scholarly journals Technical note: Water table mapping accounting for river-aquifer connectivity and human pressure

2019 ◽  
Author(s):  
Mathias Maillot ◽  
Nicolas Flipo ◽  
Agnès Rivière ◽  
Nicolas Desassis ◽  
Didier Renard ◽  
...  
Keyword(s):  
Surface Water ◽  
Water Table ◽  
Unsaturated Zone ◽  
Mapping Method ◽  
Technical Note ◽  
Underground Structures ◽  
Soft Data ◽  
Human Pressure ◽  
Hard Data ◽  
Zone Depth

Abstract. A water table mapping method that accounts for surface water-groundwater (SW-GW) connectivity and human pressure, such as pumping and underground structures occurrence, has been elaborated and tested in the heavily urbanized Parisian area. The method developed here consists in two steps. First, hard data (hydraulic head) and soft data (dry wells) are used as conditioning points for the estimation of the SW-GW connection status. A disconnection criteria is adjusted on observed unsaturated zone depth (UZD). It is a default value in areas where such data are missing. The second step consists in the final mapping of water table. Given the knowledge of the disconnection criteria, the final map is achieved with an ordinary kriging of the UZD that integrates the surface water elevation as a nil unsaturated zone where it is relevant. The methodology is demonstrated on two datasets of UZD observations that were collected under low and high flow conditions.

scholarly journals Technical note: Water table mapping accounting for river–aquifer connectivity and human pressure

2019 ◽  
Vol 23 (11) ◽  
pp. 4835-4849
Author(s):  
Mathias Maillot ◽  
Nicolas Flipo ◽  
Agnès Rivière ◽  
Nicolas Desassis ◽  
Didier Renard ◽  
...  
Keyword(s):  
Surface Water ◽  
Water Table ◽  
Unsaturated Zone ◽  
Mapping Method ◽  
Technical Note ◽  
Underground Structures ◽  
Soft Data ◽  
Human Pressure ◽  
Hard Data ◽  
Zone Depth

Abstract. A water table mapping method that accounts for surface-water–groundwater (SW-GW) connectivity and human pressure, such as pumping and underground structures occurrence, has been elaborated and tested in the heavily urbanized Parisian area. The method developed here consists of two steps. First, hard data (hydraulic head) and soft data (dry wells) are used as conditioning points for the estimation of the SW-GW connection status. A disconnection criteria of 0.75 m is adjusted on observed unsaturated zone depth (UZD). It is a default value in areas where such data are missing. The second step consists of the final mapping of the water table. Given the knowledge of the disconnection criteria, the final map is achieved with an ordinary kriging of the UZD that integrates the surface water elevation without unsaturated zone where it is relevant. The methodology is demonstrated on two datasets of UZD observations that were collected under low- and high-flow conditions.

scholarly journals Vulnerabilidade natural à contaminação do aquífero Alter do Chão na área urbana de Manaus, Amazonas, Brasil

2019 ◽  
Vol 18 (1) ◽  
pp. 7
Author(s):  
Miqueias Lima Duarte ◽  
Heron Salazar Costa ◽  
Tatiana Acácio da Silva ◽  
Mariano Vieira dos Santos
Keyword(s):  
Water Table ◽  
Unsaturated Zone ◽  
Groundwater Occurrence ◽  
Zone Depth

A utilização dos recursos hídricos subterrâneos cresce em função do crescimento populacional e da atividade produtiva, aumentando a demanda por água de qualidade, ao mesmo tempo em que crescem os riscos de sua contaminação. O presente estudo avaliou a vulnerabilidade à contaminação do aquífero Alter do Chão na área urbana do município de Manaus, com a aplicação do método GOD (Groundwater occurrence Overall Lithology of the unsaturated zone, Depth of the water table). O emprego do método possibilitou o mapeamento de áreas diferenciadas nas três classes de vulnerabilidade. A baixa vulnerabilidade à contaminação foi predominante (0,41%), seguida pela média vulnerabilidade (0,35%) e alta vulnerabilidade à contaminação (0,24%). A distribuição das classes de alta vulnerabilidade na área de estudo é motivo de preocupação, pelo potencial de contaminação associado o atual uso e ocupação do solo, também em função da direção do fluxo subterrâneo.

