# Presentation: 911512

## Thirty Million People,
Seven States,
One Colorado River

**Seven States,**
**One Colorado River**

**Eric Kuhn**
**General Manager, CRWCD**
**Glenwood Springs, CO**

***November 15, 2005***

**www.crwcd.org**

## Thirty Million People, Seven States,Two Countries, Ten Indian Tribes, Five Endangered Fish and One Colorado River  

***How should river managers deal with climate variability and change?***

## Colorado River Basin

## The Colorado River System

**As a desert river, the flow is modest. It is about the same as the Hudson River. **
**Colorado River water is used in the seven basin states and the Republic of Mexico. **
**The Colorado River is a source of municipal water for Las Vegas, Phoenix, Tucson, the Colorado Front Range, the Wasatch Front, Albuquerque and the Southern California Coastal Plain.  Exports are a major use.   **

## The Colorado River System (con’t)

**Except in wet periods like the early 1980’s all of the available water is used and not a drop makes it to the Gulf.**
**The Colorado River is highly regulated. System storage is about four times the annual discharge.  **

## The Colorado River System (con’t)

**The Colorado River Ecosystem is under severe stress; endangered fish, Grand Canyon adaptive management, salinity and selenium.**
**Recreation and hydroelectric power generation are very important to the region. **
**Water use is allocated and governed by the “Law of the River.”**

## Two Basic Types of Water Management Decisions 

**Short Term - primarily operational decisions **
**Long Term - primarily planning, investment and regulatory decisions. **

## Short Term Management Decisions  

**Climate products used by water agencies:**
**CPC seasonal and monthly forecasts**
**Western Water Assessment**
**CLIMAS**
**Colorado River forecasts and models**
**Some independent work**
**   **

## Long Term Management Decisions

**   ****An example of a long term regulatory decision now facing the Secretary of Interior is the formal development of shortage criteria for the operation of Lake Mead. **

## The First Law of Hydrologic Planning: 

**“****The future will look like the recent past.” *******

## The First Flaw of Hydrologic Planning:

**Reclamation is using 1906-2000 for the development of shortage criteria for Lake Mead.   **
**Reclamation Western Colorado Area Office is using 1975-2004 for the development of operating criteria for Blue Mesa Reservoir.  **
**Denver Water uses 1947-1991 for its planning decisions.**
**The Colorado River District Uses 1953-2004 for our water marketing decisions. **

*** No two hydrologists use          the same recent past.**

## Fundamental Problem

**   ****What if future hydrology on the Colorado is different than the past? **

**A modest change could create significant problems:**
** ****Based on the 1906-2000 hydrology and modest upstream growth, future shortages are predicted to be rare.**
** ****A 10% reduction in flow at Lee Ferry could fundamentally alter that conclusion; shortages could become the normal condition.   **

## What can climate science do to     improve water management decisions? 

**Suggestions:**
**1. Develop paleohydrology: reconstruct stream      flows from the distant past. **

**Couple these long term reconstructed flow records with climate conditions.**
**Break the “voodoo-hydrology” barrier. **
***Are there some answers that water management agencies simply don’t want to hear?*****   **

## What can climate science do...?

**Suggestions (con’t) **
**2. Investigate the use of multidecadal indices (PDO & AMO) to give us better information about the immediate future (20 to 25 years) based on similar periods in the recent past. **
***   ******More research is needed to                    support this approach. ***

## The Colorado River Gage History can be Divided into 3 Distinct Periods

**The Colorado River Gage History can be Divided into 3 Distinct Periods**

- Period    I   Early 1900’s to about 1930

** **Period   II   1931 to the early 1970’s

- The undepleted flows, climate conditions, challenges and river politics during each of these periods were all very different.

## Slide 16

## Slide 17

## What can climate science do...?

**Suggestions (con’t) **
**3. Develop better models to predict stream discharge under different climate change scenarios. **

## Central Questions

***When will the science be ready to provide data with an acceptable level of confidence?***
***Should management agencies begin today to consider climate change alternatives based on worst case assumptions? ***

## Conclusion

**Use today’s available science to discuss possible future scenarios that consider the possibility that the future **
**MAY NOT look like the past.**
**Beginning a dialogue today based on      imperfect science is far better than no dialogue at all.                                                                          **

## For more information visit: www.crwcd.org

**For more information visit:**** ****www.crwcd.org**