Hydraulic Engineering

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    ANALYSIS AND PRIDICTION OF METEOROLOGICAL DROUGHT USING STANDARDIZED PRECIPITATION INDEX: CASE STUDY OF EASTERN OROMIA
    (Hawassa University, 2019-02-14)
    Ethiopia is one of the most drought affected country in Africa and suffered from acute drought many time in recent years. The objective of this study is to understand the rainfall variation and conduct an in-depth analysis and prediction of drought for to Eastern Oromia. Standardized precipitation index (SPI) was selected to characterize drought condition in the region. Drought characteristics at a time scale of 2-month, 3-month, 6month and 12-month were computed separately for 22 selected rain gauge station. The most maximum drought characteristics at 2-month, 3-month, 6-month and 12-month time scales have been found in Hararegie over last 36 years (1979-2015). The spacial extent of drought and rainfall variation were determined from SPI and CV values computed separately for each rainfall have been interpolated between station in Arc view GIS environment. The rainfall variation shows that the rainfall over the study area is highly variable and increases from Arsi to East Harargie and in the recent last decade (2005-2015) the map of SIP-3 (Belg) shows that a spacial extent drought over study area was irregular and there were no period in recent decades (2005-2015) without drought at least mild drought and this shows that the area is vulnerable to drought. The maximum intensity of (5.33) was recorded at Fedis Station for SPI-3 (kiremt season) in a year 1996, maximum intensity of (4.04) was recorded at Kobo Station in a year 1985 for SPI-3 (Belg season), maximum intensity of (4.77 and 4.5) were recorded at Ticho Station for SPI-6 (both seasons) and SPI-12 (annual) respectively. The drought prediction was made until 2043, using the Representative Concentration Path way (RCP) 8.5 Scenario.on the basis of the drought index measured by SPI. From the analysis of the drought index through the RCP 8.5 Scenario, extreme drought intensity will be more likely to occur. The long-term forecast (12-month period unit) showed that extreme drought would occur severely at station Diksis Sude, Hirna and Adelle from 2035 to 2040 and need more attention for this area
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    ANALYSIS AND CHARACTERIZATION OF HYDROLOGICAL DROUGHT UNDER CLIMATE CHANGE IN HAMASSA WATERSHED, RIFT VALLEY BASIN
    (Hawassa University, 2024-07-20) REDIAT LEGESE SIME
    Hydrological drought occurs when there is an extended period of significantly reduced water availability, leading to depleted water sources and severe impacts on ecosystem and communities. Water scarcity caused by prolonged periods of reduced rainfall due to climate change can lead to the natural disaster of drought. However, little has been done so far on hydrological drought under climate change in Hamassa watershed. This study aimed to analyze and characterize hydrological drought under climate change in the Hamassa watershed, Rift Valley Basin, Ethiopia. Hydrological data (1992-2015), meteorological data (1992-2022), future climate data 2030-2090), spatial data, DEM, land use land cover, and soil were collected. CMhyd software package was used for bias correction of the climate data. The hydrological model soil and water assessment tool (SWAT) was used for hydrological analysis. The simulation result was calibrated and validated using the SWAT calibration uncertainty procedure (SWAT-CUP). Standard precipitation index (SPI) and stream flow drought index (SDI) are used to decide drought conditions in a watershed and to identify drought-prone areas in the watershed. Temperature projections for both the near and long term indicate an increase compared to the current period under both RCP2.6 and RCP8.5 scenarios. Meanwhile, precipitation projections suggest a decrease for the periods 2040-2060 and 2061-2072 under both RCP2.6 and RCP8.5 scenarios. The standard precipitation index (SPI) and stream flow drought index (SDI) results showed that the watershed experiences mild (-0.5- -0.999), moderate (-1- -1.49), severe (-1.5- -1.99), and extreme (≤ - 2) drought events. Droughts are projected to occur in the periods 2040-2060 and 2061-2072 under both RCP2.6 and RCP8.5 scenarios. Sub-watersheds 7, 8, 9, 10, and 11 showed high vulnerability to severe and extreme drought. Drought-mitigating structures are needed to mitigate drought in the watershed