scholarly journals The role of the hyporheic zone in the nitrogen dynamics of a semi-arid gravel bed stream located downstream of a heavily polluted reservoir (Tafna wadi, Algeria)

2008 ◽  
Vol 24 (2) ◽  
pp. 183-196 ◽  
Author(s):  
Amina Taleb ◽  
Nouria Belaidi ◽  
José-Miguel SÁnchez-PÉrez ◽  
Philippe Vervier ◽  
Sabine Sauvage ◽  
...  
2018 ◽  
Author(s):  
Daniel Donahue ◽  
◽  
José Antonio Constantine ◽  
Gregory B. Pasternack

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 694 ◽  
Author(s):  
Ellora Padhi ◽  
Subhasish Dey ◽  
Venkappayya R. Desai ◽  
Nadia Penna ◽  
Roberto Gaudio

In a natural gravel-bed stream, the bed that has an organized roughness structure created by the streamflow is called the water-worked gravel bed (WGB). Such a bed is entirely different from that created in a laboratory by depositing and spreading gravels in the experimental flume, called the screeded gravel bed (SGB). In this paper, a review on the state-of-the-art research on WGBs is presented, highlighting the role of water-work in determining the bed topographical structures and the turbulence characteristics in the flow. In doing so, various methods used to analyze the bed topographical structures are described. Besides, the effects of the water-work on the turbulent flow characteristics, such as streamwise velocity, Reynolds and form-induced stresses, conditional turbulent events and secondary currents in WGBs are discussed. Further, the results form WGBs and SGBs are compared critically. The comparative study infers that a WGB exhibits a higher roughness than an SGB. Consequently, the former has a higher magnitude of turbulence parameters than the latter. Finally, as a future scope of research, laboratory experiments should be conducted in WGBs rather than in SGBs to have an appropriate representation of the flow field close to a natural stream.


2021 ◽  
Author(s):  
Mirza A. T. M. Tanvir Rahman ◽  
Junjiro N. Negishi ◽  
Takumi Akasaka ◽  
Futoshi Nakamura

1987 ◽  
Vol 3 (3) ◽  
pp. 255-263 ◽  
Author(s):  
John A. Holt

ABSTRACTThe contribution of a population of mound building, detritivorous termites (Amitermes laurensis (Mjöberg)) to nett carbon mineralization in an Australian tropical semi-arid woodland has been examined. Carbon mineralization rates were estimated by measuring daily CO2 flux from five termite mounds at monthly intervals for 12 months. Carbon flux from the mounds was found to be due to microbial activity as well as termite activity. It is conservatively estimated that the association of A. laurensis and the microbial population present in their mounds is responsible for between 4%–10% of carbon mineralized in this ecosystem, and the contribution of all termites together (mound builders and subterranean) may account for up to 20% of carbon mineralized. Regression analysis showed that rates of carbon mineralization in termite mounds were significantly related to mound moisture and mound temperature. Soil moisture was the most important factor in soil carbon mineralization, with temperature and a moisture X temperature interaction term also exerting significant affects.


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