WHAT-IF: an open-source decision support tool for water infrastructure investment planning within the Water-Energy-Food-Climate Nexus

Abstract

Abstract. Water infrastructure investment planning must consider the interdependencies within the water-energy-food nexus. Moreover, uncertain future climate, evolving socio-economic context, and stakeholders with conflicting interests, lead to a highly complex decision problem. Therefore, there is a need for decision support tools to objectively determine the value of investments, considering the impacts on different groups of actors, and the risks linked to uncertainties. We present a new open-source hydroeconomic optimization model, linking in a holistic framework, representations of the water, agriculture, and power systems. The model represents the joint development of nexus-related infrastructure and policies and evaluates their economic impact, as well as the risks linked to uncertainties in future climate and socio-economic development. We apply the methodology in the Zambezi River Basin, a major African basin shared by eight countries, in which multiple investment opportunities exist, including new hydropower plants, new or resized reservoirs, development of irrigation agriculture, and investments into the power grid. We show that the linkage of the different systems is crucial to evaluate impacts of climate change and socio-economic development, which will ultimately influence investment decisions. We find that climate change could induce economic losses up to 2.3 billion dollars per year on the current system. We show that the value of the hydropower development plan is sensitive to future fuel prices, carbon pricing policies, the capital cost of solar technologies, and climate change. Similarly, we show that the value of the irrigation development plan is sensitive to the evolution of crop yields, world market crop prices and climate change. Finally, we evaluate the opportunity costs of restoring the natural floods in the Zambezi delta; we find limited economic trade-offs under the current climate, but potentially major trade-offs with irrigation and hydropower generation under climate change.

Using Model Predictive Control in a Water Infrastructure Planning Model for the Zambezi River Basin

“…The different climate change scenarios implicate different levels of water scarcity. In the present climate, with the present water infrastructure, net water consumption is around 11% of the available runoff (Payet-Burin et al 2019). Considering the water infrastructure investments, it is around 16% for the present climate, and varies from 11 to 35% for the four climate change scenarios.…”

“…The WHAT-IF model is an open-source hydroeconomic optimization model, linking, in a holistic framework, representations of the water, agriculture, and power systems (Payet-Burin et al 2019). In WHAT-IF water management (e.g.…”

“…We use the modelling framework and dataset of the Zambezi River Basin from Payet-Burin et al (2019). The river basin is divided in 26 catchments with runoff and precipitation time series covering 40 years; the average yearly runoff is 114 km³.…”

“…The agricultural water demand is calculated based on FAO 56, crop yields are based on FAO 33, and the crop choice is part of the optimization framework. Unlike in Payet-Burin et al (2019), rainfed production and crop markets are not represented, only irrigated agriculture is represented and valuated at the farm level using FAO data (FAO, 2018). Hydropower plants are represented individually, assuming fixed head levels and using water-energy equivalent production coefficients.…”