Final.HCI.Report.HDR

• Title: Hydro-Climate Index Study
• Prepared For: CWCB & Colorado River WCD
• Prepared By: HDR Engineering Inc.
• Date: 12/28/2007
• County: Statewide
• State: CO
• Country: USA
• Weather Modification - Doc Type: Scientific Study

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gure 1-i. Relationship of the Mar-May. Foo vs. uistrict 32 Jun. -Isep. Basin Avg. Yrecip.
lvbr -1v1ay PDO vs. July -Sept Precipitaiton in District 32
(% of normal)
•
• ♦
♦
2.50 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50
Mar -May PDO Value
D - Summer Precipitation — Days with 0.10" or treater (Mav 1- September 15
For `growing season' days the number of days with 0.10" or greater was limited
to examining two stations with sufficient daily data for, Fort Lewis and Cortez.
A look at the calculated relationships reveals a couple of interesting items. For
Cortez, there was some relationship with the MEI/SOI (El Nino) and the number of `wet'
(> 0.10 ") days with El Nino years exhibiting a propensity for more days with moisture.
An example of this relationship with respect to Cortez can be seen in Figure 14. El Nino
years have a tendency to at least deliver a normal /near normal amount of days in the
basin with some scatter in La Nina year.
At Fort Lewis, the ENSO relationships were not as clearly apparent as they were
in Cortez however, the relationship with the AMO was worth noting as positive years
indicating that a normal number of `wet' days reach the average range with a number of
notable lack of `wet' days at the station.
Given the mixed results with two stations that appear to be in relatively close in
proximity both variable might be considered if attempting to make a determination on the
potential for `wet' days in the area for spring. Also, a little more analysis might be
undertaken at a future date to refine these relationships.
21
♦
•
♦ ♦
•
__ --- _ _ ____________________________?__
♦
•
♦
♦r
2.50 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50
Mar -May PDO Value
D - Summer Precipitation — Days with 0.10" or treater (Mav 1- September 15
For `growing season' days the number of days with 0.10" or greater was limited
to examining two stations with sufficient daily data for, Fort Lewis and Cortez.
A look at the calculated relationships reveals a couple of interesting items. For
Cortez, there was some relationship with the MEI/SOI (El Nino) and the number of `wet'
(> 0.10 ") days with El Nino years exhibiting a propensity for more days with moisture.
An example of this relationship with respect to Cortez can be seen in Figure 14. El Nino
years have a tendency to at least deliver a normal /near normal amount of days in the
basin with some scatter in La Nina year.
At Fort Lewis, the ENSO relationships were not as clearly apparent as they were
in Cortez however, the relationship with the AMO was worth noting as positive years
indicating that a normal number of `wet' days reach the average range with a number of
notable lack of `wet' days at the station.
Given the mixed results with two stations that appear to be in relatively close in
proximity both variable might be considered if attempting to make a determination on the
potential for `wet' days in the area for spring. Also, a little more analysis might be
undertaken at a future date to refine these relationships.
21
♦
•
•
♦
•
♦
♦r
♦
2.50 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50
Mar -May PDO Value
D - Summer Precipitation — Days with 0.10" or treater (Mav 1- September 15
For `growing season' days the number of days with 0.10" or greater was limited
to examining two stations with sufficient daily data for, Fort Lewis and Cortez.
A look at the calculated relationships reveals a couple of interesting items. For
Cortez, there was some relationship with the MEI/SOI (El Nino) and the number of `wet'
(> 0.10 ") days with El Nino years exhibiting a propensity for more days with moisture.
An example of this relationship with respect to Cortez can be seen in Figure 14. El Nino
years have a tendency to at least deliver a normal /near normal amount of days in the
basin with some scatter in La Nina year.
At Fort Lewis, the ENSO relationships were not as clearly apparent as they were
in Cortez however, the relationship with the AMO was worth noting as positive years
indicating that a normal number of `wet' days reach the average range with a number of
notable lack of `wet' days at the station.
Given the mixed results with two stations that appear to be in relatively close in
proximity both variable might be considered if attempting to make a determination on the
potential for `wet' days in the area for spring. Also, a little more analysis might be
undertaken at a future date to refine these relationships.
21