Hydrologic Trends in the Upper Nueces River Basin of Texas—Implications for Water Resource Management and Ecological Health

Abstract

Reliable water sources are central to human and environmental health. In south Texas, USA, the Nueces River Basin (NRB) directly or indirectly plays that important role for many counties. Several NRB stream segments are designated as ecologically significant because they serve crucial hydrologic, ecologic, and biologic functions. The hydrologically significant streams recharge the Edwards Aquifer, an essential water source for the region’s agricultural, industrial, and residential activities. Unfortunately, the semiarid to arid south Texas climate leads to large inter-annual precipitation variability which impacts streamflow, and as a consequence, the aquifer’s recharge. In this study, we used a suite of hydrologic metrics to evaluate the NRB’s hydroclimatic trends and assess their potential impacts on the watershed’s ecologically significant stream segments using precipitation and streamflow data from the National Climatic Data Center (NCDC) and Hydroclimatic Data Network (HCDN) respectively from 1970 to 2014. The results consistently showed statistically significant decreasing streamflow for certain low-flow indicators over various temporal scales, likely due to water rights diversions and minimal land use changes. This research could help decision-makers develop the necessary tools to manage water resources in south Texas, given the NRB’s significance as a source of water for domestic consumption and ecological health.

Spatial and Temporal Evolution of Low Water Flows in the Sassandra River Catchment Area in Cote d’Ivoire

“…The monthly periods from January to March and February to May, according to the climatic zone. Minimum of different durations can be determined, with 3, 5 7 and 10 days is commonly used (Lang, 2011;Garcia, 2016;Thomas et al, 2019). The number of days is often chosen to smooth the effects of measurement errors in the flow or the effets of human activities.…”

“…Evaluating the presence and absence of trends in low flow for the selected stations were carried out by using the Mann and Kendall (MK) trend test (Kendall, 1975 presence of the monotonic increasing/decreasing trend. This statistical test has a variety of applications for trend analysis (Temesgen et al, 2014;Assefa & Moges, 2018;Thomas et al, 2019). The non-parametric Mann-Kendall statistical test has been affected and the most used to assess the significance of the trend in low-flow indices.…”

Low Flow Trends in Texas Stream Segments Serving Unique Hydrologic Functions

“…Low flows in streams are often used in natural resource management and environmental regulation as an indicator of overall stream health. Several researchers (e.g., Hisdal et al 2004;Jowett and Biggs 2006;Bradford and Heinonen 2008;Thomas et al 2019) have highlighted increased stress on aquatic, riparian, and hyporheic ecosystems during low flow due to decreased water availability and habitat quality. During these intervals, low flows help maintain longitudinal connectivity in the stream (Curran et al 2012).…”

“…Upon receiving this designation, the stream segment is protected from the construction of State-funded reservoirs. Most of the segments that have been recognized for their unique hydrologic function are located in the Edwards Plateau (EP) region of Texas and serve as above-ground recharge sources for the Edwards Aquifer, one of the most productive karst aquifers in the world (Thomas et al 2019). The majority of the Edwards Aquifer recharge (85%) is contributed locally by the overlying watershed while the remainder is sourced from direct precipitation and below-ground flows from adjacent aquifers (Edwards Aquifer Authority [EAA] 2003).…”

“…Without reference to any specific site or river basin, they reported an increase in the frequency of dry days in the Texas Gulf region. Thomas et al (2019) used a diverse suite of hydrological indicators to assess hydroclimatic trends in ecologically significant stream segments in the Nueces River Basin from 1970 to 2014. They reported decreasing trends in annual minimum and annual median flows in four of the six gages used in the study with no corresponding conclusive trends in precipitation.…”