HESS Hydrology and Earth System Sciences HESS Hydrol. Earth Syst. Sci. 1607-7938 Copernicus Publications Göttingen, Germany 10.5194/hess-18-5001-2014 Building a field- and model-based climatology of local water and energy cycles in the cultivated Sahel – annual budgets and seasonality Velluet C. 1 2 Demarty J. 2 Cappelaere B. 2 Braud I. https://orcid.org/0000-0001-9155-0056 3 Issoufou H. B.-A. 4 Boulain N. 2 Ramier D. 2 5 Mainassara I. 6 7 Charvet G. 2 Boucher M. 2 8 Chazarin J.-P. 2 Oï M. 2 Yahou H. 4 7 Maidaji B. 4 6 Arpin-Pont F. 9 Benarrosh N. 2 Mahamane A. 4 Nazoumou Y. 7 Favreau G. https://orcid.org/0000-0001-7358-9301 2 Seghieri J. 2 Université Montpellier 2, UMR HSM (CNRS/IRD/UM1/UM2), Montpellier, France IRD, UMR HSM (CNRS/IRD/UM1/UM2), Montpellier, France IRSTEA, Unit HHLY, Lyon, France Université de Maradi, Biology Department, Maradi, Niger Cerema, DTer IDF, Trappes-en-Yvelines, France IRD, UMR HSM (CNRS/IRD/UM1/UM2), Niamey, Niger Université Abdou Moumouni, Geology Department, Niamey, Niger IRD, LTHE, Grenoble, France CNRS, UMR HSM (CNRS/IRD/UM1/UM2), Montpellier, France 10 12 2014 18 12 5001 5024 Copyright: © 2014 C. Velluet et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://hess.copernicus.org/articles/18/5001/2014/hess-18-5001-2014.html The full text article is available as a PDF file from https://hess.copernicus.org/articles/18/5001/2014/hess-18-5001-2014.pdf

In the sub-Saharan Sahel, energy and water cycling at the land surface is pivotal for the regional climate, water resources and land productivity, yet it is still very poorly documented. As a step towards a comprehensive climatological description of surface fluxes in this area, this study provides estimates of long-term average annual budgets and seasonal cycles for two main land use types of the cultivated Sahelian belt: rainfed millet crop and fallow bush. These estimates build on the combination of a 7-year field data set from two typical plots in southwestern Niger with detailed physically based soil–plant–atmosphere modeling, yielding a continuous, comprehensive set of water and energy flux and storage variables over this multiyear period. In the present case in particular, blending field data with mechanistic modeling makes the best use of available data and knowledge for the construction of the multivariate time series. Rather than using the model only to gap-fill observations into a composite series, model–data integration is generalized homogeneously over time by generating the whole series with the entire data-constrained model simulation. Climatological averages of all water and energy variables, with associated sampling uncertainty, are derived at annual to sub-seasonal scales from the time series produced. Similarities and differences in the two ecosystem behaviors are highlighted. Mean annual evapotranspiration is found to represent ~82–85% of rainfall for both systems, but with different soil evaporation/plant transpiration partitioning and different seasonal distribution. The remainder consists entirely of runoff for the fallow, whereas drainage and runoff stand in a 40–60% proportion for the millet field. These results should provide a robust reference for the surface energy- and water-related studies needed in this region. Their significance and the benefits they gain from the innovative data–model integration approach are thoroughly discussed. The model developed in this context has the potential for reliable simulations outside the reported conditions, including changing climate and land cover.

