Informing sustainable water management options

Pressure on the world’s water resources has been mounting substantially in recent decades, and is expected to be further exacerbated by climatic and socioeconomic changes in the future. The Extended Continental-scale Hydro-economic Optimization Model (ECHO) developed by the IIASA Water Program is a useful tool for assessing the economic and environmental impacts of water scarcity and evaluating the effectiveness of management options.

Global water extractions have been increasing rapidly over the last decades to support growing food and energy needs, and increasing standards of living [1]. As a result, many basins around the world have experienced pervasive water scarcity conditions and related water management challenges [2]. These challenges are expected to become even more critical in the coming decades, as countries attempt to sustain a larger and more prosperous human population and economy under changing climatic conditions [3]. As such, policymakers in vulnerable regions need to anticipate how to adapt management practices to secure reliable future water supply that can meet the demands of different sectors. In recent decades, hydro-economic models have emerged as an important tool for informing the design of efficient and sustainable water management options, because they typically feature an integrated biophysical-technological-economic representation of water resource systems [4].

Although hydro-economic models are typically designed at basin scale, with a few designed to model systems ranging in size from household or utility level, to transboundary basin scale, they are rarely used across larger spatial scales. This provides an opportunity to integrate a detailed representation of local biophysical (e.g., available water resources) and technological (e.g., infrastructure) constraints with farther-reaching regional and global policies. This feature is particularly relevant, because the availability of water, energy, and land resources varies significantly at local scales, whereas the linkage to regional and international markets for energy and food commodities, along with transboundary treaties for water resources, have global influences [5]. The few existing large-scale hydro-economic models use a reduced number of spatial units (i.e., location-specific attributes) to minimize the computational burden, which limits their potential for integrating constraints at a local-level. In addition, most of these models only include a limited set of water management options, and many omit the implications of future management decisions in the energy and agricultural sectors.

To overcome these limitations, researchers from the Water Program developed the Extended Continental-scale Hydro-economic Optimization (ECHO) model to support the design of efficient and sustainable water management options. ECHO includes an economic objective function, as well as simplified representations of essential biophysical and technological features at sub-basin level within river basins at a continental scale. These include representations of various water supply sources (surface water, groundwater, and non-conventional water, such as desalinated water), sectoral demands (irrigation, domestic, manufacturing, and electricity), and infrastructure (surface water reservoirs, desalination plants, wastewater treatment plants, irrigation systems, and hydropower plants). The objective function of ECHO minimizes the total costs of a wide variety of water management options over a long-term planning horizon (a decade or more), to satisfy sectoral water demands across the sub-basins. Management options include both supply and demand options that span over the water, energy, and agricultural systems.

ECHO has already been applied to Africa as a case study, in order to assess important interactions between the region’s future water demands and availability under various future socioeconomic and climatic scenarios. The model is designed to operate at different spatial scales and in different regions or continents, subject to the availability of data.

References

[1] Wada Y, Flörke M, Hanasaki N, Eisner S, Fischer G, Tramberend S, Satoh Y, Van Vliet M, Yillia P, Ringler C, Burek P, & Wiberg D (2016). Modeling global water use for the 21st century: The Water Futures and Solutions (WFaS) initiative and its approaches. Geoscientific Model Development 9, 175-222.

[2] Kahil M, Dinar A, & Albiac J (2015). Modeling water scarcity and droughts for policy adaptation to climate change in arid and semiarid regions. Journal of Hydrology 522, 95-109

[3] Kim S, Hejazi M, Liu L, Calvin K, Clarke L, Edmonds J, Kyle P, Patel P, Wise M, & Davies E (2016). Balancing global water availability and use at basin scale in an integrated assessment model. Climatic Change 136, 217-231

[4] Bekchanov M, Sood A, Pinto A, & Jeuland M (2017). Systematic Review of Water-Economy Modeling Applications. Journal of Water Resources Planning and Management 143, 04017037

[5] Dalin C, Wada Y, Kastner T, & Puma M (2017). Groundwater depletion embedded in international food trade. Nature 543, 700-704