From Dust Game Guide

                            | ==================== |
                            |                      |
                            | The Thousand Sources |                       [S5]
                            |                      |
                            | ==================== |

You'll be introduced to a new totem power here: Evaporation. You'll also be 
faced with the dangers of having WAY too many sources on your map.

You should notice three sources directly in front of you. There are prickly 
plants on the other side of these sources, and there's a totem near those 
plants. First, use earth to build a bridge that blocks the smallest stream 
coming from the three sources. Then send your men over to the first totem. Note
that men cannot cross the prickly plants. After building your first village, 
the game informs you that you're in a desert. Vegetation cannot grow in the 
desert without first coming into contact with water. This won't be a problem, 
as you'll soon find out. There are three plateaus around the first totem. One
has a rock on it with a memory, one has a rock with the repel water knowledge,
and one has another totem on it. Send men to all three.

Do not bother trying to spread vegetation just yet. In fact, if you have to 
use earth, try to use earth that is near the mouth of the three sources river.
There are a ton of sources around here, and uncovering some of them will 
impede your progress. Capturing the second totem gives you the evaporation 
power, which basically just dries everything up. This is a great way of getting
rid of a lot of water. Now, send some men over to the last totem, the one that
is surrounded by prickly plants. You'll need to remove some of them, and in 
the course, you'll probably uncover sources. Cover them up quickly. One source
isn't a big deal, but the water will erode the earth around other sources, 
and soon you'll have too many.

Once you've got all three totems, you can start digging around in the dirt 
by the first two totems for sources. The prickly plants are covering up at 
least a couple, so start there. Start dumping water all over the place and 
you'll have the entire area covered in vegetation in no time. Now take your 
men to the portal. When they can go no further, use evaporation to eliminate
the water and continue to the next mission.