scholarly journals Geostatistical investigation into the temporal evolution of spatial structure in a shallow water table

2006 ◽  
Vol 10 (1) ◽  
pp. 113-125 ◽  
Author(s):  
S. W. Lyon ◽  
J. Seibert ◽  
A. J. Lembo ◽  
M. T. Walter ◽  
T. S. Steenhuis
Keyword(s):  
Spatial Structure ◽  
Shallow Water ◽  
Water Table ◽  
Indicator Kriging ◽  
Time Interval ◽  
Short Time Interval ◽  
Soft Data ◽  
Shallow Water Table ◽  
Hard Data ◽  
Long Time

Abstract. Shallow water tables near-streams often lead to saturated, overland flow generating areas in catchments in humid climates. While these saturated areas are assumed to be principal biogeochemical hot-spots and important for issues such as non-point pollution sources, the spatial and temporal behavior of shallow water tables, and associated saturated areas, is not completely understood. This study demonstrates how geostatistical methods can be used to characterize the spatial and temporal variation of the shallow water table for the near-stream region. Event-based and seasonal changes in the spatial structure of the shallow water table, which influences the spatial pattern of surface saturation and related runoff generation, can be identified and used in conjunction to characterize the hydrology of an area. This is accomplished through semivariogram analysis and indicator kriging to produce maps combining soft data (i.e., proxy information to the variable of interest) representing general shallow water table patterns with hard data (i.e., actual measurements) that represent variation in the spatial structure of the shallow water table per rainfall event. The area used was a hillslope in the Catskill Mountains region of New York State. The shallow water table was monitored for a 120 m×180 m near-stream region at 44 sampling locations on 15-min intervals. Outflow of the area was measured at the same time interval. These data were analyzed at a short time interval (15 min) and at a long time interval (months) to characterize the changes in the hydrologic behavior of the hillslope. Indicator semivariograms based on binary-transformed ground water table data (i.e., 1 if exceeding the time-variable median depth to water table and 0 if not) were created for both short and long time intervals. For the short time interval, the indicator semivariograms showed a high degree of spatial structure in the shallow water table for the spring, with increased range during many rain events. During the summer, when evaporation exceeds precipitation, the ranges of the indicator semivariograms decreased during rainfall events due to isolated responses in the water table. For the longer, monthly time interval, semivariograms exhibited higher sills and shorter ranges during spring and lower sills and longer ranges during the summer. For this long time interval, there was a good correlation between probability of exceeding the time-variable median water table and the soil topographical wetness index during the spring. Indicator kriging incorporating both the short and long time interval structure of the shallow water table (hard and soft data, respectively) provided more realistic maps that agreed better with actual observations than the hard data alone. This technique to represent both event-based and seasonal trends incorporates the hillslope-scale hydrological processes to capture significant patterns in the shallow water table. Geostatistical analysis of the spatial and temporal evolution of the shallow water table gives information about the formation of saturated areas important in the understanding hydrological processes working at this and other hillslopes.

scholarly journals Características Hidrogeológicas e Vulnerabilidade à Contaminação das Unidades Aquíferas da Bacia Hidrográfica dos Córregos Amaral e Brilhante - Jaciara (MT) (Hydrogeological features and vulnerability to contamination of aquifer units in ...)

