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SUMMARY:Generation of quick flood events by a groundwater flow - Dr Adrien
  Guerin\, Universidad Adolfo Ibáñez
DTSTART:20161006T103000Z
DTEND:20161006T113000Z
UID:TALK67937@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:River hydrographs generally exhibit intense flood events durin
 g which the discharge increases quickly during rainfall\, and decreases sl
 owly afterwards. In this seminar\, we show that the dynamics of groundwate
 r in an unconfined aquifer can account for these features.\n\nA laboratory
  aquifer (homogeneous and bidimensional)\, made of a tank filled with glas
 s beads\, is submitted to artificial rainfall. Rainwater infiltrates into 
 the porous material to join a groundwater reservoir. Groundwater then flow
 s slowly to exit this laboratory aquifer through one side of the tank. Thi
 s simplified experimental setup generates a realistic flood signal\, in th
 e absence of surface runoff.\n\nA theory based on Darcy's law and the shal
 low water approximation reveals two asymptotic regimes. At the beginning o
 f a rain event\, the water discharge increases linearly with time\, with a
  slope proportional to the rainfall rate at the power of $3/2$. Long after
  the rain has stopped\, it decreases as the inverse time squared\, as pred
 icted by Polubarinova-Kochina (1962). These predictions compare well again
 st our experimental data.\n\nField observation in the catchment of the Qui
 ock Creek\, Guadeloupe reveals a similar behaviour. The water table and th
 e river discharge evolve simultaneously during rainfall\, and exhibit the 
 same asymptotic behaviours. Like in our laboratory experiment\, this aquif
 er reacts non-linearly to forcing by rainfall. This observation suggests t
 hat these results could be extended to a broader class of groundwater flow
 s.\n\n\n
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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