(a) Define environmental balance. (b) With the aid of a diagram, explain the water cycle. (c) In what three ways is the water cycle beneficial to man?

(a) Environmental balance

Environmental balance is the stable and sustainable state in an ecosystem in which living organisms and non-living components interact through the recycling of matter and the flow of energy without upsetting the system.

(b) Water cycle

The water cycle, or hydrological cycle, is the continuous circulation of water between water bodies, the atmosphere, the land and living things.

Explanation of the diagram

1. Heat from the sun causes water in oceans, rivers, lakes and moist land to evaporate into the atmosphere as water vapour.
2. Plants also release water vapour through transpiration.
3. As the moist air rises and cools, the vapour condenses
4. When the droplets become large and heavy, they fall as precipitation, mainly rainfall.
5. Some rainwater flows over the land as surface runoff into rivers and back to the sea. Some infiltrates the soil as groundwater and also returns to rivers and the sea. The process then continues.

(c) Three benefits of the water cycle to man

1. It supplies fresh water through rainfall, rivers, springs, wells and boreholes for drinking, washing and other domestic uses.
2. It provides rainfall and soil moisture needed for agriculture and the growth of crops.
3. It replenishes rivers, lakes and reservoirs used for industrial purposes and the generation of hydroelectric power.