Seasonal rainfall variability and aptness of Geographical-Information- Systems (GIS) interpolation techniques in the arid regions of Embu county, Kenya
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Date
2013
Authors
Kisaka, O.
Mucheru-Muna, M.
Ngetich, F. K.
Mugwe, J.
Mugendi, D.
Mairura, F.
Journal Title
Journal ISSN
Volume Title
Publisher
African Crop Science Society
Abstract
This study sought to characterize inter/intra seasonal rainfall variability, drought probabilities and assess the efficacy of
geo-statistical interpolation techniques for spatio-temporal reconstruction of rainfall data in arid areas of Embu County; Kenya.
Gaps in rainfall data from two stations of Embu and Machang’a were filled using multiple imputations. Cumulative Departure Index
(CDI), Rainfall Anomaly Index (RAI) and Coefficients-of-Variance (CV) and probabilistic statistics were utilized in the analyses.
Data reconstruction utilized ArcGIS environmental tool combined with the digital elevation model (DEM) to generate average spatial
rainfall and maps using various interpolation techniques. The efficacy of interpolation techniques was assessed using root mean
square errors (RMSE), mean absolute errors (MAE) statistics plus gauged-data for validation. Rainfall homogeneity was accepted at
99% probabilities. Probabilities of rainfall exceeding cropping threshold were 50% (506.8mm) at Embu and 30% (523.7mm) at
Machang’a during Long-Rains (LRs) and Short-Rains (SRs) respectively. High variability was observed in rainfall amounts (CV=0.41
and 0.36) during LRs and (CV=0.56 and 0.38) during SRs in Machang’a and Embu respectively. Daily rainfall distribution depths
were highly skewed; small proportion of rainy days supplying a high proportion of rainfall. Variabilities in rainy days were CV=0.26
and 0.08 (LRs) and CV=0.88 and 0.27 (SRs) in respective stations above. High variability were observably in March (onset)
(CV=0.98 and 0.61) and October (onset) (CV=0.80 and 0.66) respectively. Dry-spell probabilities within growing months were high
(81%) and (60%) in Machang’a and Embu respectively. Kriging technique was identified as the most appropriate Geo-statistical and
deterministic interpolation techniques that can be used in the region. To optimize yield in the area, use of soil-water conservation and
supplementary irrigation, crop selection and timely accurate rainfall forecasting should be prioritized.
Key words: Cumulative-Departure-Index, GIS, Interpolation, Kriging, Rainfall-Anomaly-Index, Rainfall-variability
Description
Conference Proceedings
Keywords
Cumulative-Departure-Index, GIS, Interpolation, Kriging, Rainfall-Anomaly-Index, Rainfall-variability
Citation
African Crop Science Conference Proceedings, Vol. 11, pg. 883 - 893, 2013, African Crop Science Society