The largest watershed in Thailand is the Chao Phraya River Basin which covers approximately 35% of Thailand’s land mass. A watershed is all of the land area that drains into one common location such as the Chao Phraya River, a pond, wetland, lake, estuary, and eventually, the oceans.
Everybody lives in a watershed, and everyone shares the water within that watershed. Therefore everything in a watershed is in some way inter-connected which is why it is so important to think about how our actions may impact upon others.
A watershed can be quite large or extremely small. An example of a small watershed would be the soi near your home. The gutters along the sides of your house or apartment are even a kind of 'micro watershed'. Watersheds are separated from each other by areas of higher elevation called ridgelines or divides.