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Research Project: Towards Resilient Agricultural Systems to Enhance Water Availability, Quality, and Other Ecosystem Services under Changing Climate and Land Use

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Title: Water resources modeling in east Africa: Access and suitability of rainfall data

Author
item GITAU, MARGARET - Purdue University
item MEHAN, SUSHANT - Purdue University
item SEKALUVU, LAWRENCE - Purdue University
item KIGGUNDU, NICHOLAS - Makerere University
item Moriasi, Daniel
item MISHILI, FULGENCE - Sokoine University Of Agriculture

Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/3/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary: Abstract only

Technical Abstract: Daily weather data are typically used in water resources modeling applications making it especially useful to have consistent and reliable long-term datasets. In most areas of East Africa, such records are either not available or, where available, may not be easily accessible. Oftentimes, estimates from other sources such as the Climate Forecast System Reanalysis (CFSR) or weather generators are used. In this study, we examined precipitation data obtained directly from CFSR with a view to determining their effectiveness in capturing essential characteristics of observed data including basic statistical properties, distributions, rainfall occurrence, and selected extreme events. Pilot assessments were conducted for five stations in Kenya (Jomo Kenyatta International Airport, JKIA; Garissa; Mandera; Mombasa; and, Moyale) for which relatively consistent records (98.7%, 96.2%, 99.1%, 98.6%, and 99.5% respectively) were available for the period 1979-1997. Based on the analysis, rainfall amounts (daily means and average annual values) computed from CFSR data were substantially higher than those for ground-based stations except at Moyale, where values were underestimated. In the CFSR data, rainy days (days with rainfall > 0.1 mm) were spread across more days with the number varying between 54 (Mandera) and 225 (JKIA) more rainy days than obtained from observed data. Values at the extremes (99 percentile and above) were greatly underestimated with CFSR—likely attributable to the redistribution of rainfall across more days. Further analysis showed that the total number of days with rainfall greater than 50.8 mm (2 in) were underestimated by between 4 (JKIA) and 49 (Mombasa) days in CFSR data, while the number of days with no precipitation was underestimated by up to 63%. Further work is needed to determine the reliability of rainfall data from this and other sources across East Africa, and to determine their suitability for use with water resources modeling studies in the region.