Taking stock of caps on water use: fostering sustainability or falling short?

Balancing water demands with available supplies on a scale that enables sustainable water use constitutes a complex governance challenge. Water managers face the daunting task of balancing water demands amidst variable supplies impacted by climate change and unsustainable extraction leading to drying lakes, depleted rivers, and shrinking aquifers. Traditionally, water managers have focused on bolstering water supplies to meet rising demands. However, this strategy is failing in many regions because of exorbitant costs, alongside environmental, legal, and political obstacles. Despite growing focus, no single solution ensures sustainable water use. Among governance options, capping water extractions holds theoretical promise, but evidence of their efficacy is limited and inconsistent due to shortcomings in their implementation, as detailed in this study. Our paper contributes to the literature on water governance by organizing empirical evidence of different types of caps. We developed a database to analyze 47 cases spanning 14 countries utilizing various types of caps (e.g., volumetric, water level limit, and moratorium) applied to different sources of water (e.g., aquifers, lakes, and rivers). We assess their efficacy in terms of enforceability, adaptability, and performance. We illustrate the strengths and weaknesses of capping as a water management strategy and offer recommendations to enhance its effectiveness.

• A global review of caps on water use provides the first stocktake of their challenges, opportunities, and pathways for recommendations to ensure sustainable water use.

• Caps, found in unexpected regions, indicate broader applicability beyond traditionally water-scarce areas.

• Caps often transform over time, initially appearing as one type (e.g., moratorium) before becoming volumetric limits.