Water from lakes, rivers and dams is transported to the cities through long pipes. These are the water pipelines.
People have noticed that these pipelines often burst in winter when temperatures drop below 4o C. Why do you think this happens?
Anomalous expansion of water.
Heating leads to expansion (increase in volume) and cooling leads to contraction (decrease in volume). This is a general trend we observe with most materials.
Even water follows this trend most of the time. If we take water at room temperature around 25o C and begin cooling it, we will see that it contracts i.e. the volume reduces. This is as expected.
But once the temperature reaches 4o C, we notice something strange. If water is cooled beyond 4o C, it starts to expand! Remember that heating causes expansion usually but here we see that cooling leads to expansion. This is weird. That's why it's called the anomalous expansion of water. Anomalous means strange or different.
And this expansion is sometimes a problem. Since pipelines are built to transport water, we would want to pump as much water as possible. So the pipelines are usually completely filled with water. This is fine most of the time but when water expands below 4o C, the volume is more than what the pipelines can take. This causes cracks and eventually the pipes would burst.