Changing rainfall inputs in the Volta basin: implications for water sharing in Ghana

We present evidence from the analysis of gridded annual rainfall data that, increased variability and declining rainfall totals are the main cause of declining lake levels in the Volta basin above the Akosombo Dam. West Africa has undergone a period of diminished rainfall, punctuated by a series of severe droughts and marked by a shift in rainfall regime. As a result, lake levels behind the hydro-electric impoundment have fluctuated so widely at times that, power has had to be rationed. The trends in the spatial and temporal variability of annual rainfall in the riparian nations explain the low impoundment levels frequent in recent decades. The drying of Burkina Faso and Mali is particularly marked and synchronous to an apparent shift in the rainfall regime in Ghana towards a longer dry season and vanishing short dry spell, the effects which tend to negate each other. The various regional and temporal associations between El Niño-Southern Oscillation phenomenon (ENSO) are investigated as a possible cause of variation across the basin. The strengths of these associations and low frequency shifts suggest an unfortunate correspondence between national and climatological boundaries which may serve to heighten regional political tensions resulting from ENSO effects. Lack of re-investment in the Akosombo Dam as a result of management policies, political and pre-construction contractual agreements have all conspired in recent decades to make these hydro-climatological changes more devastating.

[1]  The GLOWA Volta Project: A framework for water resources decision-making and scientific capacity building in a transnational West African basin , 2007 .

[2]  P. Waylen,et al.  Trends in spatio‐temporal variability in annual rainfall in Ghana (1951‐2000) , 2009 .

[3]  W. Cai,et al.  Multidecadal variability in the transmission of ENSO signals to the Indian Ocean , 2007 .

[4]  N. Giesen,et al.  Competition for water resources of the Volta basin , 2001 .

[5]  Sharon E. Nicholson,et al.  Correction: An analysis of the ENSO signal in the tropical Atlantic and Western Indian oceans , 1997 .

[6]  James E. Ellis,et al.  Climate Patterns and Land-Use Practices in the Dry Zones of Africa , 1994 .

[7]  V. Barros,et al.  Climate Variability in Southern South America Associated with El Niño and La Niña Events. , 2000 .

[8]  G. Jenkins,et al.  The Challenges of Modeling Climate Variability and Change in West Africa , 2002 .

[9]  Francisco P. Chavez,et al.  From Anchovies to Sardines and Back: Multidecadal Change in the Pacific Ocean , 2003, Science.

[10]  M. Giordano,et al.  Driving forces behind African transboundary water law: internal, external, and implications , 2005 .

[11]  Christian Baron,et al.  Agricultural impacts of large-scale variability of the West African monsoon , 2005 .

[12]  B. Rudolf,et al.  A New Monthly Precipitation Climatology for the Global Land Areas for the Period 1951 to 2000 , 2004 .

[13]  Peter H. Gleick,et al.  Water in crisis: a guide to the world's fresh water resources , 1993 .

[14]  Kevin E. Trenberth,et al.  Recent Observed Interdecadal Climate Changes in the Northern Hemisphere , 1990 .

[15]  C. Ropelewski,et al.  Global and Regional Scale Precipitation Patterns Associated with the El Niño/Southern Oscillation , 1987 .

[16]  A. Navarra.  Beyond El Nino: decadal and interdecadal climate variability. , 1999 .

[17]  INTERANNUAL AND INTERDECADAL VARIABILITY IN STREAM FLOW FROM THE ARGENTINE ANDES , 2000 .

[18]  W. Andah,et al.  Volta Basin Water Balance , 2000 .

[19]  S. Nicholson,et al.  Contrasting Conditions of Surface Water Balance in Wet Years and Dry Years as a Possible Land Surface-Atmosphere Feedback Mechanism in the West African Sahel , 1994 .

[20]  P. Gyau-Boakye,et al.  The Volta Lake and Declining Rainfall and Streamflows in the Volta River Basin , 2000 .

[21]  Eric Servat,et al.  Climatic variability in humid Africa along the Gulf of Guinea Part I: detailed analysis of the phenomenon in Côte d'Ivoire , 1997 .