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

An examination of the plotted correlations indicate that El Nino years have a tendency to
supply `adequate' (80 % of normal and above) precipitation with very dry springs tied to
La Nina years (please see Data Appendix for more information).
Table 2. Summary of Apr. -Jun. Precipitation/HCI Relationships (dark `X' indicates a relatively
strong relationship and light 'X' indicates a relatively weak relationship)
C - Summer Precipitation (July- September) — Sin2le Seasonal Totals
Districts 26, 20 and 35
Unfortunately, little useful information was gleaned from this segment of
information as the connections between the HCl variables and all three districts were
minimal, at best. This factor may show that even in dry years these basins may have some
average precipitation production to help overcome water shortages.
D - Summer Precipitation — Days with 0.10" or greater (May 1- September 15)
Due to data requirements to analyze this variable only two stations in the basin
(Alamosa and Great Sand Dunes) met this requirement. An analysis of the values
indicates a minimal useful `connection at Great Sand Dunes, on the east side of the
valley. However, at Alamosa there was some relationship with the AMO with negative
values correlating somewhat well with average /above average days with 0.10" of
precipitation or greater and vice versa for negative AMO values. Given the lack of
stations to analyze with this data, some caution is offered to using this data as a potential
`planning' tool rather than information of note.
E — Naturalized Stream flow Volume (April — September)
One of the most important factors in the hydrologic cycle that is observed in the
state of Colorado is surface water. This section will briefly outline the `resulting' factor
of winter snows and spring precipitation and how directly calculated naturalized runoff
might be influenced by the HCl variables. Also the temporal aspect of `how' runoff
might be influenced by the HCl variables will be discussed.
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PDO
MEI
SOI
Nino 3.4
NAO
AMO
District 26
X
District 20
X
X
District 35
X
X
C - Summer Precipitation (July- September) — Sin2le Seasonal Totals
Districts 26, 20 and 35
Unfortunately, little useful information was gleaned from this segment of
information as the connections between the HCl variables and all three districts were
minimal, at best. This factor may show that even in dry years these basins may have some
average precipitation production to help overcome water shortages.
D - Summer Precipitation — Days with 0.10" or greater (May 1- September 15)
Due to data requirements to analyze this variable only two stations in the basin
(Alamosa and Great Sand Dunes) met this requirement. An analysis of the values
indicates a minimal useful `connection at Great Sand Dunes, on the east side of the
valley. However, at Alamosa there was some relationship with the AMO with negative
values correlating somewhat well with average /above average days with 0.10" of
precipitation or greater and vice versa for negative AMO values. Given the lack of
stations to analyze with this data, some caution is offered to using this data as a potential
`planning' tool rather than information of note.
E — Naturalized Stream flow Volume (April — September)
One of the most important factors in the hydrologic cycle that is observed in the
state of Colorado is surface water. This section will briefly outline the `resulting' factor
of winter snows and spring precipitation and how directly calculated naturalized runoff
might be influenced by the HCl variables. Also the temporal aspect of `how' runoff
might be influenced by the HCl variables will be discussed.
13