Daily (0000–2330 hours) mean, maximum, and amplitude of air temperature and water temperature measured at ∼1 km intervals in a ∼9 km reach of the Rio Grande below San Acacia Diversion Dam (Fig. 1), beginning on 31 May 18 and ending on 09 August 18. Cumulative total degree days (TDD) for daily mean (solid lines) maximum (dashed lines) for air along with the upstream (One) and downstream most (Eight) water temperature stations. Water temperature measured at 30-minute increments at the upstream and downstream most station beginning on 03 June 18 and ending on 27 July 18. Water temperature station name represents the approximate distance (km) below the dam. Air temperature (°C) was measured at approximately 30-minute increments from the Socorro municipal airport. The RGSM no acute lethal concentration (NALC) is designated by the horizontal blue dashed line.