A rapid population increase accompanied by unplanned developmental works have led to the pollution of surface waters by residential, agricultural, commercial and industrial wastes / effluents and decline in the number of waterbodies. Increased demands for drainage of wetlands have been accommodated. Various anthropogenic activities have altered the physical, chemical and biological processes within aquatic ecosystems. Collection of silt and pollutants are the two other important reasons for the depletion of lakes.

a. Runoff threats
While wetlands can reduce the impact of some pollutants, too much pollution will negatively impact the wetland. Thus, the quality of a wetland is dependent on the water flowing into them...and the pollutants that the water carries with it from activities in the watershed.

Runoff, originating with rainfall or snow melt, that contains pollutants-oil, grease, fertilizers or pesticides-is called nonpoint source pollution. In addition to the potential of runoff polluting wetlands, it also can pollute other surface waters such as lakes, rivers, and oceans. Eventually it can reach groundwater, which is often used for drinking water.

b. Naturally occurring events - hurricanes, droughts, erosion, drops in groundwater levels-destroyed or severely threatened some wetlands