Uncertainties and risks in reservoir operations under changing hydroclimatic conditions

Abstract

Uncertainties and risks associated with hydroclimatic variations pose a challenge to the management and planning of water resources systems. This study demonstrates the importance of understanding the changing hydrologic regime of the Feather River Basin (FRB) and its impacts on water resources decision variables (i.e., storage requirement and performance of a water supply reservoir). A simple storage–yield–reliability model (S–Y–R) is used to quantify the risk of the stationary-based designed reservoir under the temporal variation and nonstationarity in N-year blocks of the Feather River Inflow into Lake Oroville (FRI). Furthermore, the potential linkages of the long-term variability in the FRI to climate variations are investigated by applying wavelet spectrum and coherence analysis to the FRI and atmospheric–oceanic indices (e.g., ENSO and PDO). The results show substantial variations in the FRB hydrologic regime over different timescales with episodes of abrupt shifts toward significantly higher storage requirements, and decrease in the reservoir performance during historical periods of high FRI variance and lag-1 serial correlation. Although the mean inflows are high, the storage capacity is increased by (a) 38 and 48% due to the 5 and 20% increase in the FRI variance during the periods 1904–1953 and 1960–2009, respectively, and (b) 34% due to the increase in the serial correlation coefficient in the period of 1750–1799. Likewise, reservoir performance significantly decreased for the same reasons in the same critical periods. The reliability and resilience dropped to 74 and 29% (1904–1953) and to 76 and 50% (1960–2009 period) due to the increased variance of FRI, while vulnerability reached 70% during the high lag-1 correlations in 1532–1581 and 1564–1613, and 40% in 1904–1953 due to the high FRI variance. Furthermore, the wavelet coherence analysis observes strong associations between the streamflow and climate teleconnection patterns in specific periodic cycles during the same critical periods which link the variability in FRI and decision variables to the hydroclimatic variations. These linkages give a primary indication for the reservoir storage requirement characterization.

Dam System and Reservoir Operational Safety: A Meta-Research

“…Despite the role of dams and reservoirs as a climate-change risk mitigation infrastructure, climate change, in turn, directly affects the safety of dam operational objectives (e.g., flood control, hydropower generation, and water supply management) [7,[107][108][109][110][111][112][113]. Climate change intensifies weather extremes that subsequently induce a series of devastating natural hazard events (e.g., floods, droughts).…”

Influence of nonstationarity on reservoir storage-yield-reliability relationships

“…The S-Y-R relationship was thoroughly studied by R. Vogel and collaborators circa 1980-90 in a series of papers that explored its statistical properties (Vogel & McMahon, 1996;Vogel & Stedinger, 1987, 1988 and applications in the United States (Vogel et al, , 1997(Vogel et al, , 1999. More recently, the S-Y-R curve has been widely used not only for designing purposes (Silva & Portela, 2013;McMahon et al, 2007) but also as a tool for understanding the operating rules of existing reservoirs (Aljoda & Jain, 2021;Srivastava & Awchi, 2009;Vogel et al, 2007). Moreover, Kuria & Vogel (2015) employed the S-Y-R relationship to evaluate the uncertainty of water supply reservoir yields.…”

“…The authors advocate that the importance of dams will increase in a climate change scenario. Moreover, in studying the Oroville Dam (California, United States), Aljoda & Jain (2021) argued that the reservoir performance is affected significantly by streamflow nonstationarity. Both studies were conducted locally, and it is our understanding that the link between S-Y-R relationships and trends in the streamflow time series needs further investigation.…”