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HHI-DEST-373reservoirPlan with checksWatchNone datedClear

Rathbun Lake

South-central Iowa · Iowa · Appanoose County County

Field readiness

68/100

Plan with checksWatch
Official source
Status
current with same day rule check required
Last source check
37d ago
Due for re-reading
2026-11-03
Managing agency
Iowa Department of Natural Resources

Catalog tags

Season windows

No dated harvest closure published

Empty windows mean the cited source published no defensible dated harvest closure — a completed check, not a gap. Harvest is not assumed open. Bag, size and gear still apply.

What's in this reading

Five layers on this water

Open a layer to see the documented signals behind it and the unknowns it cannot close. Every layer reports what an agency published — none of it is an observation of the water today.

What the record says

  • boat launch

    Published trailered launches (see agency access list)

  • shore access

    Published bank and shoreline frontage

  • hand launch

    Published hand-launch or carry-in access

What this read cannot tell you

  • Same-day gate hours, fees and closures are set locally and are not mirrored here.
  • Facility condition (surface, dock presence, ADA status) is not tracked at record level.
  • Landowner boundaries adjacent to public corridors are outside this dataset.

Support is a hand-set weighting of how much documented material this layer rests on. It is not a probability and nothing here was measured.

Support is a hand-set weighting of how much documented material this layer rests on. It is not a probability and nothing here was measured.

Species context

What the agency documents here

Presence context only. This is never an expectation of catch, and carries no statement about timing, forage or activity. A note in brackets is the agency’s own condition on that fish and it outranks everything else on this page. Behaviour and presentation are the next instrument’s question — carry a species forward from the section below.

Temperature

Where a reading would sit against the published bands

These are reviewed temperature bands for the species the agency documents here, each one carrying the source it came from. They describe the fish, not this water. Nothing on this page knows what Rathbun Lake is doing today — put a thermometer in it and the drawing will show you where that number lands.

Detail

Stays on this device. It is not saved, not synced and not sent anywhere — this instrument has no account to attach it to.

Temperature

Walleye

Preference and distribution mixed. A band for the species, not a forecast for Rathbun Lake.

505560657075808590DEGREES F
Preferred 69.1–73.8°F The core. Where the reviewed record says this fish would rather be.
Active 53.6–82.4°F Feeding happens across this range. Wider than the core, and the edges are where a day gets difficult rather than impossible.
Edges Cold side from 53.6°F down. Warm or stressed from 87.8°F up. Outside the edges the fish is still there — it is just doing something other than feeding where you can reach it.
What you have No water temperature entered. This is the single measurement that moves the reading most, and a cheap thermometer beats a forecast every time.
What kind of number this is Preference and distribution data mixed. Treat the edges as softer than the core.
From the source Unusually well corroborated: the field preferendum (20.6–23.2 °C) and the independently measured growth optimum (22 °C) land on the same water.
What this plate is telling you

What the edges are. Cold edge: lower growth limit. Warm edge: EPA short-term maximum. These are not one consistent quantity across species. A measured avoidance temperature is where fish were seen leaving; a water-quality maximum is a regulatory ceiling written to prevent a kill, and it sits well above the point a day gets difficult.

Source. Wismer & Christie 1987, GLFC Special Publication 87-3 (field final preferenda from Coutant 1977a; growth range from Kelso & Ward 1972; optimum growth from Smith & Koenst 1975). Read it.

Warmwater species swing their preference ten degrees or more between winter and summer in the same laboratory. One band per species is a summer simplification, and it is why the drawing shows a band rather than a line.

Altitude matters more here than people expect. The same water at 9,000 feet holds about a quarter less oxygen at saturation than it would at sea level. Leave it blank for sea level.

Oxygen

What this water could hold, against what the standard asks

Enter a water temperature above and the ceiling for this water appears on the curve.

03691215405060708090WATER TEMPERATURE °FDISSOLVED OXYGEN mg/L
Saturation curve The most oxygen fresh water can dissolve at each temperature, corrected for the elevation entered. Physics, not biology: it falls as the water warms.
Your reading No water temperature entered yet. The same thermometer that answers the temperature question answers this one.
Which column applies Chosen from the fish this record documents — . A record naming both trout and warmwater species takes the coldwater column, because a criterion is a floor and the stricter floor is the one protecting what is there.

