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NORTHWEST A&F UNIVERSITY
Past Restoration Efforts, Techniques, Challenges, Successes & Future Plan
U.S.-China Exchange on Loess Landforms
Wang Li
Content
Current status of groundwater recharge
Future possible research topic4
A case study3
1 Research Background
2 Research status
6 Research plan
5
The World Loess distribution map
1 Research Background
China Loess Plateau
Loess area accounts for about 10% of global land area; The area of China Loess Plateau is 64 km2.
1 Research Background Soil and water loss in the Loess Plateau was serious, and the area
of soil erosion accounted for about 70% (47.2×104 km2) of the
total area (Yang et al., 1999); Before 1990, engineer measures contributed
54% to soil and water conservation; After
1990, vegetation restoration measures
became a major factor (57%) (Wang et al.,
2016).
Check dams Terraced fieldsFish-scale pit
2 Research status
By the end of 2016, 59 037 check dams had been built in the Loess
Plateau, including 5 829 backbone dams, 11 234 medium-sized
check dams, and 4,1974 small check dams (Hui et al., 2018).
沟道中修建的淤地坝Check dams in the gully channels
2 Research status
The function of the check dam:
Control channels erosion;
Reduce flood and sediment disasters;
Increase the farmland.
沟道中修建的淤地坝Check dams in the gully channels
2 Research status
By the end of 2012, the terraced fields area in the Loess Plateau
was 3.7 million hm2 (Ma et al., 2015).
坡地上修建的梯田Terraced fields on sloping land
2 Research status
The function of the terracing :
Reduce soil erosion;
Increase soil water content;
Increase water and nutrient use efficiency.
坡地上修建的梯田Terraced fields on sloping land
2 Research status In the much steeper slope lands and mountains, fish-scale pits
were built. And fish-scale pit has the same functions as
terraces.(Guo et al., 2017).坡地上修建的鱼鳞坑
Fish-scale pit on sloping land
2 Research status In 1999, the project of returning farmland to forests (grass) began to be implemented,
which significantly increased the vegetation cover on the Loess Plateau.
1999年 2013年
Vegetation cover change in the Loess Plateau( Chen et al., Nature Geosci., 2015 )
60 %32 %
Comparison of Vegetation Coverage in Hujia Village, Heijiapu, Yanchang County
1999年 2015年
2 Research status
From 2000 to 2008, the farmland decreased, and the grassland and forest land increased.
The grassland area was about 2.5 times that of the forest land and 1.3 times that of the farmland.
Land use type change in the Loess Plateau
in 2000-2008(Lü et al., Plos One, 2012)
2 Research status
0
20
40
60
80
100
120
140
1960~1969 1970~1979 1980~1989 1990~1999 2000~2009 2010~2016
流域输沙
量(亿t)
年份
The amount of sediment transportation in Toudaoguai-Tongguan
120×108 t
Changes of land use types in typical basins? The spatial and temporal changes of the NDVI in typical basins? Changes and causes of runoff and sediment transportation in
typical basins?
The variation of NDVI in the Loess Plateau in 1999-2013(Gao et al., 2017)
3 A case study
The study area is the typical basins in the northern Loess PlateauZhao QQ, Wang L*, Liu H, Zhang QF. Runoff and sediment variation andattribution over 60 years in typical Loess Plateau basins [J]. Journal of Soils andSediments, 2019, https://doi.org/10.1007/s11368-019-02345-z
3.1 Analysis on the change of land use type in typical basins3.1.1 Distribution characteristics of basins land use structure
The distribution of farmland in the KuyeRiver and WudingRiver Basins in Shaanxi Province decreased, while the distribution of grassland, forest and built-up land increased significantly. It mainly occurred in the north-central part of the Kuye River and the southeastern part of the Wuding River.
