Overview of Recent Mekong River Basin Floods
description
Transcript of Overview of Recent Mekong River Basin Floods
11
Overview of Recent Mekong Overview of Recent Mekong River Basin FloodsRiver Basin Floods
Overview of Recent Mekong Overview of Recent Mekong River Basin FloodsRiver Basin Floods
Third Annual Flood ForumVientiane, Lao PDR
7-8 April 2005
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1.1. To provide a preliminary overview on To provide a preliminary overview on thethe recent floods recent floods based on limited based on limited data and information received so fardata and information received so far
2.2. To initiate the invitation for To initiate the invitation for increasing increasing timely data and timely data and information sharinginformation sharing among the among the countries in the region for a better countries in the region for a better understanding of floods occurrence understanding of floods occurrence and their impacts in the regionand their impacts in the region
Main ObjectivesMain Objectives
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Today’s TopicsToday’s Topics
1. Data Used and Analytical 1. Data Used and Analytical toolstools
2.Wet season and flood analysis2.Wet season and flood analysis
3. Rainfall conditions3. Rainfall conditions
4. Conclusion and 4. Conclusion and RecommendationsRecommendations
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1. Data Used and Analytical 1. Data Used and Analytical ToolTool
Archiving and operational data Daily data up to Mar 05 Rainfall from 16 sta. Flows and water level from 8
sta.
Data UsedData Used
Decision Support Framework (DSF)
Analytical Analytical ToolTool
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2.Wet season and flood 2.Wet season and flood analysisanalysis
Vientiane City Centre. September. 1966.Vientiane City Centre. September. 1966.
Central Business Area under water for 5 weeks. Central Business Area under water for 5 weeks.
Floodpeak = 26 000 cumecs. (approximately a 1 in 100 year event.)Floodpeak = 26 000 cumecs. (approximately a 1 in 100 year event.)
o Hydrographso Wet season duration
o End date and start dateo Annual flood peak
o Flood frequency analysiso Flow volume
Adamson/03/05
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Water level of Mekong at Nong Khai
0
2
4
6
8
10
12
14
01-Jun
16-Jun
01-Jul
16-Jul
31-Jul
15-Aug
30-Aug
14-Sep
29-Sep
14-Oct
29-Oct
Time in days
Gauge h
eig
ht in
metr
es
Alarm Flood 1992 1998 2000
2002 2003 2004 Av.80-04Water level of Mekong at Pakse
0.002.004.006.008.00
10.0012.0014.0016.00
01-Jun
16-Jun
01-Jul
16-Jul
31-Jul
15-Aug
30-Aug
14-Sep
29-Sep
14-Oct
29-Oct
Time in days
Gauge h
eig
ht in
metr
es
Alarm Flood 1992 1998 2000
2002 2003 2004 Av.80-04
Water level of Mekong at Chiang Saen
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
01-Jun
16-Jun
01-Jul
16-Jul
31-Jul
15-Aug
30-Aug
14-Sep
29-Sep
14-Oct
29-Oct
Time in days
Gauge h
eig
ht in
metr
es
Alarm Flood 1992 1998 2000
2002 2003 2004 Av.80-04
Water level of Mekong at Mukdahan
