@article{fdi:010046834,
  title = {{L}and clearing, climate variability, and water resources increase in semiarid southwest {N}iger : a review},
  author = {{F}avreau, {G}uillaume and {C}appelaere, {B}ernard and {M}assuel, {S}. and {L}eblanc, {M}. and {B}oucher, {M}. and {B}oulain, {N}. and {L}educ, {C}hristian},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he water table in southwestern {N}iger has been rising continuously for the past decades (4 m rise from 1963 to 2007), despite a similar to 23% deficit in monsoonal rainfall from 1970 to 1998. {T}his paradoxical phenomenon has been linked with a change in land use from natural savannah to millet crops that have expanded in area sixfold since 1950 and have caused soil crusting on slopes that has, in turn, enhanced {H}ortonian runoff. {R}unoff concentrates in closed ponds and then recharges the aquifer; therefore, higher runoff increases aquifer recharge. {A}t the local scale (2 km(2)), a physically based, distributed hydrological model showed that land clearing increased runoff threefold, whereas the rainfall deficit decreased runoff by a factor of 2. {A}t a larger scale (500 km(2), 1950-1992 period), historical aerial photographs showed a 2.5-fold increase in the density of gullies, in response to an 80% decrease in perennial vegetation. {A}t the scale of the entire study area ( 5000 km 2), analytical modeling of groundwater radioisotope data ({H}-3 and {C}-14) showed that the recharge rate prior to land clearing (1950s) was about 2 mm a(-1); postclearing recharge, estimated from groundwater level fluctuations and constrained by subsurface geophysical surveys, was estimated to be 25 +/- 7 mm a(-1). {T}his order of magnitude increase in groundwater fluxes has also impacted groundwater quality near ponds, as shown by a rising trend in groundwater nitrate concentrations of natural origin (75% of delta {N}-15 values in the range + 4 to + 8%). {I}n this well-documented region of semiarid {A}frica, the indirect impacts of land use change on water quantity and quality are much greater than the direct influence of climate variability.},
  keywords = {},
  booktitle = {},
  journal = {{W}ater {R}esources {R}esearch},
  volume = {45},
  numero = {},
  pages = {{W}00{A}16},
  ISSN = {0043-1397},
  year = {2009},
  URL = {https://www.documentation.ird.fr/hor/fdi:010046834},
}