排序方式： 共有13条查询结果，搜索用时 31 毫秒
1.
Abebech Abera Niko E.C. Verhoest Seifu A. Tilahun Tena Alamirew Enyew Adgo Michael M. Moges 《自然地理学》2019,40(3):227-251
This study was conducted to investigate technical and socio-political attributes that lead to the underperformance of two selected irrigation schemes (Shina and Bebeks) in the Lake Tana floodplains, Ethiopia. Irrigation application efficiency (AE) at nine experimental fields showed a wide range, from 20 to 80%, but was mostly between 40 and 60%. Irrigation water-use efficiency (IWUE) varied from 1.9 to 7.2 kg m?3 for onion and 0.9 to 1.2 kg m?3 for maize. The lined and earthen canal conveyance losses in Bebeks were 0.037 and 0.047 l s?1 m?1, whereas in Shina they were 0.033 and 0.044 l s?1 m?1, respectively. The overall consumed ratio (OCR) of water was 0.58 for Bebeks and varied from 0.73 to 1.2 in Shina. Both schemes are performing below the standard based on technical performance indicators. Irrigation water user associations (WUAs) were not implemented, but irrigation committees (ICs), composed of local political leaders, are managing both schemes. Canal and reservoir sedimentation from erosion of upstream catchment areas during the rainy season was the major problem. 相似文献
2.
Ethiopia??s agriculture is predominantly rainfed and hence any irregularity in weather conditions has adverse welfare implications. Using panel data, this paper analyzes the effect of rainfall shocks on Ethiopian rural households?? food security and vulnerability over time while controlling for a range of other factors. To this end, we generate a time-variant household food security index which is developed by principal components analysis. Based on this index, households are classified into relative food security groups and their socioeconomic differences are assessed. The exploratory results show that compared to the less secured households, the more secured ones have male and literate household heads, tend to have a greater number of economically active household members, own more livestock, experience better rainfall outcome, and participate in local savings groups. Using the food security index as the dependent variable, we use a fixed effects instrumental variable regression model to identify determinants of households?? food security over time and find that rainfall variability is an important factor. Moreover, household size, participation in local savings groups, and livestock ownership positively affect food security. Results from multinomial logistic regression model complement the fixed effects instrumental variable regression results by showing that the level and variability of rainfall are important determinants of persistent food insecurity and vulnerability. The results highlight the need for efficient risk reduction and mitigation programs to improve risk exposure and coping ability of rural households. Careful promotion of investment in infrastructure to support irrigation and water resources development is one aspect worth considering. 相似文献
3.
Kassaye Aklilu Alemayehu Mohammed Abdella Kemal Angello Zelalem Abera 《Water Resources》2022,49(3):402-412
Water Resources - The hydraulic relationships of flow through the weir of different common shapes were investigated in this study. The hydraulic performances of weirs were carried out... 相似文献
4.
GeoJournal - Qoltso is a seasonal crop that grows as weedy root crop where the land is cultivated for other cerials. The production and productivity of Qoltso is rapidly declining which resulted in... 相似文献
5.
Abera Tessema 《Natural Resources Research》2017,26(4):465-488
Radial basis function link neural network (RBFLN) and fuzzy-weights of evidence (fuzzy-WofE) methods were used to assess regional-scale prospectivity for chromite deposits in the Western Limb and the Nietverdiend layered mafic intrusion of the Bushveld Complex in South Africa. Five predictor maps derived from geological, geochemical and geophysical data were processed in a GIS environment and used as spatial proxy for critical processes that were most probably responsible for the formation of the chromite deposits in the study area. The RBFLN was trained using input feature vectors that correspond to known deposits, prospects and non-deposits. The training was initiated by varying the number of radial basis functions (RBFs) and iterations. The results of training the RBFLN provided optimum number of RBFs and iterations that were used for classification of the input feature vectors. The results show that the network classified 73% of the validation deposits into highly prospective areas for chromite deposit, covering 6.5% of the study area. The RBFLN entirely classified all the non-deposit validation points into low prospectivity areas, occupying 86.6% of the study area. In general, the efficiency of the RBFLN in classifying the validation deposits and non-deposits indicates the degree of spatial relationship between the input feature vectors and the training points, which represent chrome mines and prospects. The RBFLN and fuzzy-WofE analyses used in this study are important in guiding identification of regional-scale prospect areas where further chromite exploration can be carried out. 相似文献
6.
