Trends and Variability of Precipitation: Implications for Water Resources in Lake Ziway Watershed, Central Ethiopian Rift

Precipitation is the significant climatic variable that governs the availability of water resources in the country, Ethiopia, but it is highly erratic and variable in spatial-temporal scales. The purpose of this paper was to analyse trends and variability of rainfall at seasonal to annual sales in the Ziway Lake Watershed. The non-parametric Mann-Kendall (MK) and Sen’s Slope (SS) estimation were used to detect the trends and compute the magnitudes of slopes respectively. The Coefficient of Variation (CV) was employed to reveal the variations in rainfall. The spatial interpolations mapping was made by using IDW (Inverse Distance Weighting). The results revealed that the western Ziway Lake watershed had experienced more rainfall variability than the eastern Ziway Lake watershed. The results also indicated that the annual and summer rainfall did not exhibit significant evidence of a monotonic trend. On the other hand, almost all rainfall stations in the spring season revealed decreasing trends (significant and non-significant), for instance, there are three stations (Ogalcho, Butajira, and Koshe) showed significantly decreasing trends at 5% of significant level and the two stations (Kulumsa and Meki) indicates significantly decreasing trends at 10% significant level. Moreover, the magnitudes of slope (changes in mm/year) estimated by SS for stations in the spring season that display significantly decreasing trends were as follows: -8.702, - 6.58, -4.018, and -3.681,-3.667 for Butajira, Koshe, Kulumsa, Ogalcho, and Meki respectively. Droughts can be expected to increase if the decline precipitation trend continues. This could lead to over-exploitation of the water resources. The similarities in patterns of the intra-annual variability of precipitation and river discharges imply that any changes in rainfall pattern would have effects on water availability. The results of this investigation can significantly contribute to guiding water managers and decision-makers for more efficient water resources planning and management. Keywords: Central Ethiopian Rift,, Ziway Lake Watershed, Precipitation, Variability, Trends DOI: 10.7176/JEES/10-10-03 Publication date:October 31st 2020

Dispersal and competitive release affect the management of native and invasive tephritid fruit flies in large and smallholder farms in Ethiopia

African horticulture is seriously affected by fruit flies, both native and invasive. Novel sustainable control methods need testing against the backdrop of smallholder-dominated farming of Africa. We evaluated the potential of male-specific attractants (parapheromones) laced with insecticide to suppress the alien invasive Bactrocera dorsalis and native Ceratitis capitata. In large-scale guava, methyl-eugenol (ME)-bait stations combined with toxic protein baits suppressed B. dorsalis within 8 months but resulted in a resurgence of the displaced Ceratitis capitata. In smallholder farms, intervention using SPLAT-ME laced with spinosad was surprisingly unsuccessful. Subsequent mark-release-recapture experiments showed high dispersal rates of flies, covering many times a typical farm size, leading to a continuous influx of flies from surrounding areas. Several other factors important for intervention were evaluated. SPLAT-MAT-ME dollops remained attractive for over two weeks, although gradually becoming less attractive than fresh baits. Further, competitive displacement was observed: C. capitata selectively emerged from fruits in which B. dorsalis infestation was low. Finally, we evaluated whether ME could be combined with C. capitata male attractants [trimedlure (TML) and terpinyl acetate (TA)] without affecting attraction. Combining male lures did not affect catches directly, although at very high populations of B. dorsalis attracted to ME interfered with C. capitata trap entry. Although ME-based methods can effectively suppress B. dorsalis, they were not effective at single smallholder scale due to the high dispersive propensity of tephritids. Further, competitive release implies the need for a combination of lures and methods. These observations are important for developing control schemes tailored for African smallholder settings