UNDERLYING AQUIFERS EFFECT ON RECHARGE RATES IN LOUISIANA
Although average precipitation in Louisiana varies from about 1220 mm/yr to 1630 mm/yr (48 inches/yr to 64 inches/yr) the average recharge rates throughout the state vary far more from about 2.5 mm/yr to 250 mm/yr (0.1 inch/yr to 10 inches/yr) when using the 80% rank and from about 13 mm/yr to 630 mm/yr (0.5 inches/yr to 25 inches/yr) when using the 50% rank. The difference of the highest and lowest value is 2 orders of magnitude for the 80% rank data and 1.7 orders of magnitude for the 50% data. This indicates that average recharge rate must be dependent on something that varies far more than precipitation. It is possible that this variation of nearly two orders of magnitude could be a result of the underlying aqufiers varying hydraulic conductivity. The variation of hydraulic conductivities for aquifers in Louisiana is about 1.4 orders of magnitude. The most conductive Louisiana aquifer is the Mississippi Alluvial Aquifer that has a geometric mean hydraulic conductivity of 40 m/day (130 ft/day) and the least conductive aquifer is the Wilcox Aquifer that has a geometric mean hydraulic conductivity of 1.5 m/day (4.9 ft/day). The range of aquifer hydraulic conductivities is fairly similar to the range of average recharge rates that have been estimated.