30 Jul 2021

30 Jul 2021

Review status: this preprint is currently under review for the journal HESS.

Modelling groundwater recharge, actual evaporation and transpiration in semi-arid sites of the Lake Chad Basin: The role of soil and vegetation on groundwater recharge

Christoph Neukum1, Angela Gabriela Morales Santos2, Melanie Ronelngar3, and Sara Vassolo1 Christoph Neukum et al.
  • 1Federal Institute for Geosciences and Natural Resources, Hannover, 30655, Germany
  • 2Institute for Soil Physics and Rural Water Management (SoPhy), University of Natural Resources and Life Sciences, Vienna, 1180, Austria
  • 3Federal Institute for Geosciences and Natural Resources at Lake Chad Basin Commission, Ndjamena, Chad

Abstract. The Lake Chad Basin, located in the center of North Africa, is characterized by strong climate seasonality with a pronounced short annual precipitation period and high potential evapotranspiration. Groundwater is an essential source for drinking water supply as well as for agriculture and groundwater related ecosystems. Thus, assessment of groundwater recharge is very important although difficult, because of the strong effects of evaporation and transpiration as well as limited available data.

A simple, generalized approach, which requires only a small number of field data, freely available remote sensing data, and well-established concepts and models, is tested for assessing groundwater recharge in the southern part of the basin. This work uses the FAO-dual Kc concept to estimate E and T coefficients at six locations that differ in soil texture, climate, and vegetation conditions. Measured values of soil water content and chloride concentrations along vertical soil profiles at these locations together with different scenarios for E and T partitioning and a Bayesian calibration approach are used to numerically simulate water flow and chloride transport. Average potential groundwater recharges and the associated model uncertainty at the six locations are assessed for the time-period 2003–2016.

Model results show that interannual variability of groundwater recharge is generally higher than the uncertainty of the modelled groundwater recharge. Furthermore, the soil moisture dynamics at all locations are limited by water availability for evaporation in the uppermost part of the soil and by water uptake in the root zone rather than by the reference evapotranspiration.

Christoph Neukum et al.

Status: open (until 24 Sep 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-390', Anonymous Referee #1, 14 Aug 2021 reply
    • AC1: 'Reply on RC1', Sara Vassolo, 22 Sep 2021 reply
  • RC2: 'Comment on hess-2021-390', Adane Zablon, 24 Aug 2021 reply
    • AC2: 'Reply on RC2', Sara Vassolo, 22 Sep 2021 reply
  • RC3: 'Comment on hess-2021-390', Anonymous Referee #3, 26 Aug 2021 reply
    • AC3: 'Reply on RC3', Sara Vassolo, 22 Sep 2021 reply

Christoph Neukum et al.

Christoph Neukum et al.


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Short summary
To know the renewal of groundwater is important, especially in arid and semi-arid regions with scarce precipitation. We estimate renewal in the Lake Chad Basin using measured soil water content and chloride concentrations in vertical soil profiles. We model the precipitation percolation in soil for the period 2003–2016 and reproduce the measured data. Results show that renewal does not correlate with annual precipitation, but with precipitation intensity.