Groundwater, an essential resource, is likely to change with global warming because of changes in the CO2 levels, temperature and precipitation. Here, we combine water isotope geochemistry with climate modelling to examine future groundwater recharge in southwest Ohio, USA. We first establish the stable isotope profiles of oxygen and deuterium in precipitation and groundwater. We then use an isotope mass balance model to determine seasonal groundwater recharge from precipitation. Climate model output is used to project future changes in precipitation and its seasonal distribution under medium and high climate change scenarios. Finally, these results are combined to examine future changes in groundwater recharge. We find that 76% of the groundwater recharge occurs in the cool season. Climate models project precipitation increase in the cool season and decrease in the warm season. The total groundwater recharge is expected to increase by 3.2% (8.8%) under the medium (high) climate change scenarios. 相似文献
7.
8.
Abera Tessema Haile Mengistu Emmanuel Chirenje Tamiru A. Abiye Molla B. Demlie 《Hydrogeology Journal》2012,20(2):351-368
Airborne magnetic data and Landsat imagery, as well as time-domain electromagnetic soundings, were used to assess groundwater potential of the region around the town of Mafikeng in North West Province, South Africa. Lineaments were extracted based on on-screen digital data derived from magnetic and Landsat 7 imagery. The relationship between lineament-intersection density and borehole yield was assessed using statistical analysis. The results were discussed with respect to factors that determine the groundwater potential of the area. Correlation between lineament-intersection frequency and borehole yield is 60?C65% in the south and southeastern parts, and 45?C50% within 5?C30?km radius of Mafikeng. The eastern and western parts of the study area are characterized by weak or no correlation. Areas that correspond to high correlation between lineament-intersection frequency and borehole yield suggest the significance of cross-cutting structures in controlling groundwater potential zones, while results that suggest low or no correlation represent the influence of other factors. The overall results demonstrate that the combined analysis of airborne magnetic data, satellite imagery, borehole yield and ground-based time-domain electromagnetic soundings provide the best approach for groundwater assessment within the hard rock and carbonate terrains of the study area. 相似文献
9.
Most of the water from the Nile originates in Ethiopia but there is no agreement on how land degradation or climate change affects the future flow in downstream countries. The objective of this paper is to improve the understanding of future conditions by analysing historical trends. During the period 1964–2003, the average monthly basin‐wide precipitation and monthly discharge data were collected and analysed statistically for two stations in the upper 30% of the Blue Nile Basin and monthly and 10‐day discharge data of one station at the Sudan–Ethiopia border. A rainfall–runoff model examined the causes for observed trends. The results show that, while there was no significant trend in the seasonal and annual basin‐wide average rainfall, significant increases in discharge during the long rainy season (June to September) were observed at all three stations. In the upper Blue Nile, the short rainy season flow (March to May) increased, while the dry season flow (October to February) stayed the same. At the Sudan border, the dry season flow decreased significantly with no change in the short rainy season flow. The difference in response was likely due to the construction of weir in the 1990s at the Lake Tana outlet that affected the upper Blue Nile discharge significantly but affected less than 10% of the discharge at the Sudan border. The rainfall–runoff model reproduced the observed trends, assuming that an additional 10% of the hillsides were eroded in the 40‐year time span and generated overland flow instead of interflow and base flow. Models concerning future trends in the Nile cannot assume that the landscape runoff processes will remain static. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
10.
Tesfahun Berhane Nurilign Shibabaw Aemiro Shibabaw Molalign Adam Abera A.Muhamed 《资源与生态学报(英文版)》2018,(3)
埃塞俄比亚咖啡价格波动很大,因此对国家经济发展的影响不容小视,对咖啡价格进行预测具有理论和实践意义。为了分析咖啡价格波动,我们采用来自埃塞俄比亚商品交易所(ECX)记录的2008年6月25日至2017年1月5日期间咖啡日收盘价数据。在这里,咖啡价格的性质是非平稳的,我们在单个线性状态空间模型上应用卡尔曼滤波算法来预测咖啡价格的最优值,主要通过使用均方根误差(RMSE)来评估用于预测咖啡价格的算法的性能。基于线性状态空间模型和卡尔曼滤波算法,均方根误差(RMSE)为0.000016375,说明该算法性能良好,研究结果可靠。 相似文献