Wuding River
Kuye River
Fig. 3-1-1a The distributions of land use of typical basins in 1995, 2005 and 2015
3.1 Analysis on the change of land use type in typical basins3.1.1 Distribution characteristics of basins land use structure
Fig. 3-1-1b The distributions of land use of typical basins in 1995, 2005 and 2015
Land use change mainly occurred in the entire basin of Yanhe, especially in the northeast and the northern part of the Beiluo River.
Beiluo River
Yanhe River
3.1 Analysis on the change of land use type in typical basins3.1.2 The area of different land use types in typical basins
Fig. 3-1-2 The area of different land use types in typical basins
In the four basins, in1995, 2005 and 2015,grassland was themain type of land use(except the WudingRiver in 1995 and2005).
The area of farmlandin the four riverbasins decreased, andthe area of grasslandand forest landincreased. Theincrease in forest areawas 68.3%, 76.6%,76.9% and 10.1%.
(a)Kuye River (b)Wuding River(c)Yanhe River(d)Beiluo River
1995年 2005年 2015年0
400
800
1200
1600
2000
2400
2800
3200
面积
Area (km
2 )
年份 Year
耕地 草地 林地 水域 城乡、工矿、居民用地 未利用土地
(a)
1995年 2005年 2015年0
2000
4000
6000
8000
10000
面积
Area (km
2 )
年份 Year
(b)
1995年 2005年 2015年0
1000
2000
3000
4000
面积
Area (km
2 )
年份 Year
(c)
1995年 2005年 2015年0
2000
4000
6000
8000
10000
12000
面积
Area (km
2 )
年份 Year
(d)
3.1 Analysis on the change of land use type in typical basins
3.1.2 The area of different land use types in typical basins
In the four basins in Shaanxi Province, grassland was the main land
use type in 2015.
土地利用类型Land use type
窟野河Kuye
无定河Wuding
延河Yanhe
北洛河Beiluo
耕地Farmland 1059.28 8211.11 2391.80 8540.70草地Grassland 2342.64 8551.24 3985.61 9930.03林地Forest 126.06 1617.87 1146.68 6208.72水域Water 61.66 189.01 27.28 117.55
建设用地Built-up 251.66 373.14 60.21 492.18未利用土地Unused 152.78 2905.29 28.58 23.54
Tab. 3-1-1 Land use type area of typical basins in Shaanxi Province in 2015(km2)
3.2 Temporal and spatial variability of typical basins NDVI3.2.1 Distribution of NDVI status of typical basins in 2000, 2010 and 2018
The NDVI of the Kuye River and the Wuding River Basin during the vigorous growth period was increase. From the perspective of spatial distribution, it was mainly in the north of the Kuye River and southeast of the Wuding River.
Kuye River
Wuding River
Fig. 3-2-1a Distribution of NDVI status of typical basins in 2000, 2010 and 2018
3.2 Temporal and spatial variability of typical basins NDVI3.2.1 Distribution of NDVI status of typical basins in 2000, 2010 and 2018
Fig. 3-2-1b Distribution of NDVI status of typical basins in 2000, 2010 and 2018
From the perspective of spatial distribution, the NDVI in the Yanhe and BeiluoRiver basins were mainly in the northeastern part of the Yanhe River and the northern part of the Beiluo River.
Yanhe River
Beiluo River
3.2 Temporal and spatial variability of typical basins NDVI3.2.2 Area percentage of different levels of NDVI in typical basins
2000年 2010年 2018年0%
20%
40%
60%
80%
100%
ND
VI
分级组成
ND
VI g
radi
ng c
ompo
sitio
n (%
)
年份 Y ear
≤0 (0,0.3] (0.3,0.5] (0.5,0.7] (0.7,1.0]
(a)
2000年 2010年 2018年0%
20%
40%
60%
80%
100%
ND
VI
分级
组成
ND
VI g
radi
ng c
ompo
sitio
n (%
)年份 Y ear
(b)
2000年 2010年 2018年0%
20%
40%
60%
80%
100%
ND
VI
分级
组成
ND
VI g
radi
ng c
ompo
sitio
n (%
)
年份 Y ear
(c)
2000年 2010年 2018年0%
20%
40%
60%
80%
100%
ND
VI
分级
组成
ND
VI g
radi
ng c
ompo
sitio
n (%
)
年份 Y ear
(d)
Fig. 3-2-2 Area percentage of different levels of NDVI in typical basins
The NDVI of the four basins area in the (0,0.3] were continuous reduction. The largest decrease was the KuyeRiver Basin.
