The San Juan Below Navajo Dam Is a Different River Than the One Above It

The San Juan River splits into two distinct fisheries at Navajo Dam, about 40 miles downstream from Pagosa Springs. Above the dam, near town, you fish a freestone river — cold snowmelt, pocket water, willows, and the occasional cutthroat or brown. Below the dam, the river becomes something else entirely: a tailwater fishery where cold, clear water releases from the bottom of the reservoir create year-round conditions that grow large trout and support dense populations of aquatic insects.

If you are staying in Pagosa Springs and want to fish the San Juan, you have two choices. The upper river (above Navajo Dam) is closer and requires no special permit. The lower river (below the dam) is 40 minutes away, requires a New Mexico fishing license, and fishes best from late fall through early spring when the water is coldest and clearest. Most visiting anglers make the drive to the lower river because the trout are bigger and more numerous, but the upper river is worth knowing about if you have limited time or prefer smaller water.

Key Takeaways

  • The San Juan above Navajo Dam (near Pagosa Springs) is a freestone stream with cutthroat and brown trout; the San Juan below the dam is a tailwater with larger trout and year-round fishing.
  • The lower San Juan fishes best from October through April when water temperatures drop and insect hatches are most reliable.
  • Small nymphs (size 18–22) and midges work year-round on the lower river; dry-fly fishing is possible but nymphing under an indicator is the standard approach.
  • The lower river has public access at several pullouts and a fee-fishing area called the Quality Waters, where you pay to fish a restricted section with higher catch rates.
  • You will need a New Mexico fishing license to fish the lower San Juan; Colorado license does not cover it.

Upper San Juan Near Pagosa Springs — Freestone Fishing in Pocket Water

The San Juan above Navajo Dam flows through the mountains south of Pagosa Springs as a typical high-country freestone stream. The water is cold, fast, and broken by boulders and logs. Cutthroat trout are the dominant species, with some brown trout mixed in. Fish sizes run small to medium — most cutthroat are 8 to 12 inches, with occasional fish to 14 inches.

Access is straightforward: US Highway 84 follows the river south from Pagosa Springs for about 30 miles before the road climbs away from the water. You can pull off at several spots and walk down to the river. The best fishing is usually in the pocket water — the broken current behind boulders and in the seams between fast and slow water. Small dry flies (size 16–20) work well in summer, especially in the evening. Nymphs and small streamers are effective year-round.

No special permit is required to fish the upper San Juan if you have a valid Colorado fishing license. The river is open year-round, though winter access can be difficult due to snow at higher elevations. Most anglers fish this section in summer and early fall.

Lower San Juan Below Navajo Dam — Tailwater Fishing and the Quality Waters

The lower San Juan is a different proposition. Navajo Dam holds back Navajo Reservoir, and water released from the dam's bottom intake is cold (typically 45–52 degrees Fahrenheit) and clear. This cold, stable water creates ideal conditions for trout and supports massive populations of small aquatic insects — primarily midges and small mayflies. The result is a river where 15- to 18-inch trout are common and fish over 20 inches are caught regularly.

The lower river is divided into sections with different access and regulations. The Quality Waters is a 4-mile stretch immediately below the dam where New Mexico charges a daily fee (roughly $10–15 per person, though rates vary) to fish a restricted area with higher catch rates and lower angler density. This section is stocked and managed for trophy fishing. Access is at the Quality Waters parking area, about 40 minutes south of Pagosa Springs via US 84 and NM 511.

Below the Quality Waters, the river is open to public fishing at several pullouts and access points. These sections are free but more crowded, especially on weekends. The river continues south toward the San Juan-Animas confluence, and fishing remains good throughout, though the tailwater effect diminishes as you move downstream.

What to Fish and When — Seasons and Hatches

The lower San Juan fishes well year-round, but conditions and tactics change by season. October through April is prime time. Water temperatures are lowest (45–50 degrees), which keeps the trout active and feeding. Midges hatch throughout the day, and small mayflies (especially Baetis) emerge in the afternoon. This is when most visiting anglers fish the lower river.

Summer (June–August) can be productive but requires different tactics. Water temperatures rise into the 55–60-degree range, and trout become more selective. Early morning and late evening are best. Midges remain the staple, but you may also see small caddis and occasional larger mayflies. Crowds are heaviest in summer, especially on weekends.

Spring (March–May) is a transition period. Runoff from snowmelt can muddy the water and raise flows, making fishing difficult. By late May, conditions usually stabilize and fishing improves. Fall (September–October) is excellent — water temperatures drop, insects are abundant, and crowds thin out.