 References Akkermans, T., Lauwaet, D., Demuzere, M., Vogel, G., Nouvellon, Y., Ardö, J., Caquet, B., De Grandcourt, A., Merbold, L., Kutsch, W., and Van Lipzig, N.: Validation and comparison of two soil-vegetation-atmosphere transfer models for tropical Africa, J. Geophys. Res., 117, G02013, <a href="http://dx.doi.org/10.1029/2011jg001802">https://doi.org/10.1029/2011jg001802</a>, 2012. Allen, R. G., Pereira, L. S., Raes, D., and Smith, M.: Crop evapotranspiration: Guidelines for computing crop requirements, FAO, Rome, 300 pp., 1998. Aubinet, M., Vesala, T., and Papale, D.: Eddy covariance – A practical guide to measurement and data analysis, Springer Atmospheric Sciences, Springer, Dordrecht, 438 pp., 2012. Boko, M., Niang, I., Nyong, A., Vogel, C., Githeko, A., Medany, M., Osman-Elasha, B., Tabo, R., and Yanda, P.: Africa, in: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Parry, M. L., Canziani, O. F., Palutikof, J. P., van der Linden, P. J., and Hanson, C. E., Cambridge University Press, Cambridge, UK, 433–467, 2007. Boone, A., Decharme, B., Guichard, F., de Rosnay, P., Balsamo, G., Beljaars, A., Chopin, F., Orgeval, T., Polcher, J., Delire, C., Ducharne, A., Gascoin, S., Grippa, M., Jarlan, L., Kergoat, L., Mougin, E., Gusev, Y., Nasonova, O., Harris, P., Taylor, C., Norgaard, A., Sandholt, I., Ottlé, C., Poccard-Leclercq, I., Saux-Picart, S., and Xue, Y.: The AMMA Land Surface Model Intercomparison Project (ALMIP), B. Am. Meteorol. Soc., 90, 1865–1880, <a href="http://dx.doi.org/10.1175/2009bams2786.1">https://doi.org/10.1175/2009bams2786.1</a>, 2009a. Boone, A., Getirana, A., Demarty, J., Cappelaere, B., Galle, S., Grippa, M., Lebel, T., Mougin, E., Peugeot, C., and Vischel, T.: The AMMA Land Surface Model Intercomparison Project Phase 2 (ALMIP-2), Gewex News, 19, 9–10, 2009b. Boulain, N., Cappelaere, B., Ramier, D., Issoufou, H. B. A., Halilou, O., Seghieri, J., Guillemin, F., Oi, M., Gignoux, J., and Timouk, F.: Towards an understanding of coupled physical and biological processes in the cultivated Sahel – 2. Vegetation and carbon dynamics, J. Hydrol., 375, 190–203, <a href="http://dx.doi.org/10.1016/j.jhydrol.2008.11.045">https://doi.org/10.1016/j.jhydrol.2008.11.045</a>, 2009a. Boulain, N., Cappelaere, B., Seguis, L., Favreau, G., and Gignoux, J.: Water balance and vegetation change in the Sahel: A case study at the watershed scale with an eco-hydrological model, J. Arid Environ., 73, 1125–1135, <a href="http://dx.doi.org/10.1016/j.jaridenv.2009.05.008">https://doi.org/10.1016/j.jaridenv.2009.05.008</a>, 2009b. Boulet, G., Kalma, J. D., Braud, I., and Vauclin, M.: An assessment of effective land surface parameterisation in regional-scale water balance studies, J. Hydrol., 217, 225–238, <a href="http://dx.doi.org/10.1016/s0022-1694(98)00246-7">https://doi.org/10.1016/s0022-1694(98)00246-7</a>, 1999. Braud, I.: Spatial variability of surface properties and estimation of surface fluxes of a savannah, Agr. Forest Meteorol., 89, 15–44, <a href="http://dx.doi.org/10.1016/s0168-1923(97)00061-0">https://doi.org/10.1016/s0168-1923(97)00061-0</a>, 1998. Braud, I.: SiSPAT, a numerical model of water and energy fluxes in the soil-plant-atmosphere continuum – User's manual, LTHE, Grenoble, France, 106 pp., 2000. Braud, I., Dantas-Antonino, A. C., Vauclin, M., Thony, J. L., and Ruelle, P.: A simple soil-plant-atmosphere transfer model (SiSPAT) development and field verification, J. Hydrol., 166, 213–250, 1995. Braud, I., Bessemoulin, P., Monteny, B., Sicot, M., Vandervaere, J. P., and Vauclin, M.: Unidimensional modelling of a fallow savannah during the HAPEX-Sahel experiment using the SiSPAT model, J. Hydrol., 188–189, 912–945, <a href="http://dx.doi.org/10.1016/s0022-1694(96)03177-0">https://doi.org/10.1016/s0022-1694(96)03177-0</a>, 1997. Brooks, R. H. and Corey, A. T.: Hydraulic Properties of Porous Media, Hydrology Papers, Colorado State University, Colorado, 1964. Brunel, J. P., Walker, G. R., Dighton, J. C., and Monteny, B.: Use of stable isotopes of water to determine the origin of water used by the vegetation and to partition evapotranspiration. A case study from HAPEX-Sahel, J. Hydrol., 188–189, 466–481, <a href="http://dx.doi.org/10.1016/s0022-1694(96)03188-5">https://doi.org/10.1016/s0022-1694(96)03188-5</a>, 1997. Burdine, N. T.: Relative permeability calculations from pore-size distribution data, Trans. Am. Inst. Min. Eng., 198, 71–78, 