Effect on Plants: 1.5 Marks
Effect on humans: 1.5 Marks
Plants need water to get nutrients from the soil to prepare their food. So, if water is not present in a proper amount in the soil, plants will not be able to get nutrients.
If plants do not get proper nutrition ultimately they will die.
This will have a catastrophic effect on humans. Without plants, there will be no oxygen, and no food, both of which are essential for the survival of humans. 
These are essential elements for living. Without them, we will die. So, it is necessary for us to ensure that plants get enough water.