flow under shallow groundwater conditions: A simulation study. Can. J. Soil Sci. 91: 211–221. Detailed studies of the impact of soil tongues at soil horizon interfaces are very important in understanding preferential flow processes through layered soils and in improving the accuracy of models predicting water and solute transport through the vadose zone. The implication of having soil tongues of different shapes and sizes created at the soil horizon interface on solute transport through a layered soil horizon was studied by simulating water and solute transport using the VS2DI model. This 2-D simulation study reconfirmed that soil tongues facilitate preferential flow, and the level of activeness of tongues may depend on the number of soil tongues, their spacing and distribution. Also, the size of the soil tongues (length and diameter at the interface between the soil horizons) and their shape influence the rate of preferential flow. Increasing tongue length consistently resulted in an increase in solute velocity across the entire soil profile regardless of the tongue shape; for example, a soil tongue of 0.25 m length increased solute velocity by about 1.5 times over a soil profile without tongues, but this increase might be different for soil types and groundwater conditions other than those considered in this study. Narrowing of tongues increased solute velocity, whereas increasing the number of tongues in a wider soil profile decreased the solute-front's velocity. As tongue length increased, the area containing solutes at prescribed elapsed times decreased. An implication of this study is that soil horizon tongue shape and spacing reduce pollutant residence times, hence inter-horizon boundary morphology should be considered when modelling transport through the vadose zone. As well, since the solute velocity behaviours of a triangular- and a wider rectangular-shaped tongue were nearly identical, simply measuring solute velocity in the field will reveal little information on the shape of a soil tongue.

scholarly journals GIS-based DRASTIC and composite DRASTIC indices for assessing groundwater vulnerability in the Baghin aquifer, Kerman, Iran

2020 ◽  
Vol 20 (8) ◽  
pp. 2351-2363
Author(s):  
Mohammad Malakootian ◽  
Majid Nozari
Keyword(s):  
Hydraulic Conductivity ◽  
Vadose Zone ◽  
Groundwater Vulnerability ◽  
Aquifer Vulnerability ◽  
Factors Affecting ◽  
North West ◽  
The North ◽  
Soil Media ◽  
Sensibility Analysis ◽  
The Impact

Abstract. The present study estimates the Kerman–Baghin aquifer vulnerability using DRASTIC and composite DRASTIC (CDRASTIC) indices with the aid of geographic information system (GIS) techniques. Factors affecting the transfer of contamination, including water table depth, soil media, aquifer media, the impact of the vadose zone, topography, hydraulic conductivity, and land use, were used to calculate the DRASTIC and CDRASTIC indices. A sensitivity test was also performed to determine the sensitivity of the parameters. Results showed that the topographic layer displays a gentle slope in the aquifer. Most of the aquifer was covered with irrigated field crops and grassland with a moderate vegetation cover. In addition, the aquifer vulnerability maps indicated very similar results, identifying the north-west parts of the aquifer as areas with high to very high vulnerability. The map removal sensibility analysis (MRSA) revealed the impact of the vadose zone (in the DRASTIC index) and hydraulic conductivity (in the CDRASTIC index) as the most important parameters in vulnerability evaluation. In both indices, the single-parameter sensibility analysis (SPSA) demonstrated net recharge as the most effective factor in vulnerability estimation. According to the results, parts of the studied aquifer have a high vulnerability and require protective measures.

scholarly journals Contribution of the Sensitivity Analysis in Groundwater Vulnerability Assessing Using the DRASTIC and Composite DRASTIC Indexes

2019 ◽  
Author(s):  
Mohammad Malakootian ◽  
Majid Nozari
Keyword(s):  
Hydraulic Conductivity ◽  
Vadose Zone ◽  
Groundwater Vulnerability ◽  
Aquifer Vulnerability ◽  
Geographical Information ◽  
Effective Parameters ◽  
Study Results ◽  
Vulnerability Maps ◽  
Sensibility Analysis ◽  
The Impact

