I thought I heard about huge aquifers under the staqte of arizona particularly south from phoenix to tucson. FInd what you can of these aquifers, valume, depth and any underground riviers in the area

Short answer: yes—there are big alluvial aquifers all along the Phoenix→Pinal→Tucson corridor. They’re not “underground rivers” in the caverns-and-canoes sense, but enormous bodies of water stored in sand, gravel, and silt that slowly move and recharge, especially beneath dry riverbeds like the Santa Cruz.

Here’s the useful stuff, without the hype:

# What & where
– **Phoenix area (Valley of the Sun / Phoenix AMA):** Multi-layered basin-fill aquifer system (often described as Upper/ Middle/ Lower alluvial units). Phoenix mostly runs on rivers (Salt/Verde/Colorado) and uses the aquifer for backup + recharge; recent USGS work tracks **storage change** in the **North Phoenix aquifer (2020–2023)** rather than a single “tank size.” In those years, withdrawals were small (≲3,000 acre-feet/yr) and roughly matched by injection recharge. citeturn5search4turn2search11

– **Pinal County between Phoenix & Tucson (Pinal AMA):** Big agricultural basin(s) with long-term stress. State models and updates focus on projected levels and supply gaps rather than a single fixed volume, but the AMA reports and modeling documents show why Pinal is often the pinch-point in the corridor. citeturn2search20turn2search6turn2search11

– **Tucson area (Tucson AMA: Avra Valley + Upper Santa Cruz sub-basins):** This is one of Arizona’s classic large alluvial aquifer systems. Decades of USGS/ADWR studies quantify storage and subsidence. citeturn2search4turn2search18turn2search10

# How big (order-of-magnitude storage)
– **Tucson area (shallow to moderate depths):**
– A University of Arizona WRRC summary noted that, circa 1940, **~70 million acre-feet** (MAF) of groundwater were present **above ~1,200 ft depth** in the Tucson area aquifers; by the 2000s, on the order of **6–8 MAF** had been pumped out (≈9–11%). That gives you a realistic “there’s a lot of water, but it’s finite” scale. citeturn4search5
– For **Avra Valley specifically**, classic estimates of **groundwater in storage to ~1,000 ft** range **~16.5–24 MAF** (different investigators; the range appears repeatedly in USGS/ADWR technical reports). citeturn4search4

– **Storage change (not total size):** Repeated USGS gravity surveys in Tucson/Avra have measured multi-year gains/losses of **tens to hundreds of thousands of acre-feet** depending on recharge and pumping—useful for trend, not “total volume.” citeturn2search7turn2search4

> Translation: south of Phoenix into Tucson you’re dealing with aquifers whose **total stored water is measured in the tens of millions of acre-feet** (at practical depths), but the **usable** portion depends on depth, water quality, compaction risk, and economics.

# How deep & how thick
– The **basin fill is very thick** in places. In **Avra Valley**, sediment thickness hits **~9,600 ft** in the north—one reason storage numbers get so large. (Usable water is usually considered within shallower intervals because of drilling cost, compaction, and quality.) citeturn2search21
– Depth to water varies widely (hundreds of feet common) and has **declined historically** in pumped areas, causing **land subsidence and earth fissures**—another constraint on “how deep you want to chase it.” citeturn2search1turn0search6turn0search18

# “Underground rivers”?
– In this corridor, water mostly moves through **porous alluvial sediments** (think: a giant wet sponge), **not** through open subterranean channels. Flow is slow and diffuse, with strong connection to **ephemeral streams** (e.g., Santa Cruz) that **recharge** the aquifer when they run; recent USGS work even used repeat **microgravity** along the Santa Cruz in Tucson to quantify storage changes from reclaimed-water releases. citeturn5search7turn0search9
– Arizona does have some **karst** terrain elsewhere, but the Phoenix–Pinal–Tucson aquifers are classic **alluvial basin** systems, not cavern rivers. citeturn0search18

# Quick reality checks (because desert):
– **Phoenix**: primarily surface-water city (Salt/Verde/Colorado) that **banks** water underground and maintains wells for resilience; active management focuses on **balancing** withdrawals and recharge in targeted subareas. citeturn5search8turn0search15
– **Pinal**: the stress case—agriculture-heavy, modeling and policy updates continue as the state confronts supply gaps. citeturn2search20turn0search7
– **Tucson**: historically heavy groundwater use, then CAP imports + recharge projects; careful monitoring of **storage change and subsidence** continues. citeturn2search4turn2search1

If you want, I can zoom in on a specific spot (e.g., **south of Casa Grande**, **Marana/Avra**, or **Santa Cruz through Sahuarita**) and pull the best-available **depth-to-water maps,** **storage estimates at practical depths,** and **subsidence risk** for that exact area.