The NDVI of the four basins with the high vegetation coverage area in the (0.7,1] were increase. The largest increase was the YanheRiver Basin.
3.2 Temporal and spatial variability of typical basins NDVI3.2.4 Annual average NDVI variation from 2000 to 2016 in typical basins
2000 2002 2004 2006 2008 2010 2012 2014 2016
0.16
0.18
0.20
0.22
0.24
0.26
0.28
0.30
ND
VI
年份 Year
(a)
y=0.0069x-13.79R2=0.903
2000 2002 2004 2006 2008 2010 2012 2014 2016
0.16
0.18
0.20
0.22
0.24
0.26
0.28
0.30
ND
VI
年份 Year
(b)
y=0.006x-11.915R2=0.95
2000 2002 2004 2006 2008 2010 2012 2014 2016
0.20
0.24
0.28
0.32
0.36
0.40
0.44
ND
VI
年份 Year
(c)
y=0.009x-18.027R2=0.889
2000 2002 2004 2006 2008 2010 2012 2014 2016
0.36
0.38
0.40
0.42
0.44
0.46
0.48
0.50
N
DV
I
年份 Year
(d)
y=0.0043x-8.193R2=0.762
Fig. 3-2-4 Annual average NDVI variation from 2000 to 2016 in typical basins
From 2000 to 2016, the annual NDVI of the four basins showed an increasing trend (P<0.01), with annual growth rate of 0.7%, 0.6%, 0.9%, and 0.4%, respectively. The largest rate was Yanhe.
3.3 Changes in runoff and sediment transportation in typical basins and their responses to NDVI
3.3.1 Annual runoff and sediment trends in typical basins
3.3.1.1 Annual runoff trends in typical basins
1960 1970 1980 1990 2000 2010 20200
2
4
6
8
10
12
14
径流量
Annual runoff discharge (108m3)
年份 Year
径流量 每10年径流量均值
(a)
1960 1970 1980 1990 2000 2010 20204
6
8
10
12
14
16
18
20
22
径流量
Annual Runoff discharge(108m)
年份 Year
(b)
1960 1970 1980 1990 2000 2010 20200
1
2
3
4
5
6
径流量
Annual runoff discharge (108m3)
年份 Year
(c)
1960 1970 1980 1990 2000 2010 20200
2
4
6
8
10
12
14
16
18
20
22
径流量
Annual runoff discharge (108m3)
年份 Year
(d)
The runoff of the four
basins showed a
significantly decreasing
trend from 1960 to 2016.
Fig. 3-3-1 Annual runoff trends in typical basins
3.3 Changes in runoff and sediment transportation in typical basins and their responses to NDVI
3.3.1.2 Annual sediment trends in typical basins
1960 1970 1980 1990 2000 2010 2020
0
1
2
3
4
5 输沙量 每10年输沙量均值
输沙量
Annual sediment discharge (108t)
年份 Year
(a)
1960 1970 1980 1990 2000 2010 2020
0
1
2
3
4
5
输沙量
Annual sediment discharge (108t)
年份 Year
(b)
1960 1970 1980 1990 2000 2010 2020
0
1
2
输沙量
Annual sediment discharge (108t)
年份 Year
(c)
1960 1970 1980 1990 2000 2010 20200
1
2
3
输沙量
Annual sediment discharge (108t)
年份 Year
(d)
The sediment
transportation of the four
basins showed a
significantly decreasing
trend from 1960 to 2016.
