Freshwater andGroundwater

THE MOST IMPORTANT RESOURCE OF ALL!!!!!

John SolderAndrew McCauley

Natural StateGlobally 111,000 km3/yr of

water precipitates onto the earth’s surface.

65,500 km3/yr evaporate and transpire directly back to the atmosphere.

Humans use approx. 3800 km3/yr, only about 10% of the available freshwater discharge.

30% of ET is attributed to crops and rangelands, while 90% of water consumed goes to agriculture.

Units in thousands of Km3

(Jackson et al. 2001, fig. 2)

Natural Variation

Freshwater availability is a direct result of global climate variability.

50% of total annual discharge occurs through flooding, largely due to seasonal precipitation variability.

Aquifer Use and DepletionMany areas depend on groundwater as major

resource.

Groundwater is seen as an infinite reservoir and use is commonly greater than the rate of recharge.

Groundwater OveruseSubsidence

Drying up of current wells, drilling deeper for water. Reduction of local discharge. Salt water intrusion.

Salinization Partly saltwater intrusion affects the salinity of water in the

aquifer. Largely is the concentration of dissolved minerals from

irrigation.

Chemical Alteration Lowering of water table affects oxidation reactions in sub-

surface.Sulphate soils become acidic.Release of arsenic.Release of stored carbon in peat bogs.