Saturation is the most this water could hold if it were in equilibrium with the air. Real water sits below it — respiration, decomposition and a weed bed at four in the morning all take oxygen out — so the curve is an upper bound on a good day, never a measurement. Only a meter in the water tells you what is actually there.

What this plate is telling you

Why the curve falls. Gas solubility drops as temperature rises. Water at 80°F cannot hold what the same water held at 50°F, whatever lives in it. That is why a summer warm spell and a fish kill turn up in the same week, and why the cold layer at the bottom of a stratified lake — perfect temperature, no resupply from the surface since spring — can be the emptiest water in it.

Sources. Benson & Krause 1984, Limnology and Oceanography 29(3):620–632, in the form USGS publishes for DOTABLES for the curve; U.S. EPA 1986, Ambient Water Quality Criteria for Dissolved Oxygen, EPA 440/5-86-003, Table 8 for the lines.

What this is not. Not a reading, not a forecast, and not a statement about Rathbun Lake on any particular day. Agencies publish measured dissolved oxygen at many gauges — that number outranks everything on this drawing.

No band drawn for

  • Crappie — a family, not a species. The record has not said which one, and picking a member of it to fill the space would be inventing the answer.

The fish, not the water

Where these species hold, and when

Movement, habitat and spawning timing for the species this record names, from the agencies that survey them. Read alongside the temperature band above: the band gives the number, and these give the behaviour that makes the number worth knowing.

3 reviewed for Channel catfish, Walleye. Nothing here is a rule or a season — the regulation still comes from the managing agency, on the day.

Official guide

Fish Iowa — Channel Catfish

Iowa Department of Natural Resources

checked 2026-09-08

Names the daytime cover to target — submerged logs, steep cutbanks, drift piles — and then the night move onto riffles and shallow pool edges. Just as usefully it names the water they avoid: clear cool streams, high-gradient streams and dense weed beds.

Why it made the list: Fetched 2026-09-08: page loads in the Fish Iowa species database with the day-cover and night-feeding text and the explicit habitat-avoidance list.

Open resource

Official guide

Walleye biology and identification

Minnesota Department of Natural Resources

checked 2026-09-08

Explains the eye — the tapetum lucidum that lets walleye feed in low light and stained water — and therefore why they push shallow at dawn and dusk and drop into depth or shade as light rises. Spawning peaks at 42–50°F over shallow rock and gravel.

Why it made the list: Fetched 2026-09-08: page loads on dnr.state.mn.us with the tapetum lucidum explanation, the dawn-and-dusk feeding line and the 42–50°F spawning peak.

Open resource

Video

In-Fisherman Classics: Walleye Location Secrets

In-Fisherman

checked 2026-09-08

Takes apart the assumption that walleye live on deep rock and walks through the range of structure they actually use through a season. It is about where the fish are, not what to throw at them.

Why it made the list: Fetched 2026-09-08: page loads with a video player embed and a description contrasting early In-Fisherman findings on walleye location with current understanding.

Open resource

Reading this water

Managed still water over a drowned valley. The read is about the old ground and the current level.

A reservoir is a flooded valley with the old ground still underneath it. Read the land above the waterline and continue it downward, then let the current water level tell you which of that structure is actually in play today.

Craft, not observation — this is the standing read for a reservoir. It holds no clarity, temperature, level, flow, tide or hatch for this water today, and it does not name a spot.

Detail

Water section

Managed still water over a drowned valley. The read is about the old ground and the current level.

A section through water of this class, near side on the left. It is craft, not a survey of Rathbun Lake — the shape of this particular bank is yours to read when you get there.

THERMAL BREAK12345SHORELINEOLD CHANNELYOU
1The old river channel It is the deepest, most continuous feature in the impoundment and the main travel route. Almost every good spot on a reservoir is where something else touches the channel. — likely.
2Creek arms and secondary points Arms warm and colour up first, hold spawning and staging fish, and give shelter when the main body is unfishable. — likely.
3Standing timber and flooded structure Vertical cover in open water: it holds fish at every depth and marks exactly where the old ground contour was. — worth checking.
4Riprap, the dam face and hard shorelines Rock holds heat and crayfish, and the transitions — rock to clay, rock to timber — concentrate fish far more than the middle of a long rock bank. — worth checking.
5Inflow and colour lines A colour line is an edge that fish use exactly like a weed edge or a drop-off, and it moves with the inflow. — worth checking.

Not drawn: water level is the whole read. Those describe the whole system rather than a place in it, and putting them somewhere on this picture would be inventing a location to make it look fuller.

