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41.
42.
This study aimed at characterizing land cover dynamics for four decades in Eastern Mau forest and Lake Nakuru basin, Kenya. The specific objectives were to: (i) identify and map the major land cover types in 1973, 1985, 2000 and 2011; (ii) detect and determine the magnitude, rates and nature of the land cover changes that had occurred between these dates, and; (iii) establish the spatial and temporal distribution of these changes. Land cover types were discriminated through partitioning, hybrid classification and spatial reclassification of multi-temporal Landsat imagery. The land cover products were then validated and overlaid in post-classification comparison to detect the changes between 1973 and 2011. The accuracies of the land cover maps for 1973, 1985, 2000 and 2011 were 88%, 95%, 80% and 89% respectively. Six land cover classes, namely forests-shrublands, grasslands, croplands, built-up lands, bare lands and water bodies, were mapped. Forests-shrublands dominated in 1973, 1985 and 2000 covering about 1067 km2, 893 km2 and 797 km2 respectively, but were surpassed by croplands (953 km2) in 2011. Bare lands occupied the least area that varied between 2 km2 and 7 km2 during this period. Overall, forests-shrublands and grasslands decreased by 428 km2 and 258 km2 at the annual average rates of 1% each, whereas croplands and built-up lands expanded by 660 km2 and 24 km2 at the annual rates of 6% and 16% respectively. The key hotspots of these changes were distributed in all directions of the study area, but at different times. Therefore, policies that integrate restoration and conservation of natural ecosystems with enhancement of agricultural productivity are strongly recommended. This will ensure environmental sustainability and socio-economic well-being in the area. Future research needs to assess the impacts of the land cover changes on ecosystem services and to project the future patterns of land cover changes. 相似文献
43.
利用MOD13Q1产品监测肯尼亚2001-2010年荒漠化动态 总被引:1,自引:0,他引:1
使用MODIS MOD13Q1-NDVI数据,通过NDVI累计计算,得到肯尼亚2001年和2010年植被生长状况较好时期的NDVI影像.基于像元二分模型,估算植被盖度.利用植被盖度进行荒漠化评价.结果表明,肯尼亚近10年来生态环境总体趋于改善,荒漠化发展态势并不明显,但荒漠化问题仍然严重.不同程度的荒漠化土地变化趋势不尽相同,轻度荒漠化和重度荒漠化转出面积大于转入面积,呈现减少趋势,非荒漠化和中度荒漠化变化相反,各省区的荒漠化土地变化趋势也不相同.在小范围地区内,使用Landsat-5 TM影像进行验证,发现与MODIS数据评价结果相似,但更能详尽的描述重点区域的荒漠化问题. 相似文献
44.
ROBIN W. RENAUT R. BERNHART OWEN BRIAN JONES JEAN‐JACQUES TIERCELIN CORINNE TARITS JOHN K. EGO KURT O. KONHAUSER 《Sedimentology》2013,60(2):428-468
Travertine is present at 20% of the ca 60 hot springs that discharge on Loburu delta plain on the western margin of saline, alkaline Lake Bogoria in the Kenya Rift. Much of the travertine, which forms mounds, low terraces and pool‐rim dams, is sub‐fossil (relict) and undergoing erosion, but calcite‐encrusted artefacts show that carbonate is actively precipitating at several springs. Most of the springs discharge alkaline (pH: 8·3 to 8·9), Na‐HCO3 waters containing little Ca (<2 mg l?1) at temperatures of 94 to 97·5°C. These travertines are unusual because most probably precipitated at temperatures of >80°C. The travertines are composed mainly of dendritic and platy calcite, with minor Mg‐silicates, aragonite, fluorite and opaline silica. Calcite precipitation is attributed mainly to rapid CO2 degassing, which led to high‐disequilibrium crystal morphologies. Stratigraphic evidence shows that the travertine formed during several stages separated by intervals of non‐deposition. Radiometric ages imply that the main phase of travertine formation occurred during the late Pleistocene (ca 32 to 35 ka). Periods of precipitation were influenced strongly by fluctuations in lake level, mostly under climate control, and by related changes in the depth of boiling. During relatively arid phases, meteoric recharge of ground water declines, the lake is low and becomes hypersaline, and the reduced hydrostatic pressure lowers the level of boiling in the plumbing system of the hot springs. Any carbonate precipitation then occurs below the land surface. During humid phases, the dilute meteoric recharge increases, enhancing geothermal circulation, but the rising lake waters, which become relatively dilute, flood most spring vents. Much of the aqueous Ca2+ then precipitates as lacustrine stromatolites on shallow firm substrates, including submerged older travertines. Optimal conditions for subaerial travertine precipitation at Loburu occur when the lake is at intermediate levels, and may be favoured during transitions from humid to drier conditions. 相似文献
45.
