What it shows
Pumping water from a well lowers the water table around it in a cone shape. Two close wells lower each other’s water, which is why borewells too near each other fail in summer.
The science
The water table is the top of the saturated ground. When water is pumped out, the water around the well flows in and the level drops most near the well, forming a cone of depression. Two wells close together have overlapping cones, so each draws water that the other needs.
Materials
Cost: under Rs 500. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A clear plastic box or aquarium about 40 cm long
- Clean coarse sand
- Two perforated plastic tubes with mesh as wells
- Two large syringes (50 or 60 ml) with tubing, to pump by hand
- Dyed water
- A marker and ruler
Safety
For this project: An adult must cut and drill the tubes. Place the tank on a stable table in a tray. Wipe up spills at once, and keep electrical devices away from water; pump by hand only.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
Step by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Stand the two tubes upright in the tank at each end and pack sand around them to 20 cm.
Add dyed water slowly until the water level in the sand is 12 cm.
Mark the level on the side of the tank and the water level inside each well.
Pump a fixed volume from well A and mark the new water table shape on the tank wall.
Wait until the level settles and measure the drawdown at the well.
Refill and repeat with pumping from both wells at once.
Move the wells closer together and repeat the test.
Compare the drawdown for one well, two far apart wells and two close wells.
What you should see
Pumping creates a visible cone of lowered water, and two close wells together cause a deeper drawdown than either alone.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01What is the water table?
The top surface of the saturated ground.
02What is a cone of depression?
The dip in the water table around a pumped well.
03Why do close borewells interfere?
They draw water from the same aquifer.
04How can a village protect its wells?
Space them well apart and recharge the aquifer.
Take it further
Add a layer of clay to the model and see how it changes the shape of the drawdown.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
Science projects
Earth, Space and Geography Models
Solar system, seasons, eclipses, volcanoes and the water cycle explained
Science projects
Investigatory Projects for Class 11 and 12
Topics, method and report structure for physics, chemistry and biology
Find out more about earth and space
Free, well-known places to explore the subject further. Ask a grown-up before you sign up for anything or type your name anywhere.