1953. Cappelaere, B., Descroix, L., Lebel, T., Boulain, N., Ramier, D., Laurent, J. P., Favreau, G., Boubkraoui, S., Boucher, M., Bouzou Moussa, I., Chaffard, V., Hiernaux, P., Issoufou, H. B. A., Le Breton, E., Mamadou, I., Nazoumou, Y., Oi, M., Ottle, C., and Quantin, G.: The AMMA-CATCH experiment in the cultivated Sahelian area of south-west Niger – Investigating water cycle response to a fluctuating climate and changing environment, J. Hydrol., 375, 34–51, <a href="http://dx.doi.org/10.1016/j.jhydrol.2009.06.021">https://doi.org/10.1016/j.jhydrol.2009.06.021</a>, 2009. Daamen, C. C.: Two source model of surface fluxes for millet fields in Niger, Agr. Forest Meteorol., 83, 205–230, <a href="http://dx.doi.org/10.1016/S0168-1923(96)02356-8">https://doi.org/10.1016/S0168-1923(96)02356-8</a>, 1997. Demarty, J., Ottlé, C., François, C., Braud, I., and Frangi, J.-P.: Effect of aerodynamic resistance modelling on SiSPAT-RS simulated surface fluxes, Agronomie, 22, 641–650, <a href="http://dx.doi.org/10.1051/agro:2002052">https://doi.org/10.1051/agro:2002052</a>, 2002. Demarty, J., Ottlé, C., Braud, I., Olioso, A., Frangi, J. P., Bastidas, L. A., and Gupta, H. V.: Using a multiobjective approach to retrieve information on surface properties used in a SVAT model, J. Hydrol., 287, 214–236, <a href="http://dx.doi.org/10.1016/j.jhydrol.2003.10.003">https://doi.org/10.1016/j.jhydrol.2003.10.003</a>, 2004. Demarty, J., Ottlé, C., Braud, I., Olioso, A., Frangi, J. P., Gupta, H. V., and Bastidas, L. A.: Constraining a physically based Soil-Vegetation-Atmosphere Transfer model with surface water content and thermal infrared brightness temperature measurements using a multiobjective approach, Water Resour. Res., 41, W01011, <a href="http://dx.doi.org/10.1029/2004wr003695">https://doi.org/10.1029/2004wr003695</a>, 2005. Descroix, L., Mahe, G., Lebel, T., Favreau, G., Galle, S., Gautier, E., Olivry, J. C., Albergel, J., Amogu, O., Cappelaere, B., Dessouassi, R., Diedhiou, A., Le Breton, E., Mamadou, I., and Sighomnou, D.: Spatio-temporal variability of hydrological regimes around the boundaries between Sahelian and Sudanian areas of West Africa: A synthesis, J. Hydrol., 375, 90–102, <a href="http://dx.doi.org/10.1016/j.jhydrol.2008.12.012">https://doi.org/10.1016/j.jhydrol.2008.12.012</a>, 2009. Descroix, L., Laurent, J. P., Vauclin, M., Amogu, O., Boubkraoui, S., Ibrahim, B., Galle, S., Cappelaere, B., Bousquet, S., Mamadou, I., Le Breton, E., Lebel, T., Quantin, G., Ramier, D., and Boulain, N.: Experimental evidence of deep infiltration under sandy flats and gullies in the Sahel, Journal of Hydrology, 424–425, 1–15, <a href="http://dx.doi.org/10.1016/j.jhydrol.2011.11.019">https://doi.org/10.1016/j.jhydrol.2011.11.019</a>, 2012. Descroix, L., Moussa, I. B., Genthon, P., Sighomnou, D., Mahé, G., Mamadou, I., Vandervaere, J.-P., Gautier, E., Maiga, O. F., Rajot, J.-L., Abdou, M. M., Dessay, N., Ingatan, A., Noma, I., Yéro, K. S., Karambiri, H., Fensholt, R., Albergel, J., and Olivry, J.-C.: Impact of Drought and Land – Use Changes on Surface – Water Quality and Quantity: The Sahelian Paradox, in: Current Perspectives in Contaminant Hydrology and Water Resources Sustainability, chap. 10, edited by: Bradley, P. M., Intech, 243–271, <a href="http://dx.doi.org/10.5772/54536">https://doi.org/10.5772/54536</a>, 2013. Estèves, M. and Lapetite, J. M.: A multi-scale approach of runoff generation in a Sahelian gully catchment: a case study in Niger, Catena, 50, 255–271, <a href="http://dx.doi.org/10.1016/s0341-8162(02)00136-4">https://doi.org/10.1016/s0341-8162(02)00136-4</a>, 2003. Ezzahar, J., Chehbouni, A., Hoedjes, J., Ramier, D., Boulain, N., Boubkraoui, S., Cappelaere, B., Descroix, L., Mougenot, B., and Timouk, F.: Combining scintillometer measurements and an aggregation scheme to estimate area-averaged latent heat flux during the AMMA experiment, J. Hydrol., 375, 217–226, <a href="http://dx.doi.org/10.1016/j.jhydrol.2009.01.010">https://doi.org/10.1016/j.jhydrol.2009.01.010</a>, 