Human intrusions into the water cycle

Human intrusions into the water cycle

Human intrusions into the water cycle

The water cycle

Water is continually cycling, changing from solid to liquid to gas. Water from soil surfaces, leaves of plants, bodies of water, etc., evaporates as these are treated by the sun. Water vapor in the air condenses to form clouds. When the air becomes saturated with vapor and the temperature goes down, the water vapor falls down the earth's surface as rain, snow, dew or fog. Rain that falls on land infiltrates the soil and is then absorbed by plants and is transpired or evaporated from leaf surfaces. When the soil is saturated, the excess rain may flow on land surfaces as runoff, adding water to creeks, streams, rivers and eventually to the oceans. The heat of the sun propels the continuous water cycle.

Water used for various purposes today is the same water which has been in existence since the beginning of earth. Water cycle interconnects the terrestrial and the aquatic ecosystems. Water cycle is also global in scope. Human actions can reduce the quality of water through pollution and sedimentation. This can seriously affect the environment on which we depend for our existence.

The water cycle

Effects of human activities on the water cycle

Clean water used to be abundant. But it is now becoming a precious commodity.

Human activities have damaged most of our water systems. Improper disposal of sewage, garbage and animal manure has polluted the waterways, rendering the water unfit for human consumption. These pollutants increase the nutrient content of the water and the population of disease-causing germs such as those causing gastro- intestinal disorders. Mine tailings dumped in the rivers cause heavy metal pollution which are suspected causes of cancer and genetic and nervous disorders. Agricultural fertilizers and pesticides that drain into the river system contaminate ground water and enrich the nutrient level of freshwater bodies, eventually killing much aquatic life.

Lower pumping of freshwater near the beach, as in prawn culture, may cause salt water intrusion into the ground water, damaging the source of potable water of a large segment of the population.

Forest destruction in watersheds causes erosion and sedimentation leading to the shallowing of river channels. Forest destruction alters the water cycle.

Heavy rains, strong typhoons and shallow river channels can cause flooding of low lying areas as rivers overflow. This was what happened during the Ormoc tragedy.

Siltation of dams and killing of coral animals in the marine ecosystem are also due to soil erosion carried by flowing waters.