Browsing by Author "Nyamekye, Clement"

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    Classification of time series of NDVI for Assessment of land cover change in Ghana using Noaa/A VHRR data.
    (April, 2010.) Nyamekye, Clement
    Land cover information constitutes key environmental information for many scientific, resource management and policy purposes, as well as for a range of human activities. Hence it has become a major focus for the International Geosphere-Biosphere Program (IGBP) and the International Human Dimensions Program (IHDP) at global and regional levels. Land cover information is currently scarce for Ghana. The country is currently undergoing rapid and wide-range changes in vegetation due to climate change, the practice of slash-and-burn or shifting cultivation. The stud y of these conversions necessitates the use of remote sensing because it provides data at synoptic scales and facilitates the discerning of large- scale ecosystem patterns. Although remote sensing technology has been used for mapping in Ghana for sometime now, there has been no attempt to use either unsupervised or supervised classification methods for NOAA/AVHRR images for the whole of Ghana. Therefore a qualitative approach to the use of historical series of low resolution NDVI data to produce land cover maps of Ghana and also to evaluate the relative change in land cover from 1982 to 2002 has been developed. The study was carried out through the principal component analysis and classification of long term average NDVI values. The interpretation of the resulting classes was based on the comparison between NDVI average temporal profiles of different classes and NDVI reference profiles for selected sites where detailed information about vegetation characteristics are available. The results show the potential of the proposed approach for studies at regional or national level where lack of climate data hinder the utilization of quantitative methods to determine the land cover change within the periods (1982-1992, 1992-2002 and 1982-2002). Again the results of the study shows that the dominant land coverchange process was conversion of natural vegetation to savannah and shrub thicket, which occurred at an annual rate of 4% and 6.5% respectively. Most of the land cover change process occurred in the first period (1982-1992). The overall annual rate of change in land cover (1982-1992) was highest for Savannah (3.8%) and lowest for water (1.03%). The results suggest that, year phenological behavior, as revealed by the NDVI data, can be used to map general patterns in the spatial distribution of Ghana‟s main vegetation formation.
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    Rainfall and temperature projections and the implications on streamflow and evapotranspiration in the near future at the Tano River Basin of Ghana
    (Elsevier, 2021) Larbi, Isaac; Nyamekye, Clement; Dotse, Sam-Quarcoo; Danso, Derrick K.; Annor, Thompson; Bessah, Enoch; Limantol, Andrew Manoba; Attah-Darkwa, Thomas; Kwawuvi, Daniel; Yomo, Mawulolo; 0000-0002-3679-854X
    Climate change is projected to negatively affect water security which is already a chal lenge in many areas of Ghana including the Tano river basin (TRB). This study assessed the projections of rainfall and temperature and its impact on streamflow and actual evap otranspiration (ET) in the TRB of Ghana for 2021-2050 relative to the period 1986-2015. The impact assessment focused on how climate change under Representative Concentra tion Pathways (RCP 4.5 and RCP8.5) based on an ensemble mean of two regional climate models (RCMs) would affect streamflow and ET using the Soil and Water Assessment Tool (SWAT) model. Trend analysis and quantification for the streamflow and ET were analyzed using the Mann-Kendall’s and Sen’s slope estimators. The results show that the mean annual rainfall of 1401.9 mm would increase slightly by 0.5 % with a decreasing trend (1.22mm/yr) under the RCP4.5 scenario, but would decrease by 3.2% with a decreasing trend (0.3m mm/yr) under the RCP8.5 scenario. The mean annual temperature showed an increase (2.1 °C and 2.6 °C) with a statistically significant increasing trend of 0.07 and 0.09 °C/yr under RCP 4.5 and RCP8.5 respectively. An increase in ET with a non-significant increasing trend at a rate of 0.74 and 1.07 mm/year under RCP4.5 and RCP8.5 scenarios respectively is also projected. The mean annual streamflow is projected to decrease, with the decrease been more pronounced under the RCP8.5 (37.5%) scenario compared to the RCP4.5 scenario (19.9%). In general, the outcome of this study presents a useful perspective
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    Soil and water conservation in Burkina Faso, West Africa
    (Sustainability, 2018-09) Nyamekye, Clement; Thiel, Michael; Schönbrodt-Stitt, Sarah; Zoungrana, Benewinde J.-B.; Amekudzi, Leonard K.
    Inadequate land management and agricultural activities have largely resulted in land degradation in Burkina Faso. The nationwide governmental and institutional driven implementation and adoption of soil and water conservation measures (SWCM) since the early 1960s, however, is expected to successively slow down the degradation process and to increase the agricultural output. Even though relevant measures have been taken, only a few studies have been conducted to quantify their effect, for instance, on soil erosion and environmental restoration. In addition, a comprehensive summary of initiatives, implementation strategies, and eventually region-specific requirements for adopting different SWCM is missing. The present study therefore aims to review the different SWCM in Burkina Faso and implementation programs, as well as to provide information on their effects on environmental restoration and agricultural productivity. This was achieved by considering over 143 studies focusing on Burkina Faso’s experience and research progress in areas of SWCM and soil erosion. SWCM in Burkina Faso have largely resulted in an increase in agricultural productivity and improvement in food security. Finally, this study aims at supporting the country’s informed decision-making for extending already existing SWCM and for deriving further implementation strategies.