Book 19 activities
Try it at home: 150 science activities from Book 19
Every question in A Million Whys Book 19, The River Expedition, ends with a "Think like a scientist" idea. Here they are in one place. Each one links to its question page, with the video and the full answer.
Expedition 1: A River’s Journey (25)
1. Where Does a River Begin?
On a rainy day, watch the water run down a driveway or sidewalk with a grown-up. Where do the little streams join together?
Do this with a grown-up2. What Is a Tributary?
Draw a river like an upside-down tree. Add three tributaries and label which one is the longest.
3. What Is the Mouth of a River?
Pour a little water slowly from a cup into a big bowl. Watch it spread out and slow down. That is what happens at a river mouth.
4. How Does a River Get Bigger as It Travels?
Fill a pitcher with water. Pour it into a baking pan. Add one cup at a time from other cups, like tributaries. Watch the “river” grow.
5. Why Do Mountain Streams Look So Fast and Big Rivers Look So Slow?
Tilt a baking tray a little and then a lot and pour a cup of water down it. Which slope makes the water speed up?
6. Which Rivers Are the Longest in the World?
Lay a piece of string along the Mackenzie River on a map or globe, then stretch it flat against the scale. How long is it?
7. Are Brooks, Creeks, and Rivers Different Things?
Write down the names people use for small streams where you live. Ask a grown-up what a creek is called in their hometown.
Do this with a grown-up8. Why Are River Valleys Shaped Like a V in the Mountains but Wide Near the Sea?
Draw two cross-sections of a valley: one narrow V and one wide U. Label which is near the mountains and which is near the sea.
9. How Does a River Carry Rocks and Sand Downstream?
Stir sand and pebbles in a bowl of water. Which stay up longest? Which settle first? Pour carefully so nothing spills.
10. Why Do Rivers Drop Sand and Pebbles When They Slow Down?
Shake a jar of water with sand, small stones, and soil. Let it sit still. Look at the layers that settle, big on the bottom, fine on top.
11. What Is a Watershed?
Crumple a sheet of paper and sprinkle water drops with a spray bottle. Mark where the drops run. Can you find the high ridges and valleys?
12. Where Does All the Mud Go at the End of a River?
Pour muddy water slowly from a cup onto a tray tilted into a bowl. Watch the sediment spread out. Dispose of the muddy water outdoors.
Do this with a grown-up13. What Happens Where a River Meets the Sea?
Stir plenty of salt and a drop of blue food coloring into a small glass of water. Pour plain water gently over the back of a spoon on top. Watch the two layers. Do not taste either one.
14. Why Does the Mackenzie River Run North Instead of South?
Place a book on a tray and tilt it. With a grown-up, pour a little water on it. Does the water follow the slope? Now change the tilt direction and try again. You just steered a river!
Do this with a grown-up15. Why Do Some Rivers Split Into Many Weaving Channels?
Sprinkle some flour on a tray, tilt it, and trickle a little water down. Watch the channels split and re-join. That is a braided river.
16. Why Do People Argue About Where a River Really Starts?
Look at a map and pick a river. Trace all its upstream branches with your finger. Which branch would you choose as the source? Why?
17. How Old Are Rivers?
Make a timeline strip. Mark “now,” “12,000 years ago,” and “a million years ago.” Which of these would a river’s age fit in?
18. Why Does a River Sometimes Leave an Old Loop Behind as a Crescent-Shaped Lake?
Bend a piece of string into a loop shape on a sheet of paper. Then draw a straight line across the neck. Which part becomes the oxbow?
19. Why Does River Water Turn White and Wild Over Rocks?
Pour water into a clear bowl from high up and watch the bubbles. Compare it to pouring gently. Why is one frothy?
20. Where Does a River’s Water Come From When It Hasn’t Rained for Days?
Soak a sponge in water and set it on a plate. Squeeze it gently and watch the slow drip. That is how the ground feeds a river.
21. Can a River Disappear Underground?
Pour water through a funnel filled with sand into a bowl. Notice how the water disappears and reappears below.
22. Why Do Some Rivers Have Different Names Along the Way?
Find a river that goes through two or more regions on a map. Does it have different names? Write them down.
23. Why Are River Rocks So Smooth and Round?
Rub two pieces of chalk or two sugar cubes together in your hand. Notice how the corners wear off. Rivers do this to rocks, but much slower. Brush the dust into a bin when you are done. You just did abrasion!