2017 ◽  
Vol 10 (5) ◽  
pp. 1624
Author(s):  
Vanderley Severino Santos ◽  
Reinaldo Lorandi
Keyword(s):  
Water Table ◽  
Unsaturated Zone ◽  
Mixed Type ◽  
Mato Grosso ◽  
Sources Of Pollution ◽  
Groundwater Occurrence ◽  
Potential Sources ◽  
Groundwater Mapping ◽  
Zone Depth

O aumento na demanda por água e o aumento da poluição compromete a qualidade natural das águas subterrâneas. O conhecimento da dinâmica hidrogeológica em aquíferos é importante para analisar o grau de vulnerabilidade desse sistema, bem como identificar e monitorar as fontes potenciais de poluição. Com base nesta preocupação os objetivos desse trabalho foram identificar, caracterizar e mapear as unidades aquíferas da bacia hidrográfica dos Córregos Amaral e Brilhante (Jaciara, Mato Grosso, Brasil), bem como, determinar a vulnerabilidade à contaminação das unidades aquíferas utilizando o método de G.O.D (Groundwater occurrence, Overall lithology of the unsaturated zone, Depth to the water table). Os mapas foram produzidos na escala 1:50.000. Os resultados mostram que nos 339,56 km2 da bacia ocorrem os aquíferos Cachoeirinha, Furnas e Ponta Grossa e a atividade agrícola predominante é o cultivo da cana-de-açúcar. Foi verificado também que o aquífero Cachoeirinha é do tipo poroso livre e apresenta extrema vulnerabilidade e ocupa 74,01% da área. O aquífero Furnas também é do tipo poroso livre apresenta média vulnerabilidade e ocupa 25,73% da área. O aquífero Ponta Grossa é do tipo misto apresenta baixa vulnerabilidade e ocupa somente 0,26% da área total da bacia.  A B S T R A C TThe increase in the demand for water and the increase of pollution compromise the natural quality of groundwater. The knowledge of the hydrogeological dynamics in aquifers it is basic importance to analyze the degree of vulnerability of this system, as well as identifying the potential sources of pollution. For this reason, this work aims to identify, characterize and map the aquifer units of the Amaral and Brilhante (Jaciara, Mato Grosso, Brazil) river basin, as well as assess the vulnerability to pollution of these aquifer units using G.O.D method (Groundwater occurrence, Overall lithology of the unsaturated zone, Depth to the water table). The studied basin has an area of 339.56 km²; the maps ave been created in a 1: 50.000 scale. The results show the occurrence of Cachoeirinha, Furnas and Ponta Grossa aquifers. It has been found out that sugarcane crops are predominant in the area, that the Cachoeirinha aquifer can be classified as belonging to the free porous type, that it is extremely vulnerable and occupies 74.01% of the region; the Furnas aquifer is also a free porous type aquifer, presents an average vulnerability and occupies 25.73% of the region. Finally, the Ponta Grossa aquifer belongs to the the mixed type and presents low vulnerability, occupying only 0.26% of the region. Keywords: Groundwater, mapping, risk of pollution. 

scholarly journals Geostatistical investigation into the temporal evolution of spatial structure in a shallow water table

2005 ◽  
Vol 2 (4) ◽  
pp. 1683-1716 ◽  
Author(s):  
S. W. Lyon ◽  
J. Seibert ◽  
A. J. Lembo ◽  
M. T. Walter ◽  
T. S. Steenhuis
Keyword(s):  
Spatial Structure ◽  
Shallow Water ◽  
Water Table ◽  
Indicator Kriging ◽  
Time Interval ◽  
Short Time Interval ◽  
Soft Data ◽  
Shallow Water Table ◽  
Hard Data ◽  
Long Time

