Nonpoint source pollution measures in the Clean Water Act have no detectable impact on decadal trends in nutrient concentrations in U.S. inland waters

Abstract

The Clean Water Act (CWA) of 1972 regulates water quality in U.S. inland waters under a system of cooperative federalism in which states are delegated implementation and enforcement authority of CWA provisions by the U.S. Environmental Protection Agency. We leveraged heterogeneity in state implementation of the CWA to evaluate the efficacy of its nonpoint source provisions in reducing nutrient pollution, the leading cause of water quality impairment in U.S. inland waters. We used national survey data to estimate changes in nutrient concentrations over a decade and evaluated the effect of state-level policy implementation. We found no evidence to support an effect of (i) grant spending on nonpoint source pollution remediation, (ii) nutrient criteria development, or (iii) water quality monitoring intensity on 10-year trends in nutrient concentrations. These results suggest that the current federal policy paradigm for improving water quality is not creating desired outcomes.

Evaluation of nutrient assimilative capacity in waterfowl impoundments: The role of environmental stressors

“…N and P are the most widespread stressors in these impaired water bodies (U.S. Environmental Protection Agency, 2017). Despite the fact that nutrient point sources have been better controlled over the past several decades, diffuse sources of N and P remain a persistent problem (Le Moal et al, 2019;Tomczyk et al, 2023;Wurtsbaugh et al, 2019).…”

Edge-of-Field Runoff Analysis following Grazing and Silvicultural Best Management Practices in Northeast Texas

“…Despite decades of remediation efforts since the adoption of the Clean Water Act in the United States (US), nonpoint source (NPS) pollution remains a substantial challenge and contributor to surface water quality impairments [1][2][3]. NPS runoff is a major source of nutrient loading, leading to eutrophication and oxygen depletion in downstream waterbodies [3][4][5]. NPS runoff can also transport fecal indicator bacteria and pathogens, leading to recreational impairments [6].…”