24. Where Does River Water Go After It Reaches the Sea?
Draw a loop with the sea, a cloud, a mountain, and a river. Add arrows to show how water travels in a circle.
25. How Can You Follow a Raindrop From Your Street to the Sea?
With a grown-up, find a storm drain near you and see if it has a label. Look up where your local creek goes on a map.
Do this with a grown-upExpedition 2: Reading a River (25)
26. How Can You Tell How Fast a River Is Moving?
With a grown-up in a safe place, drop a leaf in a slow stream, or float one in a bathtub or a long tray, and time it over a measured distance.
Do this with a grown-up27. Why Does Water Move Fastest in the Middle of a River?
Pour a stream of honey or syrup down a tray. Watch how the middle moves faster than the edges.
28. Why Does a River Dig Deeper on the Outside of a Bend?
Bend a trough of paper into a curve. With a grown-up, run a thin stream of water through it over a sink. Watch where the water speeds up. Watch where it drops sand. You just made a river bend!
Do this with a grown-up29. What Are Riffles and Pools?
Draw a side view of a stream bed with gentle humps and dips. Label two riffles and a pool. Draw arrows for the water.
30. Why Does a River Bottom Have Ripples Like Little Sand Dunes?
Pour a thin layer of sand in a baking pan. Gently tilt the pan back and forth with a little water. Watch ripples form.
31. What Do Ripples and Smooth Patches on a River’s Surface Tell You?
Watch the surface of a puddle or a bathtub while you drip water into it. Draw the patterns you see: smooth, rippled, or swirling.
32. What Colors Can River Water Be, and What Do They Mean?
Make a color chart of river water: use a clear glass with a drop of different food colors. Label each with a reason, like mud or algae.
33. Why Are Some Rivers Milky Turquoise?
Stir a spoonful of flour into a clear glass of water and shine a flashlight. See how the water turns cloudy. Add a drop of blue food coloring for the turquoise look.
34. Why Do Some Rivers Look Dark Like Tea?
Put a tea bag in a glass of cool water and watch the color spread. Compare the colors to river photos. Look for one that matches. Do not drink river water. You just made a tannin river!
Do this with a grown-up35. Is a River as Deep as It Looks?
Fill a bathtub or pan with water and put a ruler in at different spots. Where is it deepest? Imagine a river bed with hills and holes.
36. What Does a Stream Gauge Do?
With a grown-up, look up a gauge for a river near you online. Is the water higher or lower than usual today?
Do this with a grown-up37. How Do Scientists Measure How Much Water a River Carries?
Time how long a bathtub takes to fill with the tap running. Divide the tub’s volume by the time. That is a flow rate.
38. Why Does River Temperature Change During the Day and Seasons?
Put one glass of water in the sun and another in the shade for an hour. Measure the temperature of both with a thermometer.
39. Why Do Some Rivers Have Foam on Top?
Shake a bottle of water with a tiny drop of dish soap in it. Where does the foam collect? Rivers do the same with natural “soaps.”
40. What Is an Eddy?
Drag a spoon slowly through a sink of water and watch the little swirls at the back. Those are eddies.
41. Can Scientists Listen to Rocks Rolling Along a River Bed?
Put a few marbles in a closed tin and tilt it slowly, listening to the rolling sounds. Does tipping faster make it louder?
42. What Can River Pebbles Tell Us About Upstream?
With a grown-up, gather a few different pebbles from a path, parking area, or dry garden, not from the water’s edge. Group them by color and texture. Draw what you notice. Wash your hands afterward.
Do this with a grown-up43. What Do the Layers in a Riverbank Tell Us?
Layer sand, soil, and gravel in a clear jar. Pour in water and tilt it to see the layers shift.
44. What Is a Sandbar, and Why Does It Move?
Pour a thin stream of water onto a pile of sand in a tray. Watch sand pile up and move around.
45. How Do Scientists Follow River Water with Harmless Dye?
Drop a bit of food coloring in a glass of water and watch how it spreads. Stir gently and watch the swirl.
46. How Can You Read a River on a Map?
Pick a river on a map and trace it with your finger from source to mouth. Name each tributary that joins.
47. What Is a Seam, Where Fast and Slow Currents Meet?
Pour a stream of colored water into a slowly stirred bowl. Watch where the two flows meet and swirl.
48. How Do Whirling Pebbles Drill Holes in River Rock?
Drop a pebble in a shallow pan and swirl water around it. Watch it spin. Imagine that going on for thousands of years.
