Stream water percolates down through the soil until it reaches the zone of saturation. Other streams alternate between losing and gaining water as the water table moves up and down according to the seasonal conditions or pumpage by area wells. Most significant is the fact that developed land is more impervious than natural land. Instead of percolating into the ground, rain hits the hard surfaces of buildings, pavement, and compacted ground and runs off into a storm drain or other artificial structure designed to move water quickly away from developed areas and into a natural watercourse. The fate of precipitation in undeveloped vs. developed watersheds Survace runoff increases and ground water recharge decreases as watersheds become developed.
Less precipitation is transpired back to the atmosphere from plants.
Less precipitation percolates through the soil to become ground water. More surface runoff is generated and transported to streams. Chapter 3, Watershed Survey Methods, is designed to help volunteers learn about their watershed. Using the watershed survey approach, they will become familiar with their watershed's boundaries, its hydrologic features, and the human uses of land and water that might be affecting the quality of the streams within it. The position of the water table sometimes plays a role in determinating the amount of streamflow.