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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2018-61
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
13 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
Land use alters dominant water sources and flow paths in tropical montane catchments in East Africa
Suzanne R. Jacobs1,2,3,4,a, Edison Timbe5, Björn Weeser3,6, Mariana C. Rufino2,7, Klaus Butterbach-Bahl1,4, and Lutz Breuer3,6 1Karlsruhe Institute of Technology – Institute of Meteorology and Climate Research, Atmospheric Environmental Research (KIT/IMK-IFU), Kreuzeckbahnstr. 19, 82467 Garmisch-Partenkirchen, Germany
2Centre for International Forestry Research (CIFOR), c/o World Agroforestry Centre, United Nations Avenue, Gigiri, P.O. Box 30677 – 00100 Nairobi, Kenya
3Institute for Landscape Ecology and Resources Management (ILR), Justus Liebig University, Heinrich-Buff-Ring 26, 35392 Giessen, Germany
4Mazingira Centre, International Livestock Research Institute (ILRI), P.O. Box 30709 – 00100 Nairobi, Kenya
5Faculty of Agricultural Sciences, University of Cuenca, Av. Doce de Octubre, Cuenca, Ecuador
6Centre for International Development and Environmental Research (ZEU), Justus Liebig University, Senckenbergstr. 3, 35390 Giessen, Germany
7Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom
acurrent address: Centre for International Development and Environmental Research (ZEU), Justus Liebig University, Senckenbergstr. 3, 35390 Giessen, Germany
Abstract. Conversion of natural forest to other land uses could lead to significant changes in catchment hydrology, but the nature of these changes has been insufficiently investigated in tropical montane catchments, especially in Africa. To address this knowledge gap, we identified stream water sources and flow paths in three tropical montane sub-catchments (27–36 km2) with different land use (natural forest, smallholder agriculture and commercial tea plantations) within a 1 021 km2 catchment in the Mau Forest Complex, Kenya. Weekly samples were collected from stream water, precipitation and soil water for 75 weeks and analysed for stable water isotopes (δ2H and δ18O) for mean transit time estimation, whereas trace element samples from stream water and potential end members were collected over a period of 55 weeks for end member mixing analysis. Stream water mean transit time was similar (~ 4 years) in the three sub-catchments, and ranged from 3.2–3.3 weeks in forest soils and 4.5–7.9 weeks in pasture soils at 15 cm depth to 10.4–10.8 weeks in pasture soils at 50 cm depth. The contribution of springs and wetlands to stream discharge increased from 18, 1 and 48 % during low flow to 22, 51 and 65 % during high flow in the natural forest, smallholder agriculture and tea plantation sub-catchments, respectively. The dominant stream water source in the tea plantation sub-catchment was spring water (56 %), while precipitation was dominant in the smallholder agriculture (59 %) and natural forest (45 %) sub-catchments. These results confirm that catchment hydrology is strongly influenced by land use, which could have serious consequences for water-related ecosystem services, such as provision of clean water.
Citation: Jacobs, S. R., Timbe, E., Weeser, B., Rufino, M. C., Butterbach-Bahl, K., and Breuer, L.: Land use alters dominant water sources and flow paths in tropical montane catchments in East Africa, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2018-61, in review, 2018.
Suzanne R. Jacobs et al.
Suzanne R. Jacobs et al.
Suzanne R. Jacobs et al.

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Short summary
This study investigated how land use affects stream water sources and flow paths in an East African tropical montane area. Springs were the main stream water source in the tea plantation sub-catchment, while rainfall was the dominant source in the natural forest sub-catchment and smallholder agriculture sub-catchment. In all sub-catchments, the contribution of groundwater to streamflow increased during high flow and the mean transit time for rainfall to reach the stream was estimated at 4 years.
This study investigated how land use affects stream water sources and flow paths in an East...
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