Water Body Name: | Arroyo Mocho |
Water Body ID: | CAR2043008020010905115519 |
Water Body Type: | River & Stream |
Lines of Evidence (LOEs) for Decision ID 7571 |
LOE ID: | 4789 |
Pollutant: | Temperature, water |
LOE Subgroup: | Pollutant-Water |
Matrix: | Water |
Fraction: | None |
Beneficial Use: | Cold Freshwater Habitat |
Aquatic Life Use: | Wildlife Habitat |
Number of Samples: | 12 |
Number of Exceedances: | 6 |
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING |
Data Used to Assess Water Quality: | Comprehensive water quality assessment was conducted at the Arroyo Mocho watershed as part of SWAMP assessment. Continuous field monitoring at 15 minute increments of temperature, dissolved oxygen, pH and specific conductance was conducted to determine temporal variability in basic water quality at five locations throughout the watershed.
The measured temperatures ranged from 6.1°C to 27.72 °C and varied with season and location. The 17 °C criterion for steelhead was exceeded in 6 out of 12 deployments. High water temperatures exceeding 24 °C, that is a maximum short exposure temperature for survival of salmonids (EPA 1977) were also measured at three monitoring locations at lower and upper reaches of the Creek during spring and summer seasons. At the monitoring site in the lower reach of the Arroyo Mocho Creek high temperature persisted for up to 5.75 hours during spring while at the middle and upper reach it lasted from 5 to more than 9 hours. |
Data Reference: | Water Quality Monitoring and Bioassessment in Nine San Francisco Bay Region Watersheds: Walker Creek, Lagunitas Creek, San Leandro Creek, Wildcat Creek/San Pablo Creek, Suisun Creek, Arroyo Las Positas, Pescadero Creek/Butano Creek, San Gregorio Creek, and Stevens Creek/Permanente Creek. Oakland, CA: Surface Water Ambient Monitoring Program, San Francisco Bay Regional Water Quality Control Board |
Water Quality Objective/Criterion: | Temperature objectives for enclosed bays and estuaries are specified in the "Water Quality Control Plan for Control of Temperature in the Coastal and Interstate Waters and Enclosed Bays of California" including any revisions to the plan. In addition, the following temperature objectives apply to surface waters: The natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Water Board that such alteration in temperature does not adversely affect beneficial uses.
The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature. |
Objective/Criterion Reference: | San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan) |
Evaluation Guideline: | Sullivan et al. (2000) reviewed a wide range of studies incorporating information from laboratory-based research, field observations, and risk assessment approaches and developed criteria for assessing temperature risk to aquatic life. The 7-day mean temperature (maximum value of the 7-day moving average of the daily mean temperature) of 14.8°C was established as the upper threshold criterion for coho salmon and 17.0°C for steelhead trout. The risk assessment approach used by Sullivan et al. (2000) suggests that temperatures exceeding the above thresholds will cause 10% reduction in average fish growth compared to optimal conditions. |
Guideline Reference: | An Analysis of the Effects of Temperature on Salmonids of the Pacific Northwest with Implications for Selecting Temperature Criteria |
Spatial Representation: | Temperature was measured at five sites located on the mainstem of Arroyo Mocho Creek. The highest temperatures were recorded at the monitoring location southeast of Livermore in August 2004. High temperatures also occurred in the lower reach of the Creek during the spring season of 2004. |
Temporal Representation: | In 2004 and 2005 the SWAMP Program performed continuous monitoring of temperature at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (5 sites), spring (5 sites), and summer dry season (2 sites). |
Environmental Conditions: | |
QAPP Information: | All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002). |
QAPP Information Reference(s): | Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version) |