For fly selection, small is the rule. Nymphs in sizes 18–22 are the workhorse: Baetis nymphs, small Pheasant Tails, and generic dark nymphs all work. Midges (both larvae and pupae) in sizes 20–24 are essential year-round. Fish them under a strike indicator, adjusting depth to 3–5 feet depending on water level. Dry flies are possible but less common; when you do fish dries, small Baetis duns (size 18–20) and midge adults (size 22–24) are the patterns to try. A few anglers fish small streamers (size 12–16) in the early morning or late evening, which can produce larger fish.

Gear and Tackle Setup for the Lower San Juan

A 9-foot rod for 4- or 5-weight line is standard. The water is not wide (typically 40–80 feet across), and you will be casting short to medium distances. A 9-foot leader tapered to 4X or 5X is typical; many anglers use 6X or even 7X when fishing small nymphs to selective trout. Tippet material should be fluorocarbon — it sinks better than monofilament and is less visible to the trout.

A strike indicator (also called a bobber or float) is essential for nymph fishing. Use a small indicator — pencil-thin or smaller — because the trout are sensitive to drag and unnatural movement. Adjust the indicator so your nymphs drift 3 to 5 feet below the surface, depending on water depth and current speed. A small split shot or two will help your nymphs reach the bottom quickly.

Waders and a wading staff are necessary. The river bottom is rocky and uneven, and the current can be strong. Felt-soled wading boots provide better grip than rubber soles on the slick rocks. A net is useful but not essential — many anglers fish without one and release fish by hand.

Access, Regulations, and Licenses

To fish the lower San Juan, you need a New Mexico fishing license — a Colorado license does not cover it. You can purchase a one-day, three-day, or annual license from New Mexico Department of Game and Fish or from local fly shops in Pagosa Springs or Farmington. The lower river is open year-round with no seasonal closures.

Regulations are straightforward: the daily limit is typically 2 trout (check current rules with New Mexico Game and Fish, as regulations can change). Most of the lower river is catch-and-release only or has a slot limit that protects larger fish. The Quality Waters section has its own regulations, which are posted at the parking area.

Public access points include the Quality Waters parking area (fee required), several pullouts along NM 511 between the dam and the Quality Waters, and additional access points further downstream. The river is on public land or easements for most of its length, but always respect private property and stay within the riparian zone.

When to Go and What to Expect

The best time to visit is October through November or February through March — fall and early spring. Water temperatures are ideal, insects are active, and crowds are lighter than in summer. Winter (December–January) can be excellent for fishing but requires cold-weather gear and willingness to deal with ice and snow on the banks.

Plan to spend a full day on the lower river if you can. The drive from Pagosa Springs is about 40 minutes, and you will want at least 4–6 hours of fishing time to make the trip worthwhile. If you are staying in Pagosa Springs and want to fish both the upper and lower rivers, that is not practical in a single day — pick one and commit to it.

The lower San Juan is not a wilderness experience. You will see other anglers, especially on weekends and in the Quality Waters section. But the fishing is reliable, the trout are healthy, and the river is beautiful. If you are new to tailwater fishing or want to improve your nymphing skills, this is an excellent place to do it.

Frequently Asked Questions

Do I need a guide to fish the San Juan?

No, but a guide can be helpful if you are new to the river or to nymph fishing. Local guides know the current conditions, where the trout are holding, and which flies are working. Several fly shops in Pagosa Springs and Farmington offer guide services. If you prefer to fish on your own, the public access points are easy to find and the fishing is straightforward enough for a self-guided trip.

Can I fish the San Juan in winter?

Yes, and winter can be excellent. Water temperatures are lowest and trout are most active. The challenge is access — snow and ice can make the banks slippery and difficult to navigate. Dress warmly and bring a headlamp if you plan to fish early morning or late afternoon. Some access points may be closed due to snow; check with local fly shops before you go.

What is the difference between the Quality Waters and the public sections?

The Quality Waters is a 4-mile fee section immediately below the dam where you pay to fish a restricted area with higher catch rates and fewer anglers. The public sections downstream are free but more crowded. The Quality Waters is stocked and managed for trophy fishing, so you may catch larger fish there. If you want solitude and are willing to work harder for your fish, the public sections are worth trying.

Is the upper San Juan worth fishing if I am already going to the lower river?

Not in the same day — the drive and setup time make it impractical. But if you have two days, the upper river is worth a morning or afternoon. The fish are smaller and the water is more technical, but it is a classic freestone experience and requires only a Colorado license. Many anglers prefer the upper river for its scenery and solitude.

What flies should I bring if I have never fished the San Juan before?

Start with small nymphs: Baetis nymphs and Pheasant Tails in sizes 18–20, and a few generic dark nymphs in sizes 20–22. Add midges in sizes 22–24 (both larvae and pupae). Bring a small strike indicator, split shot, and fluorocarbon tippet in 5X and 6X. If you want to try dry flies, pack a few small Baetis duns in size 18–20. A local fly shop can give you current recommendations based on what is hatching that week.