What this plate is telling you

Solid zones are features this class of water nearly always has. Dashed ones are the subtler reads — present often enough to look for, not often enough to assume.

Nothing here is an observation of today. No gauge reading, no clarity, no temperature and no fish went into this drawing. It is the same standing craft an angler carries between waters, and the water in front of you outranks all of it.

Plan view · where along the water

A reservoir arm, seen from above

A drowned valley, which means there is a river under it. The old channel is the spine of everything here, and the level moving is the event that matters most. It is a schematic of this class of water, not a survey of Rathbun Lake — the shape of that particular shore is yours to read when you get there.

damfeeder streamOld river channelOld river channel — The original streambed running down the middle of the arm, now under water.Channel swing bankChannel swing bank — Where the old channel runs hard against one side of the arm.Shallow flatShallow flat — The broad shelf between the bank and the channel — the old floodplain.Standing timberStanding timber — Trees left in place when the valley was flooded.Creek arm mouthCreek arm mouth — Where a side arm joins the main arm.Riprap and dam faceRiprap and dam face — Engineered rock — the dam itself, causeways, bridge abutments.Back of the armBack of the arm — The shallow, silty top end where the feeder stream comes in.

Nothing on this reach is doing anything unusual. That is a normal day, and normal days are read by walking rather than by diagram. Set a wind, a water state or a tide and the picture will move.

NWind from the NNEWind from the NEEWind from the ESEWind from the SESWind from the SSWWind from the SWWWind from the WNWWind from the NWno wind set

Tap the point the wind is coming from. The shore it is blowing onto is the one that collects the drift — and the one that is least pleasant to stand on.

Water state

Tap a marked zone on the picture, or choose one by name above, for what it is, why fish relate to it, and how to find it standing there with no map. Nothing here says a fish is present — it says the physical reason that piece of water is worth a cast, and under which conditions that reason gets stronger or stops applying.

Decision flow

Four questions before the first cast

The drawing names features. This is the order that keeps them from becoming a scavenger hunt. Start with the force moving the water, find the shape that interrupts it, ask what changed, then verify the part the diagram cannot know today.

01Level / flow02Old valley03Draw / release04Level + access

Where is the drowned river?

Look for
Old channel, creek arm, channel swing, submerged point.
Why it matters
The reservoir still has a valley underneath it. That old route organizes depth and edges.

What did the level expose or cover?

Look for
Fresh bank, standing timber, dry ramp edge, newly flooded brush.
Why it matters
A level change can turn yesterday's cover into dry ground or put new cover under water.

Is generation changing the current?

Look for
Published release information and visible water movement near the channel.
Why it matters
A reservoir can behave like still water until a release makes the old river matter again.

When the water changes

It rained. They ran the dam. The wind swung.

Pick what actually happened. Nothing here reads a gauge — you supply the event, from your own eyes or the agency's page, and this says what it does to water of this class.

Still craft, not observation — this is what these changes do to a reservoir. It does not know whether any of them happened here, and it never will. The agency's page and your own eyes are the only things that do.

Detail

What this record changes about the read

  • Low-light feeders are documented here. Read breaklines and hard-bottom edges, and weight the ends of the day.
Structure

The old river channel

What it is
The flooded bed of the river or creek the reservoir was built on, still winding along the bottom.
Why fish hold there
It is the deepest, most continuous feature in the impoundment and the main travel route. Almost every good spot on a reservoir is where something else touches the channel.
How to find it
Follow the shape of the valley above the waterline and read it downward — the channel usually runs where the ground falls away fastest.
Depth

Water level is the whole read

What it is
Reservoirs are managed. Level can move metres within a season for irrigation, power, flood control or drought.
Why fish hold there
Level decides which structure is in the strike zone, which ramps are usable and what is submerged just under the surface.
How to find it
Read the bathtub ring on the bank. Then check the current level and the operating agency's plan before you commit to a launch.
Structure

Creek arms and secondary points

What it is
The side arms feeding the main body, and the points that step down into them.
Why fish hold there
Arms warm and colour up first, hold spawning and staging fish, and give shelter when the main body is unfishable.
How to find it
Work from the mouth of an arm inward. The secondary point inside the arm is often better than the main-lake point outside it.
Cover

