Rainfall Occurrences, Precipitation Deficit and Surplus Analysis for Rainfall Water Harvesting and Management in the Central highlands of Ethiopia, the Case of Bishoftu District, Oromia Region (original) (raw)
Related papers
Journal of Biology Agriculture and Healthcare, 2013
Rainfall remains the crucial component of the weather elements for improving agricultural yield in Ethiopia. Rainfall occurrence analysis is extremely helpful in planning of water resources and agricultural development. A study was conducted to asses the potential of sufficient rainfall occurrences and precipitation surplus and deficits in the central highland of Ethiopia for a selected district based on thirty three years of weather record data. The FAO(1978) and Reddy (1990) models were employed to set the threshold limits and the Weilbul frequency formula was used to calculate the probability of occurrences during the two growing seasons, belg(shorter) and kiremt (main). The results showed that the probability of occurrences of the sufficient amount of rainfall during the decades of main rainy season is promisingly stable while belg is observed to suffer from fewer occurrences of the sufficient amount even at the lower probability levels (25% probability of occurrences). Thus rainfall water harvesting during the main rainy season (Kiremt) is promising either for double cropping practices or other domestic uses.
Hydrology and Earth System Sciences Discussions, 2010
Agricultural practices and water resources management in the central highlands of Ethiopia is highly dependant and associated with climatic resources and their pattern and hence wise use of those resources is a priority for the region. Accordingly, a study was conducted to asses and critically quantity the climate resources of the central high lands of Ethiop, Bishoftu district. Thirty three years of weather record data has been used for the work. The onset, duration and end of the growing seasons were defined and quantified based on FAO and Reddy models while the dry and wet spell distributions and the drought events were calculated using the Markov chain models and the standardized precipitation index (SPI) respectively. The results revealed that the mean onset of the main (Kiremt) growing season was found to occur during the second meteorological decade and ended during the end of September. Similarly, though unreliable and only few occurred during the entire study period, the mean onset of the shorter (Belg) season was found to occur during the beginning of the first decade of April. The length of the growing season during the main rainy season, (Kiremt,) ranged from 112 to 144 days with a standard deviation of 9.6 days and coefficient of variation of 7.5%. However, the mean growing length during the Belg season was found to be 22.4 days with a standard deviation of 27 days and coefficient of variation of 122%. The results of analysis obtained both from the Markov Chain and Reddy models indicated higher probabilities of dry spell occurrences during the shorter season (Belg) but the occurrences of the same in the main rainy season (Kiremt) was very minimal. Like wise, the SPI model detected some drought events ranging from mild to severe classes in both seasons based on one a month time scale analysis. A considerable attention of maximizing crop harvest during the main rainy season is practically important.
Journal of Natural Sciences Research, 2014
The livelihood of over 80% of the people of Southern region of Ethiopia is dependent on agriculture. However, the region is known by its food insecurity problem due to increasing population growth and alarmingly increasing natural resource degradation as well as unpredictability of rainfall. Therefore, it needs to assess the seasonal rainfall variability in selected areas of the region. Instat software version 3.36 was used to analyze and estimate the onset and end of the growing season, and the Length of Growing Period (LGP). Trend analysis for 17 rainfall stations' data was also made by Mann-Kendall, Spearman test and Ordinary Least Square (OLS) methods. The Pattern of variability (coherent rainfall variability areas) was also identified by using Principal Component Analysis. The result shows that, the annual rainfall in the region varied from slightly over 780 mm in Billate station to more than 2110 mm in Gerese station with mean, SD and CV as 1200 mm, 197 mm and 25% respectively and that of kiremt varied from 157 mm in Konso to 844 mm in Welkite with mean, SD and CV as 506 mm, 202 mm and 39% respectively. Belg seasonal rain varied from 863 mm in Gerese to 246mm in Bue with mean, SD and CV of 409mm, 121mm and 30% respectively. CV of 15%-64% for kiremt, 17%-52% for March April May (MAM) and 12%-46% for annual were observed. For Kiremt season, CV greater than 30% was observed in 18 stations; between 20-30% in 10 stations and below 20% for 5 stations. The mean onset, end and LGP of the main growing season was found to be at Days of year (DOY) 92, DOY 286, and 193 days for Hosaina area; at DOY 117, DOY 290 and 169 days for Welkite area; and at DOY 84, DOY 146 and 62days for Gato area respectively. OLS apparently showed a non significant decreasing linear trend for rainfall amount in 10 stations out of 17 while significant decreasing trend at Sawla; p= 0.04(-9.15 mm/yr) and Chida; p= 0.05(-16.08 mm/yr). However, for the start of MAM, March was unreliable in Hosaina and Welkite while reliable in Gato area. In addition, two homogenous areas of coherent rainfall variability, in terms of both seasons were obtained. This classification could be used for regional water management and rainfall prediction. Therefore, time of planting crops and other soil and water conservation activities should be performed accounting these variability parameters.
