Drought conditions

I. Fall 2020

  1. Taylor, mean annual flow 10 cfs, was completely dewatered in fall 2020, as seen in the photo below.

  2. Flow subsequently returned to the stream channel, along with trout.

    Limiting | Drought | Post-fire

Drought completely dewatered Taylor, fall 2020

TaylorCrop2
 

II. July-August 2018, 2019, and 2020

  1. Flows measured in the main stem gave evidence of drought conditions during July-August 2018.

  2. The hydrological measurements are from the main-stem Rico station, 8422 ft, USGS location 09165000.

  3. Flow has been measured there since 1951.

July-August 2018, 2019, 2020, and historical flows

Rico 2018 Jul-Aug.gif
Rico 2019 Jul-Aug.gif
Rico 2020 Jul-Aug.gif

A. Data​

  1. The July-August 2018 mean flow was the 2nd lowest over the period of record for that stream gage.

  2. It was 22 cfs, as compared with the historical mean flow of 122 cfs for July-August.

  3. At 20 percent of the historical value, the July-August 2018 mean flow signaled severe drought conditions.

  4. The first hydrograph below shows July-August 2018 flows in comparison with historical flows.

  5. As seen, flows during July-August 2018 temperature measurements trended well below historical values.

B. Comparison​

  1. The second and third hydrographs show July-August 2019 and 2020 daily flows.

  2. They were above historical values in 2019, except during the last week of August.

  3. Flows trended below historical values in 2020, except for a large July spike and a small one in August.

  4. Drought conditions are expected to become more frequent and intense as a result of climate change.

  5. Reduced flows can leave streams susceptible to temperature increases from ambient air and solar radiation.

  6. Statistical testing showed that 2018 water temperatures, measured during drought, were higher than in 2019.

  7. Refuge for thermal relief was available in tributaries and upstream in the main stem.

    Limiting | Drought | Post-fire