Standing timber and flooded structure

What it is
Drowned trees, fence lines, roadbeds, foundations and bridges left in place when the valley was filled.
Why fish hold there
Vertical cover in open water: it holds fish at every depth and marks exactly where the old ground contour was.
How to find it
Treat any line of timber as a former edge — a bank, a road or a field boundary. Fish the line, not individual trunks.
Structure

Riprap, the dam face and hard shorelines

What it is
Engineered rock along the dam, causeways and bridge approaches.
Why fish hold there
Rock holds heat and crayfish, and the transitions — rock to clay, rock to timber — concentrate fish far more than the middle of a long rock bank.
How to find it
Fish the ends and the changes. A hundred metres of uniform riprap fishes like ten metres repeated ten times.
Edges

Inflow and colour lines

What it is
After rain, the upper arms run coloured and a visible line forms where stained water meets clear.
Why fish hold there
A colour line is an edge that fish use exactly like a weed edge or a drop-off, and it moves with the inflow.
How to find it
Follow the line rather than staying on a spot. The line is the structure that day.

2 further cues for this water class are held at a higher detail setting.

Watch · verify · keep reading

Useful instruction outside this app

These links teach transferable mechanics. They are not sources for today’s access, rules, weather or safety. A video can explain what a current seam is; it cannot tell you whether the ramp at a named water is open this morning.

13 reviewed for this class of water. Every link was opened on the date beside it — a dead link is a defect here, not a footnote, and a scheduled job re-checks them.

Agency and official references

Published by the bodies that measure and manage the water. These are the stable ones, and the ones to cite.

Official guide

How Streamflow is Measured

U.S. Geological Survey, Water Science School

checked 2026-09-08

Explains stage, discharge and the stage-discharge relation. Read this before treating a gauge number as if stage and flow were interchangeable.

Open resource

Official guide

Temperature and Water

U.S. Geological Survey, Water Science School

checked 2026-09-08

Why water temperature drives dissolved oxygen, and how a lake separates into layers through the season, with temperature-depth profiles from a real lake across May to October. The general-principles piece behind every seasonal temperature question in this app.

Open resource

Official guide

Lake Lanier Turnover Facts

Georgia Department of Natural Resources, Wildlife Resources Division

checked 2026-09-08

One reservoir's full annual cycle in plain language: how the three layers form, why the bottom layer runs out of oxygen by late summer, and what breaks the stratification in autumn. Read it before assuming fish are deep in August.

Open resource

Official guide

Understanding the Drawdown

Tennessee Valley Authority

checked 2026-09-08

What a drawdown is for and the sequence it follows through the year — high summer pool, faster release after Labor Day, winter flood-guide levels, refill from mid-March. The plainest answer to why a reservoir is twenty feet down in November.

Open resource

Official guide

Water Management — Nashville District

U.S. Army Corps of Engineers, Nashville District

checked 2026-09-08

A working example of what a Corps district publishes: pool and tailwater elevations, storage, hourly project data and proposed generation schedules. Use it as the template for finding the equivalent page for whichever district operates your reservoir — every district runs one.

Open resource

Official guide

Water Operations

U.S. Bureau of Reclamation

checked 2026-09-08

Daily reservoir and river operations across the five Reclamation regions, including the hydromet systems and the RISE portal. Reclamation rather than the Corps operates most western reservoirs, so this is where those levels and releases live.

Open resource

Official guide

Cold Water Hazards and Safety

NOAA National Weather Service

checked 2026-09-08

The three stages of cold water immersion, and the part most anglers have wrong: cold shock can be triggered by water as warm as 77°F, so a mild air temperature tells you nothing. Read it before spring wading and before any early-season boat or shore trip.

Open resource

Official guide

Harmful Algal Blooms

U.S. Environmental Protection Agency

checked 2026-09-08

EPA's hub, including the route to current state, tribal and local advisories. Advisories are issued locally rather than federally, so this is how you find out whether one specific water is under one right now.

Open resource

Official guide

Harmful Algal Blooms and Your Health

U.S. Centers for Disease Control and Prevention

checked 2026-09-08

What a bloom looks like in the water — foam, scum, a spilled-paint surface — and the exposure routes for people and for dogs. The practical rule is to stay out of discoloured or foul-smelling water and check the local advisory first.

Open resource

Official guide

Protect Your Waters

U.S. Fish and Wildlife Service

checked 2026-09-08

Clean, drain, dry as an actual procedure rather than a slogan: rinse the hull and gear, flush the motor, drain bilge and livewell before you leave the access, dry five days or towel down, bin unused bait. Written to be done every water, every time.