0
2
4
6
8
10
12
14
01-Jun 16-Jun 01-Jul 16-Jul 31-Jul 15-Aug 30-Aug 14-Sep 29-Sep 14-Oct 29-Oct
Time in days
Gau
ge h
eigh
t in
met
res
2004 1992 1998 2000 2002
2003 Av.80-04 Alarm Flood
Chiang Saen-PakseChiang Saen Nongkhai
Mukdahan
HydrographHydrograph
June-October
Pakse
20032003
2004 20032003
2004
20032003
2004
200320032004
average
2000
average
2000
average
2000
average
2000
77
Water level of Mekong at Kompong Cham
0.002.004.006.008.00
10.0012.0014.0016.0018.00
01-Jun
16-Jun
01-Jul
16-Jul
31-Jul
15-Aug
30-Aug
14-Sep
29-Sep
14-Oct
29-Oct
Time in days
Gauge h
eig
ht in
metr
es
Alarm Flood 1992 1998 2000
2002 2003 2004 Av.80-04
Water level of Mekong at Tan Chau
0.00
1.00
2.00
3.00
4.00
5.00
6.00
01-Jun
16-Jun
01-Jul
16-Jul
31-Jul
15-Aug
30-Aug
14-Sep
29-Sep
14-Oct
29-Oct
Time in days
Gauge h
eig
ht in
metr
es
Alarm Flood 1992 1998 2000
2002 2003 2004 Av.80-04
Water level of Bassac at Phnom Penh
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
01-Jun
16-Jun
01-Jul
16-Jul
31-Jul
15-Aug
30-Aug
14-Sep
29-Sep
14-Oct
29-Oct
Time in days
Gauge h
eig
ht in
metr
es
1992 1998 2000
2002 2003 Av.80-04
Alarm Flood 2004
Water level of Mekong at Kratie
0.00
5.00
10.00
15.00
20.00
25.00
01-Jun
16-Jun
01-Jul
16-Jul
31-Jul
15-Aug
30-Aug
14-Sep
29-Sep
14-Oct
29-Oct
Time in days
Gauge h
eig
ht in
metr
es
Alarm Flood 1992 1998 2000
2002 2003 2004 Av.80-04
Kg. Cham
Tan Chau
June-OctoberKratie-Tan ChauKratie
Phnom Penh
HydrographHydrograph
20032003 200420032003
2004
20032003
2004
200320032004
average2000
average
2000
average2000
average
2000
Jun-Oct 2003: Mekong water levels are lower than the normal level
Jun-Oct 2004: Mekong water levels fluctuate around the normal level
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Wet Season DurationWet Season Duration
Average_AllD_Var1gfedcb 2004_Var1gfedcb 2003_Var1gfedcb 2002_Var1gfedcb 2001_Var1gfedcb2000_Var1gfedcb 1966_Var1gfedc 1992_Var1gfedcb
15Dec
01Dec
15Nov
01Nov
15Oct
01Oct
15Sep
01Sep
15Aug
01Aug
15Jul
01Jul
15Jun
01Jun
15May
01May
15Apr
01Apr
15Mar
01Mar
15Feb
01Feb
15Jan
01Jan
12,500
12,000
11,500
11,000
10,500
10,000
9,500
9,000
8,500
8,000
7,500
7,000
6,500
6,000
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
Flow Hydrograph of Selected years
Tentative Threshold=1,730m3/s
Average
Wet Season
Flood Event Analysis Tool used to define tentative threshold value and wet season
Threshold value= e.g. 50% of flow values over a period of 01/01/1960-28/03/2005
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Chiang Saen
Wet Season DurationWet Season Duration
: Time Series Chart
[Th=1730cumecs, MinEvLen=1, MinIntLen=0]
