Estimating daily streamflow in the Congo Basin using satellite-derived data and a semi-distributed hydrological model

ABSTRACT

The application of remotely-sensed data for hydrological modeling of the Congo Basin is presented. Satellite-derived data, including TRMM precipitation, are used as inputs to drive the USGS Geospatial Streamflow Model (GeoSFM) to estimate daily river discharge over the basin from 1998 to 2012. Physically-based parameterization was augmented with a spatially-distributed calibration that enables GeoSFM to simulate hydrological processes such as the slowing effect of the Cuvette Centrale. The resulting simulated long-term mean of daily flows and the observed flow at the Kinshasa gauge were comparable (40 631 and 40 638 m³/s respectively), in the 7-year validation period (2004–2010), with no significant bias and a Nash-Sutcliffe model efficiency coefficient of 0.70. Modeled daily flows and aggregated monthly river outflows (compared to historical averages) for additional sites confirm the model reliability in capturing flow timing and seasonality across the basin, but sometimes fails to accurately predict flow magnitude. The results of this model can be useful in research and decision-making contexts and validate the application of satellite-based hydrological models driven for large, data-scarce river systems such as the Congo.     

The difficult combination of renting and building a house in urban Ghana: analysing the perception of low and middle income earners in Accra

This study examines the experiences of low and middle income earners in urban Ghana in combining renting and self-building a house with their meagre income. Using a case study of 3 building sites in Accra, this study employs semi-structured interview guide to gather qualitative data from fifty respondents. The conclusion of this study is that improving housing career amidst other competing responsibilities in the life course pathways imposes stress and huge financial burden on households in a manner that they are compelled to forgo or cut down on non-housing consumption such as clothing, up-keep of in-laws, marriage, higher educational qualification and cars among others. This study recommends a revisit of the discussion on the enforcement of the provisions of the Rent Act, 1963 and consideration of the practice of rent deposit and monthly rent. Affordable housing finance options should be a priority of African governments and their development partners.     

Characterization of nC7-soluble fractions of the products from mild oxidation of asphaltenes

A significant quantity of hydrocarbons (including alkanes) is occluded in the skeleton of the asphaltene molecule. The hydrocarbons are probably remnants of the “original oil” which had been retained within the asphaltene matrix and protected from the secondary alteration processes that occurred subsequently in the oil reservoirs. In this work we report that oxidation of asphaltenes by stirring with 30%H₂O₂–HAc or NaIO₄–NaH₂PO₄ can release nC₇-soluble oxidized products, including the occluded hydrocarbons. Characterization of the nC₇-soluble fractions of oxidized products can be applied to highlight some geochemical problems, such as in studies of oil–oil correlation, oil–source correlation and secondary alterations of oil reservoirs. It will be especially useful to recover the original geochemical information of some oil reservoirs heavily degraded by post-depositional processes.     

十八烷的裂解动力学研究(I):气态烃组分及其碳同位素演化特征

本文通过对纯烃类化合物——正十八烷的动力学模拟实验,阐述了正十八烷裂解过程中气态烃组分及其同位素的演化特征,获得了产自正十八烷的甲烷生成动力学参数。运用动力学参数将模拟实验结果外推到地质条件下,表明由烷烃裂解形成的甲烷主要生成于150～200℃(Easy%Ro介于1.0%～2.0%)的范围,裂解产生的甲烷、乙烷、丙烷的碳同位素分馏效应与Easy%Ro的关系曲线受升温速率的影响,不能直接应用于地质条件。     

What has Corruption Got to do with it? Understanding the Persistence of Rural-Urban and Inter-Regional Inequalities in Ghana and Zimbabwe

Inequalities are no respecter of countries, including the affluent ones. Nevertheless, these problems appear to prevail more in the developing countries, which have the dubious distinction of having the highest degrees of inequalities in the world. Inequalities exist between urban and rural areas, as well as between the various regions. This paper discusses inequalities in Ghana and Zimbabwe, emphasizing the rural–urban dichotomy. Using data from the Ghana Demographic and Health Surveys (GDHS) and the Zimbabwe Demographic and Health Surveys (ZDHS) conducted by the respective statistical authorities of both countries and Macro International, the paper analyses existing inequalities in both countries. The paper also attempts to elucidate and understand the causes. It concludes that the traditional explanation of disparities that attribute the conditions to aberrations in the operations of market forces, while having some validity, may not provide a full explanation for Ghana and Zimbabwe’s predicament. It argues that whilst the existing disparities may be rooted in history, their persistence and worsening in the post-independence era could only be understood with reference to the corruption, nepotism and the mismanagement that have characterized these states since they gained their independence.     

