Development of a distributed hydrological model for integral simulation of surface runoff and ground

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Development of a distributed hydrological model
for integral simulation of surface runoff and
groundwater with case studies in China

• Qi Zhang
• Nanjing Institute of Geography and Limnology
• Chinese Academy of Sciences (NIGLAS)
• Nanjing, China

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Location of NIGLAS
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About Nanjing

• The capital city of Jiangsu Province
• A population of about 5 million
• Many historic sites
• Delicious foods

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Research Areas at NIGLAS

• Lake Hydrology and Water Resources
• Lake Ecology
• Lake Sedimentation
• Catchment Modelling and Management
• Lake-catchment Interaction

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Outlines

• Background for this work
• Modelling objectives and model design
• Processes and equations
• Model verification
• Model applications
• Conclusions

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Background

• Lake Problems in China
• Severe pollution
• Eutrophication and algae bloom (over 70 of lakes
  in east China)
• Lake-river relationship altered by hydraulic
  engineering, e.g. the Three Gorges Dam
  South-north water transfer project

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Background

• Taihu Lake watershed, in the lower reach of the
  Yangtze River basin
• A large shallow freshwater lake of 2425 km2

Taihu Lake
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Background
Algae bloom event of Taihu Lake in April 2007
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Sources of Pollution

• Agricultural non-point pollution
• Industrial waste water
• Urban sewage
• Phosphorite mining

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Measures

• In-lake engineering to protect source areas of
  water plants
• Closure of industries
• Construction of lake-side wetlands to remove
  nutrients
• Better catchment management

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Catchment Modelling

• To quantify surface and subsurface runoffs to
  lakes
• To quantify nutrient loads to lakes
• To investigate response of hydrological processes
  to climate changes and catchment management
  strategies

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Model Capability Requirements

• Distributed parameters to provide more
  flexibility in simulating the land use conditions
  in China
• Surface runoff and groundwater flow are coupled
  to better simulate the hydrological processes and
  associated mass transport
• Computing efficiency and suitable for large scale
  catchments in the order of 104 105 km2 in China

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Literature Review

• MIKE SHE (DHI)
• MODHMS (HydroGeoLogic, Inc.)
• Other work on surface-groundwater integral
  simulation
• Deschesnes et al. (1985)
• Mulungu et al. (2005)
• Bauer et al. (2006)
• Kollet and Maxwell (2006)
• Krause and Bronstert (2007)

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Literature Review

• Models used in China
• SWAT
• Xinanjiang
• TOPMODEL
• STREAM

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New Model Design

• The subsurface is characterised by a combination
  of unsaturated soils and saturated groundwater
  aquifers
• Analytical equations are used to simulate soil
  water storage and soil water percolation for
  quick computation
• Multiple time steps can be adopted for surface
  and groundwater flow modelling for efficient
  computing
• Inclusion of different types of runoffs, e.g.
  stream flows from several rivers, direct overland
  flow from hill slopes, which are common for lake
  catchments.

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Processes and Equations

• Canopy Interception

Precipitation
ECP
Vmci
Canopy
Pg
Ground
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Processes and Equations

• Soil Water Storage

Eu
Pg
Ground
hs
Rg
WT
hs min (tsoil , dgw)
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Processes and Equations

• Surface runoff generation

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Processes and Equations

• Groundwater Recharge

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Processes and Equations

• Overland flow routing

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Processes and Equations

• Stream flow routing

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Processes and Equations

• Groundwater flow

MODFLOW (Harbaugh, 2005 )
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• Inputs to model
• Daily rainfall
• Daily potential evaporation
• Land use types
• Soil types
• DEM
• River networks

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Model Verification

• V-catchment benchmark problems
• (Panday and Huyakorn, 2004 Kollet and
  Maxwell, 2006)

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Model Verification
Surface runoff simulation
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Model Verification
Surface-subsurface simulation
BC base caseLWT lowered water table
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Model Verification
Surface-subsurface simulation
BC base caseLP lowered porosity
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Model Application

• Xitiaoxi catchment of Taihu lake
• Catchment area 1930 km2

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Model Application

• Model Setup
• 1 km ? 1 km grid size for discretisation.
• 1-day time step for surface runoff model,
  variable time steps from 1 to 30 days for
  groundwater Jan 1972 - Dec 1988.
• Land use is simulated via LAI, which is further
  linked to model parameters.

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Model Application
Comparison of daily river discharges
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Model Application
(a) Hengtangcun
Comparison of monthly river discharges
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Model Application
Comparison of groundwater levels
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Model Application

• Poyang Lake catchment
• Area of 162,000 km2

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e 0.87
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e 0.84
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e 0.66
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e 0.82
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e 0.73
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Conclusions

• The model is computationally efficient, suitable
  for large scale catchment up to 160,000 km2
• Model accuracy is comparable to other
  well-developed models
• In performing coupled surface - groundwater
  simulation, groundwater pumping conditions can be
  simulated, which better suits the situation in
  China
• The model is currently being applied to a number
  of lake catchments in China to quantify runoffs
  to lakes as demanded
• The model is also being used with mass transport
  models to calculate nutrient loads and to perform
  nutrient source apportionment modelling

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Thank youMy visit is sponsored by Flinders
Research Centre for Coastal and Catchment
Environments (FR3cE)
q.zhang_at_mail.com