On Thursday we'll test the real Tees for signs of some of these. Today we learn how.
Starter · 🤔 3 min
Healthy river, or sick river?
Finish this sentence in your head, or say it to the person next to you:
"You could tell a river was healthy if..."
Clues you can SEE
Is it clear or cloudy?
Any smell?
Fish? Birds? Bugs?
Litter or foam?
The catch
Some pollution is invisible. Clear water can still be sick. That's why we test — not just look.
I do · 🧪 6 min
The water-testing bench — tap each test.
What does each one measure? Tested: 0 / 6
👆 Tap any test on the bench. Find all 6 — that's how scientists judge a river.
We do · 🔬 4 min
Sort the clues: healthy river, or warning sign?
Tap a clue, then tap the bin it belongs in. Right = it drops in. Wrong = shake.
🟢 Healthy river
🔴 Warning sign
📌 Sorted: 0 / 6
Predict · 🗳️ 2 min
Before we go — what's your bet?
The tidal Tees at Portrack: how healthy do you think it is? Tap one vote — then tell the person next to you why.
▲ leading
🐟Healthy
▲ leading
🌫️Mixed
▲ leading
⚠️Struggling
No votes yet — tap your choice above.
NOW TALK
"I think it's ______ because ______." · Clue: it sits right next to a sewage works — but it's also a protected SSSI full of birds and seals. Both are true.
I do · 📍 4 min
Our stretch of the Tees — three things to know.
Portrack Marsh is where we're going. Tap each card for the story behind it.
History
✂️
The Big Cut
In 1830 people straightened the Tees here to speed up ships. Over 90% of the marshland was drained. Portrack is the last wetland on the lower Tees.
👆 Tap for did-you-know
Did you know? "Port Rack" comes from "racking" — horses dragging ships up the old river loop. The place is named after human muscle.
Today
🏭
The Works Next Door
A large sewage treatment works sits right beside the reserve. Cleaned water flows back to the river — a real source of the nitrate & phosphate we'll test for.
👆 Tap for did-you-know
Did you know? After heavy rain, more pollution gets washed in. That's often when a river's problems actually show up in the readings.
The tide
🌊
Why High Tide?
The Tees Barrage is 300m upstream and holds the river fresh above it. So Portrack is the last tidal stretch — at high tide the sea pushes brackish (salty) water up to the barrage.
👆 Tap for did-you-know
Did you know? Seals swim up on the tide — you might spot one. That's why our river session is timed for high water: more to see, and the tidal river at its fullest.
Watch it · 🎬 2 min
Kick sampling — watch it first.
This is one thing you might do at the river. Watch for: how they disturb the riverbed, catch the bugs in a net, then identify them to score the water.
Say it back: "Scientists ______ the riverbed, catch the ______ in a net, then ______ them. Clean-water bugs = a ______ river."
Independent · 🧪 6 min
Your lab — which river is healthier?
Two water samples. Tap the tests to run them, read the results, then decide. Your call, scientist.
Sample A · upstream
Sample B · by the works
Which is the healthier river?
Now record it. On your lab sheet: jot each reading, your verdict, and one reason. Written Q1–Q3 are on the sheet too, for your book.
On the day · 🗓️ 2 min
The day — Thursday 9 July.
⏱️ The plan
10:00 — arrive, Portrack Marsh. Meet in the Canal & River Trust car park — not the Talpore / Premier Inn one.
Morning — Rivers session (high tide): water quality & human impact.
~12:00 — lunch. Toilets at the Talpore pub.
Afternoon — Biology session: sampling the grassland (that's L1d).
2:00–2:30 — finish.
🎒 Bring
Warm layers + a waterproof (Teesside, July, still can rain).
Sturdy shoes or wellies — it can be muddy.
Packed lunch + a drink.
Sun cream / hat just in case.
Your recording sheet + a pencil.
⚠️ Water rules — non-negotiable
Respect the water. Stay behind the line staff set. Tell an adult before you move. Wash hands before eating. Listen to the Trust staff and your teachers — they know this river.
Exit · 🎫 2 min
Three quick ones. Then you're out.
Q1. Why is our river session timed for HIGH tide?
Q2. You find only worms and leeches — no mayflies. What does that suggest?
Q3. Where do we meet on Thursday 9 July?
Done
Today, you've ticked:
✓Named the ways we test a river — physical, chemical, biological.
✓Said what a reading (pH, oxygen, bugs) tells us about the water.
✓Described a human impact on the Tees — and why we go at high tide.
Quick 5-minute break → then L1d
Straight after your break: "Life in the Grass" — how we sample the grassland fairly, and our impact on it. (That's the afternoon session on the day.)
See you Thursday 9 July · 10:00 · Portrack Marsh (Canal & River Trust car park).
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TA Focus · This slide
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Cold call · random pupil
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Tier
—
🌊 Ready.
You can read a river now. Thursday, you test the real one.
L1c · Do Now — While You Settle In
Name:
Class:
Date:
Get started on your own — no phones, no looking it up. We'll begin properly in a few minutes.
1 · Warm up your brain
Write down three things that could pollute a river.
2 · True or false?
Circle T or F. Have a go even if you're not sure.
