Spatial and seasonal water level dynamics in dryland grabens along the Rift Valley of northern Ethiopia

Meaza, Hailemariam; Demissie, Biadgilgn; Hermans, L.; Haftu, Brhanu; Biruk, Birhanu; Poesen, Jean; Asfaha, Tesfaalem Gebreyohannes; Zenebe, Amanuel; Nyssen, Jan

doi:10.1080/02626667.2022.2085511

Cited by 2 publications

(2 citation statements)

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“…Local orographic differences may therefore induce strong differences in harvest yield (Bewket, 2009;Fazzini et al, 2015;Frankl et al, 2013;Hoffmann et al, 2017;Jacob et al, 2019). Flash floods in catchment headwaters and hydrological deficit in the floodplains are indicative of the increasing rainfall at increasing elevation (Eze et al, 2022;Meaza et al, 2022;Negash et al, 2019Negash et al, , 2020. Hence, irrigation is important at low elevations.…”

Section: Introductionmentioning

confidence: 99%

Topoclimate and diurnal cycle of summer rain over the Ethiopian highlands in a convection‐permitting simulation

Negash,

Van Schaeybroeck,

Termonia

et al. 2023

Intl Journal of Climatology

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Topoclimate, orographically enhanced rain on windward slopes and leeward rain shadows, control rainfall variability in tropical mountains. Such variability may cause a substantial societal impact in populated highlands such as in Ethiopia. This study aims at understanding the rainfall diurnal cycle and the orographic driving factors over the Ethiopian highlands using the ALARO‐0 regional climate model at convection‐permitting resolution, over a period of 21 years. While the evaluation against satellite‐based observations shows a too early onset of the model diurnal cycle and a too low nocturnal rainfall, several conclusions can be drawn from the model simulations presented here. Elevation is the most important determining factor for modelled rainfall with increased average rainfall and rainfall per rainfall event towards higher elevations. Ethiopia's simulated summer rain exhibits a pronounced diurnal cycle with the highest rainfall occurring during the early afternoon hours and the minimum values occurring in the late night. Average rainfall and rainfall per rainfall event are substantially larger on the windward sides than on the leeward sides of the mountains, except during the peak hours. The diurnal cycles of temperature and humidity start earlier in the morning and recede later than the cycles of wind speed and rainfall. Moreover, rainfall peaks occur earlier in the day at higher elevations, and at night in valleys and in Afar Triangle. Rain intensities around noon on the leeward side are slightly higher than those on the windward side of the highest mountains (>3000 m). This could be due to delayed onset of cloudiness and larger morning insolation on the leeward side of the mountain, but this needs further study. The prevalence of windward over leeward rainfall, the stark contrast in wind‐speed diurnal cycle between windward and leeward slopes, and the early peak hour of surface air and dew point temperature all point towards temperature‐induced rather than wind‐induced convection. These differences are likely to determine hydrology and vegetation distribution, and farmers economy at large. Hence, the need for a way out from the ‘one‐size‐fits‐all’ agro‐ecosystem management approach towards a site‐specific policy that takes into account climatic differences.

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Section: Introductionmentioning

confidence: 99%

Topoclimate and diurnal cycle of summer rain over the Ethiopian highlands in a convection‐permitting simulation

Negash,

Van Schaeybroeck,

Termonia

et al. 2023

Intl Journal of Climatology

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“…A check dam is constructed from stone bunds, filled with sediment, and has a 1-2 m height in the main channels [8,11]. Wells are used at the household and community levels to provide water for irrigation and are constructed using sand and cement [11,12] with a water level depth that varies from 5 to 20 m. Springs provide base flow for small-scale irrigation during the dry season [3,11,12].…”

Section: Introductionmentioning

confidence: 99%

Mapping Small-Scale Irrigation Areas Using Expert Decision Rules and the Random Forest Classifier in Northern Ethiopia

Mohammedshum,

Maathuis,

Mannaerts

et al. 2023

Remote Sensing

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The mapping of small-scale irrigation areas is essential for food security and water resource management studies. The identification of small-scale irrigation areas is a challenge, but it can be overcome using expert knowledge and satellite-derived high-spatial-resolution multispectral information in conjunction with monthly normalized difference vegetation index (NDVI) time series, and additional terrain information. This paper presents a novel approach to characterize small-scale irrigation schemes that combine expert knowledge, multi-temporal NDVI time series, multispectral high-resolution satellite images, and the random forest classifier in the Zamra catchment, North Ethiopia. A fundamental element of the approach is mapping small-scale irrigation areas using expert decision rules to incorporate the available water resources. We apply expert decision rules to monthly NDVI composites from September 2020 to August 2021 along with the digital elevation model (DEM) data on the slope, drainage order, and distance maps to derive the sample set. The samples were based on the thresholds obtained by expert knowledge from field surveys. These data, along with the four spectral bands of a cloud-free Planet satellite image composite, 12 NDVI monthly composites, slope, drainage order, and distance map were used as input into a random forest classifier which was trained to classify pixels as either irrigated or non-irrigated. The results show that the analysis allows the mapping of small-scale irrigation areas with high accuracy. The classification accuracy for identifying irrigated areas showed a user accuracy ranging from 81% to 87%, along with a producer accuracy ranging from 64% to 79%. Furthermore, the classification accuracy and the kappa coefficient for the classified irrigation schemes were 80% and 0.70, respectively. As a result, these findings highlight a substantial level of agreement between the classification results and the reference data. The use of different expert knowledge-based decision rules, as a method, can be applied to extract small-scale and larger irrigation areas with similar agro-ecological characteristics.

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Spatial and seasonal water level dynamics in dryland grabens along the Rift Valley of northern Ethiopia

Cited by 2 publications

References 60 publications

Topoclimate and diurnal cycle of summer rain over the Ethiopian highlands in a convection‐permitting simulation

Topoclimate and diurnal cycle of summer rain over the Ethiopian highlands in a convection‐permitting simulation

Mapping Small-Scale Irrigation Areas Using Expert Decision Rules and the Random Forest Classifier in Northern Ethiopia

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