Gebremichael, Mekonnen, Emmanouil N. Anagnostou, and Menberu M. Bitew, 2010. Critical Steps for Continuing Advancement of Satellite Rainfall Applications for Surface Hydrology in the Nile River Basin. Journal of the American Water Resources Association (JAWRA) 46(2):361-366. DOI: 10.1111/j.1752-1688.2010.00428.x. Abstract: Given the increasingly higher resolution and data accessibility, satellite precipitation products could be useful for hydrological application in the Nile River Basin, which is characterized by lack of reasonably dense hydrological in situ sensors and lack of access to the existing dataset. However, in the absence of both extreme caution and research results for the Nile basin, the satellite rainfall (SR) products may not be used, or may even be used erroneously. We identify two steps that are critical to enhance the value of SR products for hydrological applications in the Nile basin. The first step is to establish representative validation sites in the Nile basin. The validation site will help to quantify the errors in the different kinds of SR products, which will be used to select the best products for the Nile basin, include the errors in decision making, and design strategies to minimize the errors. Using rainfall measurements collected from the unprecedented high-density rain gauge network over a small region within the Nile basin, we indicate that SR estimates could be subject to significant errors, and quantification of estimation errors by way of establishing validation sites is critically important in order to use the SR products. The second step is to identify the degree of hydrologic model complexity required to obtain more accurate hydrologic simulation results for the Nile basin when using SR products as input. The level of model complexity may depend on basin size and SR algorithm, and further research is needed to spell out this dependence for the Nile basin. 相似文献
For the determination of 15 potentially toxic elements (V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Sn, Hg, and Pb) in plant and sediment samples of the Akaki River, Ethiopia, inductively coupled plasma–mass spectrometry, inductively coupled plasma–optical emission spectrometry, and a RA-915+ mercury analyzer were applied. Sediment and plant samples were mineralized using a closed-vessel microwave-assisted digestion system. The elemental concentrations varied considerably in plant and sediment samples. The minimum concentration was observed for known toxic elements (As, Hg, and Cd) while the highest concentration was observed for the elements of relatively low toxicity Zn, Mn, and Fe. The concentration of Cr, Fe, Pb, Zn, and As in Swiss chard surpassed the maximum permissible levels at specific sites. At some of the sites, the sediment quality guidelines are surpassed for Cu, Zn, and Pb. 相似文献
The current study proposes a novel and improved cigarette filtration design comprising cellulose nanofibers (CNFs) and powdered activated carbons (PACs) with different dry matter contents. The proposed filter samples were primarily analyzed to verify their applicability as cigarette filters via measurements and standard tests, such as SEM, BET, DSC, and airflow permeability analysis. The results were compared with the cellulose acetate (CA) sample used as a conventional cigarette filter. The preliminary results indicated noticeable improvement compared to the reference CA. Also, the cigarettes were tested using a smoking machine, and the filtered smoke was analyzed using GC–MS to evaluate the filters' performance in reducing the harmful substances present in the smoke. The results showed that the filters made of CNF and PAC significantly decreased the toxic substances compared with the reference but did not affect the nicotine substantially and therefore will not negatively impact the trance level of smokers.
ABSTRACTCommunity-based watershed development (CBWD) has been implemented in Ethiopia since the last three decades. However, the benefits of these watershed development interventions for climate change adaptation are not well documented. This study, therefore, assesses the contributions of CBWD in reducing farmers’ vulnerability to the impacts of climate change and variability in the northwestern highlands of Ethiopia. Data were collected from systematically selected 157 households using questionnaire. The questionnaire consists of questions on climate, ecosystem and households’ livelihood capital. Livelihood Vulnerability Index (LVI) and Inter-governmental Panel on Climate Change Livelihood Vulnerability Index (IPCC-LVI) methods were used to generate vulnerability indices. Vulnerability indices computed for three conserved watersheds were compared with one non-conserved watershed using one-way ANOVA test. LVI score for ecosystem related indicators was significantly low for Adef Wuha compared to the non-conserved watershed. Similarly, LVI scores generated from agriculture, wealth and social indicators were low for Tija Baji and Guansa watersheds. On the other hand, the IPCC-LVI result did not show significant differences in exposure; however, sensitivity scores of conserved watersheds were significantly lower compared to the non-conserved. The adaptive capacities of two conserved watersheds (Guansa and Tija Baji) were also significantly lower as compared to the non-conserved. The overall (composite) vulnerability of watersheds generated from both methods (LVI and IPCC-LVI) showed that the conserved watersheds were less vulnerable to climate change compared to the non-conserved. The findings suggest that CBWD is an important strategy to reduce vulnerability of smallholder farmers to the ongoing and future climate change. 相似文献
Steady- and transient-state simulations of groundwater flow and particle movement in the sub-watershed of the river Labe in Dě?ín town was carried out using Visual MODFLOW software. The simulations were performed for calibration and for the scenarios that the change in the water level of the river Labe was undergoing. Steady-state simulation was carried out for the sake of calibration of model outputs. For transient simulation, two different scenarios were considered in order to investigate the response of the aquifer system to the stresses applied on surface water of the river. The simulation results have shown that the surface water and groundwater interactions, and the subsequent particle movement were affected by the stresses applied on the surface water in the river Labe. The first scenario involved the rapid recharge of surface water to the aquifer in the vicinity of the river while particles still move towards the river at the places far away from the river. At the end of the second scenario, particles still tend to move towards the river slowly and finally tend to stay within the aquifer as equilibrium of hydraulic gradient is reached between the surface and groundwater levels. The time series graphs of hydraulic heads at all observation wells show that the groundwater level in the surrounding aquifer rises significantly as a result of recharges from the river. The local water balance of the study area was calculated and expressed as the rates of water entering and leaving the system. At the end of the second scenario, the difference between the rate of flow into and out of the model area was 0.73 m3 day?1. 相似文献
