This post is one of a series on presentations by CGIAR Research Program on Water, Land and Ecosystem's researchers at the recent Water in the Anthropocene conference in Bonn, looking at aspects of the water-energy-food nexus in the Aral basin, the Indus and now the Volta. Click here for the full list of presentations and blog posts from the conference.
Fred Pearce, a noted writer on water, describes climate change as “the joker in the pack” for promoters of hydroelectric schemes. Different scientists in WLE play the joker at different stages in their research. When Matthew McCartney and his colleagues set out to model the future of the water-energy-food nexus in the Volta basin in Ghana, climate change was a key consideration.
“The inability to manage rainfall variability is a key constraint to agriculture and economic development in Ghana,” McCartney told the Bonn conference, and while models of climate change differ in some of their predictions, one thing they agree on is an increase in variability.
Ghana, like many countries, needs more energy and more food, and both depend on flows in the Volta. The Akosombo dam and hydropower scheme came online in the mid 1960s, in the process creating Lake Volta, the largest artificial lake in the world. Already, however, both Akosombo and Kpong dam, downstream, have suffered from low water levels caused by droughts. Producing power when flows are low can damage the generators, so energy supplies have had to be rationed. There are, of course, other places where the Volta and its tributaries could generate hydropower, not least at Bui in the northwest of the country, where a new dam and hydropower scheme is due to start full operation later this year. The question remains: given the likelihood of increasing variability in rainfall, can the Volta sustain both energy needs and agricultural production in Ghana?
McCartney and his team took a three-stage approach to modelling the likely future. First, they simulated the impact of climate change on temperature, rainfall, and water evaporation to the atmosphere. They plugged those results into a hydrological model that predicted flows in the rivers and the recharge of groundwater. And finally, those results went into a model of water resources that looked at irrigation and hydropower. The results were not encouraging. Rainfall over the basin as a whole is predicted to drop from 835 mm in 1983-2012 to 666 mm in 2071-2100 and groundwater recharge from 76 mm to 36 mm. Flow declines from 1610 to 885 m^3 per second, although the coefficient of variation increases from 0.34 in 83-2012 to 0.67 in 2071-2100.
Those predictions can be set against development options for the Volta basin, comparing the current state of affairs with an intermediate option, which includes all projects for which there is a feasibility study, and with full development on the basis of the government’s Basin Master Plans.
“What you end up with,” McCartney says, “is increased unmet demand for irrigation as climate change kicks in, and a much lower supply of energy available as a result of decreased flow. Climate change could easily derail Ghana's development plans.”
The joker can change the outcome of the game, and while the exact impact of climate change on water resources in the Volta basin remains uncertain, there is no doubt that there will be an impact. Perhaps the most important lesson of this modelling exercise is that adaptation to climate change and economic development are linked and need to be considered together, and that this will require the planning of water storage to be much more systematic across a range of scales.
Yet another element, not considered in this study, is whether massive schemes offer the best opportunities for sustainable development. As sub-Saharan Africa considers a whole range of huge hydropower schemes, including Inga III on the Congo, many people are beginning to ask whether the money wouldn’t be better invested in more decentralized power generation based on small-scale hydro, solar and wind.
That’s a different game entirely.
For more information:
Matthew McCartney's presentation: Implications of Climate Change on Existing and Planned Water Resource Development in the Volta Basin
Blog posts from the Water in the Anthropocene Conference