49. Why Does a Wave Stay in One Place While the River Rushes Through It?
Run water from a tap onto a flat plate and look for the small wave that forms in the sink. The shape stays still while water moves.
50. How Do Scientists Map the Bottom of a River?
Clap in a big hallway and listen for the echo. The longer it takes to come back, the farther away the wall is. Sonar uses that idea.
Expedition 3: Life Along the Current (25)
51. Why Do River Fish Face Upstream?
Hold a toy boat or a paper arrow in a tray of moving water. Does it point into the flow or turn sideways? Which way is steadier?
52. How Do Fish Hold Still in Fast Water?
With a grown-up at the sink, hold a flat spoon and a round ball in a stream of tap water. Which one feels more pushed? Streamlined shapes help fish! Share what you discover with a grown-up.
Do this with a grown-up53. What Lives Under the Rocks in a River?
Look up photos of mayfly, stonefly, and caddisfly larvae online with a grown-up. Draw your favorite and label its legs and tails.
Do this with a grown-up54. How Do River Insects Breathe Underwater?
Do ten push-ups yourself and notice your breathing. Then draw a stonefly doing push-ups on a river rock.
55. Why Do Mayflies Live Only a Day as Adults?
Draw a mayfly’s life: egg, nymph in the river, then winged adult. Add a clock showing the adult stage is very short.
Do this with a grown-up56. How Do River Bugs Cling to Rocks in a Strong Current?
Place a toothpick, a coin, and a flat pebble in a tray with trickling water. Which stays put best? Flat shapes stay put.
57. Why Does Rushing Water Hold More Oxygen?
With a grown-up, shake a closed bottle of cold water hard, then open it. Watch the tiny bubbles come out. Water holds air! Share what you discover with a grown-up.
Do this with a grown-up58. How Do River Otters Stay Warm and Dry in the Water?
Rub a feather or a dry sponge with a little water and see how water beads on or soaks in. Fur works with trapped air.
59. Why Do River Insects Let Go and Drift Downstream at Night?
Sprinkle a pinch of rice grains into a tray of gently moving water. Watch how the grains drift along with the flow, just as insects do.
60. What Is a Dipper, the Bird That Walks Underwater?
Do ten dipper bobs by bending your knees quickly. Then draw a dipper on a rock by a stream.
61. How Does a Kingfisher Dive for a Snack?
Fold a paper airplane with a pointed nose and drop it into a bowl of water. Does a pointy shape slip in easily?
62. How Do American Eels Swim From Rivers to the Faraway Sargasso Sea?
Use a globe to trace a path from the St. Lawrence River to the Sargasso Sea near Bermuda. About how far is it?
63. Why Do Salmon Swim Up Rivers?
Draw the salmon life circle: eggs in gravel, little fish, ocean adventure, and then the trip home. Number the steps.
64. How Do Young Fish Grow Up in a River?
Cut a piece of paper into a river shape. Use blue paper for fast water and green for calm edges. Where would baby fish hide?
Do this with a grown-up65. Why Do Fish Leap Out of Rivers?
Stand by a wall and mark how high you can jump. How does your leap compare with a salmon’s?
66. Can Dolphins Live in Fresh Water?
Sit in a chair, close your eyes, and let a friend click a spoon on a cup in different spots. Point to where the sound comes from.
67. Why Do Frogs and Tadpoles Live in Quiet Corners of a River?
Draw a river scene with a quiet side pool. Add tadpoles and plants. Label why the quiet spot is safer.
68. How Can River Plants Bend Without Breaking?
Wave a stiff stick and a strip of ribbon in a bathtub of water. Which handles the push better? Soft and bendy wins.
69. How Do Trees Along a Riverbank Help the Animals in the Water?
Draw a river with trees on both banks. Add arrows from the leaves to the fish and from the roots to the soil.
70. How Does a River Feed the Animals Along Its Banks?
Make a web: write “river” in the middle and draw lines to animals that visit it. Add arrows showing who eats what.
71. Why Are Fallen Trees Good for a River?
Place a twig dam, a stick, or a small log in a tray of flowing water. Watch how the water swirls around it and where it slows.
72. Which Animals Wake Up Along a River at Night?
With a grown-up, sit quietly near water at dusk, away from the edge, and list five sounds you hear.
Do this with a grown-up73. What Are Freshwater Mussels Doing on the Riverbed?
