HillCountry.ai network
The San Marcos River · Texas Hill Country

The San Marcos River

Crystal-clear, spring-fed water at a constant 72° — rising right in the middle of town and running cold and clear all year. One of the most beloved tube-and-swim rivers in Texas, and one of the rarest river habitats anywhere.

Check the river level ↓ What to know
Live Conditions
San Marcos River at San Marcos · USGS 08170500 · Hays County
Full chart & history →
—
Flowcubic feet / second
—
Gauge heightfeet
Fetching live readings from USGS…
Source: USGS Water Services. The San Marcos is spring-fed, so flow stays remarkably steady and the water holds a constant 72°. These are live readings, not a safety rating — after heavy rain the river can still rise and run fast, so check in person before you go and never enter high or fast water.

About the river

Born from springs, clear and cool all year.

The San Marcos rises at the San Marcos Springs in Spring Lake — the second-largest springs in Texas — and runs clear and a constant 72° right through the heart of San Marcos before joining the Guadalupe downstream. It's a short river with an outsized reputation: the Rio Vista chutes draw tubers all summer, and the glass-bottom boats at Spring Lake have shown off its clarity for generations. Named for Saint Mark, it's spring-fed enough to stay reliable even when the rest of the Hill Country runs dry.

On the river: San Marcos · Spring Lake · Rio Vista ↗

At a glance

The San Marcos, by the numbers.

Headwaters
San Marcos Springs
Spring Lake, 2nd-largest in Texas
Length
~75 miles
to the Guadalupe River
Water
A constant 72°
spring-fed, clear year-round
Wildlife
Texas wild rice
endangered, found almost only here
Live gauge
USGS 08170500
San Marcos Rv at San Marcos
River towns: San Marcos Spring Lake Rio Vista Park

What to know

One of the rarest rivers in Texas — treat it that way.

The San Marcos Springs and upper river are home to species that live almost nowhere else on earth: Texas wild rice, the fountain darter, and the San Marcos salamander among them. That's not trivia — it's the reason to float lightly here. Stay out of the wild-rice stands, don't uproot plants, leave the gravel and banks as you found them, and pack out everything you bring in. A clear, cool river that's survived this long is worth keeping that way.

Start at Spring Lake

The headwaters at Spring Lake and the Meadows Center glass-bottom boats are the clearest look at where the river begins — and why it's protected.

Tube the chutes

Rio Vista Park's chutes are the classic summer float — cold, clear, and busy on weekends. Go early, bring a tube, leave the glass at home.

Explore the network

The San Marcos is one of ten Hill Country rivers. See them all, and the towns along each, on the HillCountry.ai rivers hub ↗

Common questions

San Marcos River, answered.

How is the San Marcos River running right now?

Check the live USGS gauge at the top of this page (station 08170500, San Marcos at San Marcos). Because the river is spring-fed from the San Marcos Springs, its flow is unusually steady and the water stays clear and a constant 72° year-round — even in drought, when other Hill Country rivers run low.

Is the San Marcos good for tubing and swimming?

Yes — it's one of the most popular tubing and swimming rivers in Texas, clear and cool all summer, with the Rio Vista chutes downtown and easy access through San Marcos. It's busiest on summer weekends. The water is famously cold-clear and a steady 72°, so it's swimmable even when the air is brutal.

Where is the San Marcos River?

It begins right in town at San Marcos Springs in Spring Lake — the second-largest springs in Texas — and runs through San Marcos before joining the Guadalupe River downstream. The easiest places to know are Spring Lake (and the Meadows Center glass-bottom boats) and Rio Vista Park.

Why is the San Marcos River ecologically protected?

The springs and upper river are home to species found almost nowhere else on earth — including Texas wild rice, the fountain darter, and the San Marcos salamander. That's why it matters to stay out of the wild-rice stands, not pull up plants, keep the gravel and banks intact, and pack out everything. It's a rare place; treat it like one.

Is the river safe and family-friendly?

Generally yes — the spring-fed water is clear and steady, and the in-town stretches are gentle and well-used. Like any river it can rise after heavy rain, and there are weirs and dams to portage around if you're paddling the length, so check the live gauge and know your stretch before you go.

When is the best time to visit?

Any time — the constant 72° spring water makes the San Marcos a year-round river. Summer is the classic tubing season and the busiest; spring and fall are quieter, and the river stays clear and cool even when the rest of Texas is dry.

Good to know

Read the water before you go.

The San Marcos is spring-fed and remarkably steady — clear, cool, and a constant 72° whether it’s August or January, so it’s swimmable and floatable nearly year-round. After heavy rain it can still rise and run fast, and there are weirs and dams to portage if you’re paddling the length. Glass is banned, there are no lifeguards, and the upper river is sensitive habitat — stay off the wild rice. Check the live gauge above before you go.

See the river levelAll Hill Country rivers
Respect This Place — Texas Hill Country The River Code Read the code ▾

Built with the locals who know these rivers best. The Frio and the Guadalupe show what happens when a river gets loved too hard — these are the few things that keep the rest the way they are.

  1. Pack out everything you bring in. Bottles, cans, butts, bait tubs — all of it. Bring an extra bag and grab what someone else left.
  2. No glass near the water. Broken glass in a swimming hole ends a perfect day in the ER. Cans and plastic only.
  3. Know where you're allowed to be. Most of this is private land. Stick to public crossings, parks, and posted access.
  4. Park with respect. Not on the crossings, the bridge, or in front of a ranch gate.
  5. Respect the water. Check the gauge; never cross a flooded crossing — on foot or in a truck.
  6. Leave the rocks where they lie. Stacked-rock towers wreck fish habitat. Let the riverbed be a riverbed.
  7. Don't drive in the riverbed. Trucks and ATVs crush the gravel beds and everything living in them. Park up top and walk down.
  8. Leave the wildlife alone. Don't feed it, chase it, or take it home — fish and turtles included.
  9. Keep it quiet, keep it dark. Skip the speaker. Leave the next person the water sounds and the stars.
  10. Mind fire and burn bans. Summers run dry and bans are common. Check before you light anything, and never leave a coal smoking.
  11. Leash 'em and clean up after 'em. Keep dogs close on shared water and private land, pick up after them every time, and don't let them chase wildlife or disturb other visitors.
  12. Spend your money in the river towns. Gas, food, supplies — the small towns are what keep these rivers accessible. Keep them alive.