“Multivariate analysis of baseflow index in complex rift margin catchments: The case of Abaya-Chamo lakes basin, southern Ethiopia”

Molla, Dagnachew Daniel; Tegaye, Tenalem Ayenew

doi:10.1016/j.gsd.2019.100236

Cited by 7 publications

(3 citation statements)

References 43 publications

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“…The geology of the watershed (Figure 2) is extraordinarily intricate and faulted, as numerous earlier studies have described [30,31]. Since the study area lies at the escarpment of the Main Ethiopia Rift Valley, local structural features are observed following the main regional structure in the north-south direction.…”

Section: Description Of the Study Areamentioning

confidence: 82%

“…Other studies in the Abaya-Chamo subbasin have come up with similar evapotranspiration patterns. According to [30], the mean annual evapotranspiration demand of 842.3 mm consumed 70.7% of annual mean precipitation. In other Ethiopian watersheds, evapotranspiration demands consumed 81% of rainfall in the Illala catchment [40], 90.7% of rainfall in the Werii watershed [9], 58.5% of rainfall in the Birki watershed [41] in the Tekeze River basin, and 70.8% of rainfall in the Upper Bilate catchment [42] in Rift Valley Lake basin.…”

Section: Discussionmentioning

confidence: 99%

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Groundwater Recharge Estimation in Upper Gelana Watershed, South-Western Main Ethiopian Rift Valley

et al. 2023

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Estimating the spatial and temporal patterns of groundwater recharge through integrated water balance modeling plays an important role in sustainable groundwater resource management. Such modeling effort is particularly essential for data-scarce regions, such as the Rift Valley Lake basin in the Basement Complex of Ethiopia, which has shallow aquifers, a proliferation of wells, and poor groundwater monitoring networks. A spatially distributed water balance model (WetSpass), along with GIS and remote sensing tools, was used for groundwater recharge estimation for its suitability and efficiency in data-scarce hydrogeological regions. The WetSpass model depicted a very good performance in simulating the groundwater recharge in the Upper Gelana watershed within the Rift Valley Lake basin. The water balance analysis revealed that about 7% of the mean annual rainfall is converted to groundwater recharge, and the remaining rainfall amounts are partitioned into surface runoff (19%) and evapotranspiration (75%). The model simulation outputs are also used to investigate the relative influences of biophysical driving factors on the water balance components. While the land use types had a greater influence on the actual evapotranspiration processes, the soil texture classes were the dominant factors in the surface runoff and groundwater recharge processes in the watershed. The groundwater recharge rates were found to be higher than 400 mm/yr in the central parts (Fisehagenent, Tore, and Gedeb) and lower than 165 mm/yr in the southern parts (Hageremariam) of the watershed. The areal proportions of the low, medium, and high recharging parts of the watershed are, respectively, estimated as 15%, 68%, and 17% of the watershed area. Therefore, the spatial and temporal patterns of groundwater recharge should be taken into consideration in developing a sustainable groundwater resources management plan for the Upper Gelana watershed. Managed aquifer recharge can be adopted in high and medium groundwater recharging parts of the watershed to capture stormwater runoff during the wet season to improve the groundwater supply during dry months. Furthermore, monthly groundwater withdrawals should be regulated according to the spatial and temporal patterns of the groundwater recharge in the watershed.

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Section: Description Of the Study Areamentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Groundwater Recharge Estimation in Upper Gelana Watershed, South-Western Main Ethiopian Rift Valley

et al. 2023

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“…These measurement approaches have their advantages and limitations (Thiemig et al , 2013). Spatial representation particularly in developing countries, the distribution of measurement stations are either too sparse to represent the spatiotemporal variability of a given rainfall pattern or do not exist at all (this includes radars) (Beighley et al , 2011), which is true for the study area that comprises of highly heterogeneous rift margin environment (Molla and Tegaye, 2019). Besides, uneven distribution and less coverage of rainfall gauge stations in Ethiopia with available short record periods, missing data discontinuity and low data quality are few challenges.…”

Section: Introductionmentioning

confidence: 99%

Performance evaluation of satellite-based rainfall estimates for hydrological modeling over Bilate river basin, Ethiopia

