Downstream Component
IQWP Ensemble Parameters (Temperature, Conductivity, pH, DO, etc.) - Downstream integrated quality-of-water project (DIQWP) sampling has been aimed primarily at establishing a robust record of mainstem temperature data under different flow conditions. Much of the downstream water quality program has been undergoing redesign and reconsideration in light of the recent PEP report and the development of a new five-year plan for the Integrated Quality-of-Water Program presented to the TWG in 2002.
In the mainstem, during the Low Steady Summer Flows of 2000, the highest temperatures in at least the last decade were observed in Grand Canyon, reaching nearly 20 deg. C at Diamond Creek. This reflected a warming of 10 deg. C above Glen Canyon Dam release temperatures, compared to a warming of 5 deg. C during the high steady flows of 1997, showing a strong inverse correlation of in-stream warming with discharge level. Warming of over 7 deg. C above main channel river temperature occurred in some main channel near-shore environments; in backwater habitats, warming of over 12 deg C above river temperatures was observed. This near-shore warming was dependent on incident solar radiation, and little or no water velocity.