Runoff from farming communities poses a problem to streams, rivers, bayous, and even the Gulf of Mexico because it contains excess nitrogen and phosphorous compounds that change the amounts of aquatic vegetation. Find recent examples of these occurrences in wetland areas. Discuss the carrying capacity of water as related to velocity. Find historical examples of destruction by fast-moving flood waters. Demonstrate the concept of how a water table works and a wetland's ability to replenish aquifers.
Older students can work in small groups and perform the activity on their own.
Place a large sponge in one end of the pan to represent a wetland. Add enough sand to the rest of the pan to make a level landscape. Add water to the pan so that the sponge is completely saturated and the sand is saturated but not covered with water. Discuss the water table. Make a stream several inches away from the wetland by making an indention into the sand from one side of the pan to the other.