Climate impacts on hydropower and consequences for global electricity supply investment needs
Introduction
Almost a fifth of the world's electrical power supply depends directly on the potential energy of water delivered to catchment headwaters by the climate system. The number of countries developing capacity to harness this power through dam construction is growing [1]. Hydroelectric dams are seen by governments as a means to stimulating economic growth through the provision of clean, renewable energy, as well as a host of other benefits including flood control and water supply for agriculture and industry [3]. At least 3700 major dams (>1 MW installed capacity) are either under construction or in planning across the developing world [55]). These projects not only ensure that hydropower will remain a vital component of global electricity supply through the 21st century; they also expose electricity supply networks to risks and opportunities associated with climate change.
Climate change is projected to manifest in alterations to the spatial and temporal distribution of water availability throughout the world [4], [56], [5], [6], [7]. Some river basins will receive less precipitation on average; others will receive more. Hydroelectric power production at dams located on affected rivers will be impaired or enhanced accordingly—demonstrated neatly by a sharp fall in hydropower production in California during a recent prolonged drought [8]. New tools have advanced our ability to study these potential impacts at the global scale. These include the latest generation of General Circulation Models and downscaling methods, Global Hydrological Models and river routing techniques [9], and detailed datasets specifying the locations and properties of hydropower facilities, including turbine, dam and reservoirs specifications [10], [11], [12]. Top-down climate impact assessments that have deployed these tools highlight significant potential impacts of climate change on 21st century hydropower production across many world regions [13], [14], [15], [16]. These studies and their underpinning methodologies can be considered a success in that results are corroborated reasonably well by a tranche of finer-detailed, localized assessments examining possible climate impacts on hydropower in specific river basins, countries and regions (e.g., [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27]). As yet, however, we know of no global scale study that has taken the next logical step of examining the consequences of long-term losses or gains in hydropower production on the electricity supply sector (herein termed “power sector”). And whilst it has been shown that climate-driven changes in hydropower production could impose significant change on planning-relevant variables through alterations to the operations of a given system [28], similar implications arising from required long-term changes in the technological composition of the power sector remain unexplored at a global scale. For some regions, these changes could create non-trivial planning and policy problems relating to the costs of power generation and associated emissions [29].
In this study, we explore potential impacts of gains and losses in hydropower generation on the technological composition of the power sector and consequent effects on 21st century carbon emissions and investment costs of new capacity. Impacts on global emissions are interesting because they may indicate the presence a reinforcing effect. Emissions drive greenhouse warming, which may intensify drying in basins important for hydropower generation. This loss of hydropower production could shift the generating composition of the power sector toward more carbon-intensive technologies, thereby driving further climate change. Such a feedback loop would be moderated by an opposing negative feedback occurring in regions experiencing increased precipitation. Nonetheless, exploring the plausibility of this phenomenon would seem prudent given the potential threat it raises. With regards impacts on power sector investments, regions that depend heavily on hydropower to meet electrical energy needs may be particularly vulnerable, because lost generating capacity implies that investments in alternative generating technologies will be required to meet growing demands for electricity. These investment risks could be affected by globally-agreed emissions targets—such as those defined under the Paris Agreement [30]—because sustained shortfalls in hydropower generating capability may have to be addressed through increased investment in expensive, low-carbon technologies to ensure nationally defined contributions are met. The relevant policy-makers ought to be attuned to these effects and the implications they carry for power sector planning and investment strategy—particularly in countries with relatively low capacity to raise finance for new capital works.
Section snippets
Method
We study the impacts of climate change on hydropower production and then power sector composition for 32 distinct world regions. This is achieved in two main steps. First, we generate hydropower projections for each region by forcing a coupled global hydrological and hydropower dam model with gridded GCM climate projections for the 21st century. Second, we feed these projections into an integrated assessment model to explore how the power sector might adapt to changes in hydropower production
Climate change impacts on 21st century hydropower production
We project a change in net global hydropower production of between −8% and +5% under RCP8.5 and between −4% and +4% under RCP 4.5 by the end of the century depending on GCM (Table 2). Power production is reduced at the majority of modelled dams under either emissions scenario (only one of sixteen GCMs counters this finding). These results are similar to findings of prior studies, although we find that when averaged across all GCMs, the net reduction in hydropower generation is slightly less
Conclusions
This study combines a global hydrological and dam model with an integrated assessment model to assess impacts of climate change on power sector technological composition and associated impacts. The approach is state-of-the-art in at least three respects: application of fine detailed dam model that captures nonlinearity in hydropower generation response to climate change; use of a comprehensive suite of input climate realizations from sixteen CMIP-5 GCMs; and inclusion of feedback between the
Acknowledgment
This research was supported by the Office of Science of the U.S. Department of Energy through the Integrated Assessment Research Program. PNNL is operated for DOE by Battelle Memorial Institute under contract DE-AC05-76RL01830. We acknowledge the World Climate Research Programme's Working Group on Coupled Modeling, which is responsible for CMIP, and we thank the climate modeling groups for producing and making available their model output. For CMIP the U.S. Department of Energy's Program for
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