Fig. 3-3-2 Annual sediment trends in typical basins
3.3 Changes in runoff and sediment transportation in typical basins and their responses to NDVI
3.3.2 Anomaly accumulations for runoff and sediment volume in typical basins
1960 1970 1980 1990 2000 2010 20200
20
40
60
径流量累积距平 输沙量累积距平
年份 Year
径流量累积距平
Runo
ff a
ccum
ulat
ion
anom
aly
(108 m
3 )
(a)
1979
1996
0
2
4
6
8
10
12
14
16
输沙量累积距平
Sedi
ment
acc
umul
atio
n an
omal
y (1
08 t)
1960 1970 1980 1990 2000 2010 20200
20
40
60
年份 Year
径流量累积距平
Runo
ff a
ccum
ulat
ion
anom
aly
(108 m
3 )
(b)
1979
1996
0
2
4
6
8
10
12
14
输沙量累积距平
Sedi
ment
acc
umul
atio
n an
omal
y (1
08 t)
1960 1970 1980 1990 2000 2010 20200
10
20
30
40
50
年份 Year
径流量累积距平
Runo
ff a
ccum
ulat
ion
anom
aly
(108m3 )
(d)
1994
0
2
4
6
8
输沙量累积距平
Sedi
ment
acc
umul
atio
n an
omal
y (1
08t)
1979
2001
The pivotal
points for the
basins of the
three rivers Kuye,
Wuding and
Yanhe were all in
1979 and 1996.
In the Beiluo
River basin, the
fluctuations were
relatively
complex.Fig. 3-3-3 Anomaly accumulations for runoff and sediment volume in typical basins
1960 1970 1980 1990 2000 2010 2020
0
2
4
6
8
10
年份 Year
径流
量累
积距
平
Runoff accumulation anomaly (108m3)
(c)
1979
1996
0
1
2
3
4
5
输沙
量累
积距
平
Sediment accumulation anomaly (108t)
3.3 Changes in runoff and sediment transportation in typical basins and their responses to NDVI
3.3.3 Precipitation-runoff and precipitation-sediment accumulation in typical basins
0 5 10 15 20 250
50
100
150
200
250
300量
累积径流 累积输沙量
累积降水量Accumulated precipitation (m)
累积
径流
量
Accumulated runoff (108m3)
0
10
20
30
40
1996
累积
输沙
量
Accumulated sediment (108t)
(a)
1979
0 5 10 15 20 250
100
200
300
400
500
600
700
800
累积降水量Accumulated precipitation (m)
累积
径流
量
Accumulated runoff (108m3)
0
10
20
30
40
50
60
累积
输沙
量
Accumulated sediment (108t)
(b)1979
1996
0 5 10 15 20 25 30 350
20
40
60
80
100
120
累积降水量Accumulated precipitation (m)
累积
径流
量
Accumulated runoff (108m3)
0
10
20
30
40
累积
输沙
量
Accumulated sediment (108t)
(c)
1979
1996
0 5 10 15 20 25 30 35 400
50
100
150
200
250
300
350
累积降水量Accumulated precipitation (m)
累积径流量
Accumulated runoff (108m3)
0
10
20
30
40
累积输沙量
Accumulated sediment (108t)
(d)1979
2001
1994
In the KuyeRiver, WudingRiver and YanheRiver basins, both curves shifted at 1979 and 1996.
In Beiluo River basin shifted at 1979 and 1994. and the 1979 and 2001.
