Woman selling fish in a market in the Mekong Delta, Vietnam. This is the third in a series of posts about how system-scale perspectives are vital to the planning and development of sustainable power systems, including hydropower. This post will focus on how system-scale planning of power systems, and of hydropower within those systems, can achieve better outcomes for communities and river ecosystems. The first post explored how hydropower development and management can lead to a range of negative impacts on rivers and the communities that depend on them. Given past impacts (hydropower dams are a primary reason only about one-third of the world’s major rivers remain free-flowing) and predicted future impacts (projected hydropower expansion would dam about half of those free-flowing rivers that remain), there is clearly a need to find ways to plan and build hydropower more sustainably. Here, I focus on the hypothesis that the best opportunity to increase the environmental and social sustainability of hydropower lies in planning and management at the scale of systems, such as a river basin, power grid or country. But this goes beyond hydropower planning. Ultimately, people use energy, not hydropower, and so solutions that balance multiple objectives—across energy, social and environmental values—are most likely to emerge at the scale of power system planning. So, a system-scale approach to hydropower can be seen as having two steps (that are, in fact, also applicable to other renewable technologies, including wind and solar): 1. Power system planning (select the right mix of renewables for a given power system). 2. Project siting (site the right renewable projects in the right places). Below, I’ll explore how applying these two steps can achieve better outcomes for river ecosystems and communities. The next post will explore how they can achieve better outcomes for governments, funders, and developers. Power system planning Energy planners can use tools such as capacity expansion models to guide their decisions about the mix of power system investments (e.g., generation, storage, and transmission) needed to meet forecasted demands. These models should be coupled with analyses of the environmental and social performance of different technologies to understand the tradeoffs of different development options. For example, in a system where hydropower expansion is projected to have large negative impacts on communities, power system planning can identify potential alternatives. For example, the government of Sarawak, on the Malaysian part of Borneo, proposed development of two coal plants and 12 large hydropower dams to meet projected energy demands. The dams would have displaced tens of thousands of people, including indigenous communities. A research team from the Renewable and Appropriate Energy Laboratory (RAEL) at the University of
California, Berkeley, used a capacity expansion model to explore alternatives . They found that the two hydropower dams already under construction plus decentralized generation (solar PV and biomass) could meet future demand at a competitive cost, allowing Sarawak to meet power demand with far lower impacts on communities and the climate. The state government suspended one of the dams that was in the planning process, the Baram Hydropower Project , but Sarawak’s overall direction for expanding power remains uncertain. The output of power system planning will include targets for different generation technologies (e.g., solar pv, wind, hydropower) and a set of potential projects to meet those targets, setting up the next step. Planning to guide project siting Planning for project siting can be used for any generation technology, but here I’ll focus on hydropower. The most important predictor of a hydropower project’s impacts on ecosystems and people is its location. For example, a dam located on the lower part of the mainstem of a river can block migratory fish from accessing most of the river basin, whereas a dam on a tributary could leave most of the basin accessible to migratory fish. More than 20 years ago, a report from the World Bank reviewed various environmental mitigation measures to improve the sustainability of hydropower dams, but emphasized that, “the single most important environmental mitigation measure for a new hydroelectric project is good site selection, to ensure that the proposed dam is will be largely benign in the first place.” Site selection of new projects can be guided by strategic planning that identifies a set of projects that could meet energy targets while minimizing negative impacts on rivers and communities. However, such strategic planning is rare, and researchers have consistently demonstrated the benefits foregone due to the lack of strategic planning to guide site selection. For example, consider the Mekong basin and a failure to balance hydropower development with maintaining the supply of sand from rivers, a resource vital to maintaining the downstream Mekong delta , home to 20 million people and much of Vietnam’s agricultural productivity. Hydropower dams capture sand in their reservoirs, preventing rivers from carrying it downstream. A 2017 study found that the current (unplanned) set of dams in the 3S Basin (a major tributary to the Mekong and one of its primary remaining sources of sand) generates 16,000 GWh/year while reducing export of river-transported sand from the basin by 90%. However, had the 3S basin been planned as a system with the goal of maintaining as much sand as possible, a planned portfolio of dams could have produced the same annual generation but with only a roughly 15% loss of sand (see Figure below). For the 3S Basin, a strategic planning approach could have produced the same generation as the ... [+] actual development trajectory, but maintained eight times as much sand exported from the basin to the downstream delta. This research outcome—a set of dams in different locations could have provided the same power generation but maintained more than eight times as much sand— dramatically demonstrates the importance of site selection and strategic planning for achieving more sustainable hydropower. Beyond highlighting missed opportunities, the same planning methods can identify more sustainable options going forward. For example, proposed dams on the Mekong River would, if completed, result in nearly complete capture of the basin’s sediment supply, essentially sealing the fate of the Mekong Delta to slip beneath the ocean. But a 2019 analysis showed that a more strategic approach to site selection for future dam development—mainly, placing new dams upstream of existing dams—could generate equal or more electricity with nearly no additional loss of sediment. Research has also demonstrated that system-scale planning can identify more balanced outcomes between hydropower and migratory fish habitat. This potential for improved outcomes should not surprise: many of the most important benefits from rivers—such as migratory fish and sediment delivery to deltas—operate at the scale of the larger system, the river basin. Thus, the search for solutions must operate at that scale, not the scale of single projects. If you want to build a house that works, you hire an architect, not eight different designers, one for each room. The compelling opportunities identified through research underscores the need to find mechanisms to translate this potential into planning reality. Doing that will require the cooperation of those who actually make decisions about planning, selecting, funding, and building hydropower projects. And while these actors may agree that better outcomes for rivers and communities are laudable, many will respond more directly to other incentives. In the next post, I explore how system-scale planning can achieve a set of outcomes that can act as incentives for these decision makers, in the form or reduced conflict, lower risk, and greater return on investment.