Impact of land management practices on water balance and sediment transport in the Morogoro catchment, Uluguru mountains (Tanzania)
Loading...
Date
2017-12-14
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Technische Universitat Dresden
Abstract
Tanzania, like other developing countries in the tropics is severely affected by the
degradation of water resources owing to improper land management practices. Such practices
affect water supply through soil erosion which does not only cause sedimentation of rivers and
water bodies but also leads to a reduction in the rainwater infiltration capacity of soils. This
thesis seeks to demonstrate how the implementation of proper land management measures can
reduce soil erosion and increase water supply in the Morogoro River catchment (Uluguru
Mountains). The proper practices referred to are the soil and water conservation (SWC)
approaches which include contour farming, fanya juu terracing and bench terracing. The thesis
combines social science and geoscience methods in a synergetic manner to address this research
problem. To understand how and to what degree SWC methods affect water fluxes and sediment
yields, the hydrological model SWAT (Soil and Water Assessment Tool) was applied. Before
carrying out the modelling procedures, it was necessary to examine the level of SWC adoption
among farmers and factors influencing the process so as to establish the baseline. To this end,
biophysical and socio-economic factors assumed to affect farmers’ adoption tendency were
examined using a household questionnaire.
Modelling results indicate that if correctly implemented contour farming, fanya juu
terracing and bench terracing would significantly reduce sediment yield at different rates. The
reduction would range approximately between 1% - 85% with the highest percentage change
achieved by practicing the three SWC methods simultaneously. However, such SWC measures
would not increase water flow annually owing to evapotranspiration losses.
Nevertheless,
according to modelling results groundwater storage would be increased by about 14% and hence
contributing to water supply during the dry season. The household questionnaire survey suggests
that the adoption of SWC methods in the study area is very low and complex. While age of the
head of household, access to extension (professional) services, household annual income and
proximity to the farm significantly influenced farmers’ decision to adopt SWC, gender of the
head of household, slope characteristics of the farm, number of adults in the household and
farmer’s perception on soil erosion effects had no considerable influence on adoption. Therefore,
to successfully realize the SWC benefits demonstrated by the modelling results, smallholder
farmers upstream of the catchment should be incentivized to implement proper land management practices. Payment for ecosystem services scheme appears to be a suitable strategy. To make this
operational, the Tanzanian government should establish a national water fund which will finance
watershed management activities. The methodological approach employed in this thesis is
transferrable to other sites with problems comparable to the studied catchment.
Description
Thesis
Keywords
Land management practices, Sediment transport, Morogoro, Uluguru mountains, Tanzania