Abstract. Shallow water tables in the near-stream region often lead to saturated areas in catchments in humid climates. While these saturated areas are assumed to be of importance for issues such as non-point pollution sources, little is known about the spatial and temporal behavior of shallow water tables and the resulting saturated areas. In this study, geostatistical methods are employed demonstrating their utility in investigating the spatial and temporal variation of the shallow water table for the near-stream region. Event-based and seasonal changes in the spatial structure of the shallow water table, which directly influences surface saturation and runoff generation, can be identified and used in conjunction to characterize the hydrology of an area. This is accomplished through semivariogram analysis and indicator kriging to produce maps combining supplemental soft data (i.e., proxy information to the variable of interest) representing seasonal trends in the shallow water table with hard data (i.e., the actual measurements) that represent variation in the spatial structure of the shallow water table per rainfall event. The area used was a hillslope located in the Catskill Mountains region of New York State. The shallow water table was monitored for a 120 m×180 m near-stream region at 44 sampling locations on 15-min intervals. Outflow of the area was measured at the same time interval. These data were analyzed at a short time interval (15 min) and at a long time interval (months) to characterize the changes in the hydrology of the region. Indicator semivariograms based on transforming the depth to ground water table data into binary values (i.e., 1 if exceeding the time-variable median depth to water table and 0 if not) were created for both time interval lengths. When considering only the short time interval, the indicator semivariograms for spring when there is excess rainfall show high spatial structure with increased ranges during rain events with surface saturation. During the summer, when evaporation exceeds precipitation, the ranges of the indicator semivariograms decrease during rainfall events due to isolated responses in the water table. When summarized over a longer, monthly time interval, semivariograms exhibited higher sills and shorter ranges during spring and lower sills and longer ranges during the summer. For this long time interval analysis, there was a good correlation between probability of exceeding the time-variable median water table and the soil topographical wetness index during the spring. Indicator kriging incorporating both the short and long time interval structure of the shallow water table (hard and soft data, respectively) provided more realistic maps that agreed better with actual observations then traditional hard data alone. This technique to represent both event-based and seasonal trends compensates for spatially sparse observations while incorporating physical hydrology of the hillslope to capture significant patterns in the shallow water table. Geostatistical analysis of the spatial and temporal evolution of the shallow water table gives information about the formation of saturated areas important in the understanding hydrological processes working at this and other hillslopes.

scholarly journals Technical Note: Development of an automated lysimeter for the calculation of peat soil actual evapotranspiration

2011 ◽  
Vol 8 (3) ◽  
pp. 5009-5033 ◽  
Author(s):  
S. Proulx-McInnis ◽  
A. St-Hilaire ◽  
A. N. Rousseau ◽  
S. Jutras ◽  
G. Carrer ◽  
...  
Keyword(s):  
Water Level ◽  
Water Table ◽  
Peat Soil ◽  
Stomatal Resistance ◽  
Technical Note ◽  
Actual Evapotranspiration ◽  
Quebec City ◽  
Surrounding Water ◽  
To Come ◽  
Number Of Publications

Abstract. A limited number of publications in the literature deal with the measurement of actual evapotranspiration (AET) from a peat soil. AET is an important parameter in the description of water pathways of an ecosystem. In peatlands, where the water table is near the surface and the vegetation is composed of nonvascular plants without stomatal resistance, the AET measurement represents a challenge. This paper discusses the development of an automated lysimeter installed between 12 and 27 July 2010, at a 11-ha bog site, Pont-Rouge (42 km west of Quebec City, Canada). This system was made of an isolated block of peat, maintained at the same water level as the surrounding water table by a system of submersible pressure transmitters and pumps. The change in water level in millimetres in the isolated block of peat was used to calculate the water lost through evapotranspiration (ET) while accounting the precipitation. The rates of AET were calculated for each day of the study period. Temperature fluctuated between 17.2 and 23.3 °C and total rainfall was 43.76 mm. AET rates from 0.6 to 6.9 mm day−1 were recorded, with a ΣAET/ΣP ratio of 1.38. The estimated potential ET (PET) resulting from Thornthwaite's semi-empirical formula suggested values between 2.8 and 3.9 mm day−1. The average AET/PET ratio was 1.13. According to the literature, the results obtained are plausible. This system, relatively inexpensive and simple to install, may eventually be used to calculate AET on peaty soils in the years to come.

