Abstract
This study describes hydrological fluctuations of Lake Abaya-Chamo via direct local measurements in relation to time-integrated climate anomalies. Reconstruction of an index involved compositing lake level and flow discharge station records in the period 1983-2009. Satellite and model interpolated rainfall, latent heat flux and run-off anomalies follow the hydrological records when summed over and lagged by one year. Correlation of ECMWF climate fields reveals that east Pacific and subtropical Atlantic surface temperature are influential on continuous flow discharge, while the Indian Ocean dipole has influence in September to November season. A predictive algorithm accounts for 44% of inter-annual fluctuations in the period 1983-2009. Rapid increases in lake level coincide with maturing El Niño and Indian Ocean dipole, bringing floods for example in October 1997. Early season dry spells prevail when the equatorial trough remains over Tanzania, and dry northerly winds accelerate evaporation such as in March 2000. Key words: Ethiopia rift lakes, hydrological fluctuations.
Highlights
Ethiopia’s Rift Valley contains many lakes and minor rivers, surrounded by > 2000 m mountains that induce seasonal rainfall, and lowlands prone to drought
Ethiopia is blessed with ample water resources to due its mountainous topography and tropical latitude (Figure 1a)
This study has described hydrological fluctuations of
Summary
Ethiopia’s Rift Valley contains many lakes and minor rivers, surrounded by > 2000 m mountains that induce seasonal rainfall, and lowlands prone to drought. Each year the rivers swell and the lakes rise ~ 0.5 m, but in some years the flow doubles while in others it is halved, stressing agrarian production. Much attention is given to the Nile River discharge from northwestern Ethiopia (Quinn, 1992; Eldaw et al, 2003; Potter et al, 2004) and its modulation by global climate (Camberlin, 1997; Camberlin et al, 2001; Segele et al, 2009; Jury, 2011). Most of Ethiopia has a unimodal wet season (June-September), when surface winds arrive from the Congo Basin and an upper easterly jet pulses every few weeks.
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