Irrigation and Drainage Engineering
Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/70
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Item MPACTS OF CLIMATE CHANGE ON RAINFED MAIZE PRODUCTION IN RIFT VALLEY LAKES BASINS OF ETHIOPIA; HAWASSA AS CASE STUDY(Hawassa University, 2017-10-18) KINDE NEGESSA DISASAAgriculture is mainstay of Ethiopian economy. Developing country like Ethiopia suffers from effects of climate change, due to their limited economic capability to build irrigation projects to reduce climate change impact on crop production. This study evaluates climate change impact on rainfed maize production in rift valley lakes basins of Ethiopia. First, outputs of 15 General Circulation Models (GCMs) under two emission scenarios (SRA1B and SRB1) are statistically downscaled by using LARS-WG software. Probability assessment of bounded range with known distributions is used to deal with the uncertainties of GCMs’ outputs. These GCMs outputs are weighted by considering the ability of each model to simulate historical records. The study result indicates that LARS-WG 5.5 model is more uncertain to simulate future mean rainfall than generating maximum and minimum mean temperatures hereby GCMs weight difference for rainfall mean is 0.83 whereas weight difference for minimum and maximum mean temperatures is 0.09. AquaCrop, version 4 developed by FAO that simulates the crop yield response to water deficit conditions, is employed to assess potential rainfed maize production in the study area with and without climate change. The study results indicate minimum and maximum temperatures absolute increase in the range of 0.34 0 C to 0.580 C, 0.940 C to 1.80 C and 1.420 C to 3.20 C and 0.320 C to 0.560 C, 0.910 C to 1.80 C and 1.340 C to 3.0350 C respectively in the near-term (2020s), mid-term (2055s) and long-term (2090s) under both emission scenarios. The expected percentage change of rainfall during these three time periods considering this GCMs weight difference into account ranges from -2.3 to 7%, 0.375 to 15.83% and 2.625 to 31.1%. Maize yields are expected to increase with the range of 3.63% to 7%, 5.39% to 14.08%, and 6.83% to 15.61%, during the same time periods. Unlike many studies in the world this study result show that maize yield increased in coming three time periods under both emission scenarios. Due to rainfall increase with temperature increase maize yield is expected to increase in future for this study area by using only rainfall. In conclusion, the results indicate that climate change will respond positively to climate change impact on maize yield production for this district if all field management, soil fertility and crop variety improved; but since there is rainfall variability among the seasons planting date should be scheduled well to combat water stress on cropsItem EVALUATING THE PERFORMANCE OF AQUACROP MODEL IN SIMULATING THE PRODUCTIVITY OF POTATO (Solanum tuberosum L.) CROP UNDER VARIOUS WATER LEVELS AT DEBRE BIRHAN, AMHARA REGIONAL STATE, ETHIOPIA(Hawassa University, 2019-10-22) TSEGAYE GETACHEW MENGISTUAgricultural sector face the challenge to produce more yield with less water. In this regard, simulation models are basic tools in evaluating the effect of water on crop production. To address this need, FAO has developed yield responses to water model named AquaCrop, which simulates attainable yields of the major field and vegetable crops from their physiological and agronomic background perspective at farm level. The aim of this study was to evaluate the AquaCrop model performance on potato crop growth parameters under various water levels at Debre Birhan, Ethiopia. The AquaCrop is a user-friendly, easy to apply, accurate and robust model, and it addresses conditions where water is a key limiting factor for crop production. The experiment was arranged with Randomized Complete Block Design, with four replications under different water levels 100%, 85%, 70% and 55 % of crop water requirement of potato, which were simulated by the AquaCrop model. The results indicated that the simulated amount of irrigation water for 100% water level was 377.2 mm of water depth in growing season. The growth parameter and tuber yield were significant differences among the water levels at p < 0.05. The fresh potato tuber yield ranges from 35.25 ton/ha to 44.37 ton/ha was obtained in 