Groundwater is a vital common pool resource that supplies nearly half of all water for domestic use, one-quarter of irrigation water, and one-third of industrial water supply globally. Groundwater reserves can buffer against variable rainfall, drought, and mounting climate change impacts. However, many groundwater systems are threatened by problems including depletion, contamination, and waterlogging. Existing institutions are often inadequate to effectively govern a shared resource that is effectively invisible, complex and hard to understand, and used by multitudes of dispersed individuals, and where impacts, such as on baseflows for rivers downstream, may extend across long distances.