Chiangsen_obs (11/Jun/1960)gfedcb Chiangsen_obs (22/Jun/1960)gfedcb Chiangsen_obs (02/Dec/1960)gfedcbChiangsen_obs (09/Jun/1965)gfedcb Chiangsen_obs (07/Jun/1966)gfedcb Chiangsen_obs (11/Jun/1970)gfedcbChiangsen_obs (26/May/1971)gfedcb Chiangsen_obs (13/Jun/1980)gfedcb Chiangsen_obs (16/Jun/1993)gfedcbChiangsen_obs (26/Jun/1993)gfedcb Chiangsen_obs (16/Dec/1993)gfedcb Chiangsen_obs (15/May/2000)gfedcbChiangsen_obs (13/May/2001)gfedcb Chiangsen_obs (28/May/2001)gfedcb Chiangsen_obs (08/Dec/2001)gfedcbChiangsen_obs (31/Dec/2001)gfedcb Chiangsen_obs (14/May/2002)gfedcb Chiangsen_obs (12/Jun/2002)gfedcbChiangsen_obs (22/Nov/2002)gfedcb Chiangsen_obs (26/Nov/2002)gfedcb Chiangsen_obs (10/Dec/2002)gfedcbChiangsen_obs (06/Jan/2003)gfedc Chiangsen_obs (07/Jun/2003)gfedcb Chiangsen_obs (15/Jun/2003)gfedcbChiangsen_obs (20/May/2004)gfedcb Chiangsen_obs (18/Jun/2004)gfedcb
Day in Year25/Dec10/Dec25/Nov10/Nov26/Oct11/Oct26/Sep11/Sep27/Aug12/Aug28/Jul13/Jul28/Jun13/Jun29/May14/May
(cum
ecs)
22,000
20,000
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
Flow event over threshold Wet Season Duration Analysis_ Chiangsen
Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution:
Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (60-04)gfedcb
Cumulative Exceedence Percentile %10095908580757065605550454035302520151050
Even
t Dura
tion (
days
)
240
235
230
225
220
215
210
205
200
195
190
185
180
175
170
165
160
155
150
195 days
Average: 195 Days
------------------------Y2000: 207 Days
Y2001: 237 Days
Y2003: 148 Days
Y2004: 179 Days
Wet Season Duration Analysis
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: Event Start Date AnalysisChiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution: Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution:
Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (60-04)gfedcbChiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (99-04)gfedcb
Day in Year25/Dec25/Nov26/Oct26/Sep27/Aug28/Jul28/Jun29/May29/Apr30/Mar28/Feb29/Jan
Cum
ula
tive E
xceedence P
erc
entil
e %
100
95
9085
80
75
70
6560
55
50
45
4035
30
25
20
1510
5Start Date: 30May
Chiang Saen
Start Date and End DateStart Date and End Date
: Event End Date AnalysisChiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution: Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution:
Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (60-04)gfedcbChiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (99-04)gfedcb
Day in Year25/Dec25/Nov26/Oct26/Sep27/Aug28/Jul28/Jun29/May29/Apr30/Mar28/Feb29/Jan
Cum
ula
tive E
xceedence P
erc
entil
e %
100
95
9085
80
75
70
6560
55
50
45
4035
30
25
20
1510
5
End Date: 5 Dec
1111
Chiang Saen
Annual Flood PeakAnnual Flood Peak
: Peak Value Data
Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution:
Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (60-04)gfedcb
Date05/Dec/200307/Dec/199509/Dec/198711/Dec/197913/Dec/197115/Dec/1963
Flo
w (
cum
ecs)
23,000
22,000
21,000
20,000
19,000
18,000
17,000
16,000
15,000
14,000
13,000
12,000
11,000
10,000
9,000
8,000
7,000
6,000
Average Flood Peak: 10,522 m3/s2004
2003
1212
Chiang Saen
Flood Frequency AnalysisFlood Frequency Analysis
Annual Flood Frequency AnalysisChiangsen_obs - Freq. Distribution: Gumbel (EV1) & GEV
Chiangsen_obs - Hazen (1960-2004)gfedcb EV1 Chiangsen_obs - HazengfedcbGEV Chiangsen_obs - Hazengfedcb
Return Period (years)1 2 4 5 10 20 25 50 100 200 500
(cum
ecs)
34,000
32,000
30,000
28,000
26,000
24,000
22,000
20,000