Open resource

Official guide

Fishing regulations

Washington Department of Fish and Wildlife

checked 2026-09-08

A good model of how a state regulations system is built: an annual pamphlet of statewide rules, water-specific exceptions that override them, and an emergency rule feed that supersedes the printed pamphlet mid-season. That three-part shape is near-universal, so it teaches you what to go looking for in your own state.

Open resource

Watch

Craft, taught by people who fish. Chosen for the instruction and the publisher’s track record, not because a recommendation algorithm surfaced them — the observed audience numbers are on each card so you can weigh that yourself.

Video

How to Read a Lake Map to Find Fish - Fishing

Flukemaster

checked 2026-09-08

Clear visual treatment of points, channels and structural breaks. It is map-based rather than a promise about fish location, which makes it useful beside the plan-view schematic.

Why it made the list: 38,986 views and 914 likes observed 2026-09-08; Flukemaster channel, 480K subscribers, published 2019.

Open resource

Video

In-Fisherman Classics: Identifying Productive Walleye Structure

In-Fisherman

checked 2026-09-08

Species-specific examples, but the useful part is structural: where bait and fish can relate to breaks, edges and basin features instead of featureless water.

Why it made the list: Page loads 2026-09-08 with the video asset present. The publisher's video CMS reshuffles ids periodically, so this is the least URL-stable entry in the library and is expected to need re-checking sooner than the rest.

Open resource

What this read cannot tell you

  • This is standing craft for this class of water, not an observation of this water today.
  • No clarity, temperature, level, flow, tide height or hatch is held here, and none is estimated.
  • Which features actually exist on this particular water is for you to confirm on the ground or from the official source.
  • Nothing here identifies a spot. It describes what to look for, not where to stand.

Getting on the water

Access & launches

3 named public facilities on record, 1 usable by a trailered boat, 1 with shore or walk-in frontage.

  • Trailer launch

    1

    A published ramp a trailered boat can use.

  • Hand launch

    1

    Carry-in access for a kayak, canoe or cartop craft.

  • Shore or walk-in

    1

    Public bank, beach or walk-in frontage.

Named public sites (3)

  • Published trailered launches (see agency access list)

    boat launch

    Status not stated

  • Published bank and shoreline frontage

    shore access

    Status not stated

  • Published hand-launch or carry-in access

    hand launch

    Status not stated

Facility names and amenity wording are reproduced from the official source, not restated. Where a status is not shown, the source did not publish one.

What this section cannot tell you

  • Gate hours, fees and same-day closures are set locally and are not mirrored here.
  • Facility condition — ramp surface, dock presence, depth at the ramp — is only known where the source stated it.
  • An amenity that is not listed is an amenity the source did not publish, not one that is absent.
  • Where a public corridor runs beside private land, the boundary is outside this dataset.
Find other launch-capable water in Iowa →

Hook the Horizon · the next step

Carry this water forward

You have answered where and what kind of water. Each instrument below answers the next question in the same workflow, and each link carries this record's water class, documented species, standing read, access position and declared job with it. Nothing is posted automatically, and no coordinates or private water travel in the handoff.

Narrow the handoff to one documented species (optional)

Species context is what the agency published for this water. It is never a statement that a fish is present today, or catchable.

  1. 01WaterYou are here

    Field Sense Navigator — which water, what kind, what to look for and what still has to be checked today.

  2. 02SpeciesSpecies & PresentationWhich of these fish are actually worth planning around, and how do they behave here?3 species are documented on this record. Carry them across instead of retyping them.
  3. 03Forage & hatchHatch MatchWhat are they likely eating on this kind of water at this time of year?Still water, so forage is tied to habitat rather than drift. The class and documented species go across.
  4. 04Optional · device validationRig SignalDo the electronics or device claims hold under the conditions you actually stated?Rig Signal is optional here: use it only when the trip depends on a device or electronics claim that should be checked against the stated conditions.
  5. 05TackleTackle Link AnalystDoes my line, leader and terminal tackle survive this water?Line and terminal tackle sized to crappie and to this water's cover.
  6. 06KnotKnot AnalystWhich connection holds for this line class and this structure?The knot is usually where it lets go. Line class and the structure you are fishing decide which one to tie.
  7. 07Field opsField Ops DeskHow does this become a trip — travel, timing, kit and the checks still open?3 same-day checks still open, plus 3 named access sites. Turn it into a trip.
Brief