Hydrological droughts are influenced by fresh water systems.
If the level of water supplies slowly decreasing.
Hydrological drought can be seen quicker in farms as the soil dries up and becomes more like dust on the top layer.
Hydrological droughts are harder to point out earlier when looking at data from a reservoir because there is more water and will take longer to dry up.
This factors are usually evident after a couple months of Meteorological drought.