Guest blog: Hydrology and climate change - how climate models can help the hydropower sector
Climate change is a complex phenomenon which is under intense study by the scientific community for the risk it poses to sustainable development. Vinod Chilkoti, researcher at the University of Windsor (Ontario, Canada) writes about possible strategies for the hydropower sector.
The global installed capacity of hydropower surpassed 1,200 GW in 2016 and currently accounts for over 16 per cent of global installed electricity capacity; more importantly, it contributes about two thirds of total energy generation in the renewable sector, and is widely recognised as one of the cleanest energy resources.
Any infrastructure project that has a lifespan of a few decades is prone to the potential dangers of climate change, unless the system is designed to withstand projected future environmental conditions. In the case of capital-intensive hydropower, the major designs are function of the project’s installed capacity, which in turn is dependent on the hydrology of the region.
There is little doubt that human-induced climate change is happening, altering climatic patterns and, therefore, hydrological flow regimes. The trend and direction of these changes will differ around the globe. As such, the changing climate poses a challenge to the reliable assessment of hydropower generation, and calls into question the feasibility of these investments.
With large number of climate models to choose from, a reasonable approach is to use a combination of different models."
At the planning stage, the potential of a hydropower installation can be assessed only based on the historical stream flow record available. Assuming that the hydrological regime follows a cyclic pattern, a reasonable assessment can be made for a new project with a certain degree of confidence. The volume of exploitable stream flow available in the future will be governed by the prevailing climatic and land cover conditions, which themselves are affected by anthropogenic factors. With these influences, the likelihood of the prevailing hydrology becoming altered in future is quite high, leading to variation in the estimated energy generation.
Rapidly-emerging knowledge within climate change science has enabled the development of numerous climate models that simulate the various climatic processes to predict future climate scenarios. These models have the potential to be used for evaluating the reliability of hydropower schemes. Advanced computational capabilities have enabled the resolution of these models to be commensurate with impact assessment study. Through the earnest effort of various modelling agencies around the world, climate scenarios looking ahead to the end of the 21st century are now available with a model resolution to the tune of 0.1 degree on a map grid, i.e. in less than 10 km intervals.
Today’s near-accurate weather prediction should give us confidence in the science of weather forecasting, and hence also in the prediction of long-term climate scenarios. With large number of climate models to choose from, a reasonable approach is to use a combination of different models. The climate model projection when forced into a calibrated hydrological model would provide the required flow series for power planning studies.
Accurate hydrological modelling, whether using a conceptual, semi-distributed or distributed model, with experienced and rational judgement on model calibration, is key to the reliable water availability estimation. In the absence of recorded data for climate variables, such as precipitation and temperature, which is often the case, gridded climate data can be utilised as a dependable model input. The adoption of satellite-based soil moisture information through various data assimilation techniques has significant potential to increase the accuracy for hydrological model calibration. Multi-objective model fit statistics, including the various flow signature measures, are being widely adopted to eliminate the inappropriate model assessment based on single-model fitness statistics.
With an ensemble of reliable flow projections in hand, a reasonable risk factor due to the climatic variations for the proposed project or even an existing hydropower installation can thus be evaluated. The associated uncertainties of such an assessment that are inherent due to the climate model, climate scenarios, downscaling method, hydrological model, and so on, have increasingly become a focus of research.
Unlike the current practice of assessing hydropower potential based on historical datasets, there is scope for hydropower planners to utilise the well-established science of hydrological modelling in conjunction with cutting-edge research on climate projections, to generate the requisite flow series that can be relied upon for planning hydropower projects. This would support climate-resilient hydropower planning and design, and therefore provide the required level of confidence to investors and project authorities.