Water-CO₂ trade-offs in electricity generation planning

In 2011, the state of Texas experienced the lowest annual rainfall on record, with similar droughts affecting East Africa, China and Australia. Climate change is expected to further increase the likelihood and severity of future droughts. Simultaneously, population and industrial growth increases demand for drought-stressed water resources and energy, including electricity. In the US, nearly half of water withdrawals are for electricity generation, much of which comes from greenhouse gas emitting fossil fuel combustion. The result is a three-way tension among efforts to meet growing energy demands while reducing greenhouse gas emissions and water withdrawals, a critical issue within the so-called water-energy nexus. We focus on this interaction within the electric sector by using a generation expansion planning model to explore the trade-offs. We show that large reductions in CO 2 emissions would probably increase water withdrawals for electricity generation in the absence of limits on water usage, and that simultaneous restriction of CO 2 emissions and water withdrawals requires a different mix of energy technologies and higher costs than one would plan to reduce either CO 2 or water alone.