Significant differences between different climate scenariosresult in different simulated recharge. All scenarios showincreasing trend in temperature while trend in precipitationcan decrease or increase (see Table 1). As shown in Figure 5,the GFDL climate model under A1FI scenario shows highestdecrease in estimated recharge due to lower precipitation,higher temperature and higher solar radiation (Table.1).Moreover, in Figure 6, recharge estimated by the RI mapshows excellent agreement with the estimated recharge bythe HELP3 model in terms of average and total rechargeamount to the aquifer system.

The computed runoff data is from 1950 to 1999. Then, weuse HELP3 to predict recharge in this period to calculate arecharge index (RI) and delineate the recharge index map forthe Southern Hills aquifer system. The recharge index isdefined as the percentage of precipitation that rechargesaquifers. Finally, the HELP3 model is applied to rechargeestimation from 2001 to 2100. A high-resolution rechargeindex map is obtained to quantify the spatial impact ofdifferent climate model scenarios on the long-termgroundwater availability for the Southern Hills aquifer systemoverlain by sixteen HUCs.

The computed runoff from USGS WaterWatch database, andthe USGS Base Flow Index map (BFI) is used to determinethe amount of runoff over each HUC. Then, the HELP3 iscalibrated by comparing the estimated runoff to WaterWatchrunoff from 1950 to 1999. Then we use the calibrated HELP3model to simulate temporal and spatial recharge underconsidered climate scenarios on the Southern Hills aquifersystem from 2001 to 2100. Delineating the spatial impact isvaluable not only in the context of groundwater resourceprotection, but also for general land use management.

Climate Change Impact on Groundwater Recharge in Southeastern Louisiana and Southwestern MississippiH13B Characterization of Groundwater Systems III | AGU Fall Meeting 2012, San Francisco, CA, USA | 5-9 December 2012

Ehsan Beigi and Frank T.-C. TsaiDepartment of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803

E-mail: ebeigi3@lsu.edu; ftsai@lsu.edu

[1] Introduction

We employ the Hydrologic Evaluation of Landfill Performance(HELP3) model as our hydrologic model in conjunction withgeographic information system (GIS) to estimate spatial-temporal distribution of potential recharge for a regional scaleover the next century[3]. The approach uses dailyprecipitation, temperature and solar radiation records inaddition to land use/land cover and soil data, which is similarto the method of Jyrkama et al. (2007)[2]. The HELP3 modelis especially suitable for our recharge study due to Louisianahumid climate and the use of a regional-scale water budgetapproach. Figure 2 shows the framework, where the HELP3model links with the climate model scenarios to estimaterecharge. We calibrate the HELP3 model using the computedrunoff of individual hydrologic units in terms of HydrologicUnit Codes (HUCs) from the USGS WaterWatch database.

Increases on concentrations of CO2 and other greenhousegases have a significant effect on climate, precipitation andhydrology, which in turn influence on aquifer recharge.Recharge is an important hydrologic process to replenish anaquifer and plays an important role in groundwater resourcesavailability. To study climate impact on groundwateravailability, this study develops a GIS-based integratedframework to connect several climate model scenarios to ahigh-resolution hydrologic model to quantify long-termgroundwater recharge for the Southern Hills Aquifer System.

Acknowledgements: The project is partially funded by the National Science Foundation EAR-10450646, the USGS-NIWR under Grant No. G10AP00136, and the Louisiana Water Resources Research Institute.

[7] Temporal Result

[2] Case Study

[4] HELP3 Input Data

1) Soil and Land Use DataDetailed surficial soil property and land cover are obtainedfrom the NRCS and the USGS database to derive a map ofcurve number for the HELP3 model. Well logs and driller’slogs are analyzed to determine stratigraphic lithology up tothe top-most major sand encountered beneath the soil layer.

2) Evapotranspiration DataLeaf Area Index (LAI) is obtained from LAI data sets for landsurface and climate modeling[4]. Evaporative zone depth iscalculated based on the maximum rooting depth ofvegetation [1].

3) Daily Weather Data and Climate Change ScenariosFor a regional scale, we use global circulation model (GCM)downscaled daily meteorological data (daily precipitation,temperature and solar radiation) obtained from USGSCASCaDE Project Climate Data as the forcing input to theHELP3 model. The emission scenarios considered in thisstudy are A2, B1 and A1FI from Parallel Climate Model 1(PCM) and from the NOAA Geophysical Fluid Dynamics Lab'sGFDL CM2.1 model. Table 1 lists the annual trend inprecipitation, temperature and solar radiation for the aquifersystem. Table 2 shows main assumptions and consequencesunder the considered climate scenarios[5].

[8] Conclusions

• Future recharge estimation is highly dependent on selectedclimate scenarios due to the substantial differences betweenthe scenarios. While groundwater recharge is predicted todecrease under GFDL(A1FI, A2) and PCM (A1FI), it willincrease under other scenarios. Also, the average annualrecharge rate is predicted to decease from 313 to 264mm/year under GFDL-A1FI scenario for the Southern Hillsaquifer system.

