Transcript Real-Time GW modelling

硝酸盐定时炸弹
Nitrate time bomb
Part 1
预测英国峰值硝酸盐到达潜水面的时间
Prediction of the arrival of peak nitrate
concentrations at the water table at the regional
scale in Great Britain
Dr Sean Burke
SAIN Beijing 25-26th 02 14
王磊
[email protected]
英国地质调查局
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农业面源污染 – 硝酸盐
Agricultural diffuse water pollution – nitrate
 Agricultural diffuse water pollution, the biggest remaining problem of
water pollution in many countries, has been identified as a major
threat to water quality and the implementation of the EU WFD 欧洲水
环境框架法令(EHS, 2000; DoE & DARD UK, 2003; Torrecilla et al., 2005)
 Nitrate water pollution is not only an environmental 环境 issue but
also a threat to economics 经济 and human health 人类健康 (Defra,
2002)
 Eutrophication in rivers, lakes and estuaries;
 The annual costs for nitrate water treatment in the UK: £16 million;
 Nitrate (>10mg N/l) in drinking water may cause blue baby syndrome
（蓝色婴儿症状）;
 A potential cancer risk （潜在的癌症风险） from high nitrate/nitrite in
water and food has been reported;
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Nitrate in UK groundwater
 Average nitrate concentrations （平均硝酸盐浓度） in the UK
groundwater have been rising with a rate of 0.35 – 0.53 mg NO3 L-1
year-1 (European Environment Agency, 1999; Roy et al., 2007; Stuart et al., 2007)
 In England, over one third of the sites exceeded the 50 mg NO3 L-1
EU drinking water standard (Stuart et al., 2007). It is estimated that ~60%
of all groundwater bodies will fail to achieve good status by 2015
(Defra, 2006; Rivett et al., 2007).
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…in a changing world
Agroclimatic zones
Now
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Increasing requirement for
water
2050
研究目标The aim of the project
背景：由于非饱和带的空隙压小于大气压，以及水面张力作用，硝酸盐
在非饱和带中运移缓慢，有可能会需要几十年的时间到达潜水面。英国
的水资源管理的决策者几乎都没有考虑到历史硝酸盐在非饱和带中的存
贮和滞后现象。It takes decades for nitrate to transport in thick
unsaturated zone, and this lag-time has been ignored in current water
resource management in the UK.
有必要回答：非饱和带的存储和滞留现象如何在国家尺度下影响地下水
硝酸盐污染长期的演变趋势， 从而帮助决策者和水公司制定投资计划。
It is necessary to address the question of how the future long-term
evolution of nitrate contamination in groundwater can be predicted at a
national scale, in order to help regulators and water companies in
capital investment planning.
目的：开发一个简单的基于过程的方法来预测英国范围内峰值硝酸盐到
达地下水的时间
To develop a simple process-based approach to predict the arrival
of peak nitrate concentrations at the water table in UK.
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Precipitation
Soil zone
Nitrogen fertilizer application
Nitrate leaching (nitrate input function)
Unsaturated zone
Nitrate transport
Nitrate transport & dilution
Saturated zone
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Pumping
borehole
Methodologies – nitrate input function
Concentration (mg N/L)
0
20
40
60
80
Nitrate input function – the time-varying
nitrate loading at the bottom of the soil
zone
2020
2000
Reduce to 40 kg
N ha-1 year -1 by
2020
ha-1
1980
70 kg N
year -1
1991
Peak nitrate loading (around 1983)
Year
1975
1960
Rising at 1.5 kg
N ha-1 year -1
Rising at 1 kg
N ha-1 year -1
1940
1920
1900
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1955
1940
25 kg N ha-1
year -1
-Red line: the derived nitrate input
function from literature data.
-Black dots: observed porewater nitrate
concentrations from BGS database.
-Blue crosses: the average observed value.
Methodologies – depth to water table 非饱和带厚度
river
‘real’ groundwater level
a
river
b
c
base level
In this cross section the base level has been
interpolated between two rivers. A borehole
has terrain surface a, a ‘real’ groundwater
level at b, and a calculated base level at c.
