Surface water–groundwater interactions along the Blanco River of central Texas, USA

Abstract

The Blanco River is a very important resource for water supplies in the Hill Country of central Texas. Some communities and properties along the river use the surface water directly. But, the Blanco River is more significant in the role it plays in providing recharge to the karstic Trinity and Edwards Aquifers. Recent studies have given a better indication of the complexity of the interactions between surface water and groundwater in the area. Besides being a water supply to a population of several hundred thousand people, water originally flowing in the Blanco River provides flow to springs that host a number of endangered species. The Blanco River is characterized by alternating gaining and losing stretches due to the presence of springs that discharge water into the river and swallets that drain water from the river. Trinity units outcrop in the western part of the study area, and Edwards units outcrop in the eastern part of the study area. Normal faulting along the Balcones Fault Zone has juxtaposed the older, stratigraphically underlying Trinity units against the Edwards units to the east. The region consists primarily of Lower Cretaceous limestone, dolomite, and marl. One of the more significant springs along the Blanco River is Pleasant Valley Spring. During below-average flow conditions, Pleasant Valley Spring becomes the headwaters of the Blanco River even though the headwaters, under wet conditions, are about 50 km upstream. These studies, summarized in this paper, provide a greater understanding of the surface water and groundwater resources in the area which will help guide policies for groundwater management and preservation of springflows and groundwater supplies.

Stream and Spring Water Evolution in a Rapidly Urbanizing Watershed, Austin, TX

“…Studies that have documented natural groundwater flow paths in central Texas show that recharge may take shallow (i.e., vadose zone), deep (i.e., phreatic zone), or mixed flow paths (e.g., Musgrove et al, ; Musgrove & Banner, ; Smith et al, ; Wong et al, ), depending on antecedent moisture conditions and the density of carbonate dissolution features (e.g., Wong et al, ). Urban development, however, complicates the controls on these flow paths due to the alteration of both surface (e.g., impervious cover) and subsurface (e.g., municipal pipe networks) characteristics.…”

“…The local phreatic water table is estimated between 5 and 68 m below ground surface, based on observation well data (n = 24; City of Austin-Watershed Protection Department personal communication, June 19, 2019) through the Fredericksburg Group (Figures 1b and 1d). Regional groundwater recharge (Hauwert, 2016;Smith et al, 2015) occurs through precipitation and losing streams that intersects outcrops of the Edwards Limestone (Figure 1b). The Edwards Aquifer Recharge Zone (e.g., unconfined Edwards Limestone) underlies much of the city of Austin (294 km 2 ), making groundwater particularly susceptible to urbanization-related contamination (e.g., storm water runoff and sewage) via conduit flow paths (Wong et al, 2012).…”

Recent advances in karst research: from theory to fieldwork and applications

“…The complexity of karst water resources, which is related to the great variability in flow characteristics and is dependent on the hydrological conditions (Ravbar et al 2011;Smith et al 2015;McCormack et al 2016), needs to be addressed. Fluctuations in karst groundwater can be several tens to hundreds of metres and, as a consequence, different types of surface-groundwater interaction can occur (Gabrovšek & Peric 2006).…”

Using Wavelet Coherence to Characterize Surface Water Infiltration into a Low‐Lying Karst Aquifer

“…In the context of karstified limestone aquifers, river bed exfiltration may constitute significant aquifer recharge (Salvador et al 2012;Smith et al 2015;Koeniger et al 2017) while the magnitude and direction of the interaction may be time variant depending on the hydrometeorological conditions (Bailly-Comte et al 2009;Charlier et al 2015b;Chapuis et al 2020). Linking (and delineating) surface water and groundwater "bodies" is a crucial aspect with regard to integrated catchment management and the protection of surface NGWA.org Groundwater waters and groundwaters, which is a priority of the European Water Framework Directive (WFD) (European Commission 2000.…”