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Proc. IAHS, 378, 3-10, 2018
https://doi.org/10.5194/piahs-378-3-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Post-conference publication
29 May 2018
Fuzzy and process modelling of contour ridge water dynamics
Alexander Mhizha1,2 and John Ndiritu2 1Department of Civil Engineering, University of Zimbabwe, Harare, Zimbabwe
2School of Civil and Environmental Engineering, University of Witwatersrand, Johannesburg, South Africa
Abstract. Contour ridges are an in-situ rainwater harvesting technology developed initially for soil erosion control but are currently also widely promoted for rainwater harvesting. The effectiveness of contour ridges depends on geophysical, hydro-climatic and socio economic factors that are highly varied in time and space. Furthermore, field-scale data on these factors are often unavailable. This together with the complexity of hydrological processes at field scale limits the application of classical distributed process modelling to highly-instrumented experimental fields. This paper presents a framework that combines fuzzy logic and process-based approach for modelling contour ridges for rainwater harvesting where detailed field data are not available. Water balance for a representative contour-ridged field incorporating the water flow processes across the boundaries is integrated with fuzzy logic to incorporate the uncertainties in estimating runoff. The model is tested using data collected during the 2009/2010 and 2010/2011 rainfall seasons from two contour-ridged fields in Zhulube located in the semi-arid parts of Zimbabwe. The model is found to replicate soil moisture in the root zone reasonably well (NSE  =  0.55 to 0.66 and PBIAS  =  −1.3 to 6.1 %). The results show that combining fuzzy logic and process based approaches can adequately model soil moisture in a contour ridged-field and could help to assess the water dynamics in contour ridged fields.
Citation: Mhizha, A. and Ndiritu, J.: Fuzzy and process modelling of contour ridge water dynamics, Proc. IAHS, 378, 3-10, https://doi.org/10.5194/piahs-378-3-2018, 2018.
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Short summary
Most farmers' fields do not have data on runoff while soil and rainfall characteristics differ from those experienced at fields where experiments could have been done. This study found established that information from experimental fields can be used to determine the soil moisture benefits of rainwater harvesting by contour ridges using a combination of fuzzy logic techniques and an understanding of the processes taking place. The method developed can be used to help determine suitable sites.
Most farmers' fields do not have data on runoff while soil and rainfall characteristics differ...
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