Fig. 3-3-4 Precipitation-runoff and precipitation-sediment accumulation in typical basins
3.3 Changes in runoff and sediment transportation in typical basins and their responses to NDVI
3.3.5 Effects of precipitation and human activities on runoff and sediment
1970 1980 1990 2000 2010 2020-10
-8
-6
-4
-2
0
2
4
6
年份 Year
影响
径流
量
Influ
ence
d ru
noff
(108 m
3 )
人类活动对径流量的影响 降水对径流量的影响
(a)
1970 1980 1990 2000 2010 2020-10
-8
-6
-4
-2
0
2
4
年份 Year
影响径流量
Influ
ence
d ru
noff
(108 m
3 )
(b)
1970 1980 1990 2000 2010 2020-2
0
2
年份 Year
影响
径流
量
Influ
ence
d ru
noff
(108 m
3 )
(c)
1970 1980 1990 2000 2010 2020-8
-6
-4
-2
0
2
4
6
年份 Year
影响径流量
Influ
ence
d ru
noff
( 108 m
3 )
(d)
For the Kuye and Wuding River basins, it can be seen that during the entire period of 1970–2016, human activities played a major role in reducing runoff. The impact of human activities was 2.77×108 m3
and 4.45×108 m3, respectively.
In the Yanhe and Beiluo River basins, precipitation obviously contributed to the reduction in runoff, with an impact on runoff of 0.61×108
m3 and 2.09×108
m3, respectively.Fig. 3-3-6 Effects of precipitation and human activities on
runoff in typical basins
3.3.5.1 Effects of precipitation and human activities on runoff in typical basins
3.3 Changes in runoff and sediment transportation in typical basins and their responses to NDVI
3.3.5.1 Effects of precipitation and human activities on sediment in typical basins
1970 1980 1990 2000 2010 2020-3
-2
-1
0
1
2
年份 Year
影响
输沙
量
Influ
ence
d se
dim
ent (
108 t)
人类活动对输沙量的影响 降水对输沙量的影响
(a)
1970 1980 1990 2000 2010 2020-3
-2
-1
0
1
2
年份 Year
影响
输沙
量
Influ
ence
d se
dim
ent
(108 t)
(b)
1970 1980 1990 2000 2010 2020-1.0
-0.5
0.0
0.5
1.0
年份 Year
影响
输沙
量
Influ
ence
d se
dim
ent
(108 t)
(c)
1970 1980 1990 2000 2010 2020-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
年份 Year
影响
输沙
量
Influ
ence
d se
dim
ent (
108 t)
(d)
In Kuye and WudingRiver, in 1970-2016, human activities contributed significantly to the reduction in sediment discharge, the impact being 0.56×108 t and 0.97×108 t, respectively.
In Yanhe and BeiluoRiver, precipitation contributed significantly to the reduction in sediment discharge from 1970 to 2016. The impact on sediment discharge was 0.25×108 t and 0.35×108 t, respectively.
Fig. 3-3-7 Effects of precipitation and human activities on sediment transportation in typical basins
3.3 Changes in runoff and sediment transportation in typical basins and their responses to NDVI
As the NDVI increasing, the runoff in the basins decreased. In Yanhe River and Beiluo River, the NDVI were increasing, but the runoff in
four basins were decreasing, the negative correlation between them were poor.
3.3.6 Trends of NDVI and runoff in typical basins
2000 2002 2004 2006 2008 2010 2012 2014 20160
2
4
6
径流量 NDVI
年份 Year
径流
量
Run
off (
10
8 m3 )
(a)
0.16
0.18
0.20
0.22
0.24
0.26
0.28
0.30
NDVI
2000 2002 2004 2006 2008 2010 2012 2014 20164
6
8
10
12
年份 Year
径流
量
Run
off (
10
8 m3 )
(b)
0.16
0.18
0.20
0.22
0.24
0.26
0.28
0.30
NDVI
2000 2002 2004 2006 2008 2010 2012 2014 20160
2
4
年份 Year
径流
量
Run
off (
10
8 m3 )
(c)
0.1
0.2
0.3
0.4
0.5
NDVI
2000 2002 2004 2006 2008 2010 2012 2014 2016
4
6
8
10
12
14
年份 Year
径流量 R
unof
f (10
8 m3 )(d)
0.30
0.35
0.40
0.45
0.50
NDVI
Fig. 3-3-8 Trends of NDVI and runoff in typical basins
The trend of average annual NDVI in the four typical basins were negative relationship with the trend of annual average sediment transportation. This shown that vegetation restoration was conducive to the reduction of sediment transportation.
