Flood control during a drought

It seems a bit of an oxymoron at first blush, but it’s a serious concern. Last winter was a very wet one by desert standards. We received so much rainfall in fact that one Phoenix-area reservoir went from 60-something percent capacity to over 90% capacity in one week.

Experts were not ready to declare Arizona’s decade-long drought ended, but the relief those storms brought was real and necessary. Apparently though, it was also temporary:

Arizona turned red with extreme drought Tuesday after one of the driest winters on record left the state's high country draped with too much brown and not enough white.The official drought monitor was moved from "severe" to "extreme" based on nearly non-existent snowpack and brittle soil and vegetation conditions. The recent rain and snow had little effect on a drought that is now entering its 11th year.

Meanwhile, back in California they experienced a similar phenomenon here locally:

The Santa Ynez Valley has enjoyed an increase in late-season showers recently, turning the hillsides green and feeding local waterways."

Cachuma's full elevation is historically 750 feet, which was reached (Tuesday)," reported Matt Naftally, a hydrologist with the Santa Barbara County Flood Control District.

Last year, a particularly wet winter that included several destructive storms saturated the area in late December and early January, bringing more than 320 percent of normal precipitation to the county. All area reservoirs were filled to spilling, including Cachuma. The Santa Ynez River, typically a sandy riverbed, overflowed its banks during the Cachuma release in early January 2005."

In pretty much all places it was one of the top 10 years," said Naftally.


A year later and we’re still sitting at near 100% capacity. A series of spring storms through the month of March raised concern here locally about needing to repeat last year’s spills. It appears though that will not be necessary:

A little wet weather this early in the spring is not posing the same problems last year's torrential rainfall posed when water from Lake Cachuma had to be released constantly.

According to the National Weather Service (NWS), the heaviest rain storm this week was expected to have passed by Tuesday night, but some light showers remained possible this morning and early afternoon. The NWS forecast called for one to two inches of rain in this storm for the coast and valleys and three to four inches for the mountains and foothills.

By Tuesday afternoon, 24-hour rainfall totals recorded by the National Weather Service were 0.55 in Lompoc, 0.40 in Santa Maria, 1.12 in Goleta, 1.47 in Santa Barbara, 0.49 in Santa Ynez, 0.36 in Pismo Beach and 1.47 at Port San Luis.

A weak storm is trailing this one, and that is expected to cause some possible showers Friday or Saturday. The weather is expected to clear up Sunday.

That is good news for the U.S. Bureau of Reclamation, which operates the Bradbury Dam at Lake Cachuma, and the Santa Barbara County Flood Control District.

“The current elevation at the reservoir is 750.4 feet and we hit the spillway gates at 752 feet,” said Jeff McCracken, a bureau spokesman. “We would begin the release of water (down the Santa Ynez River) when we reach 752.5. We've got some space.”

If there was the need for a small release of water from the dam, it would likely be a couple of thousand cubic feet of water per second, said Matt Naftaly, a hydrologist for the flood control district. The district coordinates with the Bureau of Reclamation and is alerted when water needs to be released from Lake Cachuma.

Twelve months in one state makes very little difference, while in another it’s the difference between night & day. Mother Nature is fickle.