|Better Farming Series 28 - Water: Where Water Comes from (FAO, 1981, 31 p.)|
|Why we study water|
1. Water is necessary for life. We need water for ourselves and our families to drink and to wash in,
to give to our animals to drink
and to make our crops grow.
2. We should know about water so that we can use water better.
3. This is very important if we do not have much water for long periods of the year.
4. The water we use for ourselves, for our animals and for our crops comes from the rain which falls from the clouds.
5. Even the water in swamps, lakes and streams comes first from the rain. For us, rainfall is very important.
6. In some places it rains very much but only during one or two seasons of the year. During the seasons when it does not rain, we may not have enough water.
7. We must learn how to store water when it rains so that we can have water when it does not rain.
8. In some places it rains very little and only at one season of the year. In other places, hardly any rain falls at all.
9. In these places, we have too little water and we must learn to find water in the ground or to store water when it does rain to use later.
Finiding water in the ground
10. To help us know more about the water we use, let us see:
· what happens to the water that falls as rain;
· where water goes after it rains;
· where water can be found when it does not rain.
11. When it rains, some of the water goes into the ground.
12. This water may stay near the surface or it may go very deep into the ground.
13. The water that goes very deep is called groundwater.
14. The level at which groundwater is found is called the water table.
15. If there is little groundwater, the water table becomes lower. If there is very much groundwater, the water table becomes higher.
16. If the water table becomes so high that it lies above the surface of the ground, it forms swamps, lakes and streams.
17. When it rains, all of the water may not go into the ground. Some of it may stay on the surface.
Water staying at surface
18. Water which stays on the surface will either lie in one place, if the land is flat, or it will run along the surface, if the land is hilly.
Water at surface: staying or running along
19. The water that lies on the surface is called surface water. The water that runs along the surface is called run- on water.
20. At certain times water evaporates from the surface of the soil or from swamps, lakes or streams. It becomes water vapour.
21. We cannot see water vapour. We cannot use it. Water vapour rises into the air to form new clouds.
22. Water vapour is also given off by plants.
23. Plants use the water in the ground to live and grow, and as they live they breathe and give off water vapour from stems and leaves.
Plants use water
24. This is called transpiration.
25. Like vapour given off by evaporation, the water vapour from plants rises into the air to form new clouds.
26. The water we use comes from rain which falls from the clouds.
27. Some of the water stays on the surface. Some of the water goes into the ground and some of the water that goes into the ground may go very deep.
28. Some of the water evaporates from the surface of the soil or from swamps, lakes and streams and some of it is transpired by plants. It becomes water vapour.
29. The water vapour rises into the air to form new clouds.
30. The clouds give up the water vapour as rain and the process begins again.