3.3 Changes in runoff and sediment transportation in typical basins and their responses to NDVI
2000 2002 2004 2006 2008 2010 2012 2014 20160.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20 输量沙 NDVI
年份 Year
输沙量
Sediment (10
8 t)
(a)
0.16
0.18
0.20
0.22
0.24
0.26
0.28
0.30
NDVI
2000 2002 2004 2006 2008 2010 2012 2014 20160.0
0.2
0.4
0.6
0.8
1.0
1.2
年份 Year
输沙量
Sediment (10
8 t)
(b)
0.16
0.18
0.20
0.22
0.24
0.26
0.28
0.30
NDVI
2000 2002 2004 2006 2008 2010 2012 2014 20160.0
0.2
0.4
0.6
0.8
年份 Year
输沙量
Sediment (10
8 t)
(c)
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
NDVI
2000 2002 2004 2006 2008 2010 2012 2014 20160.0
0.2
0.4
0.6
0.8
1.0
1.2
年份 Year
输沙量
Sediment (10
8 t)(d)
0.30
0.35
0.40
0.45
0.50
NDVI
3.3.7 Trends of NDVI and sediment transportation in typical basins
Fig. 3-3-9 Trends of NDVI and sediment transportation in typical basins
3.3 Changes in runoff and sediment transportation in typical basins and their responses to NDVI
3.3.8 Conclusion
The runoff and sediment transportation of the four basins showed a
significantly decreasing trend from 1960 to 2016.
The changes in sediment discharge were influenced by precipitation and
human activities. Compared with precipitation, human activities within the
more northerly Kuye and Wuding River basins have played a more
prominent role in the changes in sediment regimes. For the more southerly
Yanhe and Beiluo River basins, throughout the research period, the effect of a
reduction in precipitation on the runoff and sediment discharge has been
greater than the effect of human activities.
The trend of average annual NDVI in the four typical basins were negatively
related with the trend of annual average sediment transportation.
4 Future possible research topicWhat are the scientific issues that the Loess
Plateau really needs to study?(1)Soil erosion: many studies(2)Vegetation restoration: many studies(3)Runoff and sediment changes: many studies
Two important scientific questions:(1)Why natural forest vegetation exists only in loess and rock
mountains?(2)Recharge route and mechanism of groundwater in thick
layer loess area?
0
2
8
20
50
100 Δ
2:Contribution of deep soil water to vegetation transpiration and ratio of groundwater recharge?
Deep(m)
Deep soil
1:Movement mechanism and flux of deep soil water under deep soil conditions?
How does precipitation recharge groundwater through thick loess?
Vegetation growth and groundwater level decline
11.41.82.22.63
0.250.270.290.310.33
1979 1984 1989 1994 1999 2004 2009 2014
NDVI
NDVI
Runoff
(×
108m3yr-1)
降水
量(
0
400
800
1976 1984 1992 2000 2008
地下
水位
(m)
24
26
28
30
32降 水 水 位
Groundwater
level(
m)
2006
6 m
1990
Rainfall (mm)
年份
Possible effects on groundwater recharge after extensive vegetation increase
Deep soil
Shallow soil
Parent material Deep leakage
• Average rainfall infiltration depth
• Contains 90% root system• More large pores and
good water conductivity• depth:1-4 m
• 10% root system• Poor water conductivity• depth:2-20 m
补
Rainfall infiltration soil recharges groundwater
5 Research Status of Groundwater Recharge in the Loess Plateau
5.1 Recharge source(1)Rainfall (most scholars)
(2)Exogenous water (Chen et al., 2017)
Groundwater in the Qinghai-Tibet Plateau is recharged through underground passages
5 Research Status of Groundwater Recharge in the Loess Plateau
5.1 Recharge source
Magmatic activity and volcanic eruption caused by collision between Indian plate and Eurasian plate
(1)Rainfall (most scholars)
(2)Exogenous water (Chen et al., 2017)
Qinghai-Tibet PlateauOrdos block Taihang
Changbai
High Conductivity and Low Velocity Layer at Crust-Mantle Junction
Loess Plateau
Macropore
5.2 Recharge mechanism
Large pore dominant flow
Medium pore rapid plug flow
Small pore slow plug flow
Total flux
Bright blue staining亮蓝染色法
Isotope and Cl-
substitution
Tracer and large, medium and small pore flow
5 Research Status of Groundwater Recharge in the Loess Plateau
(1) Piston flow - thick layer aeration zone
(2) Preferential flow - large pores, holes,
cracks.
