Preprints
https://doi.org/10.5194/hess-2022-319
https://doi.org/10.5194/hess-2022-319
 
14 Nov 2022
14 Nov 2022
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, Aminu Bala4, and Sara Vassolo1 Christoph Neukum et al.
  • 1Federal Institute for Geosciences and Natural Resources, Department of Groundwater and Soil, Stilleweg 2, 30655 Hannover, Germany
  • 2University of Natural Resources and Life Sciences, Vienna, Department of Water, Atmosphere and Environment, Institute for Soil Physics and Rural Water Management, Muthgasse 18, 1190 Vienna, Austria
  • 3Federal Institute for Geosciences and Natural Resources at Lake Chad Basin Commission, Rond Point des Armes, Ndjamena, Chad
  • 4Lake Chad Basin Commission, Rond Point des Armes, 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 limited field data, freely available remote sensing data as well as 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 together with different scenarios for E and T partitioning and a Bayesian calibration approach are used to numerically simulate water flow and chloride transport using Hydrus-1D. Average groundwater recharge rates and the associated model uncertainty at the six locations are assessed for the 2003–2016 time-period.

Annual groundwater recharge varies between 6 and 93 mm and depends strongly on soil texture and related water retention and on vegetation. Interannual variability of groundwater recharge is generally greater than the uncertainty of the simulated groundwater recharge.

Christoph Neukum et al.

Status: open (until 09 Jan 2023)

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Christoph Neukum et al.

Christoph Neukum et al.

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Short summary
A generalized approach that requires limited field data and well-established models is tested for assessing groundwater recharge in the southern Lake Chad basin. E and T coefficients are estimated with the FAO-dual Kc concept at six locations. Measured soil water content and chloride concentrations along vertical soil profiles together with different scenarios for E and T partitioning and a Bayesian calibration approach are used to simulate water flow and chloride transport using Hydrus-1D.