2009. Favreau, G., Cappelaere, B., Massuel, S., Leblanc, M., Boucher, M., Boulain, N., and Leduc, C.: Land clearing, climate variability, and water resources increase in semiarid southwest Niger: A review, Water Resour. Res., 45, W00A16, <a href="http://dx.doi.org/10.1029/2007wr006785">https://doi.org/10.1029/2007wr006785</a>, 2009. Federer, C. A.: A soil-plant-atmosphere model for transpiration and availability of soil water, Water Resour. Res., 15, 555–562, <a href="http://dx.doi.org/10.1029/WR015i003p00555">https://doi.org/10.1029/WR015i003p00555</a>, 1979. Foken, T.: Micrometeorology, Springer-Verlag, Berlin, 306 pp., 2008. Foken, T., Wimmer, F., Mauder, M., Thomas, C., and Liebethal, C.: Some aspects of the energy balance closure problem, Atmos. Chem. Phys., 6, 4395–4402, <a href="http://dx.doi.org/10.5194/acp-6-4395-2006">https://doi.org/10.5194/acp-6-4395-2006</a>, 2006. François, C.: The potential of directional radiometric temperatures for monitoring soil and leaf temperature and soil moisture status, Remote Sens. Environ., 80, 122–133, <a href="http://dx.doi.org/10.1016/s0034-4257(01)00293-0">https://doi.org/10.1016/s0034-4257(01)00293-0</a>, 2002. Gash, J. H. C., Kabat, P., Monteny, B. A., Amadou, M., Bessemoulin, P., Billing, H., Blyth, E. M., deBruin, H. A. R., Elbers, J. A., Friborg, T., Harrison, G., Holwill, C. J., Lloyd, C. R., Lhomme, J. P., Moncrieff, J. B., Puech, D., Soegaard, H., Taupin, J. D., Tuzet, A., and Verhoef, A.: The variability of evaporation during the HAPEX-Sahel Intensive Observation Period, J. Hydrol., 188–189, 385–399, <a href="http://dx.doi.org/10.1016/s0022-1694(96)03167-8">https://doi.org/10.1016/s0022-1694(96)03167-8</a>, 1997. Gaze, S. R., Simmonds, L. P., Brouwer, J., and Bouma, J.: Measurement of surface redistribution of rainfall and modelling its effect on water balance calculations for a millet field on sandy soil in Niger, J. Hydrol., 188–189, 267–284, 1997. Hanan, N. P. and Prince, S. D.: Stomatal conductance of West-Central supersite vegetation in HAPEX-Sahel: measurements and empirical models, J. Hydrol., 188–189, 536–562, <a href="http://dx.doi.org/10.1016/s0022-1694(96)03192-7">https://doi.org/10.1016/s0022-1694(96)03192-7</a>, 1997. Hillel, D.: Environmental soil physics: Fundamentals, applications, and environmental considerations, Academic Press, San Diego, USA, 771 pp., 1998. Hoogmoed, W. B. and Klaij, M. C.: Soil management for crop production in the West African Sahel. I. Soil and climate parameters, Soil Till. Res., 16, 85–103, <a href="http://dx.doi.org/10.1016/0167-1987(90)90023-7">https://doi.org/10.1016/0167-1987(90)90023-7</a>, 1990. Ibrahim, M., Favreau, G., Scanlon, B., Seidel, J.-L., Le Coz, M., Demarty, J., and Cappelaere, B.: Long-term increase in diffuse groundwater recharge following expansion of rainfed cultivation in the Sahel, West Africa, Hydrogeol. J., 22, 1293–1305, <a href="http://dx.doi.org/10.1007/s10040-014-1143-z">https://doi.org/10.1007/s10040-014-1143-z</a>, 2014. Issoufou, H. B.-A., Delzon, S., Laurent, J.-P., Saâdou, M., Mahamane, A., Cappelaere, B., Demarty, J., Rambal, S., and Seghieri, J.: Change in water loss regulation after canopy clearcut of a dominant shrub in Sahelian agrosystems, Guiera senegalensis J. F. Gmel, Trees – Struct. Funct., 27, 1011–1022, <a href="http://dx.doi.org/10.1007/s00468-013-0852-6">https://doi.org/10.1007/s00468-013-0852-6</a>, 2013. Jackson, R. D.: Surface temperature and the surface energy balance, in: Flow and Transport in the Natural Environment: Advances and Applications, edited by: Steffen, W. L. and Denmead, O. J., Springer, Berlin, New York, 133–182, 1988. Jacquemin, B. and Noilhan, J.: Sensitivity study and validation of a land surface parameterization using the HAPEX-MOBILHY data set, Bound.