The Water Behind the Horses: What 2025 Tells Us

What the ADWR Report Says About the Salt & Verde Rivers

The Arizona Department of Water Resources (ADWR) has released its annual report for Water Year (WY) 2025, which runs from October 1, 2024 to September 30, 2025.
For the Salt River corridor, the most important section is the report’s discussion of the Salt and Verde watershed and SRP reservoir system, because that system directly shapes conditions along the Salt River riparian zone.

1) Fall 2024 was hot and dry, and the watershed started WY2025 already stressed

• The report states that dry conditions continued into fall 2024, with well below normal precipitation from October through December 2024 in the Salt and Verde watershed. By January 1, 2025, the watershed had essentially no snowpack(less than 1% of median), soils were dry, and streamflow on both rivers was already low.

2) Winter 2024–2025 produced weak recharge and record-low winter inflow

• From December 2024 through March 2025, total winter precipitation across the Salt and Verde watershed was only 3.00 inches (42% of normal).
• March 2025 storms temporarily pushed snowpack toward normal in mid-March, but the report explains that because conditions were so dry beforehand, there was little to no increased runoff response.
• For the winter runoff season (Jan. 1–May 31, 2025), SRP reservoirs received only 96,692 acre-feet of inflow—21% of median—the lowest on record for that period.

3) Spring 2025 did not rebuild storage

• Because runoff remained weak, the report notes storage declines during the winter runoff period. For example, Roosevelt Lake fell from 70% full to 61% full between Jan. 1 and May 31, 2025.

4) Summer 2025 monsoon moisture arrived unevenly — and inflow stayed extremely low

• The report notes a mixed monsoon pattern: wetter June, below-normal July/August, then above-normal precipitation again in September 2025.
• But despite some late-season storms, the report states that SRP reservoir inflow for July–September 2025 was still the second-lowest on record (behind 2020), totaling about 41,874 acre-feet (45% of median).

5) Bottom line for WY2025: record-low annual inflow and a major drop in storage

• For the entire Water Year 2025 (Oct 1, 2024–Sept 30, 2025), total SRP reservoir inflow was about 205,083 acre-feet (30% of median)—a new record low (previous low was 2018).
• Total Salt and Verde reservoir system storage declined to 53% (1,208,077 acre-feet) as of Sept. 30, 2025, compared to 77% at the same time the year before.

What this means for the Salt River riparian corridor  

When the Salt and Verde system receives record-low inflow and ends the year with sharply reduced storage, the Salt River corridor loses resilience. Think of the riparian zone as living off two things: steady water in the channel and wet ground just below the surface. When the upstream system is depleted, the river corridor is more likely to experience drying at the edges—exactly where cottonwood, willow, and mesquite depend on shallow moisture.

Water Year 2025 provides measurable evidence of that vulnerability. In the Verde watershed, ADWR monitoring well B-18-03 26BDDreached a record depth-to-water of 20.13 feet in September 2025, while well B-17-02 26CCD3 ended the year approximately 0.4 feet below its historical median, indicating declines in shallow aquifers that sustain riverside vegetation. 

Even modest drops in groundwater can weaken cottonwood recruitment, shorten the duration of moist soil conditions, and reduce understory productivity along the banks.

That will mean fewer persistent side channels, less sustained wet habitat, and a higher risk of stress and dieback in riparian vegetation over the hot season.

In other words, when less water flows into the Salt and Verde system, and the reservoirs end the year far lower than normal, the Salt River corridor becomes more fragile. The green riverbanks survive on two things: water flowing in the channel and moisture stored just under the ground.  When basin-wide recharge is weak and regional groundwater levels decline, the shallow moisture that sustains riparian vegetation becomes more vulnerable — even if surface releases remain stable in the short term. 

What This Means for the Horses — In Ecological Reality

The Salt River horses are not generic “desert horses.” They are a riparian-dependent herd whose daily survival revolves around three interlocking factors: surface water access, shallow groundwater–supported vegetation, and thermal refuge.

When the Salt and Verde system records record-low inflows and storage declines, the downstream consequences unfold in specific, predictable ways:

1. Loss of Shallow Riparian Productivity

Cottonwood and willow communities depend on a relatively stable, shallow water table. When groundwater drops:

• New cottonwood recruitment becomes more difficult and less likely in drier years.
• Understory grasses and forbs decline.
• Green forage persists for shorter seasonal windows.

For horses, this means:

• Less nutrient-dense grazing during late spring and early summer.
• Greater reliance on upland forage earlier in the season.
• Increased movement between patches to meet caloric needs.

Movement increases energy expenditure. In drought years, that matters.

2. Contraction of Wetted Edges

Side channels and shallow margins are not aesthetic features — they are access infrastructure for the herd.

When wetted edges shrink:

• Access points narrow.
• Bands cluster.
• Stallions defend tighter corridors.
•  Young animals may have fewer sheltered edge zones available. 

Crowding alters social spacing. In riparian herds, spacing stability reduces stress. Increased crowding can elevate behavioral stress and competition, which may influence body condition over time.

3. Heat Load and Thermal Refuge

The Salt River corridor functions as a cooling systemin extreme heat:

• Dense canopy lowers ground temperatures.
• Moist soils buffer radiant heat.
• Open water allows evaporative cooling.

When riparian vegetation thins and canopy gaps widen:

• Shade becomes fragmented.
• Surface temperatures increase.
• Horses must stand longer in water to thermoregulate.

Standing in water is adaptive — but it concentrates animals and increases bank erosion, which further destabilizes the corridor in a feedback loop.

4. Long-Term Carrying Capacity

Carrying capacity in a riparian herd is not just about numbers. It is about:

• Forage renewal rate
• Water reliability
• Spatial distribution
• Reproductive resilience

When inflow is 30% of median and storage drops from 77% to 53% in a single water year, the system loses buffering capacity.

That does not mean immediate collapse.
It means reduced margin for error.

And in ecological systems, reduced margin is what turns normal stress into cumulative stress.

5. Historical Context

Historically, horses along the Salt River have adapted to cycles of drought and flood. But two realities are different today:

• Winters are warming (+0.5°F per decade statewide, per the report).
• Reservoir management now regulates flow in ways that alter natural recharge rhythms.

This herd evolved under variability — but modern climate warming combined with regulated hydrology alters the natural disturbance and recharge patterns that historically reshaped and rebuilt portions of the corridor. 

The Bottom Line

Record-low inflow upstream does not just mean “less water.”

It means:

• Less forage renewal
• Tighter social spacing
• Greater heat stress
• Lower reproductive buffering
• Reduced ecological resilience

In short, while none of this means immediate crisis, it does mean the horses are entering another hot season with less ecological support than normal. 

• The horses will adapt, as they always have.
• Adaptation works best when habitat is stable.
• Water Year 2025 did not deliver stability.   

For a riparian-dependent herd, instability in water supply is never good news.