This chapter provides an overview of water rights management in Texas, emphasizing policy and legal aspects of environmental flow protection, particularly freshwater inflows. It seeks to summarize the regulatory setting in which freshwater inflow science has been, and is being, applied. Rights to use state-owned surface water have been recognized since the 1800s, with regular consideration of environmental flow beginning only in 1985. Because older rights have the first claim to water, that legacy of older, perpetual rights lacking flow protections creates challenges for maintaining adequate flows. In 2007, the Texas Legislature enacted Senate Bill 3 seeking a comprehensive approach for flow protection. That approach, which remains only partially implemented, includes setting aside for flow protection reasonable amounts of water not already authorized for use, adopting flow standards with flow-protection requirements for new permits and targets for proactive protection efforts, and pursuing proactive strategies for voluntary efforts to move some existing rights to flow protection. It also provides for adaptive management to continue refining those elements. Following an initial flurry of activity through 2014, implementation has largely stalled. Recent developments may lead to renewed activity and a chance to address important shortcomings in flow protection.