-Lay. Meteorol., 52, 93–134, <a href="http://dx.doi.org/10.1007/bf00123180">https://doi.org/10.1007/bf00123180</a>, 1990. Jarvis, P. G.: The Interpretation of the Variations in Leaf Water Potential and Stomatal Conductance Found in Canopies in the Field, Philos. T. Roy. Soc. Lond. B, 273, 593–610, <a href="http://dx.doi.org/10.1098/rstb.1976.0035">https://doi.org/10.1098/rstb.1976.0035</a>, 1976. Klaij, M. C. and Vachaud, G.: Seasonal water balance of a sandy soil in Niger cropped with pearl millet, based on profile moisture measurements, Agr. Water Manage., 21, 313–330, <a href="http://dx.doi.org/10.1016/0378-3774(92)90053-y">https://doi.org/10.1016/0378-3774(92)90053-y</a>, 1992. Koster, R. D., Dirmeyer, P. A., Guo, Z., Bonan, G., Chan, E., Cox, P., Gordon, C. T., Kanae, S., Kowalczyk, E., Lawrence, D., Liu, P., Lu, C. H., Malyshev, S., McAvaney, B., Mitchell, K., Mocko, D., Oki, T., Oleson, K., Pitman, A., Sud, Y. C., Taylor, C. M., Verseghy, D., Vasic, R., Xue, Y., and Yamada, T.: Regions of strong coupling between soil moisture and precipitation, Science, 305, 1138–1140, <a href="http://dx.doi.org/10.1126/science.1100217">https://doi.org/10.1126/science.1100217</a>, 2004. Lebel, T. and Ali, A.: Recent trends in the Central and Western Sahel rainfall regime (1990–2007), J. Hydrol., 375, 52–64, <a href="http://dx.doi.org/10.1016/j.jhydrol.2008.11.030">https://doi.org/10.1016/j.jhydrol.2008.11.030</a>, 2009. Lebel, T., Cappelaere, B., Galle, S., Hanan, N., Kergoat, L., Levis, S., Vieux, B., Descroix, L., Gosset, M., Mougin, E., Peugeot, C., and Seguis, L.: AMMA-CATCH studies in the Sahelian region of West-Africa: An overview, J. Hydrol., 375, 3–13, <a href="http://dx.doi.org/10.1016/j.jhydrol.2009.03.020">https://doi.org/10.1016/j.jhydrol.2009.03.020</a>, 2009. Leblanc, M. J., Favreau, G., Massuel, S., Tweed, S. O., Loireau, M., and Cappelaere, B.: Land clearance and hydrological change in the Sahel: SW Niger, Global Planet. Change, 61, 135–150, <a href="http://dx.doi.org/10.1016/j.gloplacha.2007.08.011">https://doi.org/10.1016/j.gloplacha.2007.08.011</a>, 2008. Lloyd, C. R., Bessemoulin, P., Cropley, F. D., Culf, A. D., Dolman, A. J., Elbers, J., Heusinkveld, B., Moncrieff, J. B., Monteny, B., and Verhoef, A.: A comparison of surface fluxes at the HAPEX-Sahel fallow bush sites, J. Hydrol., 189, 400–425, 1997. Lohou, F., Kergoat, L., Guichard, F., Boone, A., Cappelaere, B., Cohard, J.-M., Demarty, J., Galle, S., Grippa, M., Peugeot, C., Ramier, D., Taylor, C. M., and Timouk, F.: Surface response to rain events throughout the West African monsoon, Atmos. Chem. Phys., 14, 3883–3898, <a href="http://dx.doi.org/10.5194/acp-14-3883-2014">https://doi.org/10.5194/acp-14-3883-2014</a>, 2014. Manyame, C., Morgan, C. L., Heilman, J. L., Fatondji, D., Gerard, B., and Payne, W. A.: Modeling hydraulic properties of sandy soils of Niger using pedotransfer functions, Geoderma, 141, 407-415, <a href="http://dx.doi.org/10.1016/j.geoderma.2007.07.006">https://doi.org/10.1016/j.geoderma.2007.07.006</a>, 2007. Marshall, M., Tu, K., Funk, C., Michaelsen, J., Williams, P., Williams, C., Ardö, J., Boucher, M., Cappelaere, B., de Grandcourt, A., Nickless, A., Nouvellon, Y., Scholes, R., and Kutsch, W.: Improving operational land surface model canopy evapotranspiration in Africa using a direct remote sensing approach, Hydrol. Earth Syst. Sci., 17, 1079–1091, <a href="http://dx.doi.org/10.5194/hess-17-1079-2013">https://doi.org/10.5194/hess-17-1079-2013</a>, 2013. Massuel, S., Favreau, G., Descloitres, M., Le Troquer, Y., Albouy, Y., and Cappelaere, B.: Deep infiltration through a sandy alluvial fan in semiarid Niger inferred from electrical conductivity survey, vadose zone chemistry and hydrological modelling, Catena, 67, 105–118, <a href="http://dx.doi.org/10.1016/j.catena.2006.02.009">https://doi.org/10.1016/j.catena.2006.02.009</a>, 2006. Massuel, S., Cappelaere, B., Favreau, G., Leduc, C., Lebel, T., and Vischel, T.: Integrated surface water-groundwater modelling in the context of increasing water reserves of a Sahelian aquifer, Hydrolog. Sci. J., 56, 1242–1264, <a href="http://dx.doi.org/10.1080/02626667.2011.609171">https://doi.org/10.1080/02626667.2011.609171</a>, 2011. Mauder, M. and Foken, T.: Documentation and instruction