Hydrological Catchment Areas (WP 1)
In the course of the project two hydrological catchment areas were chosen, the Sakumono Basin and the Nabogo Basin. On the macro level, these two river basins will be the pilot regions to be studied, representing the two major issues the joint project RAIN is focusing on – drought and flood. An intelligent water management plan for both urban and rural areas to reduce the risk of flooding and drought through increased resilience is to be developed.
Sakumono – Hydrological Catchment Area
The Sakumono Basin is the hydrological catchment area of the Sakumono Lagoon, located east of Ghana’s capital Accra. This zone with a total area of 280 km2 spans between Accra and Tema and is predominantly urban, although there are a few semi-urban regions1. The main urban areas consist of the Adentan Municipal District, the city Ashaiman and parts of the city Tema. According to the last census in 2010 these three regions alone had over 600.000 inhabitants2. The nothern part of the basin is less densely populated, with woodland and fields between the residential areas.
The climate of the Sakumono Basin is semi-arid with rainy seasons from Mai to July and from September to October. Because of the climatic conditions this region experiences both floods and droughts. Especially during rainy season, sudden and heavy rainfalls that lead to flooding events are usual. Additionally the annual rainfall can be inconsistant. While the mean annual precipitation is of 805 mm, some years can be extremely dry with rainfalls of 330 mm/year and some can be very wet with up to 1650 mm/year. The average monthly temperature reaches from 24.7°C in August to 33°C in March, with an annual average of 26°C. Subsequently, these high temperatures can cause drought periods.1 All these factors make the Sakumono Basin an interesting challenge for water management questions.
The Nabogo Basin is a rural area located 40 km from Tamale in the Northern Region of Ghana. The sub-basin of the White Volta Basin drains an area of about 2900 km2.6 It overlaps parts of the districts Savelugu Nanton, Karaga and Gushiegu, which together have a total population of over 300.000 inhabitants.2
Nabogo – Hydrological Catchment Area
The Nabogo Basin is characterized by an arid to semi-arid environment and has a unimodal rainy season that starts in May, reaches its climax in July/August and diminishes in October with an otherwise dry climate. The mean annual rainfall is estimated to be 1083 mm/year. However, daily temperatures in the Northern Region are quite high, reaching from above 35°C to below 20°C.6 This area is therefore much more affected by droughts than the Greater Accra Region. The drought risk for Ghana is generally expected to increase in the future, resulting in a high risk for the Northern Region. To make this area more resistant to its current and changing climate, an intelligent water management plan is crucial.
1Ludwig, S. (2020): Beurteilung von Chancen und Grenzen der Modellanpassung am Beispiel eines Wasserhaushaltsmodells in Accra.
2Ghana Statistical Service (2012): Population and Housing Census 2010.
3World Bank (2017): Enhancing Urban Resilience in the Greater Accra Metropolitan Area. Washington, D.C. © World Bank.
4Okyere, C.Y., Yacouba, Y., Gilgenbach, D. (2012): The Problem of Annual Occurrences of Floods in Accra: An Integration of Hydrological, Economic and Political Perspectives. Theoretical and Empirical Researches in Urban Management (8), p. 45-79.
5Kasei, R., Diekkrüger, B., Leemhuis, C. (2010): Drought Frequency in the Volta Basin of West Africa. Sustainability Science (5), p. 89.
6Nsiah, E., Appiah-Abjei, E.K., Abjei, K.A. (2018): Hydrogeological Delineation of Groundwater Potential Zones in the Nabogo Basin, Ghana. Journal of African Earth Science (143), p. 1-9.