Comments on: San Pedro River Geology – Implications for water law

By: Roxanne Johnston

Roxanne Johnston — Mon, 10 May 2010 23:27:33 +0000

I was researching this site to see if there was any mention regarding the effects the May 6th 1887 earthquake originating from Mexico had on the San Pedro. The only account I have unearthed so far is a repost of a news report that can be accessed from the following source: http://www3.gendisasters.com/arizona/8851/tucson-az-earthquake-destruction-may-1887 I vaguely remember someone telling me that the San Pedro ran underground as a result of the quake, but I have not been able to verify this or any of the other eyewitness accounts in the article. Any thoughts?

By: Jonathan DuHamel

Jonathan DuHamel — Thu, 06 Aug 2009 17:42:57 +0000

Your statement “many aquifers are hydrologically connected to rivers” is true for temperate climates, but not the desert.

Most of our natural recharge of aquifers comes from monsoon rains flowing out of the mountains. This water seeps into the ground near the mountain fronts and flows underground through permeable horizons on top of the pediment, to the aquifer in the central valleys.
Recharge from stream beds is minimal because most of the rivers are underlain by impermeable clay or caliche. Water in streams generally cannot penetrate to the main aquifer. Instead, this water either continues flowing northward or makes shallow, perched aquifers which contribute nothing the our pumped water supply.

By: Michelle Harrington

Michelle Harrington — Wed, 05 Aug 2009 22:14:14 +0000

Unfortunately, the mapping answers the wrong questions. Many aquifers are hydrologically connected to rivers, and pumping directly or indirectly affects river base flow. Failing to analyze the entire hydrogeologic system fails to protect rivers or provide accurate and fair adjudication. (Adjudication based on current water law is patently unfair as it’s not based in reality.) The information provided, while interesting, fails to further any real protections for our state’s water resources.

By: ldonyo

ldonyo — Tue, 04 Aug 2009 19:51:02 +0000

There is a really good 11″ x 17″ map available at:
http://www.azgs.state.az.us/images/sanpedro_poster.jpg
Now I need to find one for the west side of Pima county so I can see the names of the rest of the mountain ranges I look at every day.