manual of the eddy covariance software package TK2, U. Bayreuth, Abt. Mikrometeorologie, Bayreuth, Germany, 2004. Merbold, L., Ardö, J., Arneth, A., Scholes, R. J., Nouvellon, Y., de Grandcourt, A., Archibald, S., Bonnefond, J. M., Boulain, N., Brueggemann, N., Bruemmer, C., Cappelaere, B., Ceschia, E., El-Khidir, H. A. M., El-Tahir, B. A., Falk, U., Lloyd, J., Kergoat, L., Le Dantec, V., Mougin, E., Muchinda, M., Mukelabai, M. M., Ramier, D., Roupsard, O., Timouk, F., Veenendaal, E. M., and Kutsch, W. L.: Precipitation as driver of carbon fluxes in 11 African ecosystems, Biogeosciences, 6, 1027–1041, <a href="http://dx.doi.org/10.5194/bg-6-1027-2009">https://doi.org/10.5194/bg-6-1027-2009</a>, 2009. Miller, R. L., Slingo, A., Barnard, J. C., and Kassianov, E.: Seasonal contrast in the surface energy balance of the Sahel, J. Geophys. Res., 114, D00E05, <a href="http://dx.doi.org/10.1029/2008jd010521">https://doi.org/10.1029/2008jd010521</a>, 2009. Milly, P. C. D.: Moisture and heat transport in hysteretic, inhomogeneous porous media: A matric head-based formulation and a numerical model, Water Resour. Res., 18, 489-498, <a href="http://dx.doi.org/10.1029/WR018i003p00489">https://doi.org/10.1029/WR018i003p00489</a>, 1982. Monteny, B. A.: HAPEX-Sahel 1992, Campagne de Mesures Supersite Central Est, ORSTOM, Montpellier, France, p. 230, 1993. Pellarin, T., Laurent, J. P., Cappelaere, B., Decharme, B., Descroix, L., and Ramier, D.: Hydrological modelling and associated microwave emission of a semi-arid region in South-western Niger, J. Hydrol., 375, 262–272, <a href="http://dx.doi.org/10.1016/j.jhydrol.2008.12.003">https://doi.org/10.1016/j.jhydrol.2008.12.003</a>, 2009. Peugeot, C., Esteves, M., Galle, S., Rajot, J.-L., and Vandervaere, J. P.: Runoff generation processes: results and analysis of field data collected at the East Central Supersite of the HAPEX-Sahel experiment, J. Hydrol., 188–189, 179–202, <a href="http://dx.doi.org/10.1016/s0022-1694(96)03159-9">https://doi.org/10.1016/s0022-1694(96)03159-9</a>, 1997. Ramier, D., Boulain, N., Cappelaere, B., Timouk, F., Rabanit, M., Lloyd, C. R., Boubkraoui, S., Metayer, F., Descroix, L., and Wawrzyniak, V.: Towards an understanding of coupled physical and biological processes in the cultivated Sahel - 1. Energy and water, J. Hydrol., 375, 204–216, <a href="http://dx.doi.org/10.1016/j.jhydrol.2008.12.002">https://doi.org/10.1016/j.jhydrol.2008.12.002</a>, 2009. Ridler, M. E., Sandholt, I., Butts, M., Lerer, S., Mougin, E., Timouk, F., Kergoat, L., and Madsen, H.: Calibrating a soil–vegetation–atmosphere transfer model with remote sensing estimates of surface temperature and soil surface moisture in a semi arid environment, J. Hydrol., 436–437, 1–12, <a href="http://dx.doi.org/10.1016/j.jhydrol.2012.01.047">https://doi.org/10.1016/j.jhydrol.2012.01.047</a>, 2012. Rockström, J. and Valentin, C.: Hillslope dynamics of on-farm generation of surface water flows: The case of rain-fed cultivation of pearl millet on sandy soil in the Sahel, Agr. Water Manage., 33, 183–210, <a href="http://dx.doi.org/10.1016/s0378-3774(96)01282-6">https://doi.org/10.1016/s0378-3774(96)01282-6</a>, 1997. Rockström, J., Jansson, P. E., and Barron, J.: Seasonal rainfall partitioning under runon and runoff conditions on sandy soil in Niger. On-farm measurements and water balance modelling, J. Hydrol., 210, 68–92, <a href="http://dx.doi.org/10.1016/s0022-1694(98)00176-0">https://doi.org/10.1016/s0022-1694(98)00176-0</a>, 1998. Rothfuss, Y., Braud, I., Le Moine, N., Biron, P., Durand, J.