Ethiopian Journal of Water Science and Technology

Remote sensing approach to evaluate the effect of short-term land cover change on flood inundation and impact, Lower Awash Basin, Ethiopia.

2025-06-25T08:04:41+03:00

Flood risk management has been severely constrained by limited information on the causes and impacts of flooding. In this study, we evaluated the contribution of short-term land cover change of Logiya catchment to flood inundation and impact on Dubti town and it’s surrounding in the Lower Awash River Basin, Ethiopia. The land cover maps were generated by applying a machine learning algorithm on the Sentinel-2 optical satellite images. Land cover and soil data were used to generate the Curve Number (CN) map of the study area for the period stretching from 2017 and 2023. Sentinel-1 based flood maps show that roads and irrigation canals were washed away by the 2020 extreme flood which led to the inundation and abandoning of the Tendaho irrigation scheme. The runoff generating potential (CN) significantly increased over 27% of the Logiya catchment between 2017 and 2023 contributing to enhance flooding. The remote sensing analysis showed that overflow of the Logiya River in 2020 was intercepted and conveyed by the main irrigation canal of the Tendaho scheme resulting in inundation of the Dubti and surrounding. Availability of earth observation data (e.g Sentinel-1 SAR on the study area every 6 days at 10m resolution for 7 years) enabled detail characterization of the cause, dynamics and impacts of the historical flood events. This study’s results can guide flood risk management in the study area and serve as a reference for future studies in flood affected area.

Effectiveness of alternative furrow irrigation methods on cabbage yield and water productivity in Angacha District, Central Ethiopia Region

2025-06-25T08:08:45+03:00

This study aimed at investigating the effectiveness of alternative furrow irrigation methods on the head yield of cabbage and water productivity at Guder Irrigation Scheme in Angacha district Kembata Zone Centeral Ethiopia Region. Three levels of treatment were replicated five times, in Randomized Complete Block Design (RCBD). Farmers were used as replication from farmers’ research extension groups. The maximum head yield (52.8t/ha) was obtained from conventional furrow, following the second maximum head yield (49.07t/ha) at alternate furrow irrigation method. The minimum yield (38.112t/ha) was obtained from farmers’ practice of irrigation method. Their yield advantages (26.8%) and (22.3%) were recorded from conventional furrow, and alternate furrow irrigation, respectively. The highest water productivity (22.23kg/m³) was obtained from alternate furrow irrigation, following the second maximum water productivity form conventional furrow irrigation (11.96kg/m³) and minimum water productivity (8.15kg/m³). Farmers obtained a net income of (1,278,300 ETB/ha), (1,190,730 ETB/ha) and (909,903.3ETB/ha) from conventional furrow, alternate furrow, and farmers’ practices, respectively. Highest benefit cost ratio (18.63) was recorded form alternative furrow irrigation method :( 17.83) from every furrow and (14.15) from farmers’ practice. This implies that alternative furrow irrigation saves half of irrigation water when assimilated with conventional furrow and doubles net income on the farm gate. Therefore alternative furrow irrigation method should be recommended as a best agricultural water management technology without limiting fresh head yield of cabbage, and water productivity. The technology should be scaled up in to other irrigation schemes with the same agro ecology.

Key Words: - Alternate Furrow Irrigation, Head Cabbage, Yield, Water Productivity, Farmer Practice, Fertilizer, Guder

Analysis of Precipitation Variability in the Kulfo River Watershed: Insights from Wavelet Analysis and Back-Trajectory Approaches

2025-08-14T11:35:57+03:00

Analysis of precipitation time series is a fundamental undertaking in meteorology and hydrology. The heavy precipitation scenario of the Kulfo River watershed is studied using wavelet analysis and the advanced atmospheric transport model. Daily rainfall data for the 1991-2020 study periods are collected from the office of the Ethiopian Meteorology Institute. Meteorological fields on a three-dimensional grid at 1^o x 1^o spatial resolution and daily temporal resolution are also obtained from the Global Data Assimilation System (GDAS). Wavelet analysis of the daily precipitation processed with the lag-1 coefficient reveals some high power recurred once every 38 to 60 days with greater than 95% confidence for red noise. The analysis also identified inter-annual periodicity in the periods 2002 - 2005 and 2017 - 2019. Back trajectory analysis for 3-day periods up to the heavy precipitation day during the main and short rain seasons indicates the Indian Ocean and Gulf of Eden source; trajectories crossed the southern and eastern African escarpment to arrive at the Kulfo watershed. Atmospheric flows associated with the Western Indian monsoon redirected by the low-level Somali winds and Arabian ridge are responsible for the moisture supply. The spatial distribution of relative humidity (RH) during heavy precipitation events ranges from 50% to 88%. The findings indicated that the time-localization of the wavelet power spectrum yields valuable hydrological information and the back-trajectory approaches provide useful characterization of air mass sources and pathways.

Keywords: Back trajectory; Extreme Precipitation Events; Kulfo Watershed; Power Spectrum