13,461 segments of stream are designated habitat

Thirty-one federally listed species hold designated critical habitat on Arizona streams, across 13,461 segments of the national stream network. Fewer than one in five of those segments is water the mapping says runs all year. That sounds like a mistake and it is not one. It is the single most Arizona fact in this dataset.

What the drawing is

The drawing above is the Arizona stream network with every final designation on it. Click any lit segment to see what it is designated for; the catchment above it fills in behind your click. That upstream trace is drainage and nothing more. It says which ground sheds water toward a point, not who may use it.

Most designated habitat here is not year-round water

Of the 13,461 Arizona segments carrying a designation, 66.5 percent are classed intermittent and 14.6 percent perennial. Species by species it gets starker. The jaguar's Arizona designation is 97 percent intermittent across 911 segments. The desert tortoise's is 97 percent across 530. The Acuña cactus sits on 58 segments, every one of them intermittent, with no perennial stream inside its designation at all.

The temptation is to read that as a failure of the designation or a failure of the map. It is neither. Water in the Sonoran and Chihuahuan deserts arrives in pulses, and the species that live with it are built for exactly that. A channel that runs after monsoon rain and holds pools the rest of the year is habitat. The chart above is really a picture of how water works in this part of the country, drawn through the species that depend on it.

And some of it is not a stream line at all

Where a designation follows the Colorado River, much of it is water too wide to be drawn as a line. The national dataset maps it as an area and threads a routing line through the middle, and that line carries the river's name. It is 95 percent of the bonytail's Arizona segments, 83 percent of the humpback chub's and 63 percent of the razorback sucker's. Those shapes are published too, so the map draws them: inside a basin the river through Marble Canyon is the width it really is, and Lake Mead is a lake. Which of them is a reservoir and which a river the national dataset does not say, and neither does the map.

What the dots are

Pick a group in the panel and the map fills with observation records from GBIF: specimens in collections and sightings other people have verified. A designation is a rule about a place. A record is a note that something was seen there. Most of GBIF is bird checklists, so a basin holding millions of bird records and a couple of thousand fish records is telling you where birdwatchers go as much as what lives in the water.

What this does not tell you

• That a species is present. A designation covers an area. It is not a survey and nothing here is an observation record.
• That the water is protected. A designation constrains federal actions and federal permits. It is not a right to water and it does not reserve any.
• That a designation is current. The published layer carries a placeholder where a vacate date belongs, so a designation struck down by a court cannot be told apart from a live one here. Only final rules are shown.
• That an intermittent channel is dry ground. It is a channel whose year-round flow the mapping does not assert, which is a statement about the record.

Arizona has no surface-water priority system in this warehouse and nothing on this page implies one. What joins it together is the NHDPlus COMID, the identifier for a single stream segment, which is what lets habitat, flow regime and observation records be asked about the same piece of river at once.