-L., Vauclin, M., and Bariac, T.: Factors controlling the isotopic partitioning between soil evaporation and plant transpiration: Assessment using a multi-objective calibration of SiSPAT-Isotope under controlled conditions, J. Hydrol., 442–443, 75–88, <a href="http://dx.doi.org/10.1016/j.jhydrol.2012.03.041">https://doi.org/10.1016/j.jhydrol.2012.03.041</a>, 2012. Saux-Picart, S., Ottle, C., Decharme, B., Andre, C., Zribi, M., Perrier, A., Coudert, B., Boulain, N., Cappelaere, B., Descroix, L., and Ramier, D.: Water and energy budgets simulation over the AMMA-Niger super-site spatially constrained with remote sensing data, J. Hydrol., 375, 287–295, <a href="http://dx.doi.org/10.1016/j.jhydrol.2008.12.023">https://doi.org/10.1016/j.jhydrol.2008.12.023</a>, 2009a. Saux-Picart, S., Ottle, C., Perrier, A., Decharme, B., Coudert, B., Zribi, M., Boulain, N., Cappelaere, B., and Ramier, D.: SEtHyS_Savannah: A multiple source land surface model applied to Sahelian landscapes, Agricultural and Forest Meteorology, 149, 1421-1432, <a href="http://dx.doi.org/10.1016/j.agrformet.2009.03.013">https://doi.org/10.1016/j.agrformet.2009.03.013</a>, 2009b. Schlenker, W. and Lobell, D. B.: Robust negative impacts of climate change on African agriculture, Environ. Res. Lett., 5, 014010, <a href="http://dx.doi.org/10.1088/1748-9326/5/1/014010">https://doi.org/10.1088/1748-9326/5/1/014010</a>, 2010. Shin, Y., Mohanty, B. P., and Ines, A. V. M.: Soil hydraulic properties in one-dimensional layered soil profile using layer-specific soil moisture assimilation scheme, Water Resour. Res., 48, W06529, <a href="http://dx.doi.org/10.1029/2010wr009581">https://doi.org/10.1029/2010wr009581</a>, 2012. Shuttleworth, W. J. and Wallace, J. S.: Evaporation from sparse crops – An energy combination theory, Q. J. Roy. Meteorol. Soc., 111, 839–855, <a href="http://dx.doi.org/10.1256/smsqj.46909">https://doi.org/10.1256/smsqj.46909</a>, 1985. Šimůnek, J., Angulo-Jaramillo, R., Schaap, M. G., Vandervaere, J.-P., and van Genuchten, M. T.: Using an inverse method to estimate the hydraulic properties of crusted soils from tension-disc infiltrometer data, Geoderma, 86, 61–81, <a href="http://dx.doi.org/10.1016/s0016-7061(98)00035-4">https://doi.org/10.1016/s0016-7061(98)00035-4</a>, 1998. Sjöström, M., Ardö, J., Arneth, A., Boulain, N., Cappelaere, B., Eklundh, L., de Grandcourt, A., Kutsch, W. L., Merbold, L., Nouvellon, Y., Scholes, R. J., Schubert, P., Seaquist, J., and Veenendaal, E. M.: Exploring the potential of MODIS EVI for modeling gross primary production across African ecosystems, Remote Sens. Environ., 115, 1081–1089, <a href="http://dx.doi.org/10.1016/j.rse.2010.12.013">https://doi.org/10.1016/j.rse.2010.12.013</a>, 2011. Sjöström, M., Zhao, M., Archibald, S., Arneth, A., Cappelaere, B., Falk, U., de Grandcourt, A., Hanan, N., Kergoat, L., Kutsch, W. L., Merbold, L., Mougin, E., Nickless, A., Nouvellon, Y., Scholes, R. J., Veenendaal, E. M., and Ardö, J.: Evaluation of MODIS gross primary productivity for Africa using eddy covariance data, Remote Sens. Environ., 131, 275–286, <a href="http://dx.doi.org/10.1016/j.rse.2012.12.023">https://doi.org/10.1016/j.rse.2012.12.023</a>, 2013. Soegaard, H. and Boegh, E.: Estimation of evapotranspiration from a millet crop in the Sahel combining sap flow, leaf-area index and eddy-correlation technique, J. Hydrol., 166, 265–282, <a href="http://dx.doi.org/10.1016/0022-1694(94)05094-e">https://doi.org/10.1016/0022-1694(94)05094-e</a>, 1995. Taconet, O., Bernard, R., and Vidal-Madjar, D.: Evapotranspiration over an agricultural region using a surface flux/temperature model based on NOAA-AVHRR data, J. Clim. Appl. Meteorol., 25, 284–307, 1986. Tanguy, M., Baille, A., González-Real, M. M., Lloyd, C., Cappelaere, B., Kergoat, L., and Cohard, J. M.: A new parameterisation scheme of ground heat flux for land surface flux retrieval from remote sensing information, J. Hydrol., 454–455, 113–122, <a href="http://dx.doi.org/10.1016/j.jhydrol.2012.06.002">https://doi.org/10.1016/j.jhydrol.2012.06.002</a>, 2012. Taylor, C. M., Gounou, A., Guichard, F., Harris, P. P., Ellis, R. J., Couvreux, F., and De Kauwe, M.: Frequency of Sahelian storm initiation enhanced over mesoscale soil-moisture patterns, Nat. Geosci., 4, 430–433, <a href="http://dx.doi.org/10.1038/ngeo1173">https://doi.org/10.1038/ngeo1173</a>, 2011. Taylor, C. M., de Jeu, R. A. M., Guichard, F., Harris, P. P., and Dorigo, W. A.: Afternoon rain