Flow Path Reality

Why the Canyon Ranch Discharge Will Not Behave as Modeled

Understanding the actual flow path of Canyon Ranch’s wastewater is essential to evaluating risk. The permit assumes a simple, predictable movement through a perennial stream. But the reality is far more complex. The discharge enters a dry, storm‑driven channel, interacts with karst terrain, crosses multiple fracture zones, and travels through an area where the Cow Creek Formation is exposed at the surface.

This page explains how wastewater will actually move once it leaves the pipe — and why the permit’s assumptions do not reflect the real conditions on the ground.

The Flow Path: From Outfall to the Guadalupe River

The Canyon Ranch outfall sits at approximately 1,350 feet elevation. From there, wastewater begins a three‑mile descent toward the Guadalupe River, dropping to just under 900 feet at the confluence.

Along this path, the effluent will:

1. Enter an undesignated tributary (in Canyon Ranch, through Mystic Shores backyards) to Devils Hollow

2. Travel through the Mystic Shores Nature Preserve

3. Interact with exposed Cow Creek limestone

4. Cross multiple mapped fracture zones

5. Cross three major faults, including the Spring Branch Fault

6. Reach the Guadalupe River during storm events or via subsurface pathways

Ron Harris’s cross‑section shows this clearly:

“It will travel nearly three miles to where it gets down in the river… and on its journey it encounters fractures, faults, and exposed Cow Creek.”

This is not a simple surface flow. It is a complex, multi‑pathway system.

Devils Hollow: A Storm‑Driven, Normally Dry Channel

Devils Hollow is dry most of the year. It only carries water during rainfall events. This matters because wastewater behaves very differently in a dry channel than in a flowing stream.

In a dry channel, effluent tends to:

• Spread out

• Pool in low areas

• Infiltrate rapidly

• Follow fracture zones

• Move underground

• Bypass surface flow entirely

Ron explains: “When wastewater is discharged into a dry creek, it behaves very differently… it spreads out, it pools, it infiltrates, and it finds low points, fracture zones, and voids.”

This is the opposite of the slow, predictable movement assumed in the permit.

Interaction With Exposed Cow Creek Limestone

Inside the Nature Preserve, the Cow Creek Formation — a major drinking‑water aquifer — is exposed at the surface.

This means:

• wastewater has direct contact with drinking‑water limestone

• infiltration is rapid and efficient

• fractures and voids provide direct pathways into the aquifer

• surface water can enter groundwater without filtration

Ron’s field observations confirm this: “Once it’s in the preserve… it will be in direct contact with the Cow Creek Formation.”

For nearly two miles, wastewater will interact with exposed Cow Creek limestone — one of the most permeable formations in the Middle Trinity aquifer.

Recharge Zone Reality

While the Canyon Ranch outfall itself sits in the Trinity Aquifer Contributing Zone, the flow path immediately downstream enters the Trinity Aquifer Recharge Zone. In this part of northwestern Comal County, the Cow Creek Formation — a major drinking‑water aquifer — is exposed at the surface and actively recharges through faults, fractures, and dissolution‑enhanced pathways. Unlike the Edwards Aquifer Recharge Zone, the Trinity recharge zone has no special protections, even though its geology is equally vulnerable. Groundwater in the Middle Trinity ultimately migrates into the Edwards aquifer along fault‑controlled pathways, meaning infiltration along this flow path can affect both aquifers. This makes the Canyon Ranch discharge location uniquely sensitive and significantly under‑protected. 

Fracture Zones Along the Flow Path

Between the outfall and the Guadalupe River, the flow path crosses numerous mapped fracture zones. These fractures:

• act as conduits

• accelerate infiltration

• enlarge over time through dissolution

• create unpredictable underground pathways

• allow water to bypass surface channels entirely

Ron’s photos from Devils Hollow show:

• vertical fractures

• dissolution‑enlarged cavities

• caves forming along fracture planes

His observations in the dry Guadalupe River bed (no longer visible due to June rainfall) show:

• parallel fracture sets

• open cracks

• direct infiltration routes

“Fractures are many, and they’re three‑dimensional in nature.”

These fractures are not hypothetical. They are visible, mapped, and active.

Major Faults Along the Flow Path

The flow path crosses three major faults, including the Spring Branch Fault. Faults create:

• vertical displacement

• open pathways

• enhanced permeability

• rapid downward movement

Ron’s cross‑section shows:

• Fault 1 near Honey Creek

• Fault 2 approaching the Nature Preserve

• Fault 3 near the Guadalupe River

Faults dramatically increase the likelihood that wastewater will move underground rather than remain on the surface.

Surface Flow vs. Subsurface Flow

The permit assumes:

• slow movement

• predictable surface flow

• perennial stream conditions

• minimal infiltration

The reality is:

• rapid infiltration

• unpredictable subsurface movement

• dry‑channel discharge

• karst terrain

• exposed Cow Creek

• faults and fractures

• storm‑driven flow

Ron summarizes the issue: “Surface waters will flow into the groundwater very quickly, potentially with faults and fractures.”

This is the fundamental flaw in the permit’s modeling.

Why This Matters

Effluent will not stay on the surface.

It will infiltrate, move underground, and interact with the Cow Creek Formation.

Wells lie directly along the flow path.

Cypress Cove public‑supply wells are near the outfall and along the channel. Cross Canyon Ranch and Canyon Lake Estates rely heavily on wells. Many wells are shallow, older, or near fracture zones.

The permit does not account for karst infiltration.

No fracture analysis. No karst vulnerability assessment. No hydrogeologic modeling. No environmental impact study.

The flow path is complex, sensitive, and highly vulnerable.

This is one of the worst possible locations for daily effluent discharge.

The Takeaway

Wastewater discharged into Devils Hollow will not behave as modeled. It will:

• infiltrate

• move through fractures

• travel underground

• interact with the Cow Creek Formation

• reach wells

• reach the aquifer

• potentially reach Canyon Lake

Any long‑term wastewater plan in this region must begin with an accurate understanding of the actual flow path — not the simplified model used in the permit.

The geology tells us how wastewater moves. The flow path confirms why this location is uniquely vulnerable.

Supporting Materials

Detailed Geology Video

A full, detailed explanation by geophysicist Ron Harris is available here.