Statistical analysis of rainfall and streamflow time series in the Lake Tana Basin, Ethiopia

Tigabu, Tibebe B.; Hörmann, Georg; Wagner, Paul D.; Fohrer, Nicola

doi:10.2166/wcc.2018.008

Cited by 20 publications

(14 citation statements)

References 22 publications

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“…The rainy season in the study area occurs from June to September (Enyew et al., 2014; Tigabu et al., 2018). Thus, the months from June to August were considered as the wet season, and due to low rainfall amount, the months of March to May were considered as the dry season.…”

Section: Resultsmentioning

confidence: 99%

“…In general, the climate in the basin is divided into rainy and dry seasons. The rainy season mainly spans from June to September (Tigabu et al., 2018), which account for 70–90% of the rainfall amount (Enyew et al., 2014). The dry season occurs from October to April (Tigabu et al., 2018) and characterized by no rainfall events.…”

Section: Methodsmentioning

confidence: 99%

“…The rainy season mainly spans from June to September (Tigabu et al., 2018), which account for 70–90% of the rainfall amount (Enyew et al., 2014). The dry season occurs from October to April (Tigabu et al., 2018) and characterized by no rainfall events. However, in the southern parts of the basin, less intense sporadic rainfall occurs in April and May.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Impacts of land surface model and land use data on WRF model simulations of rainfall and temperature over Lake Tana Basin, Ethiopia

Teklay

Dile

Asfaw

et al. 2019

Heliyon

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The Weather Research and Forecasting (WRF) model is one of the regional climate models for dynamically downscaling climate variables at finer spatial and temporal scales. The objective of this study was to evaluate the performance of WRF model for simulating temperature and rainfall over Lake Tana basin in Ethiopia. The WRF model was configured for six experimental setups using three land surface models (LSMs): Noah, RUC and TD; and two land use datasets: USGS and updated New Land Use (NLU). The performances of WRF configurations were assessed by comparing simulated and observed data from March to August 2015. The result showed that temperature and rainfall simulations were sensitive to LSM and land use data choice. The combination of NLU with RUC and TD produced very small cold bias (0.27 °C) and warm bias (0.20 °C) for 2m maximum temperature (Tmax) and 2m minimum temperature (Tmin), respectively. WRF model with RUC and NLU captured well the observed spatial and temporal variability of Tmax, while TD and NLU for Tmin. Moreover, rainfall simulation was better with NLU; especially NLU and Noah configuration produced the smallest mean bias (2.39 mm/day) and root mean square error (6.6 mm/day). All the WRF experiments overestimated light and heavy rainfall events. Overall, findings showed that the application of updated land use data substantially improved the WRF model performance in simulating temperature and rainfall. The study would provide valuable support for identifying suitable LSM and land use data that can accurately predict the climate variables in the Blue Nile basin.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Impacts of land surface model and land use data on WRF model simulations of rainfall and temperature over Lake Tana Basin, Ethiopia

Teklay

Dile

Asfaw

et al. 2019

Heliyon

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“…The mean, standard deviation (SD), and coefficient of variation (CV) in Equation (1) formed the first analysis for the rainfall, temperature, and river-flow data. These methods have been used by [9,11,18,26]. The analysis was carried out at the individual stations' level and over the entire sub-catchment.…”

Section: Discussionmentioning

confidence: 99%

Variabilities and Trends of Rainfall, Temperature, and River Flow in Sipi Sub-Catchment on the Slopes of Mt. Elgon, Uganda

Luwa

Majaliwa

Bamutaze

et al. 2021

Water

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The variabilities in rainfall and temperature in a catchment affect water availability and sustainability. This study assessed the variabilities in rainfall and temperature (1981–2015) and river flow (1998–2015) in the Sipi sub-catchment on annual and seasonal scales. Observed daily rainfall and temperature data for Buginyanya and Kapchorwa weather stations were obtained from the Uganda National Meteorological Authority (UNMA), while the daily river-flow data for Sipi were obtained from the Ministry of Water and Environment (MWE). The study used descriptive statistics, the Standardized Precipitation Index (SPI), Mann–Kendall trend analysis, and Sen’s slope estimator. Results indicate a high coefficient of variation (CV) (CV > 30) for August, September, October, and November (ASON) seasonal rainfall, while annual rainfall had a moderate coefficient of variation (20 ˂ CV ˂ 30). The trend analysis shows that ASON minimum and mean temperatures increased at α = 0.001 and α = 0.05 levels of significance respectively in both stations and over the entire catchment. Furthermore, annual and March, April, and May (MAM) river flows increased at an α = 0.05 level of significance. A total of 14 extremely wet and dry events occurred in the sub-catchment during the post-2000 period, as compared to five in the pre-2000. The significant increased trend of river flow could be attributed to the impacts of climate and land-use changes. Therefore, future studies may need to quantify the impacts of future climate and land-use changes on water resources in the sub-catchment.

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“…The null hypothesis assumed that there was no significant difference between means and the alternative hypothesis was assumed that a significant difference exists in means at a 5% significance level. The Tukey's HSD appraoch has been applied to test the hydrological variation in decedal resolution in Lake Tana Basin, Ethiopia (Tigabu et al 2020).…”

Section: Discussionmentioning

confidence: 99%

Flow Indices Variability in Humid Subtropical of Upper Awash River Basin, Ethiopia

Tola

Shetty

2021

Preprint

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Investigating the hydrological extremes indices at high resolutions describing the whole stream spectrum is essential for the comprehensive assessment of watershed hydrology. The study focuses on a wide-ranging assessment of river discharge in annual mean, peak, and high and low percentiles flow at the Upper Awash River basin, Ethiopia. Statistical tests such as coefficient of variation, flood variability to characterize the flow regime and Tukey’s test to detect decadal variability. Modified Mann-Kendall test, Sen’s slope estimator, innovative trend analysis and Pettitt’s test were applied to see trends, and change points in time series, respectively. Results showed that the basin was characterized by moderate to high variability. Spatially, main tributaries showed a higher variability, almost in all-time step and characterized by higher flood variability. The large discharge receiving rivers resulted in a moderate to high and lower discharge variability. Test statistics resulted in a positive increasing trend dominating most time scales at a 5% significant level and higher magnitude of slope trend in peak flow. A negative trends were also exhibited. Hombole main outlet site experienced decreasing trend in high percentile flow. In comparison, complete trend direction agreements were observed (except in few series). Flow indices showed an upward shift and downward shift mainly in the year 2000s and the significant decadal variation resulted in comparable with change points. The study provides an understanding of water resources variability, which will be necessary to apply operational water resources strategies and management to restrain the potential impacts of variability nature of the streamflow.

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Statistical analysis of rainfall and streamflow time series in the Lake Tana Basin, Ethiopia

Cited by 20 publications

References 22 publications

Impacts of land surface model and land use data on WRF model simulations of rainfall and temperature over Lake Tana Basin, Ethiopia

Impacts of land surface model and land use data on WRF model simulations of rainfall and temperature over Lake Tana Basin, Ethiopia

Variabilities and Trends of Rainfall, Temperature, and River Flow in Sipi Sub-Catchment on the Slopes of Mt. Elgon, Uganda

Flow Indices Variability in Humid Subtropical of Upper Awash River Basin, Ethiopia

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