scholarly journals Groundwater Storage Changes in the Major North African Transboundary Aquifer Systems during the GRACE Era (2003–2016)

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2669 ◽  
Author(s):  
Frédéric Frappart
Keyword(s):  
Water Loss ◽  
North African ◽  
Groundwater Storage ◽  
Aquifer System ◽  
Water Abstraction ◽  
Nubian Sandstone ◽  
Sandstone Aquifer ◽  
Aquifer Systems ◽  
Terrestrial Water ◽  
Transboundary Aquifers

Groundwater is an essential component of the terrestrial water cycle and a key resource for supplying water to billions of people and for sustaining domestic and economic (agricultural and industrial) activities, especially in arid and semi-arid areas. The goal of this study is to analyze the recent groundwater changes which occurred in the major North African transboundary aquifers in the beginning of the 21st century. Groundwater storage anomalies were obtained by removing soil moisture in the root zone (and surface water in the case of the Nubian Sandstone Aquifer System) from the terrestrial water storage anomalies estimated using the Gravity Recovery and Climate Experiment (GRACE) over the 2003–2016 time period. Spatio-temporal changes in groundwater storage contrast significantly among the different transboundary aquifers. Low changes (lower than 10 km3) were observed in the Tindouf Aquifer System but they were found to be highly correlated (R = 0.74) to atmospheric fluxes (precipitation minus evapotranspiration, P − ET) at annual scale. The GRACE data revealed huge water loss in the North Western Sahara and the Nubian Sandstone Aquifer Systems, above 30 km3 and around 50 km3, respectively. In the former case, the aquifer depletion can be attributed to both climate (R = 0.67 against P − ET) and water abstraction, and only to water abstraction in the latter case. The increase in water abstraction results from an increase in irrigated areas and population growth. For these two aquifers, a deceleration in the water loss observed after 2013 is likely to be attributed either to an increase in rainfall favoring rain-fed agriculture or to measures taken to reduce the over-exploitation of the groundwater resources.

scholarly journals Irrigation-Intensive Groundwater Modeling of Complex Aquifer Systems Through Integration of Big Geological Data

2021 ◽  
Vol 3 ◽  
Author(s):  
Hamid Vahdat-Aboueshagh ◽  
Frank T.-C. Tsai ◽  
Dependra Bhatta ◽  
Krishna P. Paudel
Keyword(s):  
Groundwater Modeling ◽  
Flow Direction ◽  
Well Log ◽  
Vertical Flow ◽  
Groundwater Model ◽  
Entire Region ◽  
Groundwater Storage ◽  
Aquifer System ◽  
Fine Grained ◽  
Aquifer Systems

This study identifies hydrogeologic characteristics of complex aquifers based on constructing stratigraphic structure with large, non-uniform well log data. The approach was validated through a modeling study of the irrigation-intensive Chicot aquifer system, which is an important Pleistocene-Holocene aquifer of the Coastal Lowlands aquifer system in the southwestern Louisiana. Various well log types were unified into the same data structure, prioritized based on data sources, and interpolated to generate a detailed stratigraphic structure. More than 29,000 well logs were integrated to construct a stratigraphy model of 56 model layers for the Chicot aquifer system. The stratigraphy model revealed interconnections of various sands in the system, where 90% of the model domain is covered by fine-grained sediments. Although the groundwater model estimated a slight groundwater storage gain during 2005–2014 for the entire region, groundwater storage in the agricultural area was depleted. Nevertheless, the quick groundwater storage recovery during the non-irrigation seasons suggests that the Chicot aquifer system is a prolific aquifer system. The groundwater modeling result shows that the gulfward groundwater flow direction prior to pumping has been reversed toward inland pumping areas. The large upward vertical flow from the deeper sands indicates potential saltwater migration from the base of the Chicot aquifer system.

The Distribution of Volatile Organics in a Leachate Plume, Gloucester, Ontario

1987 ◽  
Vol 22 (1) ◽  
pp. 49-64 ◽  
Author(s):  
J.F. Devlin ◽  
W.A. Gorman
Keyword(s):  
Organic Contaminants ◽  
Source Area ◽  
Unconfined Aquifer ◽  
High Concentration ◽  
Organic Contamination ◽  
Aquifer System ◽  
Aquifer Systems ◽  
Volatile Organic ◽  
Volatile Organic Contaminants ◽  
Aquifer Sediments

