Hydropower droughts and fossil backfill: A Bayesian hierarchical and instrumental-variable analysis of 57 power systems, 2015–2026
Hidroelektrik kuraklıkları ve fosil ikame: 57 elektrik sisteminin Bayesçi hiyerarşik ve araç değişkenli analizi, 2015–2026
This paper is under review at a peer-reviewed journal. The journal name and full text will be added after acceptance.
Abstract
Hydropower supplies about a seventh of global electricity, and its output varies with precipitation. When droughts reduce hydropower, other sources must fill the gap, often fossil plants. This study quantifies this chain for 57 countries with a hydropower share of at least 5%, using monthly electricity data to October 2026 and standardised precipitation indices weighted by the location of hydropower capacity. A Bayesian hierarchical model estimates country-specific responses of hydropower to precipitation anomalies at three- and twelve-month scales; instrumental-variable regressions with a precipitation-predicted instrument estimate how the shortfall is replaced. A one-standard-deviation drought on both scales lowers hydropower by 10% in the median country (10–90% range across countries 2–23%). Across all countries, each terawatt-hour of precipitation-driven shortfall is replaced by 0.41 TWh of fossil generation and 0.66 TWh of net imports; in Asia, Africa and Oceania fossil plants replace it almost one-for-one, whereas European countries import most of it. Precipitation-driven shortfalls added 127 Mt of CO₂ in 2023, mainly in China, whereas wet years after 2023 avoided emissions. Lagged precipitation adds little to forecasts beyond the persistence of hydropower anomalies.
Keywords
Hydropower; Drought; Standardised precipitation index; Bayesian hierarchical model; Instrumental variables; Power-sector emissions
Open code and data
Loading code…