• The GFDL climate model predicts more intense change inprecipitation and temperature compared to those of thePCM model.

• The recharge map shows recharge variation in differentareas in the Southern Hills aquifer system due to variationsin land use, underlying soil characteristics and groundwaterlevel.

• The calculated recharge index map shows good agreementto the total estimated recharge by the HELP3 model underall considered scenarios.

• [1] Canadell,J., Jakson, R.B., Ehleniger,J.R., Mooney, H.A., SALA, O.E., Schulze, E.D, 1996. Maximum rooting depth of vegetation type at the global scale. Oecologia, 108:583-595.

• [2] Jyrkama, M.I., Sykes, J.F., 2007. The impact of climate change on spatially varying groundwater recharge in the Grand River watershed (Ontario). Journal of Hydrology 338, 237–250.

• [3] Schroeder, P.R., Dozier, T.S., Zappi, P.A., McEnroe, B.M., Sjostrom, J.W., Peyton, R.L., 1994. The Hydrologic Evaluation of Landfill Performance (HELP) Model: Engineering Documentation for Version 3. EPA/600/R-94/168b.

United States Environmental Protection Agency, Office of Research and Development, Washington, DC, USA.• [4] Yuan, H., Dai, Y., Xiao, Z., Ji, D., Shangguan, W., 2011. Reprocessing the MODIS Leaf Area Index Products for

Land Surface and Climate Modelling. Remote Sensing of Environment, 115(5), 1171-1187. doi:10.1016/j.rse.2011.01.001

• [5] IPCC. 2008. Climate Change and Water. IPCC Technical Paper VI

References

H13B-1317

[3] Methodology

Figure 2: The framework for groundwater recharge estimation.

The Southern Hills aquifer system shown in Figure 1, locatedin southeastern Louisiana and southwestern Mississippi, is oneof the sole source aquifer which provides more than 50percent of the drinking water consumed in the area overlyingthe aquifer and has no substitute drinking water source(s).The aquifer system covers 14 counties of Mississippi Stateand 10 parishes of Louisiana State. The study area is dividedinto 145,256 different subareas, each of which has a uniqueclimate zone, land use, and soil type characteristic.

Climate

Downscaled

Model

Annual Trend

Scenarios Precipitation

(mm/year)

Temperature

(°C/year)

Solar radiation

(Langley/year)

PCM B1

A2

A1FI

−0.25

+0.18

−0.92

+0.022

+0.030

+0.042

−0.0018

−0.0024

−0.0014

GFDL B1

A2

A1FI

+0.61

−1.77

−2.78

+0.028

+0.047

+0.059

+0.003

+0.009

+0.0011

Table 1: Annual trend in Precipitation, Temperature and Solar Radiation from 1950 to

2100 for Southern Hills Aquifer System

[5] Model Application and Result

[3] Methodology

[6] Spatial Result

Figure 5: Cumulative difference in recharge with respect to the average

recharge from 1950 to 1999 for all scenarios.

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

2000 2020 2040 2060 2080 2100

Re

cha

rge

Dif

fere

nce

(m)

Time (year)

GFDL-A1FI-HELP3

GFDL-A1FI-Recharge Index

0

5

10

15

20

25

30

35

2000 2020 2040 2060 2080 2100

Re

cha

rge

Cu

mu

lati

ve

(m)

Time (year)

GFDL-A1FI-Recharge index

GFDL-A1FI-HELP3

Figure 6: Cumulative recharge estimated by the HELP3 compared to that using the

recharge index map under the same precipitation.

The recharge index map in Figure 3(a) is obtained from theHELP3 estimated recharge divided by precipitation during1950 to 1999. The recharge time lag map in Figure 3(b) isobtained by time delay between precipitation and recharge.

Recharge index map can be applied to estimating recharge foreach subarea given precipitation. In this study, the estimatedrecharge using the RI map is compared to the HELP3

simulated recharge. Moreover, the mean annual rechargechange in the Southern Hills aquifer system from 1950 to2100 is shown in Figure 4 under A1FI scenario and GFDLmodel. The average annual recharge rate decreases 49mm/year from 313 to 264 mm/year, according to theTable 1, which shows decrease trend in the amount ofprecipitation and increase in temperature.

Figure 3: (a) Recharge index map and (b) recharge time lag map for the Southern

Hills aquifer system.

-6

-5

-4

-3

-2

-1

0

1

2

2000 2020 2040 2060 2080 2100

Re

cha

rge

Cu

mu

lati

ve

Dif

fere

nce

(m

)

Time (year)

GFDL-A1FI GFDLA2 GFDLB1

PCM-A1FI PCMA2 PCMB1

B1 A2 A1FI

homogeneous world

Globalization

Sustainable and Environmental

1.1 - 2.9 °C

heterogeneous world

Regionalization

Economic development

2.0 - 5.4 °C

homogeneous world

Regionalization

Rapid economic growth

1.4 - 6.4 °C

Table 2: Characteristic of Emission Scenarios Used