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Effects of Non-native Vegetation Removal on Rio Grande Shallow Alluvial Groundwater

This study aims to quantify the hydrological response to the removal of exotic trees in riparian areas along the Rio Grande and determine if long-term removal efforts increase water availability. The study site is located on State Land Trust land in the South Valley of New Mexico. The study analyzes the diurnal groundwater amplitude and average depth to the water table before and after tree removal. Results show that pre-removal amplitudes were statistically greater than post-removal amplitudes by 1.16 cm (21%). The study estimates that approximately 625 m3 of shallow groundwater are retained per day due to non-native removal. Ongoing projects include exploring the SW/GW connectivity and using diurnal groundwater data to estimate ET rates.

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Effects of Non-native Vegetation Removal on Rio Grande Shallow Alluvial Groundwater

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  1. The effects of Non-native vegetation removal on Rio Grande shallow alluvial ground water Maceo Carrillo Martinet, UNM Bosque Hydrology Group Meeting December 15, 2005 Sevilleta National Wildlife Refuge

  2. Background • Why remove non-natives • Native establishment, reduce fire damage, improve recreational value, reduce excessive water use • Estimated $64 million over 10-yr for 5 river systems (Rio Grande, Canadian, San Juan, Gila, San Francisco)

  3. Purpose of this study • “Quantifying the hydrologic response to exotic tree management is one of the more important research questions.” • “The key will be to determine if long term exotic tree removal and restoration efforts will increase water availability.” Strategy for long-term management of exotic trees in riparian areas for New Mexico’s five river systems, 2005 – 2014, USDA report

  4. Study Site (State Land Trust land) South Valley Site

  5. Pre removal (2000 – 2002) Marcel Reynolds Chelsea Crenshaw

  6. Post removal (2004 – 2005) (2003 was a transition year) Chelsea Crenshaw

  7. Hypothesis 1) The diurnal groundwater amplitude of the growing season will be greater in pre-removal years (2000 – 2002) compared to post-removal years (2004 - 2005). 2) The average depth to water table will be greater in pre-removal years (2000 – 2002) compared to post-removal years (2004 - 2005).

  8. Highest ET Lowest ET

  9. Diurnal groundwater amplitude Highest ET Lowest ET Max - Min

  10. Average Amplitudes for July 1 – Aug 31units in cm ? Yes, using Wilcoxon-Mann-Whitney nonparametric (95% CI) by 1.16 cm (21%)

  11. Why July – Aug ??

  12. Hypothesis 1) The diurnal groundwater amplitude of the growing season will be greater in pre-removal years (2000 – 2002) compared to post-removal years (2004 - 2005). 2) The average depth to water table will be greater in pre-removal years (2000 – 2002) compared to post-removal years (2004 - 2005).

  13. Hypothesis 2) The average depth to water table will be greater in pre-removal years (2000 – 2002) compared to post-removal years (2004 - 2005). No – we have to normalize the groundwater data for changes in the Rio Grande

  14. How much water saved?..(with a little hand waving) • Assuming the 1.16 cm diurnal reduction is consistent throughout the research site, and the site’s boundaries are 281 m by 192 m we estimate that about 625 m3 of shallow groundwater are retained per day. 625 m3 or 0.5066957 ac-ft 281 m 192 m

  15. Results • Between 2000 – 2005 (growing season), groundwater fluctuated 4 – 6 cm and ranged from 1.3 – 1.8 m deep. • The pre-removal amplitudes were found to be statistically greater than the post-removal amplitudes by 1.16 cm (21%) Gina Dello Russo

  16. Next Steps • Finish statistical analysis of 2005 data • Use data from all wells to estimate quantity of water saved due to non-native removal, and extrapolate to entire site • Perform this analysis at other long term sites

  17. Ongoing projects • Look more in depth at SW/GW connectivity • Look into using diurnal GW data to estimate ET rates, see how this compares to ET tower data (Loheide et al. 2005, White 1932)

  18. Acknowledgements • Project Collaborators Jim Thibault, James Cleverley, Cliff Dahm, Dale Rankin (USGS), Paul Tashjian (USFWS), Joaquin Baca, Nathaniel Todea (USDA) • Yasmeen Najmi (MRGCD), Matt Kirk, Darrell Kundargi, Chelsea Crenshaw,

  19. Questions? Yasmeen Najmi

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