Bring Stoney Home – How Much Water Do We Need?

 

Bring Stoney Home !!

Why won’t Stoney come home? Exactly how much water do we need to bring trout and stoneflies back to the Denver South Platte?

Carson Nature Center Reach before R2CROSS reconfiguration.

 

    Interview with Stoney, the homeless Denver South Platte Stonefly. He was driven from his home by the flood of 1965 and was then unable to live in the reconstructed, flattened and widened Denver South Platte below Chatfield Reservoir. Stoney is quite interested in Denver Trout Unlimited’s push for aquatic restoration and wants to make sure we understand the conditions under which he would return. 

    The Drift – Stoney, why don’t you just come back home?

     Stoney – I can’t live in a place without enough water. The flows in the Denver South Platte since construction of the Chatfield Reservoir are all over the map. What if they cut off your oxygen every couple of weeks, raised the temperature of your condo so high your sperm count dropped, and lowered the humidity to the point where 3 times a day moisturizer couldn’t  keep you from looking like an alligator? You wouldn’t go back to a place like that either.

     The Drift – But Stoney, we reconstructed the stream bed in Carson Nature Center and we’ve got a big project going on at the Overland Park stretch to improve the channels. What are you waiting for?

      Stoney – Water.  There are great looking dry stream beds in Arizona, but I’m not moving there either. Colorado developed a great habitat method for determining what I need. It’s called R2CROSS and you can use it to calculate the flow at a particular riffle where I can survive and be healthy. If I’m healthy, the trout you love will be healthy. 

      The Drift – You mean you need an actual number of cubic feet per second before you’d come home? Why?

        Stoney –  I’ll make it easy for you. As runoff from snow or rain starts to fill a stream it gets deeper and deeper of course. As it gets deeper the velocity of the water increases due to gravity. This is important for you to remember when you are wading. Water that you waded yesterday that came up to your knees will be moving much faster today when it comes up to your thighs. At some point additional depth will really jack up the flow and you’ll be at flood stage even though the stream is just a fraction deeper. Flood stage really wrecks my home life which can be a good thing if there hasn’t been a flushing flow for awhile. On the other hand if there is not a minimum stream velocity of about 1 ft/sec, a reasonable depth, and an interesting stream bottom my lifestyle will be cramped to extinction.

     The Drift – Can’t you just give us a number and we’ll go out and buy it?

     Stoney – No you dodo. The minimum flow I need depends on the slope of the stream bed, the depth of the water, the width of the stream, and the season. To calculate it an engineer can use the R2CROSS method. This method is based on US Forest Service Region 2 stream habitat studies in the Rocky Mountain and focuses on the cross section of the stream at a particular point. R2CROSS, get it? It specifies the depth, velocity, bank full wetted perimeter %, and stream top width necessary for fish passage, egg incubation and food production. R2CROSS is accepted by the Colorado Water Conservation Board and the Water Courts for calculations of in stream minimum flows necessary for me to come back. You actually look at the same factors when you decide where to cast a fly  to a trout lying in a feeding zone. 

     The Drift – Ok end of story. What do you need and when will you be come back home?

     Stoney – Denver Trout Unlimited commissioned an engineering study to figure that out. The Chatfield Dam, since 1972 has only been used for flood control but it could be the magic ingredient that could release borrowed or leased water into Carson Nature Center to allow me back home. The Stonefly family is excited about it. Some trout are already there. Stay tuned.

     The Drift – Is it one minimum flow for the whole stream? This sounds too easy.

      Stoney – I’m only really interested in my own neighborhood. In the Carson Nature Center stretch you changed the width of the stream from 88 feet to 40 feet, increased the depth, and the slope in the riffle section from 1/4% to 1%.  I love it in this area. When you change the cross section of the stream, add in some curves and  increase the slope you actually  REDUCE the amount of water I need flowing by. I can live here on modest flows. After the flood control project of 1972, I just couldn’t survive the winter here so I had to move out along with most of the trout.

Reconstructed stretch of Carson Nature Center – Stoney and Trout love this section.

       The Drift – The Overland Park stretch will give you another healthy stretch. 

        Stoney – Great, but don’t quit now. You need to connect those two areas and secure the R2CROSS minimum flows in each renovated section. I’ll come back but if you want a healthy Denver South Platte through the city, just  keep working.