This is from the same article I just previously quoted, but it is so important to understand that I thought it worth doing a double-post.
Here’s a little experiment you can do at home to drive home how big an impact that vegetation changes can have. Fill two containers with soil and then wet them both with the same amount of water. Get them good and soggy. Cover one container with 30-50 cm of mulch. It doesn’t matter exactly how much you add, but the more you add, the bigger impact you’ll see. Now, place the containers out in the sun. Weigh them from time to time and watch the weight change during the day as the soil dries out. When a friend of mine did this during a soil science course, the mulched container lost 4.5 grams per hour of water and the unmulched container lost 28.2 grams per hour. Wow!