Analysis of Rainfall Variability for Mekelle Meteorological Station, Northern Ethiopia (1960-2009)
Civil and Environmental Research, 2019
Nowadays rainfall variability is threatening the world. Despite this, studies related to the determination of variations, trends and fluctuations of rainfall have little local and regional specificity. Hence, this study aimed to analyze the trend and variability of the annual and seasonal rainfall occurrence at Mekelle Airport meteorological station, Northern Ethiopia. Historical rainfall data for the period 1960-2009 of the rain gauge station were obtained from National Meteorological Service Agency. Annual, seasonal and monthly rainfall trends; onset and cessation date of kiremt rainfall; growing period length and the number of rainy days and dry spell length were considered. Standardize anomaly index (SAI) and coefficient of variance was employed to analyze the rainfall data variability using INSTAT plus, SPSS version 20 and Excel. Analysis of the historical data showed extremely severe drought happened in the area in 1984 which resulted in the death of one million people, 8 million people highly affected, and 2.3 million people food in secured. 1961 was an extremely wet year. Generally, 70%, 18% and 12% years were normal, dry and wet respectively for the last 50 years. High annual, seasonal and monthly rainfall variability was observed. Though the station showed both increasing (1984-1988) and decreasing trends (1961-1968) of annual rainfall totals a declining trend was more pronounced. Besides, one to two weeks variability on the onset and cessation date was observed. The minimum and maximum kiremt season rainy days recorded in 1987 (27days) and 1986 (86 days) respectively while the maximum dry spell days recorded in the 50 years was in 1969. Thus, devising agronomic practices that retain moisture at the plant root zone and reduce crop failure due to variability of rainfall including extended dry spell could be important.
Rainfall analysis for rain-fed farming in the Great Rift Valley basins of Ethiopia
Journal of Water and Climate Change
Rainfall is the most important source of water for crop production in Ethiopia. However, its temporal and spatial variability is leading to serious food shortages and insecurity in the country. This study was aimed at investigating the characteristics of selected agroclimatic variables over the great Rift Valley regions of Ethiopia. Long term (1981–2010) climate data were analyzed for 17 stations selected based on agroecology representation. Selected descriptors for climate variability and the Mann–Kendall trend test were employed. Onset, cessation, length of growing period (LGP), water requirement satisfaction index and dry spell occurrence during the growing period were determined. The results showed low to very high rainfall variability (14–35%), LGP (20–256 days) and dry spell probability (50–100%) during the main season. Significant (P ≤ 0.05) annual and seasonal rainfall trends were observed in some stations. The probability of occurrence of a dry spell during the seasons was ...
Journal of Water and Climate Change, 2016
The national economy and food security of many sub-Saharan countries relies on rain-fed agriculture, hence the impact of rainfall variability is highly significant. The intent of this study is to characterize rainfall variability and trend in Awash River Basin for agricultural water management using standard rainfall statistical descriptors. Long-term climate data of 12 stations were analyzed. Onset and cessation dates, length of growing period (LGP) and probability of dry spell occurrences were analysed using INSTAT Plus software. The Mann–Kendall test and the Sen's slope method were used to assess the statistical significance of the trend. The results show high variability of rainfall (38–73%), LGP (30–38 days) and high probability of dry spell occurrence (up to 100%) during the Belg season (the short rainy season from March to May) compared with the Kiremt season (the main rainy season from June to September) in all stations. Belg season showed a non-significant decline trend...
