Rain falling within the Blacktown LGA will ultimately end up in one of the three major water bodies of the Sydney Basin: Sydney Harbour, the Georges River or the Hawkesbury-Nepean River. There are 22 major sub-catchments within Blacktown, feeding water into over 230 kilometres of defined drainage lines, including 153 kilometres of natural waterways. The waterways of the Blacktown LGA vary greatly in condition and in the values that may be attributed to them.
Through the removal of vegetation and additional impervious surfaces, such as roads and roofs, urban development has a major impact on the amount and speed in which stormwater is delivered to local waterways. Urban areas also generate large amounts of pollutants that affect the health of local waterways. As a result, it is common to see erosion of creeks, loss of vegetation, and pollution fouling local waterways - all of which leads to a loss of the biodiversity of plants and animals.