Groundwater and Climate Change:Groundwater and Climate Change:Forcing, Feedbacks, and Integrated

W t h d RWatershed Response

Reed Maxwell and Ian Ferguson

Anthropogenic climate change will have a continued affect on global temperatures

Meehl et al 2007, AR 4 Ch 10 Fig 10.4

Effects of regional climate change, climate change, increased temp, uncertain precipitationuncertain precipitation

Christensen et al 2007, AR 4 Ch 11from Fig 11.11 

Christensen et al 2007, AR 4 Ch 1, from Table 11.1

Land surface conditions influence atmospheric dynamics regional climateatmospheric dynamics, regional climate

Koster et al. (2005)

We have a coupled system and… We need to understand the interactions

Global Climate Change

Local & Regional Local & Regional Response

Local Water-Energy Feedbackseedbac s

We think of this in terms of control

Energy Controlled

Groundwater Controlled

Moisture ControlledControlled

(T, U, SW)Controlled Controlled

(P)

Water Table Depth [m]p [ ]Kollet and Maxwell (2008)

Objectives• Investigate integrated hydrologic response under

changing climate conditions using a fully-coupled watershed model:

Groundwater recharge and loss Groundwater recharge and loss

Stream discharge

Surface water-energy balance (ET)

Study SiteLittle Washita River watershed, Central Oklahoma• Mid-size watershed

(~700 km2)

• Available observations: ARM, OK-Mesonet, AmeriFlux, USGS, SCAN, ,

• Important agricultural region, known for climate extremes

• Previous studies demonstrate important role of hydrologic feedback in regional weather eedbac eg o a weat eand climate

Modeling ApproachP Fl f ll i t t d t h d d l

• Groundwater flow: Atmospheric Forcingi

ParFlow: fully-integrated watershed model

variably‐saturated three‐dimensional Richards equation

• Overland flow/surface runoff: f f l d fl b d

LSMLSM

LSMLSM Vadose Zone

Root Zone

Vegetation

Land Surface

free‐surface overland flow boundary condition (Mannings + kinematic wave)

L d f t d fl

LSMLSMLSM

LSMLSM

LSM

LSM

Vadose Zone

• Land surface water and energy fluxes: Common Land Model (CLM), includes infiltration, canopy and vegetation processes, and coupled water‐energy 

` LSM

p , p gybalance

• Fully‐coupled, mass conservative, parallel implementation

G d tKollet and Maxwell (2008), Kollet and Maxwell (2006), Maxwell and Miller (2005), Dai et al. (2003), Jones and Woodward (2001); Ashby and Falgout (1996)

Groundwater

Model, Domain, & ScenariosLittl W hit t h d

C t l

Little Washita watershed, Central Oklahoma• Control run: Water year 1999T, P, etc. from NARR

• Perturbation scenarios:Hot:  T + 2.5°C, PHot‐Dry: T + 2.5°C, P – 20%Hot Dry:  T   2.5 C, P  20%Hot‐Wet:  T + 2.5°C, P + 20%

e.g., Christensen et al. (2006)

(Kollet and Maxwell 2008, Maxwell and Kollet 2008, Ferguson and Maxwell 2010)

Results: Stream DischargeΔ(Qpeak) ≈ -20%Δ(Qbase) ≈ -40%

Δ(Qpeak) ≈ -60%Δ(Qbase) ≈ -65%

Δ(Qpeak) ≈ +25%Δ(Qbase) ≈ +10%

Ferguson and Maxwell (2010)

Results: Stream Discharge

+29%

f

-20%

-61%

Ferguson and Maxwell (2010)

Results: Water Table DepthHot

H t W tHot-WetHot-Dry

Results: Groundwater Storage Yearly‐Averaged LH FluxLH Flux Difference

Maxwell and Kollet NGeo (2008)

Yearly‐AveragedP‐E AnomalyP‐E Anomaly

Maxwell and Kollet NGeo (2008)

Summary and Conclusions:d h f l h• Integrated approach is necessary for climate change impact 

analysis

• Impacts depend on feedbacks between groundwater processes, runoff processes, and surface water‐energy b lbalance

• Impacts on hydrology and water resources differ between water limited and energy limited regimes

Further analysis needed to understand role of lateral surface and subsurface flows in land‐atmosphere feedbacks and regionalatmosphere feedbacks and regional climate

Implications:d f l• An integrated management strategy is necessary for climate 

change impact analysis that considers the “bigger picture”

• A “one size fits all” management approach may not work for different basins

• Because impacts depend on feedbacks between groundwater processes and the surface water‐energy balance, we need to think of other factors

(e.g. pumping and irrigation) in these( g p p g g )

contexts as well.

Questions?Questions?

Study SiteLittle Washita River watershed, Central Oklahoma

Elevation Land Cover

300m 450m375m