Devils River watershed: Southern Edwards-Trinity Aquifer

Abstract

The Devils River in south-central Texas is recognized as one of the remaining pristine rivers in the state. Adding to its importance, the Devils River is a key tributary to the Rio Grande, providing essential freshwater flows to south Texas and the Rio Grande Valley. An efficient conveyance system for groundwater is shown to have formed in the karst carbonate watershed, located in a semiarid environment with modest distributed recharge, oftentimes less than 1-2 cm/yr. This conveyance system comprises preferential flow pathways that developed coincident with river channels. A strong correlation between wells with high well yield and proximity to higher-order river channels (i.e., within 2.5 km) was used as evidence of the presence of preferential flow pathways. An important observation is that groundwater flow in the Devils River watershed appears to be controlled by the morphology of the area more than the bulk hydraulic properties of the rocks. Flow measurements in the Devils River measured under relatively high-and low-flow conditions support the hypothesis that the river is gaining in downstream reaches. This characteristic leads to perennial river flow being restricted to only the lower reach of the river. Last, essentially all of the recharge to Amistad Reservoir that is derived from the Devils River watershed is contributed as surface flow from the river, and there is minimal underflow or cross-formational flow from the watershed at the point where the watershed abuts Amistad Reservoir.

Thermal tolerance exceedances of an endangered unionid mussel in the Rio Grande Basin, with implications for river management

“…The differences in thermal exceedances between the Black and Devils rivers can probably be explained by human activity. The Devils River is a spring‐fed system with limited human impacts: in fact, it has often been described as ‘pristine’ (Randklev et al, 2016; Green et al, 2019; Robertson et al, 2019; Caldwell et al, 2020). In contrast, the Black River is heavily used by the agricultural and oil and gas industries, which extract both groundwater and surface water for activities such as irrigation and the fracking of fossil fuels (Bren School of Environmental Science & Management, 2014).…”

Low Flow Trends in Texas Stream Segments Serving Unique Hydrologic Functions

“…From a natural resource management perspective, water levels in the J17 and J27 wells are used by the EAA as the criterion for distinguishing stages of drought as part of a critical period management (CPM) plan. In Uvalde County, the water level of well J27 has been reported to be the most suitable indicator of drought severity by Green and Bertetti (2010), as river discharge did not appear to be useful. However, the cross-correlation at a 1-year lag between mean flows at gages 08190000 and 08195000, and the mean of daily-high water levels at well J27, as well as the moderately strong but statistically significant r 2 between the two, suggest that discharge at these two gages merits consideration for an early warning or preliminary drought trigger system for Uvalde County.…”

The Edwards Aquifer

“…The plateau west of the Pecos River is referred to as the Stockton Plateau. Key studies of the Edwards-Trinity Aquifer have been conducted by the U.S. Geologic Survey (Kuniansky, 1989;Kuniansky and Holligan,1994;Barker et al, 1994;Barker and Ardis, 1996), the Texas Water Development Board (Walker, 1979;Rees and Buckner, 1980;Mace et al, 2000;Anaya, 2009, 2019;Mace and Angle, 2004;Jones et al, 2011;Hutchison et al, 2011), and Green and Bertetti (2010). The combined groundwater flow system of the Edwards-Trinity (Plateau) Aquifer and the Hill Country portion of the Trinity Aquifer covers about 100,000 km 2 (39,000 square miles).…”