Ibrahim

Molla

Lohani

2022

WJE

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Purpose The purpose of this study is to address a highly heterogeneous rift margin environment and exhibit considerable spatiotemporal hydro-climatic variations. In spite of limited, random and inaccurate data retrieved from rainfall gauging stations, the recent advancement of satellite rainfall estimate (SRE) has provided promising alternatives over such remote areas. The aim of this research is to take advantage of the technologies through performance evaluation of the SREs against ground-based-gauge rainfall data sets by incorporating its applicability in calibrating hydrological models. Design/methodology/approach Selected multi satellite-based rainfall estimates were primarily compared statistically with rain gauge observations using a point-to-pixel approach at different time scales (daily and seasonal). The continuous and categorical indices are used to evaluate the performance of SRE. The simple scaling time-variant bias correction method was further applied to remove the systematic error in satellite rainfall estimates before being used as input for a semi-distributed hydrologic engineering center's hydraulic modeling system (HEC-HMS). Runoff calibration and validation were conducted for consecutive periods ranging from 1999–2010 to 2011–2015, respectively. Findings The spatial patterns retrieved from climate hazards group infrared precipitation with stations (CHIRPS), multi-source weighted-ensemble precipitation (MSWEP) and tropical rainfall measuring mission (TRMM) rainfall estimates are more or less comparably underestimate the ground-based gauge observation at daily and seasonal scales. In comparison to the others, MSWEP has the best probability of detection followed by TRMM at all observation stations whereas CHIRPS performs the least in the study area. Accordingly, the relative calibration performance of the hydrological model (HEC-HMS) using ground-based gauge observation (Nash and Sutcliffe efficiency criteria [NSE] = 0.71; R2 = 0.72) is better as compared to MSWEP (NSE = 0.69; R2 = 0.7), TRMM (NSE = 0.67, R2 = 0.68) and CHIRPS (NSE = 0.58 and R2 = 0.62). Practical implications Calibration of hydrological model using the satellite rainfall estimate products have promising results. The results also suggest that products can be a potential alternative source of data sparse complex rift margin having heterogeneous characteristics for various water resource related applications in the study area. Originality/value This research is an original work that focuses on all three satellite rainfall estimates forced simulations displaying substantially improved performance after bias correction and recalibration.

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Temporal and spatial variability of suspended sediment rating curves for rivers draining into the Ethiopian Rift Valley

et al. 2022

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Quantification of suspended sediment dynamics is a proxy for the intensity of soil erosion processes in a catchment. However, direct measurement of suspended sediments is difficult. Long-term-based discharge-suspended sediment relationships often fail to provide sufficiently accurate results due to the temporal variations in sediment supply. This study evaluates temporal variations in suspended sedimentdischarge relations for six stations in two selected catchments within the Gamo Highlands in the southern Ethiopian Rift Valley. During a three-year period (2018-2020), discharge was monitored at a 10-min interval using a TD-diver, while 1938 samples of suspended sediment concentration were taken at specific events. Observed suspended sediment concentration varied between 0.04 and 130 kg m À3 for discharge ranging between quasi-zeros to 339 m 3 s À1 . The results show that pooled annual datasets lead to unsatisfying sediment rating curves and large errors in estimated sediment load. However, stratification of the data into three rainy season periods strongly improved the performance of the sediment rating curves. The development of a vegetative cover throughout the rainy season largely controls sediment supply from hillslopes to the river channel and hence the shape of the sediment rating curves. Furthermore, localized bank erosion and gully head dynamics also lead to important interannual changes in sediment rating curves within one river system, as well as between different rivers. Thus, attention should be given to possible errors due to high temporal and spatial variability while using discharge-suspended sediment relations to quantify sediment load.

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“Multivariate analysis of baseflow index in complex rift margin catchments: The case of Abaya-Chamo lakes basin, southern Ethiopia”

Cited by 7 publications

References 43 publications

Groundwater Recharge Estimation in Upper Gelana Watershed, South-Western Main Ethiopian Rift Valley

Groundwater Recharge Estimation in Upper Gelana Watershed, South-Western Main Ethiopian Rift Valley

Performance evaluation of satellite-based rainfall estimates for hydrological modeling over Bilate river basin, Ethiopia

Temporal and spatial variability of suspended sediment rating curves for rivers draining into the Ethiopian Rift Valley

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