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Project of the Week 24: Crowdwater

This week we're visiting an app named Crowdwater, built on the Spotteron platform we wrote about last November.

What does this project do?
Crowdwater studies hydrology, the movement of water through the land in the form of rivers, groundwater and more. To do this on a large, social scale, it invites people to monitor their local river, soil, or sudden appearances and disappearances of water in their local area.

What do I have to do?
Go to and sign up for an account. After a short while you will get an e-mail and be able to make a profile. It will work by far the best on your phone.

Then go to a spot where there is water, such as your local river. This is Beverly Brook in Richmond Park, London - well worth a visit, especially if you also like iNaturalist.

Open your app there and tap "Create a Spot".

You'll be asked if you want to measure a river's depth, the moisture of the soil or record a temporary stream. This guide will teach you about the river - there's quite a lot you can do!

The map will show you where your spot is:

Take a picture of the river. You'll notice that a vertical line of numbers will appear in the middle of the picture:

This is a marker, for how high the bank, river surface and river bed are. You can choose your marker type for whether it's a deep, medium or shallow river - high, medium or low water level. (In the case of this river, I chose "low water level" - there was far more bank above the surface than below.)

Swipe the screen with your fingers, to push the marker up or down. You can make it longer or shorter. Its top should touch the top of the riverbank, the blue "0" in the middle should touch the surface of the stream and the bottom should touch the riverbed on the photo:

This spot is now marked where people can see it. You, or anyone else, can return another time, to see if the water level has changed. (It will be a bit subjective and may vary from person to person, but it should be roughly accurate. Roughly is enough to tell us if there are changes we should monitor - such as to predict droughts or floods: it has been found that this citizen science approach is sufficient to help hydrologists calibrate their models.)

This will be enough to get your spot recorded, but you can do a great deal more, such as comment on the type of river bed:

And you can also record the speed at which the water flows, and add more comments:

So as you can see, it can be quite a short task, or quite a detailed one, depending on what you choose. Ideally, you would return to the spot a few times to monitor any changes.

You can watch their tutorial on YouTube of this process - in very different weather.

Where can I find out more?
Crowdwater: About
Crowdwater: News
University of Zurich
Google Play store

What’s the Citizen Science Project of the Week?
Citizen Science Project of the Week is a regular feature at Doing It Together Science. What project would you like to see featured? Please let us know on the contact form, Facebook page or email us at Please put "Project of the Week" in the subject line and send us a link to the project, some information about it and why you'd like it featured. If you want us to, we'll credit you and tag you on Facebook!

More details
Crowdwater was started by two PhD students, Barbara Strobl and Simon Etter. Barbara gave a talk at the ECSA conference a few weeks ago, sharing what they've learned about how people respond to the app. They found that while people enjoy the opportunity to read around the science of hydrology, it's not helpful to combine this with the actual task - you overload people with too much to take in at once. So they put their instructions and the wider science on separate pages. They also find that offering people the opportunity to do just a small task - photographing the river and moving the marker, for instance, without requiring all the detailed work such as measuring the flow speed - is beneficial, because to demand too much led many volunteers to not finish their observations.

We covered the ECSA conference here, and so did the French publication Le Temps, which quoted Barbara as saying: "Local people know their river or stream much better than us and we have to learn to listen to them" - a theme that came up may times in that conference.

This app was developed in Switzerland, and a look at (ink: text: the map) will show you how much of the activity is taking place there. However, it's spread further afield and is now addressing some very urgent causes, such as the drought in Bangalore.

Even more details

Water or H2O is a fascinating and unusual molecule. It's also vital to life as we know it: it dissolves many substances and transports more, and makes roughly 60% of our bodymass. It has been said that when we left the ocean, we had to bring our oceans along inside us, which carried the salts our nerves use to send messages and the oxygen we breathe and the carbon dioxide we excrete. It also helps us regulate our temperature. Many plants rely on it to stay upright, which is why a plant will wilt if it's not watered for too long.

Most molecules of water's weight are gases, but water holds together more strongly (at Earthly temperatures and pressures anyway) because oxygen is very electronegative or greedy to hang onto the hydrogen's single electron, which draws the three atoms tightly together and creates in them a dipole, a slightly negative and positive end. This means that water molecules are very attracted to each other, and cling together - as you'll see when a drop of coffee trickles determinedly from your spoon onto the rim of the mug, or if you very slightly overfill a paper cup and rather than the water running down the sides, it makes an upward bulge. This property, surface tension, can be viewed as Colonel Chris Hadfield wrang out a wet towel on the International Space Station! Another effect of this attraction between the molecules means you have to put more energy into water to heat it than for the same amount of oil - which helps spread out the temperatures on the Earth as heat is transported from the equator to the globe by the water cycle. (You readily get all three states of water on Earth: solid - ice; liquid - water; gas - steam. This is definitely not the case for most things of which our planet is made, such as sand or air or rocks.)

As water cools, it reaches its densest point at 4ºC, then a new structure starts developing - a more triangular structure, that of ice, which is thus less dense and floats. Most liquids do not behave this way, but floating ice protects the liquid water underneath and allows pond and river life to survive cold winters. We also now know that warm water can freeze faster than cold water due to the Mpemba effect - it is disputed why this comes about, but it could be simply that heat is better transported by warmer water! Most intriguingly of all, water has been described as being "not one liquid, but two" - this is because of the behaviour of the nuclei of the hydrogen atoms. If the nuclei of both hydrogen atoms on the H2O molecule are spinning the same way, this is called "ortho-water". If they are spinning opposite ways, this is called "para-water". Para-water is able to attract other water molecules more strongly and undergo faster reactions. As far as I know, nobody has yet been able to separate the two.

(It probably doesn't matter about the spin of the oxygen, because it has a swarm of eight protons, eight electrons and eight, nine or ten neutrons, so there will be plenty of spinning - opposite ways and same ways - within the same atom. And of course it does not have a fellow oxygen atom to spin along with or against, even if there was an imbalance.)

So whether you're interested in the planet or the molecule, water is a very important subject to make an app to study!