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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #317794
Title: Simulating the hydrologic impact of Arundo donax invasion on the headwaters of the Nueces River in Texas

Author
item JAIN, SHAILEE - Texas A&M University
item ALE, SRINIVASULU - Texas A&M Agrilife
item MUNSTER, CLYDE - Texas A&M University
item ANSLEY, R - Texas A&M Agrilife
item Kiniry, James

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2015
Publication Date: 8/20/2015
Publication URL: https://handle.nal.usda.gov/10113/61271
Citation: Jain, S., Ale, S., Munster, C.L., Ansley, R.J., Kiniry, J.R. 2015. Simulating the hydrologic impact of Arundo donax invasion on the headwaters of the Nueces River in Texas. Journal of Hydrology. 2:134-147.

Interpretive Summary: Giant reed (Arundo) is a robust herbaceous plant that has invaded the riparian zones of the Rio Grande River and the rivers of the Texas Hill Country. Arundo was first observed along the Nueces River in central Texas in 1995, then spread rapidly downstream. In many places along the river it completely displaced the native vegetation, primarily switchgrass. It was hypothesized that Arundo reduced streamflows due to higher water use by Arundo when compared to native switchgrass. The goal of this study was to assess the impacts of Arundo invasion on hydrology of the headwaters of the Nueces River through observed long-term streamflow and precipitation data analysis, and simulation modeling with the Soil and Water Assessment Tool (SWAT). Streamflow and weather data analysis indicated that there was no significant change in monthly precipitation between the pre-Arundo invasion (1979-1994) and post-Arundo invasion (1995-2010) periods. Streamflows changed significantly showing a positive (slightly increasing) trend during the pre-invasion period and a negative (slightly decreasing) trend during the post-invasion periods. The simulated average (1995-2010) annual evapotranspiration of Arundo was higher by 137 mm when compared to switchgrass. The water uptake by Arundo was 7.2% greater than for switchgrass. The simulated average annual water yield (streamflow) under Arundo was 17 mm less than for switchgrass. In conclusion, our model indicated that Arundo invasion in the Nueces River has caused significant increases in water uptake and reductions in streamflow compared to the native switchgrass, which previously dominated the headwaters.

Technical Abstract: Arundo donax (hereafter referred to as Arundo), which is a robust herbaceous plant, has invaded the riparian zones of the Rio Grande River and the rivers of the Texas Hill Country over the last two decades. Arundo was first observed along the Nueces River in central Texas in 1995 by the Nueces River Authority (NRA). It then spread rapidly downstream due to its fast growth rate and availability of stream flow for its consumptive use, and it completely displaced the native vegetation, primarily Panicum virgatum (hereafter referred to as switchgrass) in the riparian zone. It was hypothesized that Arundo reduced streamflows due to higher water use by Arundo when compared to native switchgrass. The overall goal of this study was to assess the impacts of Arundo invasion on hydrology of the headwaters of the Nueces River through observed long-term streamflow and precipitation data analysis, and simulation modeling with the Soil and Water Assessment Tool (SWAT). The observed data analysis indicated that while there was no significant change in monthly precipitation between the pre-Arundo invasion (1979-1994) and post-Arundo invasion (1995-2010) periods, streamflows changed significantly showing a positive (slightly increasing) trend during the pre-invasion period and a negative (slightly decreasing) trend during the post-invasion periods. The simulated average (1995-2010) annual evapotranspiration of Arundo was higher by 137 mm when compared to switchgrass. The water uptake by Arundo was therefore higher by 7.2% over switchgrass. The simulated average annual water yield (streamflow) under Arundo was less by about 17 mm as compared to switchgrass. In conclusion, our model indicated that Arundo invasion in the Nueces River has caused a statistically significant increase in water uptake and reduction in streamflow compared to the native switchgrass, which previously dominated the headwaters.