Criteria, acronyms

I. Criteria, standards

A. Water temperature

  • 62.6 F, Colorado (CO) chronic criterion.

  • 71.1 F, CO acute criterion.

  • 64.6 F, brook trout chronic criterion.

  • 64.9 F, rainbow trout chronic criterion.

  • 67.3 F, brown trout chronic criterion.

​B. Water quality​

  • pH:​ 6.5-9.0.

  • Dissolved oxygen (DO): 6.0 mg/l; 7.0 mg/l, during spawning.

  • E. coli: 126 per 100 ml.

  • Nitrate: 10 mg/l.

  • Ammonia: calculated based on pH.

  • Metals (arsenic, cadmium, copper, lead, manganese, silver, zinc): calculated based on hardness.

  • Selenium: 4.6 ug/l.

  • Total nitrogen as nitrate: 1.25 mg/l (interim standard).

  • Total phosphorus as phosphate: 0.11 mg/l (interim standard).

  • (Total coliform: 200 per 100 ml).

II. Acronyms, abbreviations​

A. General

  • CCR, Code of Colorado Regulations.

  • CS-1, cold stream tier 1.

  • TVS, table value standard.

B. Water temperature

  • 30T, 30-minute temperatures.

  • WAT, weekly average temperatures.

  • MWAT, maximum weekly average temperature.

  • TAT, two-hour average temperatures.

  • MTAT, maximum two-hour average temperature.

  • DM, daily maximum; same two-hour calculation as MTAT.

C. Water quality

  • DO, dissolved oxygen.

  • E. coli, Escherichia coli.

  • M&E, monitoring and evaluation.

  • mg/l, milligrams per liter, equivalent to parts per million.

  • ug/l, micrograms per liter, equivalent to parts per billion.


  1. Code of Colorado Regulations, Water Quality Control Commission, 5 CCR 1002-31, Regulation No. 31, "The Basic Standards and Methodologies for Surface Water."

  2. Code of Colorado RegulationsWater Quality Control Commission, 5 CCR 1002-34, Regulation No. 34, "Classifications and Numeric Standards for San Juan River and Dolores River Basins."

  3. Todd, A. S., M. A. Coleman, A. M. Konowal, M. K. May, S. Johnson, N. K. M. Vieira, and J. F. Saunders, "Development of New Water Temperature Criteria to Protect Colorado's Fisheries," Fisheries, vol. 33, no. 9, pp 433-443, 2008.