Interpolation of groundwater levels
from topography and river stages
Unsaturated zone thickness
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Results – nitrate travel time in unsaturated zone
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Results – peak nitrate arriving time after 2009
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Results – average nitrate concentration at the water table
达到不同含水层潜水面的平均硝酸盐浓度时间序列
140
Nitrate concentration (mg l-1)
120
100
80
60
40
20
White Chalk
Triassic Sandstone
0
1925 1935 1945 1955 1965 1975 1985 1995 2005 2015 2025 2035 2045
Date
Predicted time series of nitrate concentration arriving at the water
table of the two major aquifers of Great Britain
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Part 2
通过综合模型研究硝酸盐在厚砂岩非饱和带中的运移
Investigating nitrate transport in a thick sandstone
unsaturated zone based on integrated modelling –
the Eden Valley, UK
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The aim of the Study
 通过联合模拟,建立地下水中的硝酸盐和其历史渗漏的关系 To understand
the nitrate lag time in the Permo-Triassic sandstone (PT-SS)
unsaturated zone (USZ), and build up the linkage between the nitrate in
groundwater and their historic leakage years, through the integrated
modelling.
 回答以下问题，来支持Eden集水面内的水资源管理决策
 什么原因造成了研究区内不均衡分布的地下水硝酸盐浓度What caused
the uneven distribution of groundwater nitrate concentration in the area?
 目前在地下水中的硝酸盐是什么时候渗漏的When the nitrate currently in
the groundwater was loaded into the USZ and eventually reached the
water table? And
 历史的峰值硝酸盐输入是否已经到达了潜水面 Whether the historic peak
nitrate loading has reached the water table in the EV?
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The Eden Valley
Mainly covered by farming land
population density: 0.2 hectare-1
The study area is 56 km long and
4.6 –13.9 km wide
Average annual rainfall is 1000
mm year-1
B
The Penrith Sandstone and St
Bees Sandstone form the major
aquifers in the study area
Pennines
Lake District
A
A
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B
Methodologies – nitrate dilution modelling
 GISGroundwater地下水模型
 Nitrate time bomb 硝酸盐定时炸弹模型
 GIS nitrate dilution model in saturated zone 地下水稀释模型
 To simulate yearly nitrate concentration at a borehole;
 The dilution process was simplified.
Precipitation
Soil zone
Nitrogen fertilizer application
Nitrate leaching (nitrate input function)
Unsaturated zone
Nitrate transport
Nitrate transport & dilution
Saturated zone
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Pumping
borehole
Results – GISGroundwater flow modelling
190
Observed GWLs (m)
170
y = 0.91x + 9.8485
R² = 0.9197
150
130
110
90
70
50
50
70
90
110
130
150
170
190
Simulated GWLs (m)
Correlations between observed and modelled long-term
steady-state groundwater heads
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Penrith Sandstone K: 3.5m day-1
St Bees Sandstone K: 0.6m day-1
Simulated groundwater heads for the Eden Valley
Results – nitrate dilution modelling in the Bowscar SPZ
43
38
Modelled
Observed
mg NO3/l
33
28
The modelled results can well
reflect the trend of nitrate
concentration in the borehole.
23
18
13
8
1970
1975
1981
1986
1991
1997
2002
2008
Year
The modelled and observed yearly nitrate concentration in Bowscar borehole.
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This implies that the
understanding of the nitrate travel
velocity (3 m year-1) in the P-T SS
USZ is correct; the method for
deriving the thickness of the USZ
is reliable; and the nitrate input
function can be used for this study.
Results
The study area has a variable thickness of the USZ (0 – 182.8m) hence a
large range of nitrate transport time (lag time) in the USZ (0 – 61 years)
Calculated thickness of USZ for the Eden Valley
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Modelled nitrate travel time in the USZ of the Eden Valley
Results
the peak nitrate loading (around 1983) has affected most of the study area,
and will arrive at the water table in some SPZs in the next 34 years.
The loading time for nitrate arriving at the water table of the Eden
Valley in 2010
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The future arriving time for the peak nitrate loading (around
1983) from 2010
Results
180
Nitrate concentration (mg NO3/l)
160
140
120
100
80
Penrith Sandstone
60
St Bees Sandstone
40
20
0
1919 1930 1941 1952 1962 1973 1984 1995 2006 2017 2028 2039 2050
Date
The time series of the AVERAGE nitrate concentration at
the water table (before groundwater dilution) of two
major aquifers in the Eden Valley
The total amount of nitrate entering groundwater in whole area is
declining, but the areas with thicker USZ, which have not been affected by
the peak nitrate loading, will be having a localised high or increasing
groundwater nitrate concentrations in the next few decades.
The trend of nitrate concentration at the water table (before
groundwater dilution) in the next few decades
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Thank You
我想我们不在漏水
的那一头很好！
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