Thu, Sept. 19

Drought conditions not drying up<br><i>Discussion highlights impact on water resources</i>

Photos by Steve Ayers

JULIO Betancourt has been a USGS research scientist for 21 years. His studies indicate that surface temperatures of the oceans control drought conditions throughout the world.

If USGS research scientist Julio Betancourt is correct, the answer may lie in the fact that the American Southwest experienced one of several mega-droughts at the time.

According to Betancourt, the mega-drought of the late 16th century was one of the worst in the last 1,500 years to affect the Southwest and he estimates that it lasted 40 years.

Betancourt, along with Charlie Ester, manger of the Salt River Project’s (SRP) Water Resource Operations, spoke Thursday to members of the Verde Watershed Association about the current drought and the history and predictability of future droughts.

Speaking first to the standing-room-only crowd, Ester gave an overview of the current drought and its impact on water resources in the Salt and Verde River watersheds, along with its impact on the Colorado River.

Ester pointed out that the current drought began in the summer of 1995, and with the exception of 1998, every year since has seen below average rainfall and runoff over the Salt and Verde River watersheds.

Four of those years, 1996, 1997, 2000 and 2002 are among the five driest years on record for the state. In fact, it is estimated that 2002 was the driest year in Arizona in the last 1,400 years.

"Most people don’t know it, but SRP came about as a result of a similar drought that affected central Arizona at the turn of the last century," said Ester.

The drought has caused Salt River Project to cut allocations of water to its customers for the last two years in a row.

"This has only happened for two consecutive years once before, in 1946-1947," Ester pointed out.

Ester’s presentation went over the record of wet and dry cycles for the last century, pointing out that "what we have observed is only a snapshot" of the longer trend of drought and wet cycles.

"If we look at tree ring evidence for the last 1,500 years we see compelling evidence that we have been living in a relatively wet period for the last century," said Ester.

"It is during this period, especially the wet period of 1900 to 1930, that we formulated our water allocations for the Colorado River, and as a result, we have over allocated that resource,’ said Ester, "We have a built-in water crisis."

Long-term evidence derived from tree rings indicates the average flow of the Colorado River closer to 13 million acre feet per year, not the 16.5 million that is currently allocated.

"It’s not the drought so much as it is that we don’t have enough water during normal times.

"Arizona, unfortunately, with its junior water rights, will be among the first to suffer the effects of a long-term drought," said Ester.

Estimates show that 25 million people currently live in the Colorado River Basin, and predictions are that the population will rise to 40 million by 2040.

Ester pointed out that more evidence is coming forward to show that ocean water surface temperatures cause droughts, and that the influence of warm water in the North Atlantic Ocean is largely responsible for the current drought conditions.

That evidence and the conclusions resulting from it has been the work of the second speaker, Julio Betancourt.

Betancourt is research scientist and author of numerous scientific papers dealing with the causes of climate variations and their influence on droughts in North America.

His presentation entitled "Climatic and Historical Context of Severe Drought in the Western United States" was a technical overview of the studies he has worked on over the last 20 plus years.

Betancourt’s investigations into climate changes have shown that there is interconnectivity between the surface temperatures of ocean water and the amount of precipitation.

The surface temperatures used in his studies refer to the temperature variations upper three feet of the ocean surface.

"This upper 1 meter of is a signature of a larger cycle of ocean currents known as the thermalhaline circulation," said Betancourt, "We don’t understand how the oceans work, but we can observe the surface expression of this conveyor belt effect of moving water."

A pocket of water moving in the thermalhaline cycle can take 1000 years to rotate through, according to Betancourt.

The rising and falling of the oceans’ surface temperatures causes changes in the jet stream, barometric pressure differences and when combined with certain combinations of surface temperatures variations in different oceans around the world, it causes drought.

Betancourt’s studies indicate that that the largest influence on weather in the southwest is the surface water temperatures in the North Atlantic, followed by surface water temperatures in the North Pacific.

The well-known "El Nino" off the coast of South America does not have as much influence on Arizona’s weather as the other two.

According to Betancourt, when the North Atlantic is warm and the North Pacific is cold, Arizona will be in a drought.

Various combinations of cold or warm surface waters in the Atlantic and Pacific result in different climatic trends in different regions of North American Continent, according to Betancourt.

"Primarily, when it is warm in the north Atlantic, like now, there is less precipitation on the Colorado River Basin," said Betancourt, "and when it heats up, it tends to stay that way for some time — usually decades."

Betancourt’s investigations used tree ring evidence to validate his conclusions.

He took tree ring samples from the last 100 years and made predictions as to what the surface water temperatures would be at various locations around the world. When those predictions were compared against actual evidence from instruments, his predictions proved to be incredibly accurate.

Betancourt studied tree rings from various areas in the west and created an overlapping history of the tree rings going back 1,500 years. From that history he was able to reconstruct a climatic history of the area.

"These relationships between ocean water surface temperatures and precipitation are real," said Betancourt, "and we should pay attention."

Betancourt recommended that we take advantage of this ability to predict drought cycles and use that information to evaluate the long-term risk of decisions along with the long-term consequences.

"What Julio is saying is that we should take advantage of surpluses when they occur, but we should learn to live at a level that is sustainable over the longer period," said Ester.

Both Betancourt and Ester agree that the current drought will last for sometime to come.

"I would say you should expect it to last until at least 2010," said Ester, "I can’t say that for sure, but I think we should prepare for it."

"The waters of the north Atlantic don’t change temperature but every few decades," said Betancourt, "and evidence points out that historically we have had several long-term mega-droughts."

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