In recent decades, public and private environmental entities have been purchasing or leasing water rights across the Western United States (U.S.) in efforts to restore river flows and aquatic ecosystems. The need to pay for flow restoration arises from the fact that state governments did not begin to reserve water for instream purposes until the 1970s, long after water rights had become over‐appropriated and flows were substantially depleted in most rivers. As a consequence, flow depletion has become the leading cause of fish endangerment in the U.S., including the imperilment of two‐thirds of all native fish species in the Colorado River system. This paper takes stock of the progress made in buying water for the environment, specifically by reviewing and analyzing more than 50 transactions executed by public and private entities and the sources of funding underpinning these transactions. We conclude that nongovernmental actors — such as environmental organizations and state water trusts — are integral to regional efforts to restore river flows; these nongovernmental actors executed more than two‐thirds of the transactions we documented. However, we also conclude that the long‐term success of these nongovernmental actors depends upon the availability of sustained public funding that enables them to build capacity and engage in the large number of transactions needed to restore flows across each state.

中文翻译：

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买我一条河：购买水权以恢复美国西部的河流流量

近几十年来，公共和私人环境实体一直在美国西部购买或租赁水权，以努力恢复河流流量和水生生态系统。州政府直到1970年代才开始为河溪目的储备水，这是由于水权被过度使用且大部分河流的水量基本上耗尽之后，州政府才开始为河水的蓄水付费。结果，水流枯竭已成为美国鱼类濒危的主要原因，其中包括科罗拉多河系统中所有本地鱼类物种的三分之二受到威胁。本文总结了在为环境购买水方面取得的进展，特别是通过审查和分析由公共和私人实体执行的50多项交易以及作为这些交易基础的资金来源。我们得出的结论是，非政府参与者（例如环境组织和州水信托基金）对于恢复河流流量的区域性努力不可或缺。这些非政府参与者执行了我们记录在案的三分之二以上的交易。但是，我们还得出结论，这些非政府行为者的长期成功取决于能否获得持续的公共资金，使他们能够进行能力建设并参与大量交易，以恢复各州的资金流动。我们得出的结论是，非政府参与者（例如环境组织和州水信托基金）对于恢复河流流量的区域性努力不可或缺。这些非政府参与者执行了我们记录在案的三分之二以上的交易。但是，我们还得出结论，这些非政府行为者的长期成功取决于能否获得持续的公共资金，使他们能够进行能力建设并参与大量交易，以恢复各州的资金流动。我们得出的结论是，非政府参与者（例如环境组织和州水信托基金）对于恢复河流流量的区域性努力不可或缺。这些非政府参与者执行了我们记录在案的三分之二以上的交易。但是，我们还得出结论，这些非政府行为者的长期成功取决于能否获得持续的公共资金，使他们能够进行能力建设并参与大量交易，以恢复各州的资金流动。