Question

give any two causes that leads to a decrease in ground water level

Answer 1

ground water level depends on the replenishment rate , which is done by natural rainfall. so if ground water level is going down , it means that due to insufficient rainfall is happening or may be rainfall is adequate but surface runoff is more, so ground is not able to absorb water. Secondly if there is a situation of drought may be because of elnino southern oscillation effect in indian situation if you are considering that and thirdly due to excessive groundwater usage for farming and residential purposes.

Answer 2

extended irrigation and use of pesticides which end up in the ground