Securing water for the environment is a challenge, particularly in water-stressed regions of the world with high human water demands for agriculture and cities. Despite legal and scientific mandates to protect the economic, social, and cultural heritage benefits that environmental water aims to deliver, there is often strong political opposition to increasing water allocations for the environment. Such resistance is grounded in perceptions that environmental water limits current and potential access to human uses, especially for agriculture and drinking water systems. Yet, the nature of such trade-offs are rarely quantified in a robust manner. Further, the potential role of environmental water in enhancing social equity and building climate-resilience is generally over looked. Tools are needed to better quantify the costs and benefits of environmental water allocations. Here, we describe a collaborative modeling approach to support inclusive and equitable water management in California, USA. Through a participatory research process, we have designed alternative water future scenarios using a statewide systems operations model. We evaluate a diverse range of scenarios, including those in which environmental water requirements are enhanced in the state’s major rivers. An evaluation of scenario outcomes reveals that enhanced environmental water allocations result in localized impacts to specific agricultural water users, but has limited effects on community water systems and overall system water supply reliability. Environmental flow scenarios are effective at shifting indicators of ecosystem health out of critically at risk states to more stable conditions, suggesting climate resilience benefits. Overall, the work demonstrates that environmental water allocations can be integrated in complex water systems and provides a road map for balancing the needs of multiple of water users, while also considering the consequences of water allocation decision-making for equity and resilience.