Article Preview
Top1. Introduction
Climate Change affects all countries in the world. In the last twenty (20) years, the issue of global warming has entered the international political agenda (Müller-Kuckelberg, 2012). Muller hinted that the UN Conference on Environment and Development in Rio de Janeiro in 1992 was a milestone which led to the adoption of “The United Nations Framework Convention on Climate Change” (UNFCCC), which came into force in 1994. According to Haris et al. (2008) climatic variability combining with human induced emission of greenhouse gases resulted in an increase of global mean temperature which in turn, lead to higher evaporative demand and accelerated the hydrological cycle. In changing climatic scenarios variable rainfall characteristics directly affected ecosystem, agricultural practices and water resource management. In Ghana, the climate has changed over the last years. Crops are getting destroyed due to periods of extreme heat and heavy rains, General Agriculture Workers Union GAWU, 2012. Rajeev and Mahesha (2008) have studied the effect of climate change on water resources system. The effect of global warming on water resources systems is the thrust-area among hydrologists in the recent years. From the recent findings, the decrease in precipitation leading to global warming will result into increased extreme events and hence increased risk of both flooding and droughts. Rainwater is noted for its multi-purpose usage ranging from domestic and industrial water supply, sanitation and disease prevention and rain-fed agriculture. It is thus evident that water forms an integral part of the development of human societies. The most critical factor that sustains crop productivity in rain fed agriculture is the availability of water. According to the Ghana statistical service (2019), agricultural production services as the second most important economic sector having significant growth rate of 4.8% and also employing majority of people in the country. Statistics from the Ghana statistical service (2018), indicates that agricultural production contributed about 18.7% and 18.3% in 2016 and 2017 respectively to Gross domestic product (GDP) while crops farming only and largely contribute 14.2% to GDP of Ghana. In Ghana, agricultural production serves as the main economic sector, employing about 56% of the work-force and accounting for about 28% of GDP (De Bon, Parrot, & Moustier,2010; Logah,Obuobie & Kankam-Yeboah,2015). However, this sector depends heavily on rainfall. For instance, cocoa production which contribute significantly to the GDP in Ghana is heavily dependent on rainfall (Asante and Amuakwa-Mensah, 2015). Due to increasing population pressure, fallow periods have reduced and crop rotation declined, leading to loss of soil fertility and less food production per unit area of cultivated land. This is so in the face of highly variable climatic conditions (extremely dry years and highly variable onset and cessation dates of the rainy season) in recent decades (Mawunya,2013; Yorke and Omotosho 2010). These variable climatic conditions have led to unstable and unsustainable agricultural practices, inefficient water resource management in the area of industry, hydropower and other services which could result in famine and food insecurity. Variability of rainfall from season to season greatly affects soil water availability to crops, and thus risks crop productivity. Most studies conducted in Ghana on rainfall variability and distributions showed the risk of a dry spell during the rainy season to be higher in the south of the country than in the north (Logah et al). Antwi-Agyei et al.,(2012), also observed similar trends in the intra-seasonal rainfall variability of Accra in the south and Tamale in the north. Studies have shown that in Ghana, the variability and distribution of average annual rainfall ranges from 1000-1400mm covering at least 50% of the entire country (Logah, Obuobie and Kankam, 2015; Anang, 1977). To understand the impact of the rainfall variability which is one of the key climate response factors in the region, it is very important to study the trends of onset, cessation dates, and the seasonal rainfall amount, a study which is crucial for developing early warning system prediction model.