Groundwater

Where’s the Water? Water can be reached from anywhere on Earth if a deep enough well is drilled All water on and in Earth’s crust makes up the hydrosphere – 97% of all Earth’s water is in the oceans – 3% of all Earth’s water is considered freshwater 90% of all freshwater is in polar ice caps and glaciers 10% that remains is groundwater – <0.5% is easily accessible (lakes, streams, etc)

Zone of Saturation Depth at which groundwater completely fills all the pores of a material – Gravitational – trickles downward due to the force of gravity – Capillary – drawn upward from the water table and held in pore spaces due to surface tension The upper boundary of this zone is the water table

Location Matters Water table follows the topography of the land above it Water table depth depends upon local conditions – Stream valleys Few meters deep – Swampy areas At Earth’s surface – Hilltops, arid regions Tens to hundreds of meters deep

Groundwater Movement Rate of movement depends on two factors – Permeability of material (most important) – Slope of the water table Most groundwater flows through permeable layers called aquifers Aquicludes are impermeable layers – Clay (most impermeable), silt, shale