Rates of water movement via throughflow are usually low. Rates of maximum flow occur on steep slopes and in pervious sediments. The lowest rates of flow occur in soils composed of heavy clays. Rates of throughflow in these sediments can be less than 1 millimeter per day. Hydrologic movement of water beneath the Earth's surface.
Water usually enters the surface sediments as precipitation .
This water then percolates into the soil layer. Some of this water flows horizontally as throughflow . Water continuing to flow downward eventually reaches a permanent store of water known as the groundwater . The movement of groundwater horizontally is called groundwater flow . The top of this zone is called the water table .