Squeeze a clean sponge underwater, then let go and watch it pull water in. A mussel pulls water in through a tube, keeps the food, and pushes the cleaner water back out.
74. Why Do Sturgeon Look Like Dinosaurs?
Measure a space on the floor to show 6 feet, the length of a big lake sturgeon. Lie down next to it.
75. How Do Animals Cross a Rushing River?
Build a leaf boat and see how many pennies it can hold before sinking. Do it in a bathtub or sink.
Expedition 4: Boats, Mills & River Towns (25)
76. Why Did People Build Towns Next to Rivers?
Look at a map of your region with a grown-up. How many towns can you find along rivers? Circle them.
Do this with a grown-up77. How Did Rivers Become Highways?
Trace a river route between two cities on a map. How far would you have to paddle?
78. Why Were Birchbark Canoes So Clever?
Fold a paper boat or a foil canoe and test how many pennies it holds in a sink of water. Redesign it to hold more.
79. How Does a Paddle Move a Canoe Forward?
In a bathtub, push a toy boat by moving a spoon behind it. Does pushing water backward move the boat forward?
80. Why Do Flat-Bottomed Boats Work Well in Shallow Rivers?
Float a flat tray and a rounded bowl in a tub and load each with pennies. Which sits higher? Measure how deep each sinks.
81. How Can a Ferry Cross a River Without an Engine?
Hold a small paper boat in a tray of moving water, tilted at an angle. Which way does the water push it? Try a different angle.
82. What Is a Ford, and Why Were Fords Important?
Look up where your town’s name came from. Does it have “ford,” “bridge,” or “river” in it?
83. How Does a Canal Lock Lift a Boat Uphill?
Fill a plastic box with water and push a toy boat into a shallow side compartment. Slowly add water and watch it rise.
84. How Is a Canal Different From a River?
Draw a river with curves and a canal with straight lines side by side. Label which is natural and which is made by people.
85. How Did Boats Travel Upstream Before Engines?
Tie a string to a toy boat and pull it along a tub with a gentle stream running from the tap. Is it easier to pull with the flow or against it?
86. How Did Paddlewheel Steamboats Work?
Make a paddle wheel from cardboard and a pencil. Hold it under a gentle stream from a faucet and watch it spin.
87. How Can a Barge Carry So Much?
Now, think like an engineer! With a grown-up, float a baking tray in a tub. Add pennies, one by one. How many can it hold before it sinks? Share what you discover with a grown-up.
Do this with a grown-up88. How Do River Pilots Avoid Hidden Sandbars?
Draw a river map with two sandbars and mark a safe path for a boat. Add red and green markers.
89. How Does a Water Wheel Turn?
Cut notches in a plastic cup or use spoons attached to a cork. Hold it under a gentle trickle of water and watch it spin.
Do this with a grown-up90. How Did a Water Mill Grind Grain Into Flour?
Grind a spoonful of oats between two flat stones or in a mortar and pestle. Watch how they turn into coarse flour. Wash your hands afterward.
91. How Does a Hydroelectric Dam Make Electricity?
Hold a pinwheel under a gentle tap. It spins like a turbine. What would happen if the water flowed faster?
92. What Are the Gates and Spillway on a Dam For?
Make a small dam from clay in a tray. Cut a notch in the top for a spillway and pour water in. Does the notch keep the dam safe?
Do this with a grown-up93. How Do Fish Get Past a Dam?
Build a ladder out of paper cups in steps and slowly pour water from the top. Imagine fish hopping up each cup.
94. How Did Loggers Float Trees Down Rivers?
Float some sticks in a tub and use a ruler to guide them toward one end. Imagine managing thousands.
95. How Does a Life Jacket Keep You Afloat?
Now, think like a detective! In a bowl of water, float a piece of foam and a stone. Which one floats? Foam traps air, so it keeps things up! Share what you discover with a grown-up.
Do this with a grown-up96. How Can Ocean-Going Ships Sail Deep Inside a Continent?
Trace the route from the Atlantic Ocean to Lake Superior on a map. How many Great Lakes can you name?
97. What Is a River Port?
Stack small boxes to build a model dock with a crane made of craft sticks. Practice loading a toy boat.
98. How Did Early Explorers Map Rivers?
Draw a map of a route in your neighborhood by pacing steps and noting turns. Use a compass if you have one.
99. What Is a Weir?
Place a ruler across a shallow pan and pour water slowly. Watch the water spill over. What happens when you pour faster?
