ADWR completes groundwater flow model update of North Santa Cruz AMA

5.10.2019 Santa_Cruz_River

Photo courtesy of University of Arizona Water Resources Research Center

Arizona Department of Water Resources hydrologists have completed an update  to the North Santa Cruz Active Management Area groundwater flow model, the first such updates since the release of modeling reports on the NSCAMA in 2007 and 2010.

The model is updated to include data for the approximately 14-year period beginning in 2002 through water year 2016. The calibrated, extended model will be used to provide model-simulated estimates of natural recharge and discharge components for the draft Fourth Management Plan for the Santa Cruz AMA.

Overall, the NSCAMA model update did not produce any big surprises or changes in the Department’s interpretation of the hydrology in  the area.

However, the groundwater flow model update did reinforce the importance to the NSCAMA aquifer of “episodic flood pulses” — episodes, usually lasting days or weeks, when runoff from large rainfall events flows into the Santa Cruz River and increases the amount of surface flow, often by orders of magnitude.

Water levels in the Santa Cruz AMA are largely dependent on stream recharge, which varies significantly from year to year in response to streamflow coming down the Santa Cruz River. That recharge mostly occurs as a result of those episodic flood pulses generated by substantial rain events.

The North Santa Cruz AMA aquifer is a narrow, shallow basin that provides less long-term storage capacity than wider, deeper aquifers such as that of the Tucson and Phoenix AMAs. Especially following major rain events, water flows through the aquifer quickly because the soil properties are such that the conductivities are very high.

The model update found that groundwater pumping in the southern Tucson AMA is continuing to impact water levels in the northern Santa Cruz AMA north of the town of Tubac.

From 1997 to 2016, water levels in this area have been steadily dropping – up to 45 feet, using 1997-1998 as the baseline.

The northern portion of the Santa Cruz AMA is simulated as a model separate from the southern portion due to the  distinct hydrologic regimes along the upper and lower reaches of the Santa Cruz River within the AMA.

For further information regarding the model update of the North Santa Cruz AMA, contact Sally Stewart Lee at ADWR. sslee@azwater.gov

 

 

 

Soggy Tucson: UA researchers find Old Pueblo gets more monsoon action than anywhere else

california-rainstorm

What happens in Tucson appears to stay in Tucson — at least when the things “happening” in the Old Pueblo are the effects of strong summer thunderstorms.

Tucson and southern Arizona get more Wagnerian excitement –– and suffer more economic harm — from severe “monsoon” storms than any other Southwestern metropolis, according to a pair of researchers from the University of Arizona.

At over 6.08 inches of rain falling during the hot, muggy monsoon season, Tucson leads the Southwestern pack. It gets nearly an inch more than the next soggiest community, El Paso, and easily twice as much as that place north of the Gila River, metro Phoenix.

Like Phoenix, Tucson is an extraordinarily stable environment. It is not in an earthquake zone. Hurricanes rarely make it to southern Arizona intact. And damaging winter weather is a non-starter. There’s a good reason why the local chambers of commerce tout the climate.

Indeed, the report’s authors go out of their way to note that “Tucson’s weather also provides opportunities for economic activity, including a vibrant winter tourism economy and growing solar industry across Southern Arizona.”

And, really, in an environment that in recent years has endured chronic drought, the main effect of summer monsoons is a big attraction. We like water falling in great gobs from the sky.

But something has to top every community’s list of “most damaging” weather effects, even if those effects themselves are comparatively modest.

In Tucson, it’s those often-sensational monsoons, which according to UA researchers Laura A. Bakkensen and Riana D. Johnson account for 84 percent of all “extreme” weather events there and 96 percent of all property losses.

Notably, the Bakkensen/Johnson white paper did not include the net impact of long-term drought.

On the other hand, it did illustrate the most effective ways to mitigate the impacts of those unpredictable monsoons, most of which Southwesterners already “get.”

Like not driving on Interstate 10 between Tucson and Phoenix when it gets dark and windy. Like not pushing the limits of “stupid driver” laws by driving into running washes after summer storms. And, not least, buying a little home and car insurance.