There are four major routes through which pesticides reach the water: it may drift outside of the intended area when it is sprayed, it may percolate, or leach, through the soil, it may be carried to the water as runoff, or it may be spilled, for example accidentally or through neglect.
Tudi kapljice škropljenih pesticidov ali delci pesticidov v obliki prahu lahko potujejo z vetrom na druga območja, ali pa se prilepijo na delce, ki jih razpiha veter, kot na primer prašni delci.