Clear water is always clean and healthy.T / F
Warm water holds less oxygen than cold water.T / F
The kinds of bugs in a river can tell you how clean it is.T / F
Sewage and farm fertiliser can add nutrients to a river.T / F
3 · Getting ready
Tick anything that's true for you:
I know where Portrack Marsh is.
I've done a science test outdoors before.
I've got a waterproof / wellies for Thursday.
I know we meet at 10:00.
One thing I still need to sort before Thursday:
L1c · Reading the River — Knowledge Organiser
Name:
Class:
Date:
Lesson learning outcomes
Name the ways scientists test if a river is healthy
Say what a reading (pH, oxygen, invertebrates) tells us
Describe one human impact on the Tees at Portrack — and why we go at high tide
The water-testing toolkit
Temperature (physical)Warm water holds less oxygen — bad for fish.
Turbidity (physical)How cloudy the water is. Cloudy blocks light & clogs gills.
pH (chemical)Acidic or alkaline. Most river life needs 6.5–8.0.
Dissolved oxygen (chemical)The gas fish & bugs breathe. Low = river in trouble.
Nitrate / phosphate (chemical)Nutrients from sewage & fertiliser. Too much feeds algae.
Invertebrates (biological)Indicator species. Mayfly = clean; worms only = polluted.
Key facts — our stretch
Where: Portrack Marsh, Stockton — the last wetland on the lower Tees, and an SSSI.
Tidal limit: the Tees Barrage (300m upstream) holds the river fresh above it; Portrack is the last tidal, brackish stretch.
Human impact: straightened in 1830 (>90% of marsh lost); a sewage works sits right next door.
Why high tide: the sea pushes brackish water up to the barrage — the tidal river at its fullest (and seals may come up).
Trip: Thu 9 July, 10:00 — Canal & River Trust car park (NOT the Talpore). Finish 2:00–2:30.
Key terms
Indicator speciesA creature whose presence reveals the water's health.
TurbidityHow cloudy or clear the water is.
BrackishA mix of fresh and salt water.
Tidal limitThe furthest point the tide reaches upstream.
Nutrient pollutionToo much nitrate/phosphate feeding algae.
SSSISite of Special Scientific Interest — legally protected.
L1c · We Do — Healthy River or Warning Sign?
Name:
Class:
Date:
✅ Completed together as a class. Here is how we sorted the clues. Tick each one you got right.
🟢 Healthy river
Lots of mayflies & stoneflies
Clear water — you can see the bottom
High dissolved oxygen
🔴 Warning sign
Only worms & leeches
Green algae over the surface
Smells of sewage
One clue I want to remember on the day — and why:
L1c · Run the Tests — Lab Record
Name: Sample / spot:
Use this at the river. Predict first, then measure, then decide.
Test
What I predict
What I measured
Temperature (°C)
Turbidity (clear/cloudy)
pH
Dissolved oxygen
Nitrate / phosphate
Invertebrates (which bugs?)
My verdict
This water looks healthy / mixed / struggling (circle one) because…
The reading that convinced me most was…
L1c · Your Work — Reading the River
Name:
Pick the question that's right for you — or do all three if you can. Use the word banks and sentence starters to help.
Q1. Name two tests we will do, and say what each tells us. F
One test is ________________. It tells us ________________.
Another test is ________________. It tells us ________________.
Q2. Portrack sits next to a sewage works. Predict our nitrate and oxygen readings — and why. M
Chain to followsewage/fertiliser → nutrients → algae grow → algae use up oxygen
I predict the nitrate will be… because…
I predict the oxygen will be… because…
Q3. Explain why we test in three ways — physical, chemical AND biological. H
Using more than one test is better because…
For example, a single chemical reading might miss…
The examiner wants: the idea that one reading is a single moment, but invertebrates show the long-term story — and that clear water can still be polluted.
🌟 Finished? Plan your fair test
Write WHERE you'd sample, HOW two groups could compare fairly (same method, same time), and one SAFETY rule.
L1c · Revision & Self-Quiz
Name:
Self-quiz · cover the answers
Q1. Name the three types of water test.
Q2. What does turbidity measure?
Q3. What pH range do most river creatures need?
Q4. Why is warm water bad for fish?
Q5. Where do nitrate and phosphate come from?
Q6. What is an indicator species?
Q7. Which bugs mean clean water? Which mean polluted?
Q8. What does "brackish" mean?
Q9. Why is our trip timed for high tide?
Q10. Which car park do we meet at on 9 July?
Memory hooks
Three tests: "Physical, Chemical, Biological — Please Check Bugs." 🐛
pH range: "Six-and-a-half to eight — life feels great." 🧪
Oxygen & heat: "Warm water, less air — fish gasp everywhere." 🫧
Bugs: "Mayfly means clean; worms alone mean mean." 🦐
High tide: "Barrage above, brackish below — that's why at high tide we go." 🌊
Common mark-losers
Saying clear water is definitely clean (pollution can be invisible).
Mixing up high nutrients (bad) with high oxygen (good).
Thinking one test is enough — you need all three types.
Forgetting the tide: Portrack is the last tidal stretch, below the barrage.
Meeting at the Talpore car park — it's the Canal & River Trust one.