The refuge is made up of many wetland units. Do you know what a wetland is?
A wetland is an area of land saturated with water for an extended period of time during the year. This means that in a wetland area, you can dig down into ground that doesn't have water covering it, and find lots of water below the surface, while in other months of the year there won't be any water at all. In the Lahontan Valley, many of the wetland areas will dry up over the hot summer, but then will refill a little bit in the Fall & Winter with the small amount of falling rain and snow. The areas will receive most of their water in the Spring, with all the snowmelt off the mountains.
Wetlands are also characterized by the plants growing there. Usually they are water loving, like the Bulrush plants pictured above, and other plants such as Tule, in the background of the photo, and cattails. These are all emergent plants, which means their roots are in the soil that's under the water while their leaves and branches come up out of the water.