@article{fdi:010042607,
  title = {{L}and clearance and hydrological change in the {S}ahel : {SW} {N}iger},
  author = {{L}eblanc, {M}. {J}. and {F}avreau, {G}uillaume and {M}assuel, {S}ylvain and {T}weed, {S}. {O}. and {L}oireau, {M}aud and {C}appelaere, {B}ernard},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n the {W}est {A}frican semiarid belt of the {S}ahel, for the second half of the {XX}th century, lasting droughts (1970s-1980s) and one of the {W}orld's highest population growths have resulted in major land cover and hydrological changes that can be quantified using aerial photographs. {T}his paper aims to provide one of the longest combined observations of land cover and hydrological changes for semiarid areas using a time series of normalised mosaics of aerial photographs dating back from 1950, field inquiries, and updated groundwater data. {T}he 500 kin 2 study area in southwest {N}iger was chosen (i) for its rural environment representative of the rain-fed agriculture belt of the {S}ahel and (ii) to encompass the main hydrological study sites investigated in this region over the past two decades ({H}apex-{S}ahel and {AMMA} experiments, 1990-2000s). {R}esults have significant implications for future freshwater availability and food security in the {S}ahel. {B}etween 1950 and 1992, similar to 80% of the study area has been cleared, firstly to open new areas for agriculture and secondly for firewood supply (59% of the plateaux, 42% of the valley bottoms, and 87% of the hillslopes). {I}ntermediate aerial photograph surveys (1960, 1975) attest an accelerated loss in the woody savannah that could not be recovered on the short term. {A} strong, indirect impact of land clearance is observed on the water resources. {L}and clearance has resulted in a modification of the soil properties and infiltration capacity and has led to an increase in {H}ortonian runoff collected in numerous gullies and ponds. {B}etween 1950 and 1992, aerial photographs show a similar to 2.5 fold increase of the drainage density with the development of large drainage systems and new ponds. {G}roundwater data also indicate a continuous rise in the water table, mostly noticeable since the 1980s with a mean groundwater level rise of similar to 4 in for the 1963-2005 period (+ 15% in aquifer reserves). {T}he relatively short similar to 30 year time-lag between the onset of land clearance and the beginning of the water table rise is linked to the process of indirect groundwater recharge and is timed with the connectivity of the drainage network and the formation of new ponds. {F}inally, the sustained increase in surface runoff and groundwater recharge during the past four decades indicates that the indirect impact of land clearance on the terrestrial water balance has been stronger than that of the long-lasting {S}ahelian drought. {A}s the rate of land clearance increased for the past century in semiarid {A}frica, its main hydrological effects may not yet be fully perceptible.},
  keywords = {remote sensing ; global change ; land use ; {W}est {A}frica ; semiarid area ; climate change and feedbacks ; gully erosion},
  booktitle = {},
  journal = {{G}lobal and {P}lanetary {C}hange},
  volume = {61},
  numero = {3-4},
  pages = {135--150},
  ISSN = {0921-8181},
  year = {2008},
  DOI = {10.1016/j.gloplacha.2007.08.011},
  URL = {https://www.documentation.ird.fr/hor/fdi:010042607},
}