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Research Article
Spatio-Temporal Variability and Trends of Annual and Seasonal Rainfall in Wolaita Zone, Ethiopia
Adugna Arba*
Issue:
Volume 11, Issue 2, June 2025
Pages:
16-23
Received:
1 April 2025
Accepted:
23 April 2025
Published:
29 May 2025
Abstract: This paper examined the spatiotemporal variability and trends of rainfall in the Wolaita Zone, Ethiopia. Rainfall data from fifteen stations from 1991 to 2020 is included, as well as data from important stations with longer observation periods. The variability of rainfall at the annual and seasonal scales was analyzed by using the coefficient of variation (CV) and standardized rainfall anomalies (SRA) over the study area. Mann-Kendall test was used to determine trend and Sen’s slope estimator was used to determine magnitude of the trend. Rainfall was highly variable during Belg season. The Belg season is the second rainy season, which received from 309.3 mm to 694.5 mm. Rainfall was moderately variable during the Kiremt season. The Kiremt season is the main rainy season, which received from 379.5 mm to 752.8 mm. Rainfall is less variable during annual times. At the annual time, rainfall was recorded from 910.3 mm to 1465.9 mm. At the annual and Kiremt time, almost all stations show increases in trend when P values < 0.005. On the other hand, at the Belg season, almost all stations show decreases in trends when P values < 0.005. The spatial distribution of rainfall is increasing in the highland area while decreasing in the lowland area of the Wolaita zone. The studying of rainfall variability and trend at temporal and spatial scales is hence useful for communities, local-level actors, and decision-makers for planning activities and devising appropriate adaptive strategies as well as to take informed decisions.
Abstract: This paper examined the spatiotemporal variability and trends of rainfall in the Wolaita Zone, Ethiopia. Rainfall data from fifteen stations from 1991 to 2020 is included, as well as data from important stations with longer observation periods. The variability of rainfall at the annual and seasonal scales was analyzed by using the coefficient of va...
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Research Article
Performance Evaluation and Adaptation of Mini-sprinkler Irrigation through Cabbage Production
Lalisa Ofga*,
Jemal Nur,
Ayala Tade
Issue:
Volume 11, Issue 2, June 2025
Pages:
24-29
Received:
17 April 2025
Accepted:
3 May 2025
Published:
19 June 2025
Abstract: The activity was conducted with the objectives of adapting and evaluating the performance of mini sprinkler irrigation technology through cabbage production. The result indicates that the distribution uniformity obtained was 78.60%, uniformity coefficient determined was 81.5% and application efficiency was 80.70%. From the result, all performance indicators for min-sprinkler irrigation; distribution uniformity, coefficient of uniformity and application efficiency were in good and recommended range of indicators classes. The study indicates that, the mini-sprinkler irrigation evaluated was performed with wind speed property of the study area. The result also shown that, maximum water productivity (9.34 kg/m3) was obtained by mini-sprinkler irrigation and the lowest water productivity (7.10 kg/m3) was obtained from conventional furrow irrigation method. The result shown that, the cabbage yield produced by mini-sprinkler irrigation method was 395 qt/ha. Based on the result obtained, the mini-sprinkler irrigation is recommended for further use for production of cabbage with application efficiency (80.70%), distribution uniformity (78.60%), uniformity coefficient (81.85%) and water productivity (9.34 kg/m3) for the study area and same agro-ecology. Concerning stakeholder should demonstrate this technology to improve irrigation water productivity.
Abstract: The activity was conducted with the objectives of adapting and evaluating the performance of mini sprinkler irrigation technology through cabbage production. The result indicates that the distribution uniformity obtained was 78.60%, uniformity coefficient determined was 81.5% and application efficiency was 80.70%. From the result, all performance i...
