Hydropower is the leading source of renewable electricity generation worldwide. Traditionally, hydropower has been perceived as a cheap, reliable and a low greenhouse gas emitting energy source. However, evidence suggests that, given hydropower’s dependency on the hydrological cycle, it could be particularly vulnerable to the effects of climate change. In addition, hydropower infrastructure has shown to be prone to significant cost overruns and delays, due to the inherent complexities that accompany its deployment. Previous research has quantified these issues but little investigation has taken place to assess them in an integrated manner. The interest of this research is to assess how assumptions about climate change, policy and costs can induce shifts in generation portfolio optima, particularly of power systems that are based or plan to be based on hydropower in the long-term. For this purpose, a series of hydrological, hydropower and energy system models have been developed in order to take these factors into account, and search generation alternatives regarding technical characteristics (i.e. power system operation, energy system configuration, demand), economic specificities (i.e. technology costs, resource prices, cost risk) and geospatial factors (i.e. water resource distribution, precipitation, climate change). The proposed method is illustrated with a case study for the Republic of Ecuador until 2050, a South American country that relies heavily on hydropower and plans to continue harnessing its potential in the future. Findings have identified that hydropower will remain an important least-cost and low emitting electricity source in Ecuador’s future, however its share in the electricity generation matrix could vary greatly. Furthermore, portfolio analysis has revealed the trade-off between generation portfolio cost and risk. Suggesting that shifting away from run-ofriver hydropower, gas and oil-fired generation towards a system with larger shares of hydropower with reservoir, solar PV and geothermal energy can help hedge the power system against the uncertainties of climate change, fossil fuel price volatility and electricity infrastructure cost overruns. Failing to diversify the power system could create a lock-in to natural gas. This research adds to the literature seeking to provide insights for new hydropower developments particularly concentrated in emerging economies of South East Asia, South America and Africa
