This document discusses the future of drought in Texas and its relationship to groundwater. It notes that climate change is likely to decrease annual precipitation and increase temperatures in Texas, exacerbating drought conditions. This could negatively impact both surface water supply from rivers and groundwater supply. The document outlines work being done with stakeholders like water districts to help them prepare for potential impacts on water demand and supply. It also discusses efforts to provide regional climate projections and tools to help water managers assess how climate change may affect their local resources.

1. The Future of Drought in Texas:
What Does It Have to Do With Groundwater??
John W. Nielsen-Gammon
Texas A&M University
and…

2. …and a cast of several!
• Jay Banner, UT Austin
• Benjamin Cook, NASA GISS
• Darrel Tremaine, UT Austin
• Corinne Wong, UT Austin
• Robert Mace, Texas State
• Huilin Gao, Texas A&M
• Zong-Liang Yang, UT Austin
• Marisa Flores Gonzalez, City of
Austin
• Richard Hoffpauir, Hoffpauir
Consulting, Bryan
• Tom Gooch, Freese and Nichols,
Fort Worth
• Kevin Kloesel, Univ. of Oklahoma
• With help from Katharine Hayhoe,
Ron Anderson, and Tim Finley
Supported by: The National Science Foundation Coupled Natural and Human Systems program,
grant number AGS-1518541, the Cynthia and George Mitchell Foundation grant number G-
1809-55892, and by The University of Texas at Austin’s Planet Texas 2050 Bridging Barriers
research initiative.

3. -1
0
1
1900 1920 1940 1960 1980 2000 2020
Degrees
Celsius Annual Temperature Anomalies
HadCRUT GISTEMP Hist+RCP8.5 Texas 9yRM a b
Degrees/Decade
°F °C
0.25 - 0.28
0.28 - 0.31
0.31 - 0.33
0.33 - 0.36
0.36 - 0.39
0.39 - 0.42
0.42 - 0.44
0.44 - 0.47

4. 0
200
400
600
800
1000
0
10
20
30
40
1895 1910 1925 1940 1955 1970 1985 2000 2015
Millimeters
Inches
Texas Annual Precipitation
a b

6. Benjamin I. Cook et al. Sci Adv 2015;1:e1400082
Copyright © 2015, The Authors

7. What about Texas?

15. What does this mean for surface water supply?
• Uncertainty for future
• How much carbon dioxide etc.?
• How much will the climate system respond?
• How do we infer local details, given the climate system response?
• How do we model the hydrology?
• How important is all of this compared to natural variability?
• Tool: calibrated hydrologic model for major rivers
• Tool: combined hydrology-reservoir model that is management-aware
• Also relevant: demand and flood resilience

16. What does this mean for groundwater supply?
• Fast-recharge aquifers: supply-driven impacts
• Slow-recharge aquifers: demand-driven impacts
• In between: demand-driven impacts + future supply-driven impacts

17. What do stakeholders need?
Example: Small groundwater management districts
• Prediction of demand-side response driven by climate change
• Technical expertise
• Short-term and long-term outlooks tailored to needs

18. Why more droughts? Or more aridity?
• On the drying side…
• Decreases in annual precipitation
• Changes in temperature
• Changes in rainfall extremes, month
to month
• Changes in rainfall seasonality
• Changes in biomass (short term)
• On the wetting side…
• Increases in annual precipitation
• Changes in biosphere water use
efficiency
• Changes in biomass (long term)
• On the mixed effects side…
• Changes in rainfall extremes, single
storms
• Changes in soil moisture

19. What did Austin Water do?
• Water Forward: a 100-year integrated water resources plan
• Input: Global climate model projections of temperature and precipitation
• Input: Historical statistical relationship with streamflow
• Tool: Future scenarios = drought of record and 3x drought of record
• All info tailored for direct input to Water Availability Model
• Key: working directly with climate scientists

20. Research for scientists and stakeholders
• Reconstructing last 8,000 years of arid-wet dividing line in Texas
• Developing tools to connect downscaled projections and local streamflow
• Adjusting the ‘drought of record’ to ensure equivalent future resilience
• Transparent communication and understanding of unknowns
Paper online, open access: google Nielsen-Gammon Earth’s Future
Email me: n-g@tamu.edu