Three-Dimensional Modeling of Groundwater Ages and ... · Sustainable Groundwater Management in the...

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Fig.1. Desert and plains under desertification.

Three-Dimensional Modeling of Groundwater Ages and Implications for

Sustainable Groundwater Management in the Ordos Basin, Northwest China Cheng Yu1 (beimingyu@gmail.com), Guoliang Cao2, Yingying Yao1, Fusheng Hu3, Chunmiao Zheng1,2

1: Center for Water Research, Peking University, China. 2: Department of Geological Sciences, University of Alabama, USA. 3:China University of Geosciences (Beijing), China

Introduction

Basin scale groundwater flow models are

often required in sustainable groundwater

management. But scarcity and unreliability of

data would produce significant uncertainties.

Direct simulation of groundwater ages has

made great contribution to basin scale ground

water modeling and management, because

A. Comparison between computed age

distribution and age data from isotopic dating

could constrain the flow model calibration and

reduce uncertainties in model prediction.

B. Groundwater age is an indicator of

groundwater renewable capacity and could

help in sustainable groundwater management

and industrial planning.

Ordos Basin

Age Modeling

Acknowledgements

Ordos Basin has 38% of coal, 50% of gas

and 6% of oil of the national reservations. But

economy is hampered by severe water scarcity.

Deserts and plains along Yellow River used

to be significant pasturing area but is now

subject to desertification (Fig .1).

Sustainable management of limited ground

water resources is of major concern.

Hydrogeological Conditions

Fig. 4. Conductivity distributions.

Fig. 5. Spatial discretization, horizontal: 180 x

330(2km x 2km); vertical: 4 layers.

Fig. 6. Boundary conditions.

Flow Modeling

We acknowledge the financial and technical support from National Natural Science Foundation of China and Xi’an Regional Center of China Geological Survey.

Layer 1. Layer 2. Layer 3. Layer 4.

Cretaceous aquifer was separated into four

layers (Fig. 4).

Fig 7. Head Calibration. Conductivities were adjusted using PEST. Head was well calibrated to fit 53 observed heads.

Fig. 2. Geography.

Conclusions

Ordos Basin consists of deserts and Leoss

Plateau with Baiyu Mountain as watershed

(Fig .2). There are four aquifer types (Fig. 3) .

Only Cretaceous aquifer was simulated.

A. Age simulation provided strong support for

flow model for the well matched ages. Age

calibration helped flow model improvement

as another constraint in head calibration.

B. Age simulation could present not only the

flow path and also the interaction between

ground water mass or between ground

water and surface water.

C. Age indicates refresh speed. Much of deep

aquifer groundwater may be nonrenewable

within a practical time frame. Mining in old

ground water might be unsustainable.

Fig. 8. Age simulation (using MT3DMS) and comparison with C14 sampling age data at 46 points.

Fig. 3.

Four aquifer types.

Only Cretaceous

aquifer of the four

was simulated.