Abstract. The present study estimates Kerman–Baghin aquifer vulnerability by applying the DRASTIC and composite DRASTIC (CDRASTIC) indexes. The factors affecting the transfer of contamination, including the water table depth, soil media, aquifer media, the impact of the vadose zone, topography, hydraulic conductivity, and land use, were ranked, weighted, and integrated using a geographical information system (GIS). A sensitivity test has also been performed to specify the sensitivity of the parameters. The study results show that the topographic layer displays a gentle slope in the aquifer. The majority of the aquifer covered irrigated field crops and grassland with a moderate vegetation cover. In addition, the aquifer vulnerability maps indicate very similar results, recognizing the northwest parts of the aquifer as areas with high and very high vulnerability. The map removal sensibility analysis (MRSA) revealed the impact of the vadose zone (in the DRASTIC index) and hydraulic conductivity (in the CDRASTIC index) as the most effective parameters in the vulnerability evaluation. In both indexes, the single-parameter sensibility analysis (SPSA) showed net recharge as the most effective factor in the vulnerability estimation. From this study, it can be concluded that vulnerability maps can be used as a tool to control human activities for the sustained protection of aquifers.

scholarly journals Assessment of Aquifer Vulnerability Using Multi-Criteria Decision Analysis around Akure Industrial Estate, Akure, Southwestern Nigeria

2019 ◽  
pp. 1-13
Author(s):  
A. D. Adebiyi ◽  
S. O. Ilugbo ◽  
O. E. Bamidele ◽  
T. Egunjobi
Keyword(s):  
Hydraulic Conductivity ◽  
Aquifer Vulnerability ◽  
Geophysical Investigation ◽  
Southwestern Nigeria ◽  
Current Electrode ◽  
Longitudinal Conductance ◽  
Industrial Estate ◽  
Vulnerability Map ◽  
Very High ◽  
Vulnerable Zones

This study is aimed at evaluating of aquifer vulnerability in a typical basement complex environment of Akure industrial estate, Akure, Southwestern Nigeria. A multi-criteria model is developed for achieving this aim; the vulnerability model which is based on topsoil resistivity, longitudinal conductance, thickness of layer overlying aquifer, and hydraulic conductivity of each sounding point across the study area is successfully used to evaluate the aquifer vulnerability of the area for future groundwater development programme in the area. Geophysical investigation involving vertical electrical sounding is carried out across the study area. A total of thirty one (31) vertical electrical soundings (VES) data were acquired using Schlumberger array with maximum half-current electrode separation of 100 m. Three to five geoelectric layers were delineated across the study area. The curve types obtained are the A, H, K, KH, HA, AA, QHA and KHA.The map of topsoil resistivity, longitudinal conductance, thickness of layer overlying aquifer, and hydraulic conductivity were generated and synthesized to producing the vulnerability map. The vulnerability map shows that the area is characterized by five zones; very low, low, moderate, high and very high. The mid-western, southeastern and closure at the northern part of the study area are delineated to be very low to low vulnerable zones, followed by the eastern and part of the western and central part of the study area which are categorized as moderate vulnerable zones, and finally the southern and northern part of the study area which are characterized by high and very high vulnerable zone.

scholarly journals Groundwater vulnerability based on GIS approach: Case study of Zeuss-Koutine aquifer, South-Eastern Tunisia

2017 ◽  
Vol 56 (2) ◽  
Author(s):  
Hanen Jarray ◽  
Mounira Zammouri ◽  
Mohamed Ouessar ◽  
Fadoua Hamzaoui-Azaza ◽  
Manuela Barbieri ◽  
...  
Keyword(s):  
Groundwater Resources ◽  
Groundwater Vulnerability ◽  
Aquifer Vulnerability ◽  
Southeastern Part ◽  
Intensive Exploitation ◽  
Groundwater Vulnerability Mapping ◽  
Dry Water ◽  
Potential Pollution ◽  
The Impact