5.3 Research method
5 Research Status of Groundwater Recharge in the Loess Plateau
chloride concentration
(1)Chlorine mass balance method; (2)Tritium Peak Method;(3)Stable isotope method; (4)Thermal tracer method; (5)Model simulation
Chloride ion in the environment has high solubility and stability, and can migrate with water molecules in the vadose zone. When water is evaporated, chlorine is retained in the vadose zone, and its concentration and amount of water consumed by evapotranspiration In direct proportion.
5.3 Research method
3H distribution of soil profiles at different slope positions
Tritium content(TU)
0 20 40 60
Dep
th(m
)
0
5
10
15
20
upper middle lower
上坡
中坡
下坡
氚含量(TU)
5 Research Status of Groundwater Recharge in the Loess Plateau
(1)Chlorine mass balance method; (2)Tritium Peak Method ;(3)Stable isotope method; (4)Thermal tracer method; (5)Model simulation
Assume that the depth of the peak in the aeration zone in 1963 is S[L], the sampling time is t years, and the average volumetric water content of soil above D is θ, then the recharge amount R[LT-1] is:
𝑅𝑅 = 𝑆𝑆 � 𝜃𝜃/(𝑡𝑡 − 1963)
5.3 Research method5 Research Status of Groundwater Recharge in the Loess Plateau
(1)Chlorine mass balance method; (2)Tritium Peak Method ;(3)Stable isotope method; (4)Thermal tracer method; (5)Model simulation
Oxygen isotope water source division
The isotope composition of precipitation changes with the seasons, and the winter is low in summer. This seasonal variation can be reflected in the recharge water, which can be used to estimate the recharge of groundwater. By comparing the stable isotope characteristics of precipitation and groundwater, it can be determined whether groundwater is derived from atmospheric precipitation.
5.3 Research method5 Research Status of Groundwater Recharge in the Loess Plateau
Drilling fiber sensor layout diagram
Some scholars have found that the temperature distribution of the past climate deviates from the steady state. In the thick vadose zone, the magnitude of the deviation represents the recharge intensity, which can be used as a tracer to estimate groundwater recharge.
Most hydrological models include groundwater modules that can be used to simulate groundwater recharge based on the principle of water balance.
