Hydropower Costs of Environmental Flows and Climate Warming in California's Upper Yuba River Watershed

Abstract

Understanding the trade‐offs between water for the environment and water for hydropower in regulated rivers can inform decision making about hydropower system planning, policy and operations, especially with anticipated climate warming–induced changes in runoff. This study used a multireservoir optimisation model to assess the hydropower effects of increasing minimum instream flows (MIFs) and imposing weekly scale down ramp rates (DRRs) in three locations in California's Upper Yuba River (UYR). The UYR is currently used for hydropower generation yet has high potential for freshwater habitat restoration. Trade‐offs between DRRs, MIFs and hydropower generation and revenue are explored with uniform air temperature increases of 0 °C, 2 °C, 4 °C and 6 °C to approximate anticipated regional climate warming. With 6 °C warming, the most ecologically beneficial MIF and DRR reduced hydropower generation by 7.9% and revenue by 5.5% compared with base case management and a historical climate. This has important implications for licensure of the UYR project and other hydropower projects, where multiple benefits under current and potential future conditions must be balanced. This study provides a methodological approach that can be used by water managers, regulators and stakeholders to better understand inherent trade‐offs in allocating water for multiple beneficial uses in a nonstationary hydroclimate. Copyright © 2012 John Wiley & Sons, Ltd.

Modelling Tools to Analyze and Assess the Ecological Impact of Hydropower Dams

“…For instance, Rheinheimer et al [14] assumed that gains and losses were neglected from groundwater and from precipitation and evaporation on water bodies, respectively. Grand et al [55] also assumed that backwater morphology remains constant; however, in reality, flood events can typically occur in the spring and may also occur later in the year.…”

“…Using an integrated model allows gaining insight into the processes that occur on the river besides the direct impacts observed related to dam construction or wastewater discharges [138]. Models can be used qualitatively and quantitatively to consider climate change impacts on hydropower systems for hydropower relicensing [14]. Given their numerous strengths and opportunities, their use to assess the impact of hydropower dams deserves further investigation.…”

“…Therefore, an ecological impact assessment of hydropower dams on the river ecosystems before construction, during operational phases and after dam removal is highly recommended. A thorough understanding of the trade-offs between water for the environment (ecological aspect) and water for hydropower in regulated rivers (socio-economic aspect) is needed in the decision-making about the planning, policy and operations of hydropower dams [14,15]. In this context, ecological models can help to conceptualize the potential effects of constructing a hydropower dam on the surrounding ecosystem.…”

Planning for climate change impacts on hydropower in the Far North

“…Hydroclimate models can be used to understand glacier and snowmelt dynamics (Huss et al, 2008;Jonsdottir, 2008;Schaefli et al, 2007;Johannesson, 2006), but they can also be linked with energy market models to understand financial and technical feasibility; economic vulnerability to climate change (Cherry et al, 2005b;Harrison et al, 2003;Harrison and Whittington, 2002); and they can provide a methodological approach to understand tradeoffs (Rheinheimer et al, 2013). Because getting to detailed, precise information at the watershed scale requires intensive effort and significant computing power, these methods have mostly been applied to case studies of particular basins (Bennett et al, 2012;Shrestha et al, 2012 in the Far North).…”

“…Several suggestions that have emerged in the literature include adaptive licensing, shorter-term licenses, and more integrative licenses across basins. Explicit adaptive licensing could include specific operational responses to thresholds (Rheinheimer et al, 2013) or more frequent assessment of performance (ICOLD, 2013;Brekke et al, 2009;Madani, 2011). Brekke et al (2009) and these other studies reiterate that we can no longer assume a stationary hydrological future and licensing structures need to reflect this.…”