more likely over drier soils, Nature, 489, 423–426, <a href="http://dx.doi.org/10.1038/nature11377">https://doi.org/10.1038/nature11377</a>, 2012. Timouk, F., Kergoat, L., Mougin, E., Lloyd, C. R., Ceschia, E., Cohard, J. M., de Rosnay, P., Hiernaux, P., Demarez, V., and Taylor, C. M.: Response of surface energy balance to water regime and vegetation development in a Sahelian landscape, J. Hydrol., 375, 178–189, <a href="http://dx.doi.org/10.1016/j.jhydrol.2009.04.022">https://doi.org/10.1016/j.jhydrol.2009.04.022</a>, 2009. Trenberth, K. E., Fasullo, J. T., and Kiehl, J.: Earth's global energy budget, B. Am. Meteorol. Soc., 90, 311–323, <a href="http://dx.doi.org/10.1175/2008BAMS2634.1">https://doi.org/10.1175/2008BAMS2634.1</a>, 2009. Tuzet, A., Castell, J. F., Perrier, A., and Zurfluh, O.: Flux heterogeneity and evapotranspiration partitioning in a sparse canopy: the fallow savanna, J. Hydrol., 188–189, 482–493, <a href="http://dx.doi.org/10.1016/s0022-1694(96)03189-7">https://doi.org/10.1016/s0022-1694(96)03189-7</a>, 1997. van Genuchten, M. T.: A Closed-form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils, Soil Sci. Soc. Am. J., 44, 892–898, <a href="http://dx.doi.org/10.2136/sssaj1980.03615995004400050002x">https://doi.org/10.2136/sssaj1980.03615995004400050002x</a>, 1980. Vandervaere, J. P., Peugeot, C., Vauclin, M., Angulo Jaramillo, R., and Lebel, T.: Estimating hydraulic conductivity of crusted soils using disc infiltrometers and minitensiometers, J. Hydrol., 188–189, 203–223, <a href="http://dx.doi.org/10.1016/s0022-1694(96)03160-5">https://doi.org/10.1016/s0022-1694(96)03160-5</a>, 1997. van Vliet, N., Reenberg, A., and Rasmussen, L. V.: Scientific documentation of crop land changes in the Sahel: A half empty box of knowledge to support policy?, J. Arid Environ., 95, 1–13, <a href="http://dx.doi.org/10.1016/j.jaridenv.2013.03.010">https://doi.org/10.1016/j.jaridenv.2013.03.010</a>, 2013. Velluet, C.: Multi-year modelling and analysis of the hydrologic and energetic functioning of two dominant ecosystems in the cultivated Sahel (SW Niger), Ph.D. thesis, University Montpellier 2, Montpellier, France, 2014. Velluet, C., Cappelaere, B., Demarty, J., Braud, I., et al.: <i>Interactive comment on</i> "Building a field- and model-based climatology of local water and energy cycles in the cultivated Sahel – annual budgets and seasonality" by C. Velluet et al., Hydrol. Earth Syst. Sci. Discuss., 11, C2352–C2353, 2014. Verhoef, A., Allen, S. J., and Lloyd, C. R.: Seasonal variation of surface energy balance over two Sahelian surfaces, Int. J. Climatol., 19, 1267–1277, <a href="http://dx.doi.org/10.1002/(sici)1097-0088(199909)19:11<1267::aid-joc418>3.0.co;2-s">https://doi.org/10.1002/(sici)1097-0088(199909)19:11<1267::aid-joc418>3.0.co;2-s</a>, 1999. Verhoef, A., Ottlé, C., Cappelaere, B., Murray, T., Saux Picart, S., Zribi, A., Maignan, F., Boulain, N., Demarty, J., and Ramier, D.: Spatio-temporal surface soil heat flux estimates from satellite data; results for the AMMA experiment, Fakara supersite, Agr. Forest Meteorol., 154–155, 55–66, <a href="http://dx.doi.org/10.1016/j.agrformet.2011.08.003">https://doi.org/10.1016/j.agrformet.2011.08.003</a>, 2012. Wallace, J. S., Wright, I. R., Stewart, J. B., and Holwill, C. J.: The Sahelian energy balance experiment (SEBEX): ground based measurements and their potential for spatial extrapolation using satellite data, Adv. Space Res., 11, 131–141, 1991. Weiss, M., Baret, F., Smith, G. J., and Jonckheere, I.: Methods for in situ leaf area index measurement, part II: from gap fraction to leaf area index: retrieval methods and sampling strategies, Agr. Forest Meteorol., 121, 17–53, 2004. Wolters, D., van Heerwaarden, C. C., de Arellano, J. V. G., Cappelaere, B., and Ramier, D.: Effects of soil moisture gradients on the path and the intensity of a West African squall line, Q. J. Royal Meteorol. Soc., 136, 2162–2175, <a href="http://dx.doi.org/10.1002/qj.712">https://doi.org/10.1002/qj.712</a>, 2010.