(1)Chlorine mass balance method; (2)Tritium Peak Method ;(3)Stable isotope method; (4)Thermal tracer method; (5)Model simulation
5.4 Recharge amountNumber research area Method Rainfall(mm) Recharge(mm) 文献
1Hilly and gully regions of Loess
Plateau/Zhifanggou watershed/AnsaiChlorine mass balance method /
stable isotope method500 55-90 Gates et al. (2011)
2Hilly and gully regions of Loess
Plateau/Hequanhe watershed/GuyuanChlorine mass balance method /
stable isotope method450 50-100 Huang et al. (2013)
3Loess-sand/Wudan Town/Inner Mongolia
Wengniute BannerTritium Peak Method 360 47 Lin and Wei (2006)
4Hilly and gully regions of Loess
Plateau/Pingding County/YangquanTritium Peak Method 550 68 Lin and Wei (2006)
5Hilly and gully regions of Loess Plateau/Xifeng Plateau/Qingyang
Chlorine mass balance method 523 33 Huang and Pang (2011)
6Hilly and gully regions of Loess
Plateau/Changwu Plateau/ChangwuSHAW Model simulation 545 9.3-18.3
Huang and Gallichand(2006)
7Hilly and gully regions of Loess
Plateau/Luochuan Plateau/LuochuanCoupModel Model simulation 568 17 Zhang et al. (2007)
8Hilly and gully regions of Loess
Plateau/Heihe watershed/ChangwuChlorine mass balance method /
stable isotope method584 107 Li et al. (2017)
9Hilly and gully regions of Loess
Plateau/Wuding River Basin/SuideMRC Curve simulation 409 11.4~15.7 Zhu et al. (2010)
10Hilly and gully regions of Loess
Plateau/Chabagou watershed/SuideMRC Curve simulation 480 1.5-15.1 Ma et al. (2018)
11Gully area of the Loess Plateau/Wangdonggouwatershed/Changwu
Tritium Peak Method 584 20-27 Li et al. (2016)
12Hilly and gully regions of Loess Plateau/Yangou watershed/Xi’an
CoupModel Model simulation 537 37 Wang et al. (2012)
5 Research Status of Groundwater Recharge in the Loess Plateau
5.5 Problem(1)Whether it is the source of replenishment, the replenishment path, or the replenishment mechanism, the current research conclusions are vastly different and there is no unified understanding.(2)The depth of research is shallow and it is difficult to reflect the actual situation of thick layer of loess.(3)The replenishment mechanism remains unclear and the current conclusions have not been widely recognized by the academic community.(4)Research methods need to be expanded.
5.6 Research content(1)What is the chloride ion characteristics and groundwater recharge history of thick layer loess profiles?(2)What is the dynamic variation characteristics of groundwater in thick loess area and its influencing factors?(3)Analysis on the ways and process of recharge of groundwater in thick loess area?(4)Effects of land use change on deep seepage and groundwater recharge in thick layer loess?(5)Simulation and mechanism analysis of groundwater recharge in thick loess area?
5 Research Status of Groundwater Recharge in the Loess Plateau
∆𝑺𝑺= R-T-D
Shallow soil
Deep soil
Rootless soil
Groundwater
(R)(T)
6 Research plan
Deep soil water supply mechanism
Soil water absorption deep roots to deep layers
Deep leakage
(D)
6 Research plan
6.1 Sample Layout
loess Liang/Mao area
loess Yuan/Valley
Platform
River
6 Research plan6.1 Sample Layout
Loess Plateau
Vertical section of thick yellow soil layer(Taking Luochuan Tableland as an example)
Xifeng Tableland
6 Research plan
Malan Loess
Upper part of Lishi loess
Lower part of Lishi loess
Wucheng Loess
黄土芯剖面Loess core profile
Loess Mao-small hill
6 Research plan
Lishi Loess
6.1 Sample Layout
Malan Loess
Wucheng Loess
Shallow groundwater
Deep groundwater
Lishi Loess
Loess Yuan-Loess tableland
6 Research assumption6.1 Sample Layout
Malan Loess
Lishi Loess
Wucheng Loess
Deep groundwater
钻探探测
水泥粘土填充Cement clay filling
同时钻探、取样、测量水文特性Simultaneous drilling, sampling, and measurement of hydrological characteristics
液气平衡原位抽提Liquid-gas equilibrium in-situ extraction
同位素注入Isotope inject
亮蓝注入Bright blue inject
大型观测取样井Large observation sampling well
含水量、水势高频监测Water content, water potential high frequency monitoring
6.2 Research plan-Deep soil hydrological characteristics and determination method of groundwater recharge process
Drilling detection