Rc. Brunet et Kb. Astin, Spatio-temporal variation in some physical and chemical parameters over a 25-year period in the catchment of the river Adour, J HYDROL, 220(3-4), 1999, pp. 209-221
The catchment of the river Adour (SW France) has been examined in order to
analyse spatio-temporal variations in a number of key variables (flow, susp
ended matter, nitrate and dissolved orthophosphate concentrations) over a 2
5-year period (1972-1996).
Within the catchment area, it has been possible to discern how hydroclimati
c fluctuations have affected the watershed, with dry periods in 1972-1976 a
nd 1983-1993 alternating with wetter phases in 1977-1982 and 1994-1995. The
anthropogenic activity, primarily, involving the use of water for agricult
ural purposes, has also had a major impact during this period, particularly
in the downstream areas of the catchment.
Suspended matter fluxes display regular downstream increases with significa
nt erosion being evident in the mountainous region contrasting with retenti
on in the floodplains area downstream. These fluxes exhibit temporal and sp
atial variations with peaks occurring every 3-5 years, 1975-1977, 1979, 198
2, 1985, 1987 and 1992. Some of these peaks are suggested to be related to
anthropogenic activity involving river management, including the cutting of
meanders and the construction of dykes for flood prevention.
Nitrate concentrations evince a similar pattern to the suspended matter flu
xes with enhanced levels of downstream. The confluence of the Adour with th
e Midouze appears not to have any major impact on the nitrate concentration
. In the downstream areas, an uptake of nitrate is registered indicating th
e activity of the riparian vegetation. For the entire catchment, maximal ni
trate concentrations are observed in 1979, 1982, 1987, 1991-1992 and 1995.
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