Browsing by Author "Agyare, W. A."

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    Assessing sediment inputs to small reservoirs in Upper East Region, Ghana
    (Lakes & Reservoirs Research & Management, 2009-10) Adwubi, Afua; Amegashie, Bright Kofi; Agyare, W. A.; Tamene, Lulseged; Odai, Samuel Nii; Quansah, Charles; Vlek, Paul
    Many small dams and dugouts have been constructed in the Upper East Region of Ghana to address the problem of regional water scarcity. The reservoirs were constructed primarily as water supplies for agricultural irrigation and livestock watering, aquaculture and domestic use. However, many of the reservoirs dry up during the dry season, affecting the livelihoods of their basin inhabitants. A major cause for the dried reservoirs is siltation, which reduces the reservoir’s storage capacities. The goal of this study is to quantify the annual siltation rate of four study reservoirs, using a bathymetric survey and reservoir soil sampling. The sediment yield and its relation to catchment area also were assessed. The results of this study indicate that the annual siltation rates are 1272, 3518, 2764 and 6135 t year)1 for Doba, Dua, Zebilla and Kumpalgogo reservoirs, respectively. Analyses of the sediment yield and catchment areas illustrated that the sediment yields decreased with increasing catchment area. All the study reservoirs have lost their dead storage capacity, which was meant to store sediment until the end of their anticipated design lives. The decreasing storage capacity because of siltation will affect the livelihoods of the local basin inhabitants, as the reservoirs will not be able to achieve all their intended purposes. The results of this study indicate that, because siltation is not the only factor threatening the benefits gained from the reservoirs, the integrated assessment of all relevant factors is required.
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    Challenges to maize fertilization in the forest and transition zones of Ghana
    (African journal of agricultural research, 2013-11) Agyare, W. A.; Asare, Isaac Kwadwo; Sogbedji, Jean; Clottey, Victor Attuquaye
    Maize (Zea mays) is Ghana’s most important cereal crop grown in all agro-ecological zones by smallholder farmers. The average yield of maize (1.7 tha-1) is far below attainable yield of 5.5 tha-1. This is due to reliance on rain fed farming, local seed varieties and low inputs use. Farmers face many challenges in their attempt to adopt the use of fertilizer to improve their maize production. To unearth these challenges, data on the potential and limitations to maize fertilization in the maize belt of Ghana were collected through a farm level survey in October 2011. A four stage randomized sampling procedure was used to select 168 maize farmers who were interviewed using formal questionnaire. Some of the farmers especially, settlers do not have land of their own and have to rely on tenancy arrangements to access land for farming. Farmers were of the view that their crop lands are gradually declining in fertility. Almost 55% of the farmers practise continuous maize cropping. The lack or low accessibility to credit and high cost of fertilizer are the key constraints to farmers’ ability to expand their maize farming. Additionally, the mode and distance needed to transport fertilizer to the farm is a disincentive.
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    DISTINGUISHING LAND USE TYPES USING SURFACE ALBEDO AND NORMALIZED DIFFERENCE VEGETATION INDEX DERIVED FROM THE SEBAL MODEL FOR THE ATANKWIDI AND AFRAM SUBCATCHMENTS IN GHANA
    (ARPN Journal of Engineering and Applied Sciences, 2012-01) Salifu, Tayari; Agyare, W. A.
    Distinguishing land use types is mostly done through field surveys which does not easily capture the spatial changes in the land use/cover types. In this study, the Surface Energy Balance Algorithm for Land (SEBAL) model was used to estimate surface albedo and NDVI, for different land use/cover types for two sub-catchments (i.e., Atankwidi and Afram) in the Volta Basin of Ghana. The mean coefficient of variation (CV) for individual land use/cover types compared to the mean CV for a given site was then used to distinguish among the land use/cover types. It was found that these parameters derived from the SEBAL model can be used to distinguish among different land use/cover types in the two subcatchments. SEBAL estimates for surface albedo and NDVI across the different land use/cover types varied from 0.05 to 0.22 and -0.41 to 0.38, respectively. The range of CVs for surface albedo and NDVI, were 5-22% and 7-175%, respectively across the different land use/cover types for the two catchments. The results of this study demonstrate that SEBAL’s derived surface albedo and NDVI can be used to distinguish land use/cover types in catchments similar to those of the study areas with few ground measurements.
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    Estimating Actual Evapotranspiration using the SEBAL Model for the Atankwidi and Afram Catchments in Ghana
    (International Journal of Applied Agricultural Research, 2012-01) Salifu, Tayari; Agyare, W. A.; Kyei-Baffour, Nicholas; Mensah, Ebenezer; Ofori, Emmanuel
    Evapotranspiration (ET) monitoring has important implications on global and regional climate modelling. It is important for the hydrological cycle and assessment of environmental stress that affects ecosystems. Accurate measurement and estimation of ET is a basic input in computing water balance and to estimate water availability and requirements. Most methods for ET computation can only provide point estimates of ET for a specific location and fails to provide ET on a regional scale and makes it inadequate for proper water resource management. In this study, the Surface Energy Balance Algorithm for Land (SEBAL) model is used to estimate actual evapotranspiration (ETa) for different land use/cover types (closed woodlands, gallery forests, open woodlands, farmlands, water bodies, barelands, rocky areas and built-up areas) for the Atankwidi and Afram catchments in the Volta Basin of Ghana. It was found that the SEBAL model can successfully estimate and distinguish ETa among different land use/cover types in the two catchments. SEBAL estimates of ETa varied from 1.4 to 7.30 mm/day across the different land use/cover types. The range of CVs for ETa was 5−75% across the different land use/cover types for the two catchments. The results confirms SEBAL is an appropriate algorithm for estimating ETa using satellite images in catchments similar to that of the study areas, where few or no ground measurements are available.