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Freshwater is essential to human communities and stream ecosystems, and governments strive to manage water to meet the needs of both people and ecosystems. Balancing competing water demands is challenging, as freshwater resources are limited and their availability varies through time and space. One approach to maintain this balance is to legally mandate that a specified amount of stream flow be maintained for stream ecosystems, known as an environmental flow. But laws and regulations do not necessarily reflect what happens in practice, potentially to the detriment of communities and natural systems. Through a case study of Puerto Rico, we investigated whether water management in practice matches legislative mandates and explored potential mismatch drivers. We focused on two governance targets—equitable allocation and water use efficiency—and assessed whether they are enshrined in the law (de jure) and how they manifest in practice (de facto). We also explored agency accountability through identifying agency structure and whether consequences are enforced for failing to carry out responsibilities. Our results indicate there are mismatches between how freshwater is governed by law and what occurs in practice. This study suggests that agency accountability may be necessary to consider when developing environmental flow legislation that will effectively achieve ecological outcomes. 

Abstract Freshwater migratory shrimp in Puerto Rico depend on watershed connectivity, from stream headwaters to the ocean, to complete their life cycle. Moreover, shrimp populations in different watersheds are known to be connected in an island‐wide metapopulation. However, low‐head dams paired with water intakes on streams draining the El Yunque National Forest (EYNF) reduce streamflow. Here, we examine the cumulative effects of low‐head dams on shrimp habitat connectivity over 37 years across seven EYNF watersheds. We calculate total and refugia habitat connectivity (where refugia habitat is defined as predator‐free upstream reaches above waterfalls >5 m in height) at a monthly time step using a habitat‐weighted index of longitudinal riverine connectivity, which incorporates location and operation of water intakes and streamflow variability. Findings indicate total and refugia habitat connectivity declined over 37 years (by 27% and 16%, respectively) as additional water intakes have been placed in lower reaches of watersheds. On a monthly time step, the proportion of streamflow withdrawn has the largest effect on habitat connectivity, with the result that connectivity is ~17% lower during drought years than in nondrought years and ~7% lower in dry compared with wet seasons. Our analysis of this long‐term dataset highlights how cumulative effects of low‐head dams paired with water intakes have reduced shrimp habitat connectivity. These results underscore the importance of reducing existing withdrawal rates in EYNF, and locating intakes where effects on connectivity are minimal, if conserving shrimp habitat is a management objective.