Aquifer storage and recovery systems using multiple partially penetrating wells (MPPW-ASR) can form a viable solution to the problem of freshwater buoyancy when using brackish aquifers for freshwater ...storage. This study presents the result of a series of laboratory experiments that aimed at visualizing the shape of freshwater bodies injected into a brackish aquifer and determining the effect on the recovery efficiency (RE) of several MPPW-ASR operational variables. A model aquifer was built in a Plexiglas tank using glass beads and water was injected and abstracted through point and vertical wells, which were operated in various combinations. Numerical models were used to support the interpretation of the time-lapse photographs, and showed that three-dimensional flow effects had to be considered for a correct interpretation of the visible dye patterns. Upward migration of both fresh (during injection) and brackish water (during recovery) along the vertical wells was observed, indicating that the role of well infrastructure as conduits is a critical design criterion for real-world systems. Gravitational instabilities formed when freshwater did not extend all the way to the top of the aquifer, and this negatively impacted the RE by causing greater mixing. The positive freshwater buoyancy led to freshwater bodies that became narrower with depth, and the formation of thin, elongated buffer zones along the aquifer top in multicycle experiments. Up-coning below abstraction wells resulted in lower RE values, reinforcing the potential of scavenger wells to enhance MPPW-ASR system performance.
The Lake Chad Basin is Africa’s largest endorheic basin. Because water supply for the rural population and most of the urban population depends on groundwater, assessment of groundwater recharge is ...crucial. Recharge sources for the upper Quaternary aquifer are precipitation, rivers, and swamps. Using water chemistry, and environmental (
18
O,
2
H,
3
H) and carbon (
14
C) isotopes, recharge processes can be assessed and groundwater ages roughly estimated. For this purpose, more than 1,000 samples from groundwater, surface water and precipitation were analysed for hydrochemistry and environmental stable isotopes. Furthermore,
3
H measurements and
14
C values of dissolved inorganic carbon for groundwater from the northeastern part of the Basin are included in the evaluation. The environmental isotope distribution shows recent recharge from precipitation north of Lake Chad (Kanem Region), where very low
3
H values indicate occurrence before the 1960s bomb peak. Focused recharge from fresh river water is typical for Salamat Region in south Chad and the Komadugu Yobe wetlands between Nigeria and Niger. Slightly high δ-values in water occur in the Waza Logone area between Chad and Cameroon. Groundwater along the Lake Chad shore and the Bahr el Ghazal corridor show high δ-values (δ
18
O –0.78 to 7.45‰, δ
2
H –13.6 to 30.8‰). Recharge is caused by surface water that undergoes evaporative processes before percolation. Groundwater ages of 600–4,150 years, estimated from
14
C analyses combined with high SO
4
concentrations, along the Bahr el Ghazal indicate that recharge was caused by residuals of the Mega Lake before it dried out completely.
Forschung wird zunehmend aus Sicht ihrer Ergebnisse gedacht - nicht zuletzt aufgrund der Umwälzungen im System Wissensschaft. Der Band lenkt den Fokus jedoch auf diejenigen Prozesse, die ...Forschungsergebnisse erst ermöglichen und Wissenschaft konturieren. Dabei ist der Titel Doing Research als Verweis darauf zu verstehen, dass forschendes Handeln von spezifischen Positionierungen, partiellen Perspektiven und Suchbewegungen geformt ist. So knüpfen alle Beitragenden auf reflexive Weise an ihre jeweiligen Forschungspraktiken an. Ausgangspunkt sind Abkürzungen - die vermeintlich kleinsten Einheiten wissenschaftlicher Aushandlung und Verständigung. Der in den Erziehungs-, Sozial-, Medien- und Kunstwissenschaften verankerte Band zeichnet ein vieldimensionales Bild gegenwärtigen Forschens mit transdisziplinären Anknüpfungspunkten zwischen Digitalität und Bildung. (DIPF/Orig.)
Forschung wird zunehmend aus Sicht ihrer Ergebnisse gedacht - nicht zuletzt aufgrund der Umwälzungen im System Wissensschaft. Der Band lenkt den Fokus jedoch auf diejenigen Prozesse, die ...Forschungsergebnisse erst ermöglichen und Wissenschaft konturieren. Dabei ist der Titel Doing Research als Verweis darauf zu verstehen, dass forschendes Handeln von spezifischen Positionierungen, partiellen Perspektiven und Suchbewegungen geformt ist. So knüpfen alle Beitragenden auf reflexive Weise an ihre jeweiligen Forschungspraktiken an. Ausgangspunkt sind Abkürzungen - die vermeintlich kleinsten Einheiten wissenschaftlicher Aushandlung und Verständigung. Der in den Erziehungs-, Sozial-, Medien- und Kunstwissenschaften verankerte Band zeichnet ein vieldimensionales Bild gegenwärtigen Forschens mit transdisziplinären Anknüpfungspunkten zwischen Digitalität und Bildung.
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