CLIMATE CHANGE IMPACTS ON THE HYDROLOGICAL PROCESSES OF DENSU RIVER BASIN (DRB) USING THE SWAT MODEL

ABSTRACT
The impact of climate change is now posing a greater threat on the hydrological cycle leading to drought and water stress in small basins. Matters of climate change have now become a primary concern to most nations due to the implication on society and humanity. The study used 17 ensemble climate model from the Coupled Model Intercompersion Project Phase 5 (CMIP5) to estimate the future climatic condition for the 2050s (2035 to 2065) under Representative Concentration Pathways (RCP) 4.5 and 8.5. The Soil and Water Assessment Tool (Arc SWAT) model was used in assessing the effect of the generated climate change on the hydrological processes (rainfall, water yield, soil water storage and evapotranspiration) in the Densu River Basin (DRB). After calibration and validation of the SWAT model, there was a strong correlation between the simulated and the observed stream discharge with a coefficient of determination (R2) of 0.84 for the calibration and 0.77 (validation). The CMIP5 estimated an annual mean increase of 2.7 oC and 1.3 oC for maximum and minimum temperature respectively and 20.1 mm in rainfall by 2050s. Simulation from ArcSWAT predicted an increase of 60% in actual evapotranspiration and 80 mm increase in soil water storage and a sharp decline of 23 mm in water yield by 2050s. The condition predicted in the future gives an indication that dry condition will occur at the DRB since increase in temperature and soil water aid increased evapotranspiration causing an acute decline in water yield which contribute to stream flow at the basin.


CHAPTER ONE
INTRODUCTION
Climate change in recent years has gained centre stage of attention in the world, due to its effects on many other natural and human systems. The changes in climatic condition have shown significant impact on the hydrological cycle and it is leading to droughts, floods, changes in rainfall, temperature and water stress. According to the Inter-Governmental Panel on Climate Change (IPCC, 2014a), the changing climate will be intensive in sub-Saharan Africa (SSA).

Climate change refers to increase in the average global surface temperatures caused mainly by an anthropogenic increase in the concentration of greenhouse gases, particularly carbon dioxide (CO2) in the earth’s atmosphere (Kankam-Yeboah, Amisigio, & Obuobi, 2010).

Historically, there has been a variation in the earth’s climate which is mainly by natural and anthropogenic causes. The natural causes slow climate variations and it takes a longer period to occur unlike the anthropogenic. The Fourth Assessment report of the (IPCC, 2007) confirms that since the mid-20th century, the global climate change is directly proportional to anthropogenic drives. The effect of these climate changes has manifested in agricultural and forestry management, human health, industry, settlement and society and water resources.

Water is a requirement for all aspects of human life. Availability and assess to clear, fresh and safe drinking water is considered a basic human right (Gleick, 2009). Availability of water resource in sub-Saharan Africa is important in economic growth and social development particularly in the livelihood of the poor in the Sub-region (Vörösmarty, Douglas, Green, & Revenga, 2005). The economy of Ghana depends on water resource for economic and social activities such as water supply and sanitation, agriculture, industry, urban development, hydropower generation, inland fisheries, transportation and recreation. Water resources (both quantity and quality) and its management are affected by climate change and most importantly by human activities such as population growth and economic activities.

water resources, population growth and settlement around the banks of water resources present a global concern for the availability and consumption of water (Pereira, Cordery, & Iacovides, 2002). Climate change and its impact on water resources availability in space and time have posed further challenges to the sub-Saharan African (SSA) countries in their aspiration to harness the water and improve food security.

In Ghana, all observed and projected climate change in the 21st century predicts a rise in temperature but that of rainfall is uncertain(Asante & Amuakwa-Mensah, 2014). From the historical records, the temperatures for the coastal savannah regions have increased by 2.35 OC with an anticipated increase of 1.68 OC to 2.54 OC by 2050 (Stanturf et al., 2011). The rainfall pattern along the coastal region has not seen that much changes from the past decades while projected reports show both an increase and decrease pattern by 2050 (Stanturf et al.,). The changes in temperature and rainfall for the past decade have had significant impact on water resources and it has reflected in the area of domestic water supply, hydropower generation (Amisigo, McCluskey, & Swanson, 2015) and crop production (Arndt, Asante, Thurlow, & Rosen, 2015).

The impact of the changing climate has been assessed in some of the major basins in Ghana, notable among than are the Volta and the Pra basins which researcher project an increase in temperature, reduction in rainfall and stream flow by 2050 (Kankam-Yeboah et al., 2010; Kankam-Yeboah et al., 2013; Amisigo et al., 2015). Globally, more attention has been given to the impact of climate change on small basins, not much of these assessments has been reported across the country. All these assessments are essential and help decision makers in formulating policies.

The study intended to focus on how Climate Change affects the hydrological system of the Densu River Basin (DRB) using Soil and Water Assessment Tool (SWAT) model.

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Item Type: Ghanaian Postgraduate Material  |  Attribute: 94 pages  |  Chapters: 1-5
Format: MS Word  |  Price: GH50  |  Delivery: Within 30Mins.
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