Sources of Groundwater

Sources of Groundwater

Besides the replenishment of groundwater reservoirs by direct rainfall on the land above, there are other sources. Where the surfaces of lakes and streams are higher than the water table, and their beds are permeable, surface water seeps into the aquifer. Of course, movement goes the other way when the water table is higher than the surface water.

The rate at which groundwater is replenished depends, then, upon both a supply of water above the zone of saturation and the permeability of the soil and other formations through which the water must move in order to reach the groundwater reservoir.

Other factors also are important:

The condition and moisture content of the soil at the time of rainfall

The slope of the land

The rate at which rain falls on the land

Whether subsoil beneath melting snow is frozen

Soil which already contains a great deal of moisture will allow greater runoff of rainfall to surface water reservoirs. Steep slopes increase runoff (and flat land tends to have more tightly packed soil which slows infiltration and favors greater evaporation back into the atmosphere). Heavy rainfalls compact the soil, decreasing its permeability, while also encouraging greater surface runoff.

Thus, replenishment of groundwater is affected by two groups of factors:

Physical conditions of the area in which the aquifer exists

Climatic conditions