Oil-source correlation of Lower-Triassic oil seepages in Ni’erguan village,Southern Guizhou Depression,China

There are abundant bitumens and oil seepages stored in vugs in a Lower-Triassic Daye formation (T₁d) marlite in Ni’erguan village in the Southern Guizhou Depression. However, the source of those oil seepages has not been determined to date. Multiple suites of source rocks of different ages exist in the depression. Both the oil seepages and potential source rocks have undergone complicated secondary alterations, which have added to the difficulty of an oil-source correlation. For example, the main source rock, a Lower-Cambrian Niutitang Formation (?₁n) mudstone, is over mature, and other potential source rocks, both from the Permian and the Triassic, are still in the oil window. In addition, the T₁d oil seepages underwent a large amount of biodegradation. To minimize the influence of biodegradation and thermal maturation, special methods were employed in this oil-source correlation study. These methods included catalytic hydropyrolysis, to release covalently bound biomarkers from the over mature kerogen of ?₁n mudstone, sequential extraction, to obtain chloroform bitumen A and chloroform bitumen C from the T₁d marlite, and anhydrous pyrolysis, to release pyrolysates from the kerogen of T₁d marlite. Using the methods above, the biomarkers and n-alkanes released from the oil samples and source rocks were analysed by GC–MS and GC-C-IRMS. The oil-source correlation indicated that the T₁d oil seepage primarily originated from the ?₁n mudstone and was partially mixed with oil generated from the T₁d marlite. Furthermore, the seepage also demonstrated that the above methods were effective for the complicated oil-source correlation in the Southern Guizhou Depression.     

Kinetic studies of asphaltene pyrolyses and their geochemical applications

Pyrolysis kinetics are determined for a series of asphaltene samples associated with different types of kerogens. The activation energy distributions obtained for asphaltenes related to type I kerogens cover a wide range, with significant hydrocarbon generation with activation energies above 350 kJ/mol. The ranges of activation energy distributions are relatively narrow for asphaltenes associated with type II and III kerogens, with little hydrocarbons generated with activation energies above 350 kJ/mol. If the type of associated kerogen can be reasonably constrained, the pyrolysis kinetics of the asphaltenes is potentially a very useful tool for assessing the maturity levels of reservoired oils. The results of pyrolysis kinetics indicate that there is still significant potential for asphaltenes to regenerate hydrocarbons.     

The Changing Geography of Export Trade in Ghana under Structural Adjustment Programs: Some Socioeconomic and Spatial Implications

Like many other countries in Africa, Ghana has traditionally depended on a few export products—namely, cocoa, timber, and mineral resources—as the mainstays of its economy. The often‐volatile nature of the world market price of these products made the economy very vulnerable to fluctuations in the prices of export commodities. Moreover, the geographical distribution of these resources meant that only a few regions could participate in their production and export. This resulted in wide spatial and socioeconomic disparities between the producing and nonproducing regions. Within the past eighteen years, however, a shift seems to have taken place. Under the auspices of the ongoing structural adjustment programs, emphasis is being placed on nontraditional export goods. This is not only helping to reduce the vulnerability of the economy by diversifying the sources of export earnings, but also engendering participation in the export trade by regions that have been traditionally left behind. This study analyses the changing geography of the export trade of Ghana using data from the International Monetary Fund/World Bank, the Ghanaian government, the World Trade Organization, and field observation. The study argues that while these new trends and efforts are laudable, they cannot bridge the gap between the export producing and nonproducing areas and cushion the economy against the vagaries of the export market unless deliberate attempts are made to improve transportation and other basic infrastructure in the less‐endowed areas.     

‘The germs are not harmful’: health risk perceptions among consumers of peri-urban grown vegetables in Kumasi,Ghana

Consumption of peri-urban grown vegetables has raised public health concerns due to potential risks of contamination from pathogens, pesticides and heavy metals. Understanding how the public perceives of risk is key in managing the population at risk of consuming contaminated vegetables. However, health risk perceptions research of consumers has largely been given little attention. Using both quantitative and qualitative research techniques, and drawing on risk perception theory, this study examined consumers’ health risk perceptions in relation to urban vegetable consumption in the Oforikrom sub-metropolitan area of the Kumasi Metropolis in Ghana. Results suggest that heath risk perceptions of consumers of urban-grown vegetables is generally low, an indication that consumers’ perceptions have not changed a decade after similar results were reported in Ghana. Consumers’ interpretation of the quality of vegetables and associated health risks deviates from scientific health risk assessments which, does not translate into desired risk mitigation behaviour. Continuous public education on potential health risks of consuming these vegetables and appropriate health risk mitigation measures could be vital in reducing the population at risk.