Greatly Exaggerated in Canada: Diverging Data and Media Bailouts

2021 ◽  
Vol 46 (3) ◽  
Author(s):  
Marc W Edge
Keyword(s):  
News Media ◽  
Research Centre ◽  
Policy Outcomes ◽  
Think Tank ◽  
Soft Data ◽  
Hard Data ◽  
Media Research ◽  
Using Data ◽  
Media Narratives ◽  
Financial Losses

Background: The Canadian government allocated $595 million in subsidies over five years to news media in 2019, but the bailout was based on questionable data. Financial losses were exaggerated; a think tank report was criticized for using data selectively; data from a university research project differed sharply from annual industry counts; and job loss figures were disputed. Analysis: Hard data can diverge markedly from soft data accepted in pursuit of policy outcomes. Conclusions and implications: A second campaign underway on behalf of entertainment industries could yield a bailout several times larger than the first. Closer scrutiny should be exercised of media narratives and offered data. An independent media research centre should collect and verify data for policy purposes.Contexte : En 2019, le gouvernement canadien a octroyé aux médias d’information 595 millions de dollars en subventions étalées sur cinq ans, un montant évalué à partir de données douteuses. En effet, on a surestimé les pertes financières dans le milieu; le rapport influent d’un groupe de réflexion se fondait sur des données sélectionnées pour les besoins de la cause; les données provenant d’un projet de recherche universitaire différaient beaucoup de celles fournies annuellement par l’industrie; et on a exagéré les pertes d’emploi. Analyse : Les données dures peuvent différer énormément des données molles acceptées dans le but d’atteindre certains objectifs politiques. Conclusion et implications : Une seconde campagne menée pour aider les industries du divertissement pourrait bénéficier de subventions encore plus généreuses que les premières. Avant de procéder, il serait judicieux d’examiner de près les narratifs des médias et les données proposées. À cet égard, on devrait créer un centre indépendant pour la recherche sur les médias qui pourrait lui même recueillir et vérifier les données utilisées pour formuler des politiques.

scholarly journals A Hydrologic Landscapes Perspective on Groundwater Connectivity of Depressional Wetlands

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 50 ◽  
Author(s):  
Brian P. Neff ◽  
Donald O. Rosenberry ◽  
Scott G. Leibowitz ◽  
Dave M. Mushet ◽  
Heather E. Golden ◽  
...  
Keyword(s):  
Surface Water ◽  
Water Table ◽  
Conceptual Knowledge ◽  
Groundwater Discharge ◽  
Depressional Wetlands ◽  
Hydrologic Connectivity ◽  
Site Specific ◽  
Depressional Wetland ◽  
Resource Managers ◽  
Flow Through

Research into processes governing the hydrologic connectivity of depressional wetlands has advanced rapidly in recent years. Nevertheless, a need persists for broadly applicable, non-site-specific guidance to facilitate further research. Here, we explicitly use the hydrologic landscapes theoretical framework to develop broadly applicable conceptual knowledge of depressional-wetland hydrologic connectivity. We used a numerical model to simulate the groundwater flow through five generic hydrologic landscapes. Next, we inserted depressional wetlands into the generic landscapes and repeated the modeling exercise. The results strongly characterize groundwater connectivity from uplands to lowlands as being predominantly indirect. Groundwater flowed from uplands and most of it was discharged to the surface at a concave-upward break in slope, possibly continuing as surface water to lowlands. Additionally, we found that groundwater connectivity of the depressional wetlands was primarily determined by the slope of the adjacent water table. However, we identified certain arrangements of landforms that caused the water table to fall sharply and not follow the surface contour. Finally, we synthesize our findings and provide guidance to practitioners and resource managers regarding the management significance of indirect groundwater discharge and the effect of depressional wetland groundwater connectivity on pond permanence and connectivity.

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