modelling of surface water and groundwater exchange and ...xiaoling sun, youen grusson, grégory...
TRANSCRIPT
Xiaoling Sun, Youen Grusson, Grégory Espitalier-Noël, Léonard Bernard-Jannin,
Jeffrey G. Arnold, Sabine Sauvage,
Raghavan Srinivasan, José Miguel Sánchez Pérez
Modelling of surface water and groundwater
exchange and denitrification process in the floodplain
shallow aquifer at the catchment scale
River water
Riparian
wetlands
Groundwater
Floodplain
• Biodiversity conservation
• Flood water retention
• Water quality control
• e.g. NO3 removal from agricultural area
Groundwater surface water
organic matters nutriment elements
Denitrification
riparian wetlands
Introduction
3
1 km² 10 km² 1000 km² 10 000 km² 100 000 km² 1 000 000 km²
Hydrological Models
Physically based model
Conceptual model
Input ex: precipitation
Output ex: discharge
Empirical model
MODFLOW
MOHIDBraunschweig et al., 2004
Mcdonald and Harbaugh 1988
HBV
GR4J
GR1A
Perrin et al. 2007
Seibert et al. 1997
Makhlouf 1994
Complex
Require detail input data
Long computation time
Simple
Basic input data
SW-GW exchange is not included
o Quantify SW-GW exchange
in the floodplain
o Quantify nitrate removal in a
simplified way
o Apply at large catchment scale
NO3 + Carbon
Denitrification
Objectives
SWAT-LU (Landscape Unit) model
Watershed
subbasin
HRU
River
Slope
position
high
Low
Divide (LU3)
Hillslope (LU2)
Floodplain (LU1)Landscape Unit
Volk et al. 2007
6
Subbasin-LU
LU1
LU2
LU3
S
S
L
LL
GG
I
I
I
G
S
WL
GWL
Impermeable layer
F
SWAT-LUD (Landscape Unit Darcy) model
𝑄 = 𝐾 × 𝐴 ×∆𝐻
𝐿
Darcy’s equation (1856):
LU1 LU2LU3LU1
LU2LU3
Based on flooded water volume
Channel
Subbasin-LU
Sun et al. Hydrological
processes. Accepted
7
Nitrogen and organic carbon in SWAT-LUD model
Shallow aquifer
Deep aquifer
River
LeachingPlant uptake
Soil
Shallow aquifer
Dissolved
Organic Carbon
Organic Carbon
Particulate
Organic Carbon
inputOrganic pool
Organic C, N, P
LU1
LU2
LU3
Impermeable layer
DOC
POC
LU1LU2LU3
Flood leaching
Denitrification
SWAT-LUD model-denitrification
𝑅𝑁𝑂3 = −0.8(𝜌1−𝜑
𝜑. 𝑘𝑃𝑂𝐶 𝑃𝑂𝐶 .
106
𝑀𝐶+𝑘𝐷𝑂𝐶 𝐷𝑂𝐶 ).
𝑁𝑂3
𝑘𝑁𝑂3+ 𝑁𝑂3
POC particulate organic carbon
𝑅𝐷𝑂𝐶 = −𝑘𝐷𝑂𝐶 𝐷𝑂𝐶
Parameters Units Description
𝜑 - Sediment porosity
𝜌 kg.dm-3 Dry sediment density
𝑘𝑃𝑂𝐶 d-1 Mineralisation rate constant of POC
𝑘𝐷𝑂𝐶 d-1 Mineralisation rate constant of DOC
𝑘𝑁𝑂3 μM Half-saturation for nitrate limitation
Nitrate consume rate:
DOC consume rate:
DOC dissolved organic carbon
POC consume rate:
𝑅𝑃𝑂𝐶 = −𝑘𝑃𝑂𝐶 𝑃𝑂𝐶
8
CO2
N2O
N2
bacteria
Organic carbon
NO3-
. 𝑎𝑛𝑎𝑒𝑟𝑜𝑏𝑖𝑜𝑠𝑒 𝑡𝑒𝑟𝑚
9
Study sites
Area: around 4 600 km2
Daily discharge: 200 m3·s-1
Alluvial soil: 4%
Agriculture: 72%
Area: around 51 500 km2
Discharge: 600 m3·s-1
Alluvial soil: 6%
Agriculture: 31%
10
Results – floodplain section
Input: discharge of Portet
Nitrate input: 5mg·L-1
SL1
SL2
SL3
11
Results – Floodplain
LU1 LU2 LU3
SL1
SL2
SL3
Nitrate input: 5 mg·L-1
Groundwater nitrate concentration
12
Results – Floodplain
-10
-8
-6
-4
-2
0
2
4
6
8
97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13
107m
3
Annually river-aquifer exchanged water quantity
flooded river to aquifer
aquifer to river recharged
net
0
50
100
150 Annually dentirification rate (kg N/ha/y)DOC denitrification
POC denitrification
13
Results – Denitrification
0
50
100
150
200
250
300
To
n·d
-1Observed and simulated nitrate flux
SimulatedObserved
R² = 0.56
0
50
100
150
200
250
0 50 100 150 200 250
ob
serv
ed
Simulated
RMSE = 20.71
PBIAS = 33.38
River water
Groundwaterlevel
5671 T
434 T821 T
6057 T
Denitrification
14
Results – Garonne Catchment
-8
-6
-4
-2
0
2
4
6
8
00 01 02 03 04 05 06 07 08 09 10
10
8m
3
Year
Annually SW-GW exchanged water volume in the Garonne catchmentFlood
R to G
G to R
Net
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
J-00 J-01 J-02 J-03 J-04 J-05 J-06 J-07 J-08 J-09 J-10
m3s-1
Simulated river water discharge of SWAT and SWAT-LUD
model observations at the Tonneins Gauging stationSWATSWAT-LUDObserved
SW-GW exchanged water accounted for
around 5% of the river dischargeR² = 0.57
0
1000
2000
3000
4000
5000
0 2000 4000 6000
Ob
served
(m3
s-1
)
Simulated (SWAT-LUD) (m3s-1)
R² = 0.26
0
1000
2000
3000
4000
5000
0 5000 10000
Ob
served
(m3
s-1
)
Simulated (SWAT) (m3s-1)
NS = 0.57
NS = 0.05
Conclusion and perspectives
SWAT-LUD could represent the SW-GW exchange and shallow aquifer
denitrification appropriately at the floodplain scale
The main water flow direction is from aquifer to river: 66% of the total
exchanged water volume
Consumed nitrate correspond to 50% of nitrate originated from the
surrounding area
Simulation of dynamic variation of organic carbons
Connection of upland and floodplain subbasin-LU
Sensitivity analyses of the added parameters
Application of the SWAT-LUD model at large catchments
Perspectives
Conclusions
18
Definition of Landscape Unit
Landscape Unit
LU3: ten or more years flood return area
Flood return area
The area has the probability to be
flooded in certain period (N years)
LU1: one-year return flood area
LU2: two to five years flood return area