Groundwater vulnerability mapping is largely used as a modeling tool to delineate areas susceptible to pollution and to protect groundwater resources from this threat. The Zeuss-Koutine aquifer, which constitutes an important source of drinking water in the Southeastern Tunisia, is subjected to an intensive exploitation and threatened by pollution due mainly to the industrial zone of Koutine. The groundwater circulates in fissured and karstified limestone. Aquifer vulnerability has been assessed using the SINTACS method. The different parameters of the SINTACS model were collected from several sources and converted into thematic maps using ArcGis. Each SINTACS parameter was assigned a weight and rating based on a range of information within the parameter. The weight of each parameter depends on the impact of potential pollution. The analysis of vulnerability map to pollution shows that the Southeastern part of the aquifer and the Wadis beds are more susceptible to pollution. The measured nitrate concentrations of two sampling campaigns carried out in high and dry water seasons are coherent with the SINTACS model results.

scholarly journals Robust Inferences from a Before-and-After Study with Multiple Unaffected Control Groups

2013 ◽  
Vol 1 (2) ◽  
pp. 209-234 ◽  
Author(s):  
Pengyuan Wang ◽  
Mikhail Traskin ◽  
Dylan S. Small
Keyword(s):  
Sensitivity Analysis ◽  
Control Groups ◽  
Two Stage ◽  
Time Effects ◽  
Unaffected Control ◽  
Group Time ◽  
Before And After ◽  
Group Variation ◽  
The Impact ◽  
Before And After Study

AbstractThe before-and-after study with multiple unaffected control groups is widely applied to study treatment effects. The current methods usually assume that the control groups’ differences between the before and after periods, i.e. the group time effects, follow a normal distribution. However, there is usually no strong a priori evidence for the normality assumption, and there are not enough control groups to check the assumption. We propose to use a flexible skew-t distribution family to model group time effects, and consider a range of plausible skew-t distributions. Based on the skew-t distribution assumption, we propose a robust-t method to guarantee nominal significance level under a wide range of skew-t distributions, and hence make the inference robust to misspecification of the distribution of group time effects. We also propose a two-stage approach, which has lower power compared to the robust-t method, but provides an opportunity to conduct sensitivity analysis. Hence, the overall method of analysis is to use the robust-t method to test for the overall hypothesized range of shapes of group variation; if the test fails to reject, use the two-stage method to conduct a sensitivity analysis to see if there is a subset of group variation parameters for which we can be confident that there is a treatment effect. We apply the proposed methods to two datasets. One dataset is from the Current Population Survey (CPS) to study the impact of the Mariel Boatlift on Miami unemployment rates between 1979 and 1982.The other dataset contains the student enrollment and grade repeating data in West Germany in the 1960s with which we study the impact of the short school year in 1966–1967 on grade repeating rates.

scholarly journals A Model for the Thermal Behaviour of an Offshore Cable Installed in a J-Tube

Proceedings ◽  
2020 ◽  
Vol 58 (1) ◽  
pp. 31
Author(s):  
Jeremy Arancio ◽  
Ahmed Ould El Moctar ◽  
Minh Nguyen Tuan ◽  
Faradj Tayat ◽  
Jean-Philippe Roques
Keyword(s):  
Sensitivity Analysis ◽  
Numerical Model ◽  
Thermal Behaviour ◽  
Energy Production ◽  
Power Transmission ◽  
Temperature Fields ◽  
Sobol Indices ◽  
Lumped Element ◽  
Thermal Phenomena ◽  
The Impact

In the race for energy production, supplier companies are concerned by the thermal rating of offshore cables installed in a J-tube, not covered by IEC 60287 standards, and are now looking for solutions to optimize this type of system. This paper presents a numerical model capable of calculating temperature fields of a power transmission cable installed in a J-tube, based on the lumped element method. This model is validated against the existing literature. A sensitivity analysis performed using Sobol indices is then presented in order to understand the impact of the different parameters involved in the heating of the cable. This analysis provides an understanding of the thermal phenomena in the J-tube and paves the way for potential technical and economic solutions to increase the ampacity of offshore cables installed in a J-tube.

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