This study evaluates variability and trends in rainfall amount and extreme event indices in the Omo-Ghibe River Basin of Ethiopia based on observed records from six stations. Nine daily rainfall indices were defined and analyzed based on the World Meteorological Organization guideline. Sen’s slope estimator and Mann–Kendall’s trend test were used to determine the magnitude and statistical significance of the rainfall changes, respectively. The results show complex patterns of rainfall variability and local-scale trends. Statistically significant increasing changes were observed at Key Afer for most of the indices. On the other hand, the increasing trends in the number of very heavy rainfall events (R20 mm) were statistically significant at three (Jinka, Key Afer and Wolaita Sodo) out of the six stations. On the other hand, significant decreasing trends were found at Sawla for the maximum one day (Rx1 day) and the number of very heavy rainfall event (R20 mm). No systematic trends were found for the number of wet and dry day-related rainfall indices. However, the annual total rainfall averaged for the entire basin and at two stations (Key Afer and Wolaita Sodo) showed statistically significant increasing trends, both at the 0.01 level. Generally, the results of this study contradict with previous studies that reported significant declining trends in annual and Kiremt (main rainy season) rainfall amounts over this part of the country, suggesting the reviving of rainfall during the last two decades. Also, the results of this study agree with previous researches that reported the absence of systematic patterns of trends in daily rainfall indices in different parts of the country. The study has important implications for an effective management of water resources and climate risk management particularly in view of the fact that five hydropower plants and large-scale sugarcane plantations are planned, and some are under construction in the basin. 相似文献
The level of some OCPs in human and cow milk collected from Asendabo, Serbo and Jimma in South-West Ethiopia were analyzed using GC–ECD. Results of the analysis indicated that all samples contained detectable quantities of p,p′-DDT and its metabolites, p,p-DDE and p,p-DDD, but none of the other OCPs analyzed. Mean levels of total DDT in the human and cow milk samples in the three areas were 12.68 and 0.389 μg g?1 respectively. The distributions of p,p-DDT, p,p-DDE and p,p-DDD in the human milk samples from the three locations followed the same trend in which the proportion of p,p-DDT was the highest in all the three cases, comprising 55–71% of total DDT, followed by p,p-DDE, 26–39%, and the least, p,p-DDD of 2–5%. The mean ratio of DDT/DDE concentration for the three areas was calculated to be 2.01. This value was much higher than the values reported from other countries in earlier studies and indicates the existence of a higher quantity of DDT from a fresh input in the three study areas. The mean estimated daily intake of DDT by infants from mother’s milk in the three locations was found to be 62.17 μg kg?1 body weight, which is about three times higher than the acceptable daily intake set by WHO/FAO for total DDT, 20 μg kg?1 of body weight. This alarmingly high daily intake value is a cause for concern, since children are highly susceptible to effects from such environmental contaminants. The study has revealed that people in the study areas are facing exposure to DDT from recent use. The observed contamination of mother’s milk and the possible transfer of the contaminant from mother to child is an obvious risk associated with breast-feeding in the study areas and possibly in other parts of the country too. 相似文献
Poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC) blends with different levels of chain extender were prepared and cast into films. The effect of chain extender on the mechanical, thermal and barrier properties of the films were investigated. With the inclusion of the chain extender, the compatibility and interfacial adhesion between the two polymer phases were significantly improved by a mean of forming a PLA–chain extender–PPC copolymer. Reactions between the chain extender, PLA and PPC were observed through FTIR study. SEM study also confirmed the improved compatibility and interfacial adhesion. The elongation at break of the compatibilized film with optimal amount of chain extender showed dramatic increase by up to 1940 %. DSC studies revealed that chain extender hindered the crystallization of the film which explained the decrease in both water and oxygen barrier when adding chain extender. PLA was found to be able to enhance both oxygen and water barrier of the blend as compared to neat PPC, while in the case of the blend with chain extender, oxygen and water barrier properties exhibited reduction at the beginning. However, when increasing chain extender concentration, these two barrier performance exhibited an upward trend. It was found that PLA/PPC blend showed much better oxygen barrier property than both parent polymers, which can be ascribed to the acceleration effect of PPC on the crystallization of PLA. 相似文献
West and East Africa experience high variability of rainfall that is expected to increase with climate change. This results in fluctuations in water availability for food production and other socioeconomic activities. Water harvesting and storage can mitigate the adverse effects of rainfall variability. But past studies have shown that when investments in water storage are not guided by environmental health considerations, the increased availability of open water surface may increase the transmission of water-related diseases. This is demonstrated for schistosomiasis associated with small reservoirs in Burkina Faso, and for malaria in Ethiopia around large dams, small dams, and water harvesting ponds. The concern is that the rush to develop water harvesting and storage for climate change adaptation may increase the risk for already vulnerable people, in some cases more than canceling out the benefits of greater water availability. Taking health issues into account in a participatory approach to planning, design, and management of rainwater harvesting and water storage, as well as considering the full range of water storage options would enable better opportunities for enhancing resilience against climate change in vulnerable populations in sub-Saharan Africa. 相似文献