Variability of rainfall and its current trend in Amhara region, Ethiopia
AFRICAN JOURNAL OF AGRICULTURAL RESEEARCH, 2012
In most of African countries whose economy is heavily depending on rainfed agriculture, accurate estimation of the spatial and temporal distribution of rainfall and observing its trends are crucial input parameters for securing sustainable agricultural production. This paper examines the spatial and temporal rainfall characteristics of Amhara Region, Ethiopia; using standard rainfall statistical descriptors. For this purpose, 10 meteorological stations with 30 years of daily rainfall data have been used. Variations of rainfall were found in every month in all stations. The spatial distribution of annual rainfall was varied from 850 to 1485 mm. Belg ("small rainfall" in March -May) rain makes a considerable contribution to the annual total in the central and eastern stations of the region. Annual rainfall has shown negative and positive anomalies for much of the 1980s and 1990s, respectively. Although the long term movements of rainfall in a time series did not show any increasing or decreasing trend, contraction of the length of growing period due to early cessation of rainfall had been observed in recent years. However, for improving precision and reliability of the application of the findings for practical use, increasing the number of study stations is found central.
Scintific paper, 2015
This study attempts to analyze seasonal rainfall variability in terms of its onset, end date, length of the growing period. Two different methods were used. The first was done with INSTAT and the second with the Hargreaves method. Hence, this study presents a detailed account of the rainfall variability statistics with a view to achieving one specific objective for possible application to cropping system management in the study area. The results show that seasonal rainfall amount was found to decrease with significance for 42 years period (1970-2012) (P<0.05) while monthly rainfall statistics showed a high variation (CV oscillating between 80.6 and 34.4 % across months). Minimum and maximum temperatures showed an increasing trend at the interannual scale (0.21ºC and 0.14ºC per decade respectively). The onset window varies between June 9 (DOY 159) and July 5 (DOY 186) across methods. The probability of dry spells longer than 15 days remains 0 from the end of June till the third dekad of August. While, the dry spell length probability of greater than 7 and 10 days curves converge to their minimum only during the peak rain period (June and August or DOY 180-222) and turn upward again around September (240-280 DOY), signaling the end of the growing season. Therefore, more attention is needed for the planning of agricultural water for crop production. The introduction of different agronomic practices that prolongs soil moisture-holding capacity and reduce evaporation loss could be used as management options in order to offset different magnitude of dry spells.
Analysis of long-term rainfall trend, variability, and drought in the Awash River Basin, Ethiopia
Changes in rainfall and drought significantly impact agriculture and water management, making it vital for effective planning and management. This study aimed to analyze rainfall trends and drought conditions in the Awash River Basin, Ethiopia. Twenty meteorological (1985-2021) and nine streamflow (1985-2014) station data were used to analyze rainfall trends, variability, and drought conditions based on the Mann-Kendall test, innovative trend analysis, standardized precipitation index, agricultural standardized precipitation index, reconnaissance drought index, effective reconnaissance drought index, and streamflow drought index. Based on Mann-Kendall's test results rainfall during the Bega season showed a decreasing trend at all stations while Tsedey and Kiremt seasons showed an increasing trend at the majority of the stations. However, the Belg season and annual rainfall showed no clear trend at the majority of the stations. A significant (p < 0.05) increase at Debre Berhan and a decrease at Awash7kilo and Ginchi were observed in annual rainfall by 44.1, 102.4, and 116.4 mm per decade, respectively. The innovative trend analysis revealed the Tsedey and Bega seasons showed increasing and decreasing trends in the majority of the stations for all rainfall categories, respectively. However, the annual, Belg, and Kiremt rainfall showed no clear trend in the majority of the stations for different rainfall categories. Annual rainfall showed increasing (Debre Berhan, Mojo, and Sheno) and decreasing (Awash7kilo, Dire Dawa, and Ginchi) trends for all rainfall categories. Generally, there is high variability in rainfall during Tsedey, Bega, and Belg, moderate and low variability during Kiremt, and annual with moderate and irregular rainfall distribution for the majority of the stations. The drought analysis revealed that 15.7, 17.3, 30.7, and 16.3% of drought periods were detected with annual standardized precipitation, agricultural standardized precipitation, reconnaissance drought, and effective reconnaissance drought indices, respectively. Hydrological drought conditions also showed a high probability of occurrence amounting to 47.6 and 48.2% for annual and three-month with severe indices of about-2.58 and-4.26 found at Awash Melka Sedi and Metehara gauge stations, respectively. Moderate to extreme hydrometeorological droughts have occurred approximately every six to eight years, with significant drought events