肯尼亚交通优势度及其空间分异格局分析 总被引:1,自引:0,他引:1
基于2018年肯尼亚铁路、公路、机场、港口等交通基础设施数据,设定交通优势度指数及交通网络连接度指数和交通对外通达度指数2个分指数,采用探索性数据分析法对肯尼亚交通优势度及其空间分异格局进行分析,并对其影响因素进行探讨。研究发现:①肯尼亚交通优势度空间差异十分显著,以内罗毕、蒙巴萨和基苏木为主要交通节点的铁路沿线地区交通优势度水平明显高于其他地区;②肯尼亚交通优势度空间分异格局总体上呈现出较强的非均衡性,交通网络连接度呈现出以内罗毕为核心,以铁路沿线为轴带呈圈层状向四周递减的空间分异格局,而交通对外通达度呈现出北部和西北部较低而南部和东南部较高的空间分异格局。③地形地貌、气候、水文、人口集聚、经济发展等是形成肯尼亚交通优势度空间分异的主要影响因素。对交通基础设施空间分布进行优化调整,积极引导经济空间合理布局,是推动肯尼亚经济健康持续发展的重要途经。 相似文献
46.
47.
Variations of the Effective Temperature Index (ET) in Kenya 总被引:2,自引:0,他引:2
George Lukoye Makokha 《GeoJournal》1998,44(4):337-343
Using the Effective Temperature Index (ET) as a measure of climatic comfort conditions in Kenya, this study analyses its spatial,
seasonal and diurnal variations. This index is computed using data collected from 57 weather stations spread throughout the
country. Isarithmic mapping technique and the conditioning square method are used in this analysis. The results indicate that
there exists in Kenya marked spatial, seasonal and diurnal variations of climatic comfort conditions. A classification of
the country using this index and the Terjung (1968) system of climatic classification yields six climatic comfort zones. This
type of physio-climatic studies has significant implications for Kenya in aspects such as building, clothing, recreation and
sporting.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
48.
Kenya has been promoting equitable urban and regional development since the 1970s despite the lack of a clearly formulated national urban policy or an urban and regional development policy. A key element of the country’s equitable urban and regional development effort is the promotion of secondary cities that would relieve population pressure in the countryside, help to better integrate the country’s rural and urban economies, help to reduce congestion and improve the quality of life in the metropolitan cities of Nairobi and Mombasa, and help increase the modernization spin-off which urban centers provide to the surrounding rural areas. Using recent census and economic survey data, this paper examines the current state of Kenya’s secondary cities in the context of its urban and regional development strategies. The paper finds that: (1) the country’s urban and regional development strategies have failed to work as planned largely because of insufficient devolution of power and fiscal responsibility to municipal and other local government units, (2) the country’s secondary cities are faced with immense challenges that undermine their ability to live up to expectations, (3) some of these cities have significantly grown economically over the last four decades despite immense challenges, and (4) Nairobi’s dominance of Kenya’s economy continues because of policies that unwittingly concentrate investments there. The paper concludes with strategies that could enhance the country’s urban and regional development programs and, in the process, aid the development of its secondary cities. 相似文献
49.
Climate change impacts the quantity and seasonality of rainfall, threatening Africans' ability to maintain satisfactory yields on rain-fed farms. On the semi-arid northwestern slopes of Mount Kenya, irrigation systems structured around Community Water Projects (CWPs) provide households with piped water, which helps mitigate drought impacts and enhances resilience to increasingly variable rainfall patterns. The vision of these irrigation systems is to equitably distribute water resources among CWP members both for household consumption and to maintain or improve agricultural yields. However, not all households receive equal quantities of water from their CWPs, and little is known about the impact of water provisioning on farmers' opinions or perceptions of CWP performance.In this study, we relate respondents' satisfaction with their CWPs to the quantity of water delivered. Not surprisingly, farmers who received low quantities of water from their CWPs expressed above-average rates of concern regarding drought. In contrast, satisfaction with one's CWP was unrelated to the absolute quantity of water received (log liters/minute), but it was strongly associated with relative measures of water delivery: respondents who received less water than other members of the same water project experienced high rates of dissatisfaction, as did respondents who received less water than in the past. These results suggest that Kenyan farmers may feel particularly dissatisfied—and, perhaps, particularly driven to demand improved water governance—when they perceive inadequate water delivery relative to some reference group.Because relative water quantity dictates satisfaction even after controlling for factors that can be resolved internally at the CWP level (by, for example, striving for uniformity of water flows across and within households), water project managers are limited to some degree in their ability to improve satisfaction through better governance. That said, governance actions that prevent declines in flows over time (e.g. maintaining infrastructure to reduce leaks) could ostensibly lead to meaningful improvements in member satisfaction. 相似文献
50.
Farming among urban dwellers in Sub-Saharan Africa is a common phenomenon. The present study, carried out in a medium-sized town in Kenya, not only confirmed this but also showed that farming by urban dwellers in the rural areas was even more important for these households’ livelihoods than farming in town. However, those who could benefit most from farming, i.e. the urban poor, appeared to be underrepresented among urban farming households and those urban poor who did farm, either in urban or in rural areas, performed worse than the farming non-poor. The importance of farming as a livelihood source is illustrated by the fact that in years with very little or no harvest due to drought, many of the poor farming households faced food shortages. 相似文献