---
kind: "unit"
title: "40"
title_heading: "Protection of Environment"
key: "chI/subchD/part131"
level: "part"
label: "Part 131"
heading: "Water Quality Standards"
release: "ecfr-current"
date: "2026-08-27"
url: "https://uscodex.org/cfr/40/chI-subchD-part131"
sections_count: 35
---

# Part 131 — Water Quality Standards

Title 40 C.F.R. — Protection of Environment › Chapter I — Environmental Protection Agency › Subchapter D — Water Programs

## Contents

- [Subpart A — General Provisions](/cfr/40/chI-subchD-part131-subpartA.md)
- [Subpart B — Establishment of Water Quality Standards](/cfr/40/chI-subchD-part131-subpartB.md)
- [Subpart C — Procedures for Review and Revision of Water Quality Standards](/cfr/40/chI-subchD-part131-subpartC.md)
- [Subpart D — Federally Promulgated Water Quality Standards](/cfr/40/chI-subchD-part131-subpartD.md)