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Research Article
Advancement of Intensity Duration Frequency (IDF) Curve Through Possible Probability Distribution Method Using Disaggregated Precipitation Data; The Case of Wolkite, Ethiopia
Issue:
Volume 11, Issue 2, June 2025
Pages:
30-39
Received:
26 April 2025
Accepted:
15 May 2025
Published:
25 June 2025
Abstract: Rainfall is one of the key inputs for surface water resources and groundwater recharges. This rainfall is recorded in depth format (mm or in) using a rain gauge in the gauging station. Some models need this rainfall record in intensity format (example, mm/hr or in/hr). In addition, design discharge, especially flood-related structures, requires extreme rainfall intensity values. In Ethiopia availability of on hand rainfall intensity data in shortest duration is in scarce and the same for the selected area called Wolkite. Therefore, this study aims in developing Intensity Duration Frequency curve through probability distribution methods using disaggregated data that fits the study area. For this purpose, six distribution methods, namely, general extreme value I, Gumbel, normal, log-normal, Pearson, and log-Pearson were examined based on different comparison criteria. Normal distribution method found to be the best method that fits the data applied and Intensity duration curve was developed using this method. Finally, the developed Intensity Duration Frequency curve was calibrated and evaluated with Non-Probability Intensity Duration Frequency Models and results a Performance indicator value of Coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE) and Percent bias (PBIAS) of 0.96, 0.964, and -6.35% which are in acceptable ranges. Therefore, the derived Intensity Duration Frequency values were possible to apply in developments of any urban and water related structure for required duration specifically in Wolkite town. Also, the research is applied as a guideline in areas where availability of rainfall intensities of shortest duration is in scarce.
Abstract: Rainfall is one of the key inputs for surface water resources and groundwater recharges. This rainfall is recorded in depth format (mm or in) using a rain gauge in the gauging station. Some models need this rainfall record in intensity format (example, mm/hr or in/hr). In addition, design discharge, especially flood-related structures, requires ext...
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Research Article
Prediction of Sediment Yeild to Lake Ziway Reservoir and Assessing Reduction methods (Using Arc-swat)
Alemayehu Kassa Ewentie*,
Peniel Bafe Unto
Issue:
Volume 11, Issue 2, June 2025
Pages:
40-50
Received:
18 May 2025
Accepted:
10 June 2025
Published:
30 June 2025
Abstract: Sediment accumulation in Lake Ziway is an escalating concern driven by poor land use practices, ineffective watershedmanagement, and the absence of adequate soil and water conservationmeasures. This study aims to estimate sediment yield in the Lake Ziway watershed using the Soil and Water Assessment Tool (SWAT) integrated within ArcGIS. Themodel was calibrated and validated usingmeteorological and spatial data across 11 sub-basins and 116 hydrologic response units (HRUs), covering a calibration period from 2001 to 2009 and a validation period from 2010 to 2012. Calibration was performed using the Sequential Uncertainty Fitting version 2 (SUFI-2) algorithm within the SWAT-CUP interface.model performance was satisfactory, with coefficients of determination (R²) and Nash–Sutcliffe efficiency (NSE) values ranging from 0.72 to 0.76 for discharge and 0.72 to 0.84 for sediment yield. The average annual sediment yield was estimated at 2.69 tons/ha/year, and the gross sediment inflow into Lake Ziway was calculated at approximately 1.04million tons/year, with a deposition rate of 38.5%. Sub-basins 4 and 5 were identified as sediment hotspots, with yields exceeding 6 tons/ha/year. Three conservation scenarios were evaluated using the current watershed condition as a baseline: terracing reduced sediment yield by 72%, filter strips by 42%, and grassed waterways by 58%. These results highlight the critical role of soil and water conservation strategies in sustaining Lake Ziway’s capacity and ecosystem.
Abstract: Sediment accumulation in Lake Ziway is an escalating concern driven by poor land use practices, ineffective watershedmanagement, and the absence of adequate soil and water conservationmeasures. This study aims to estimate sediment yield in the Lake Ziway watershed using the Soil and Water Assessment Tool (SWAT) integrated within ArcGIS. Themodel wa...
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