Navigating low inflows – experiences of a hydro power generator

Hydro Tasmania is Tasmania’s main power generator and the guardian of many of its waterways with unique natural values. The water that powers the island state, as well as part of the mainland Australia, is a valuable shared resource between all Tasmanians environmentally, culturally, and economically. Hydro Tasmania needs to navigate several different objectives of providing the right amount of affordable energy to its residents, while meeting farmers’ irrigation requirements, maintaining lake levels appropriate to various types of recreational users, and protecting Tasmania’s vulnerable environment and endangered fauna.

Tasmania’s hydro power stations are mostly located in areas that historically receive high rainfall and inflows, but this is becoming less frequent with the climate change. The magnitude of the inflows our catchments collected over the last year was smallest in decades. Climate change also brings other extreme events such as flooding after drought and bushfires. The only way to successfully mitigate the impact of reduced inflows is by having an accurate inflow forecasting system. When water is scarce, optimisation and planning become an essential asset. It is required for scheduling of the power stations, for ensuring dam safety and for protecting the communities and environment. To complicate the problem further, Tasmania is located in the middle of different weather systems, and has a challenging topography with mountains and valleys, forests and plains, and it is surrounded by sea. This makes inflow forecasting at specific locations extremely challenging.

Until recently, our inflow forecasts were hydrographs based on deterministic models that were used as the best estimate across all the applications and end-users. These models are robust, and easy to interpret, but they do not provide information about uncertainties and probabilities of the extreme inflows. Our answer to the challenge is an all-purpose hydrological forecasting system. It consists of three timescales; short-term, outlook and long term, but more importantly, instead of resulting a single forecast, it provides an ensemble of 200 forecasts. This supplies the decision makers more visibility to the probability of different events which enables more optimised planning and using of water.

In this talk, we describe our new inflow forecasting system, and share experiences of how this has been a valuable asset in navigating one of the driest years in recorded history of Tasmania.