55% and 100% water levels respectively. The water productivity ranges from 11.59 kg/m3 to 12.67 kg/m 3 was obtained in 100%and 55% water level respectively. Concerning its performance, the AquaCrop model simulated very well in the canopy cover, dry aboveground and tuber biomass and soil water content of the potato crop. The statistical indicators; Nash-Sutcliffe efficiency (NSE), Normalized Root mean square error (NRMSE) index of agreement (d) and Coefficient of determination (R 2 ) showed very well to excellent efficiency observed on dry aboveground and tuber biomass, there values were found to be in the ranges of 0.78 to 0.94, 35.50 to 16.30, 0.96 to 0.99 and 0.98 to 0.96 respectively. However, for soil water content before irrigation, which was found to be poor ranges 0.00 to -0.63, 10.2 to 10.8, 0.78 to 0.51, 0.45 to 0.03 were observed respectively.in the above order. From the results of the study can conclude in two scenarios: first, in case of water scarce area, it may be more profitable for a farmer to maximize crop water productivity instead of maximizing the harvest per unit of land. The saved water can be used to irrigate extra units of land. Second, in case of no water scarce area, it may be more profitable to maximize the yield harvest than crop water productivity. Under the first scenario farmers should adopt 70% of crop water requirement with a 10-days interval, which 16.65% saved water with 10.1% yield penalty over 100%. On the other hand, they should adopt 100% of crop water requirement within 10-days interval In the case of no water scarce area. The future studies shall consider various other stresses such as soil fertility and mulchingItem IMPACTS OF CLIMATE CHANGE ON RAINFED MAIZE PRODUCTION IN RIFT VALLEY LAKES BASINS OF ETHIOPIA; HAWASSA AS CASE STUDY(Hawassa University, 2017-10-07) KINDE NEGESSA DISASAAgriculture is mainstay of Ethiopian economy. Developing country like Ethiopia suffers from effects of climate change, due to their limited economic capability to build irrigation projects to reduce climate change impact on crop production. This study evaluates climate change impact on rainfed maize production in rift valley lakes basins of Ethiopia. First, outputs of 15 General Circulation Models (GCMs) under two emission scenarios (SRA1B and SRB1) are statistically downscaled by using LARS-WG software. Probability assessment of bounded range with known distributions is used to deal with the uncertainties of GCMs’ outputs. These GCMs outputs are weighted by considering the ability of each model to simulate historical records. The study result indicates that LARS-WG 5.5 model is more uncertain to simulate future mean rainfall than generating maximum and minimum mean temperatures hereby GCMs weight difference for rainfall mean is 0.83 whereas weight difference for minimum and maximum mean temperatures is 0.09. AquaCrop, version 4 developed by FAO that simulates the crop yield response to water deficit conditions, is employed to assess potential rainfed maize production in the study area with and without climate change. The study results indicate minimum and maximum temperatures absolute increase in the range of 0.34 0 C to 0.580 C, 0.940 C to 1.80 C and 1.420 C to 3.20 C and 0.320 C to 0.560 C, 0.910 C to 1.80 C and 1.340 C to 3.0350 C respectively in the near-term (2020s), mid-term (2055s) and long-term (2090s) under both emission scenarios. The expected percentage change of rainfall during these three time periods considering this GCMs weight difference into account ranges from -2.3 to 7%, 0.375 to 15.83% and 2.625 to 31.1%. Maize yields are expected to increase with the range of 3.63% to 7%, 5.39% to 14.08%, and 6.83% to 15.61%, during the same time periods. Unlike many studies in the world this study result show that maize yield increased in coming three time periods under both emission scenarios. Due to rainfall increase with temperature increase maize yield is expected to increase in future for this study area by using only rainfall. In conclusion, the results indicate that climate change will respond positively to climate change impact on maize yield production for this district if all field management, soil fertility and crop variety improved; but since there is rainfall variability among the seasons planting date should be scheduled well to combat water stress on crops