100. Why Are Many River Towns Built Above the Water, Not Right at the Edge?
Build a model of a river town on a tray with blocks. Put the river at one end and decide where to place houses, docks, and parks.
Expedition 5: Rise, Fall & Freeze (25)
101. Why Do Rivers Rise Every Spring?
Pack snow or crushed ice into a tray with a slope, and watch the meltwater flow as it warms in a room. Where does the water go?
102. Why Can a River Be High on a Sunny Day?
Pour a cup of water at one end of a long tray and time how long it takes to reach the other end. Imagine that trip taking days.
103. How Do Forecasters Know a River Is About to Flood?
Make a pretend weather report for a river. Include the rain upstream, river height, and a safety message.
104. What Does “Flood Stage” Mean?
Mark a ruler with “normal,” “flood stage,” and “major flood.” Stand it in a bucket and add water to see each level.
105. Why Is the Land Near a River So Rich for Farming?
Sprinkle a pinch of garden soil in a glass of water and watch it settle in layers. The finest layer is the silt.
106. What Is a Levee?
Build a model river in a tray with sand and add a clay levee along one side. Pour water slowly and see how high it can go.
107. Why Is Floodwater Stronger than It Looks?
, safely indoors! Fill a tub with water and ask a grown-up to help. Push a plastic cup against the flow. Feel how the water pushes back. That is a tiny taste of its force. Never go near real floodwater!
Do this with a grown-up108. Why Does Rain Run Off Pavement Faster than It Soaks Into Grass?
Pour a cup of water on a plate and a cup on a tray of soil. Which one soaks in? Which runs away?
109. How Do Forests and Wetlands Slow Down a Rising River?
Drop water onto a dry sponge. Then drop the same amount onto a flat plate. Which one holds the water? Which one sheds it? Then tell a grown-up what you learned!
Do this with a grown-up110. Why Do Rivers Get Smaller in Late Summer?
Fill a shallow dish with water and leave it in the sun for a few days. Mark the level each day. How fast does it shrink?
111. What Happens to River Animals When the Water Gets Low?
Draw a low river with deep pools and gravel bars. Show where fish, insects, and frogs might wait for rain.
112. How Can You See a Drought in a River?
Mark the water level in a container. Leave it for a week, then mark it again. Look for your own bathtub ring. Then tell a grown-up what shrank!
Do this with a grown-up113. What Can a Dry Riverbed Tell Us?
Draw a dry riverbed with ripples in the sand, smooth stones, and cut banks. Label what each clue tells you.
Do this with a grown-up114. Why Do Rivers Freeze Later than Ponds and Lakes?
Fill two containers with cold water and put them in the freezer. Stir one every few minutes. Which one freezes later?
115. Why Does Ice Grow Out From the Riverbank First?
Put a shallow dish of water in the freezer and see where ice starts. Look at the edges first.
116. What Is Frazil Ice?
Make a slush by stirring crushed ice in salty water. Watch how it forms a mushy mix.
117. Can Ice Grow on the Bottom of a River?
Draw a river with anchor ice on the bottom, frazil slush in the water, and ice on top. Label each type.
118. Why Does River Ice Boom and Groan?
With a grown-up, listen to recordings of cracking ice online. Imagine what the ice looks like for each sound. Draw what you think is happening. Then play your favorite sound for your family!
Do this with a grown-up119. How Can Ice Pile Up and Block a River in Spring?
Float ice cubes down a narrow tray with a little water. Put a block in one spot. Watch the cubes pile up.
120. What Is Spring Breakup on a Northern River?
Make a calendar of spring signs: ice melting, birds returning, and flowers. When do you think your local “breakup” happens?
121. Why Is River Ice Never Safe to Walk On?
Make a safety poster that says “Stay off the ice.” Add pictures of reasons that ice may be thin.
122. How Do Fish Survive Under River Ice?
Fill a clear container with water and ice. Place a toy fish below the ice. Notice how the water under the ice looks.
123. Can the Ocean Push a River Backward?
Draw a river meeting the sea at high tide and at low tide. Use arrows to show which way the water flows.
124. What Does a Flood Leave Behind?
Pour muddy water onto a cookie sheet and let it dry. Look at the cracks and layers it leaves behind.
Do this with a grown-up125. How Can Scientists Tell How Big a Flood Was Long Ago?
