Abstract

Water-level fluctuations in wells completed in the Mississippi River Valley alluvial aquifer in eastern Arkansas were compared to variability in annual precipitation, an indicator of climate variability. The wettest year on record in Little Rock, Arkansas, occurred in 2009 with 81.79 inches of precipitation compared to an average of 47.1 inches per year. In contrast, 2005 and 2010 were the 7th and 14th driest years on record with 34.55 and 36.52 inches per year, respectively. This variability in precipitation was reflected in water-level altitude changes between 2004 and 2008 and 2006 and 2010. Generally, drier conditions between 2004 and 2008 led to an average decline in water levels of 1.62 feet, whereas wetter conditions between 2006 and 2010 led to an average rise in water levels of 1.36 feet. Drier periods likely resulted in less recharge compared to wetter periods. Groundwater use from the alluvial aquifer peaked in 2000 and has since declined, in part, because of conservation measures and substantial reduction in aquifer saturated thickness. Groundwater-flow model results showed some areas of the alluvial aquifer simulated as dry in 2010, indicating a reduced capacity of the alluvial aquifer to produce water in those areas. Additional factors affecting groundwater use include the types of crops grown in an area and the availabitiliy of crop subsidies. Real-time continuous water-level measurements in wells allow for a more accurate assessment of the effect of variability in precipitation and water use than periodic water-level measurements.

First posted February 19, 2013