sustainable and efficient water use - from water footprint accounting to setting targets
Rick Hogeboom is a PhD student in the research group Water Engineering and Management (WEM). His supervisor is prof.dr.ir. A.Y. Hoekstra from the faculty of Engineering Technology (ET).
Humans consume freshwater in all sectors of the economy and across all layers of society. Growing populations, economic development and climate change add to already large pressures on freshwater resources in many places around the world. The challenge for authorities, planners – and also businesses, farmers and investors – is to strike an acceptable and sensible balance in allocating limited freshwater resources to the various demanding and often competing uses without compromising nature.
Two policy instruments that have emanated from the field of Water Footprint Assessment (WFA) are particularly promising to help transition to sustainable and efficient use of freshwater worldwide. The first is setting water footprint (WF) caps at the river basin level, aimed at preventing overshoot of limited natural endowments and to reconcile human freshwater appropriation with conservation. The second is formulating water footprint benchmarks per water-using activity, aimed at identifying reference levels of ‘reasonable’ WFs for specific water-using activities. This research investigates these two instruments in five different studies.
The first study quantifies maximum sustainable WF levels for all river basins in the world, using multiple state-of-the-art Global Hydrology models and Environmental Flow methods. The study proposes various WF caps that set an upper limit to aggregate WFs in a basin and their implications, thereby effectively quantifying humanity’s safe operating space in terms of freshwater consumption.
The next three studies of the thesis focus on efficient use of water. First, we quantify WF benchmarks of global crop production, using a newly developed model, Aqua21, that calculates WFs of major crops on a high spatiotemporal resolution at a global scale. The study reveals that large water savings can be made if producers of crops would reduce their WFs to benchmark levels. Moreover, the analysis shows that much of the blue water savings thus made can be achieved in severely water-scarce regions, thereby potentially alleviating blue water scarcity.
Second, we estimate WFs of manmade reservoirs worldwide and attributes that WF to a the various purposes of the reservoirs: hydroelectricity generation, irrigation, residential and industrial water supply, flood protection, fishing and recreation. The study found that reservoirs are large water consumers that add substantially to humanity’s blue WF.
In the third and last efficiency-focussed study we move from a global to a local perspective and zoom in on a case study on silk production in Malawi. The research analyzed the WF of mulberry shrubs (the leaves of which are fed to the silk worms) under various farm management systems, and compared these to crops usually grown in the area. The study thus informs farmers on water considerations when deciding which crops to grow.
Establishing and maintaining sustainable and efficient water consumption is a shared responsibility, where a role is to be played by each of the actors involved. Therefore, the last study focuses on an under-emphasized yet influential actor, namely institutional investors. In this study, a framework is developed and applied to assess to what extent investors incorporate water sustainability targets in their investment decisions. Although the results show that concerns over widespread water scarcity and inefficient water use are largely invisible to them, the study provides investors with systematic handles to give substance to their improvement efforts.
Research on setting WF caps at the river basin level and formulating WF benchmarks for water-using activities is in its infancy. There are few practical examples of uptake in policy, despite a sensed urgency to act by many actors. This research presents various new studies on WF caps and benchmarks as well as several rich datasets that can be used in future research. It thereby significantly advances the discourse on how to transition to sustainable and efficient use of freshwater resources worldwide.
