Water governance and stakeholder engagement are receiving research attention for their role in formulating and implementing solutions to the world’s critical water challenges. The inspiration for this Special Issue came from our desire to provide a platform for sharing results and informing the global water governance community about the wealth of excellent interdisciplinary and transdisciplinary research and projects being carried out around the world. The 20 peer-reviewed papers collected in this Special Issue have been grouped into three categories: stakeholder engagement, tools for building water management and governance capacity, and perspectives on water management and governance. Following a brief summary of the papers, concluding remarks that reflect on what the papers, taken as a whole, contribute to our understanding are provided.

Stakeholder participation is a foundation of good water governance. Good groundwater governance typically involves the co-production of knowledge about the groundwater system. Models provide a vehicle for producing this knowledge, as well as a “boundary object” around which scientists and stakeholders can convene the co-production process. Through co-production, stakeholders and scientific experts can engage in exchanges that create system knowledge not otherwise achievable. The process involves one-way transfer of information, active two-way conversations, and integration of multiple kinds of knowledge into shared understanding. In the Upper Santa Cruz River basin in Arizona, USA, the University of Arizona Water Resources Research Center (WRRC) convened a project aimed at providing scientific underpinnings for groundwater planning and management. This project, entitled Groundwater, Climate, and Stakeholder Engagement, serves as a case study employing the first two stages of knowledge co-production using a hydrological model. Through an iterative process that included two-way communication, stakeholders provided critical input to hydrologic modeling analyses. Acting as a bridging organization, the WRRC facilitated a co-production process, involving location-specific and transferability workshops, which resulted in new knowledge and capacity for applying the model to novel problems.

The state of Arizona has created a unique water management tool in response to water scarcity and population growth. In 1994, Arizona’s state legislature authorized the creation of long-term storage credits (LTSCs) through aquifer recharge with Colorado River water or effluent. LTSCs represent a quantity of water the owner is entitled to recover and use once the water has remained underground for a full calendar year. Owners may also sell their LTSCs to others by a simple credit account transfer. LTSCs have emerged as a tool for water users to achieve compliance with groundwater regulations in the most populated areas of the state, such as the cities of Phoenix and Tucson. Using data collected and maintained by the state’s water resources regulator, this study examines sales of LTSCs to reveal patterns of market-based transactions. Analysis of 23 years of public records shows several trends: (1) LTSC transactions have been increasing since 2003; (2) municipal water providers and investment firms have been active participants in LTSC transactions; (3) the greatest transaction volumes involve governmental entities established by state law with groundwater recharge and replenishment obligations. This analysis reveals how LTSCs have contributed to achieving water policy goals in Central Arizona and suggests how the LTSC system can be used to improve water use efficiency through voluntary redistribution in other water scarce regions.

In Arivaca, Arizona, groundwater isotope measurements (stable O and H, tritium, and carbon‐14) were made in conjunction with water level measurements and climate data. Recharge is predominantly young (post‐1950) and is mainly from summer monsoon precipitation. Following a five‐month period of unusually low δ¹⁸O and δ²H in precipitation in 2014–2015, corresponding shift in groundwater δ¹⁸O and δ²H was observed only at a site with recently built gabions. Water levels near the basin outlet increase in summer following periods of high storm frequency. Water levels also rebound in winter, possibly because of cessation of transpiration. The young groundwater is vulnerable to climate change, e.g., to protracted periods with summers that are drier or hotter than normal. Rapid assessment of groundwater and its connection to climate can provide valuable information to local water managers and citizens for whom more expensive studies are not feasible. Such assessments, based on relatively inexpensive isotope analyses and groundwater level data collected by volunteers, engage the community in management of its water resources. In Arivaca, the community responded to the results of the assessment with heightened interest in managing their water for sustainability and the construction of gabions to increase recharge from stormwater.