Look at tree trunks near a stream with a grown-up and spot any scars or rough marks. Draw what you find.
Do this with a grown-upExpedition 6: River Helpers & Detectives (25)
126. What Makes a River Healthy?
Make a “river health” checklist with five clues: clear water, bugs, plants on the banks, no litter, and fish. Which clues could you check?
127. Why Does a Clean River Have Lots of Different Bugs?
Make a bug score card with three columns: sensitive, in-between, and tough. Place pictures of river bugs in the right column.
128. How Do Scientists Tell How Cloudy a River Is?
Drop a white button or coin into a glass of clear water, then add soil and stir. How deep can you see it now?
129. Why Does a River Need Oxygen?
Fill one glass with cold tap water and another with warm tap water, and leave them for an hour. Which has more tiny bubbles on the sides? Bubbles show dissolved air coming out as water warms.
130. What Does a Water Test Kit Check?
Test your own tap water, a glass of lemon water, and a glass of baking-soda water with pH strips and a grown-up. Compare the colors.
Do this with a grown-up131. What Makes Green Slime Grow in a River?
Fill two clear cups with tap water that has sat out for a day. Add a pinch of plant food to one and loosely cover both. Set them in a sunny window for a week. Which turns green faster? Never drink it. Wash your hands, keep it away from pets, and pour it outside when done.
Do this with a grown-up132. How Do Detectives Find Where Pollution Is Entering a River?
Set a long tray with a gentle trickle running from one end to the other. Add a drop of food coloring partway along. Which part of the tray turns colored: upstream or downstream?
133. How Does Litter Travel Down a River?
Float a few bits of clean plastic and paper in a tub. Which float away? Which sink? Pick them up afterward and recycle.
134. How Can a Water Wheel with Googly Eyes Clean a River?
Design your own trash wheel on paper with a water wheel, a conveyor, and a name. Give it a funny face.
135. How Can a Strip of Plants Catch Muddy Runoff Before It Reaches the River?
Pour muddy water through a tray with grass or moss in it and another tray without. Which tray gives clearer water?
136. How Do Scientists Bring the Wiggles Back to a Straightened River?
Draw a straight stream and then a wiggly stream. Label where fish could rest and bugs could hide in each.
137. How Do Scientists Count Fish They Can’t See?
Make a tally chart of cars passing your house in 10 minutes. This is similar to how scientists count fish passing a gauge.
138. How Can a Cup of River Water Tell Who Lives There?
Brush a dry paintbrush over a surface and rinse it in a cup. Imagine the leftovers as DNA traces in the water.
139. How Do Satellites and Drones Watch a Whole River at Once?
Look at a river on an online satellite map with a grown-up. Zoom in and out and find sandbars and bends.
Do this with a grown-up140. How Do Sensors Keep Watch on a River Day and Night?
Take your own “sensor readings” of the weather each day: temperature, wind, and clouds. Chart them for a week.
141. How Do Floating Trackers Show Where River Water Goes?
Drop a leaf into a slow-flowing creek from a safe spot with a grown-up, or in a sink. Predict its path first.
Do this with a grown-up142. How Can Kids Help Look After a River?
Pick one river job from the list and ask a grown-up to help you do it this month.
Do this with a grown-up143. What Jobs Do People Do with Rivers?
Pick a river job and write three things you would do on a typical day. Draw yourself at work.
144. How Can Old Maps Show That a River Has Moved?
Draw a river on tracing paper. Draw a second version on another sheet with a shifted bend. Lay them over each other.
145. What Is a Rain Garden?
Draw a rain garden next to a house, with arrows showing water flowing from the roof into the garden. Choose three flowers to plant.
146. How Do Experienced Boaters Decide Whether a River Is Safe to Paddle?
Make a pre-trip checklist with five things to check: weather, water level, life jackets, plan, and a grown-up. Tape it to the fridge.
Do this with a grown-up147. How Does a River Help Clean Itself?
Pour dirty water through a coffee filter to see what a filter catches. Mussels and plants do this naturally.
148. Are There Rivers on Other Worlds?
Draw a river delta on Mars with channels branching out. Add a rover exploring it.
149. How Can You Safely Explore a River?
Make a river explorer checklist: grown-up, shoes, life jacket for boats, camera, notebook, hand wash. Check it before your next outing.
Do this with a grown-up150. Which River Secrets Can Nobody Explain Yet?
Write your best river question. How could you investigate it safely with a grown-up?
Do this with a grown-up