7,591 segments of stream are designated habitat

Every other page on this site is about who may take water. This one is not about rights at all. It is the federal government's answer to a different question: which stretches of river are legally recognised as habitat a listed species needs, drawn onto the national stream network one segment at a time.

What the drawing is

The drawing above is every mapped stream in Colorado, with USFWS designated critical habitat placed on it. The faint lines are the rest of the network, there so the lit ones have somewhere to be. Click any water to see what it is designated for. The catchment above your click fills in behind it, because what happens upstream is what arrives, and that trace is drainage and nothing else. It says which ground sheds water toward a point. It does not say who may use it.

Colorado is the wet half of this story

Read the flow regime before anything else. A perennial stream runs year-round, an intermittent one for part of the year, an ephemeral one only after rain. Of the 7,591 Colorado segments carrying a designation, 52.3 percent are perennial and 27.7 percent intermittent. That is a mountain state: the designations sit on snowmelt-fed water that is mostly there when you go and look.

Arizona, on the same map drawn the same way, is 14.6 percent perennial. The comparison is worth making because it shows the measurement is not an artefact of the method. The two states really are that different, and a designation means something different in each of them.

Where the river is not a line

Some designations follow water too wide to be drawn as a line at all. The national dataset maps it as an area and threads a routing line through the middle, and that line keeps the river's name. It accounts for 69 percent of the razorback sucker's Colorado segments and 53 percent of the Colorado pikeminnow's. The shape itself is published, so the map draws it: zoom into a basin and the reservoirs and the wide river appear as water rather than as a line standing in for water. What NHDPlus cannot tell you is which is which, and the map does not guess.

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. Read the counts with that in mind, and with one more thing: most of GBIF is bird checklists. A basin holding a million bird records and a thousand fish records is telling you where birdwatchers go as much as what lives in the water. Nobody photographs a minnow.

What this does not tell you

• That a species is present. A designation covers an area. It is not a survey, and nothing drawn in habitat colour is an observation record.
• That the water is protected. A designation constrains federal actions and federal permits. It is not a water right and it reserves nothing.
• That the designation is current. The published layer writes a placeholder string 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 drawn.
• That an intermittent channel is dry ground. It is a channel whose year-round flow the national mapping does not assert, which is a statement about the record.

Everything here is joined on one key. The NHDPlus COMID that identifies a stream segment is the same identifier the water rights, the diversion structures and the upstream traversal elsewhere on this site are keyed to. That is the only reason a question about habitat and a question about diversions can be asked of the same reach at once.