Economists argue that transferable water rights can move scarce water toward users willing to pay more for it. A legal scholar accepts that trades may reduce some waste but emphasizes that a transaction between buyer and seller can affect people and ecosystems outside the contract. [She concedes that prices can reveal competing private demands, yet notes that a river reach left dry has no buyer able to bid on behalf of habitat, downstream culture, or water quality.] The scholar therefore supports trading only after minimum flows and third-party protections are defined.