Abstract The Gloucester Landfill is located near Ottawa, Ontario, on a northeast trending ridge of Quaternary age. The ridge comprises outwash sediments which make up two aquifer systems. A confined system exists next to bedrock, and is overlain by a silty-clayey stratum (the confining layer) which is, in turn, overlain by an unconfined aquifer system. Two independent volatile organic plumes have previously been identified at the landfill: the southeast plume, which has penetrated the confined aquifer system, and the northeast plume which is migrating in the unconfined aquifer. The distribution of volatile organic contaminants at the northeast plume site appears to be a function of two factors: (1) heterogeneities in the aquifer sediments are causing the channeling of contaminants through a narrow path; (2) the low fraction of organic carbon in the unconfined aquifer sediments at the northeast site is resulting in little retardation of the contaminants there, relative to those at the southeast site. Acetate was the only volatile fatty acid detected in the leachate. It was measurable only in areas where the volatile organic contamination was significant. Although methane was detected in the contaminated sediments, suggesting that microbial activity was present, the high concentration of acetate (>1000 ppm) which was detected down-gradient from the source area indicates that any biodegradation which is occurring is proceeding at a very slow rate.

The Migration Behaviour of Transuranium Elements in Gorleben Aquifer Systems: Colloid Generation and Retention Process

1988 ◽  
Vol 127 ◽  
Author(s):  
J. I. Kim ◽  
G. Buckau ◽  
H. Rommel ◽  
B. Sohnius
Keyword(s):  
Migration Process ◽  
Transuranium Elements ◽  
Aquifer System ◽  
Migration Behaviour ◽  
Aquifer Systems ◽  
Migration Study

ABSTRACTThe colloid generation as a part of the migration process of trans-uranic ions has been studied in the Gorlben aquifer system. From the migration study for the Gorleben repository site, typical examples are selected to demonstrate the influence of colloids. The quantification of colloid generation and its influence on the dissolution and geochemical sorption of transuranium elements are discussed.

scholarly journals Recent changes in terrestrial water storage in the Upper Nile Basin: an evaluation of commonly used gridded GRACE products

2017 ◽  
Vol 21 (9) ◽  
pp. 4533-4549 ◽  
Author(s):  
Mohammad Shamsudduha ◽  
Richard G. Taylor ◽  
Darren Jones ◽  
Laurent Longuevergne ◽  
Michael Owor ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Lake Victoria ◽  
Water Storage ◽  
Terrestrial Water Storage ◽  
Nile Basin ◽  
Lake Victoria Basin ◽  
Groundwater Storage ◽  
Terrestrial Water ◽  
Substantial Uncertainty

Abstract. GRACE (Gravity Recovery and Climate Experiment) satellite data monitor large-scale changes in total terrestrial water storage (ΔTWS), providing an invaluable tool where in situ observations are limited. Substantial uncertainty remains, however, in the amplitude of GRACE gravity signals and the disaggregation of TWS into individual terrestrial water stores (e.g. groundwater storage). Here, we test the phase and amplitude of three GRACE ΔTWS signals from five commonly used gridded products (i.e. NASA's GRCTellus: CSR, JPL, GFZ; JPL-Mascons; GRGS GRACE) using in situ data and modelled soil moisture from the Global Land Data Assimilation System (GLDAS) in two sub-basins (LVB: Lake Victoria Basin; LKB: Lake Kyoga Basin) of the Upper Nile Basin. The analysis extends from January 2003 to December 2012, but focuses on a large and accurately observed reduction in ΔTWS of 83 km3 from 2003 to 2006 in the Lake Victoria Basin. We reveal substantial variability in current GRACE products to quantify the reduction of ΔTWS in Lake Victoria that ranges from 80 km3 (JPL-Mascons) to 69 and 31 km3 for GRGS and GRCTellus respectively. Representation of the phase in TWS in the Upper Nile Basin by GRACE products varies but is generally robust with GRGS, JPL-Mascons, and GRCTellus (ensemble mean of CSR, JPL, and GFZ time-series data), explaining 90, 84, and 75 % of the variance respectively in "in situ" or "bottom-up" ΔTWS in the LVB. Resolution of changes in groundwater storage (ΔGWS) from GRACE ΔTWS is greatly constrained by both uncertainty in changes in soil-moisture storage (ΔSMS) modelled by GLDAS LSMs (CLM, NOAH, VIC) and the low annual amplitudes in ΔGWS (e.g. 1.8–4.9 cm) observed in deeply weathered crystalline rocks underlying the Upper Nile Basin. Our study highlights the substantial uncertainty in the amplitude of ΔTWS that can result from different data-processing strategies in commonly used, gridded GRACE products; this uncertainty is disregarded in analyses of ΔTWS and individual stores applying a single GRACE product.

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