Discharge variability for an artesian spring of the Edwards Aquifer: Comal Springs (1933–2007)

Abstract

Daily discharge volumes of Comal Springs, the largest artesian spring of the Edwards Aquifer (EA) in Central Texas, were utilized to characterize the flow of Comal Springs for the period of record spanning . The influence of water extraction (pumping) on discharge characteristics during the record was examined and found to be statistically significant for both volume and variability of spring discharge (p < 0.01). Pumping explains approximately a quarter of the variation in annual discharge (r 2 = 0.25) and nearly a third of the daily variability (r 2 = 0.32) within the Comal Springs discharge record.Statistically significant teleconnections to flow are demonstrated within the discharge record of Comal Springs. The El Niño-Southern Oscillation (ENSO, as measured by the Southern Oscillation Index) and the Pacific Decadal Oscillation (PDO) are shown to exhibit statistically significant correlations with annual mean flow from Comal Springs. PDO modulation of ENSO results in mean flow anomalies of 21.9% between extreme quintile years. The Atlantic Multi-decadal Oscillation (AMO) appears to exert influence based on the magnitude of the index value, irrespective of its positive or negative condition (p < 0.01), with the highest quintile (based on magnitude) years correlating with strong positive flow anomalies. A composite index was developed which combines the AMO, PDO and SOI. The extreme quintile years of this index demonstrate a 32.4% divergence in flow (p < 0.01) while demonstrating a stronger skill at capturing negative flow anomalies than positive anomalies.Precipitation data, at 4-km spatial resolution, were utilized to examine the temporal and spatial correlation of water input to the EA with rates of average monthly discharge from Comal Springs. The spatial dependence of the correlation between precipitation and Comal Springs discharge indicates significant seasonal variability. Overall, the correlation between precipitation and discharge is significant for spring, summer and fall seasons and not significant for winter.

Probability-based classifications for spatially characterizing the water temperatures and discharge rates of hot springs in the Tatun Volcanic Region, Taiwan

“…Moreover, springs can also be classified according to the volume of water they discharge (Alfaro and Wallace 1994;Krešić 2010). Generally, various factors affect the discharge rates of springs, including the geomorphology; geological fabrics (i.e., rock types and tectonic features, such as folds, fractures, and faults); hydrology (i.e., the recharge of precipitation and river water); and nearby groundwater use (Negi and Joshi 2004;Hao et al 2006;Anderson and Fairley 2008;Cox et al 2009;Krešić 2010;Ozdemir 2011). The overexploitation of spring water occurs frequently in many Taiwanese spring resorts (Erfurt 2011), including those in the Tatun Volcanic Region, resulting in a considerable decrease in water levels and temperature at affected springs.…”