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
20042003
1313
Chiang Saen
Flow VolumeFlow Volume
6.839E+106.956E+10
8.554E+10 8.554E+10
7.305E+10
4.725E+10
6.997E+10
0.000E+00
1.000E+10
2.000E+10
3.000E+10
4.000E+10
5.000E+10
6.000E+10
7.000E+10
8.000E+10
9.000E+10
Avge_1960_2004
19992000
20012002
20032004
Flo
od
_V
olu
me
Flood_Volume
Comparison Wet Season flow Volume at Chaingsen
Year
1414
SummarySummaryStation Indicators Avg. 1978 2000 2001 2002 2003 2004
Chiang Saen
Duration (Days) 196 189 207 237 242 148 179
Start Date 30-May 15-May 15-May 13-May 14-May 07-Jun 20-May
End Date 05-Dec 20-Nov 08-Dec 05-Jan-02 11-Jan-03 02-Nov 15-Nov
Peak (cms)
Tr (yr)
10,522 11,400
3
10,700
2
10,700
2
12,700
4
6,880
<2
10,715
2
Volume(m3) 6.84E+10 8.58E+10 8.55E+10 8.54E+10 7.31E+10 4.73E+10 7.00E+10
Pakse Duration (Days) 187 188 202 203 207 161 170
Start Date 04-Jun 28-May 14-May 26-May 23-May 03-Jun 29-May
End Date 05-Dec 02-Dec 02-Dec 15-Dec 16-Dec 11-Nov 15-Nov
Peak (cms) 36,807 56,000 45,148 42,318 39,343 34,159 38,556
Volume(m3) 3.20E+11 4.02E+11 4.01E+11 3.88E+11 3.97E+11 2.59E+11 3.09E+11
Kratie Duration(Days) 183 216 206 213 174 162
Max. WL (m) 21.45 23.08 23.37 22.97 20.98 21.19
Phnom Penh
Duration(Days)
Max. WL (m) 8.6 11.21 10.77 10.09
1515
Seasonal Flood Hydrograph Seasonal Flood Hydrograph VolumeVolumeYear
Chiang Saen
Luang Prabang
Chiang Khan
VTE Nakhon Phanom
Mukd’an Khong Chiam
Pakse Stung Treng
Kratie
1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
Seasonal flood hydrograph volume (SFHV)
SFHV below “normal”, less than the 1:2 yr ARI
SFHV> 2 and < 5 yr ARI
SFHV> 5 and < 10 yr ARI
SFHV> 10 and < 20 yr ARI
SFHV> 20 yr ARI
Figure 5.1 The flood history of the Lower Mekong Basin 1960 to 2003. The analysis is based on a statistical analysis of the annual volumes of flow during the six flood months (June to November).
Overview Mekong Hydrology, November 2004, p.35
1616
3.Rainfall 3.Rainfall conditionsconditions
1717
Chiang Saen
0
400
800
1200
1600
2000
2400
Jun Jul Aug Sep Oct Nov Dec. Jan Feb
Acc
um
ula
tive
Ra
infa
ll (m
m).
Average 1992-93 1998-992000-01 2003-04 2004-05
Luang Prabang
0
400
800
1200
1600
2000
2400
Jun Jul Aug Sep Oct Nov Dec. Jan Feb
Acc
um
ula
tive
Ra
infa
ll (m
m).
Average 1992-93 1998-992000-01 2003-04 2004-05
Average Annual Rainfall by Sub-basin
Rainfall ConditionsRainfall ConditionsJun-Feb
average
2004
average2004
Mukdahan
0
400
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2000
2400
Jun Jul Aug Sep Oct Nov Dec. Jan Feb
Acc
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Ra
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m).
Average 1992-03 1998-992000-01 2003-04 2004-05
Pakse
0
400
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2000
2400
Jun Jul Aug Sep Oct Nov Dec. Jan Feb
Acc
um
ula
tive
Ra
infa
ll (m
m).
Average 1992-93 1998-992000-01 2003-04 2004-05
average
2004
average
2004
Stung Treng
0
400
800
1200
1600
2000
2400
Jun Jul Aug Sep Oct Nov Dec. Jan Feb
Acc
um
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tive
Ra
infa
ll (m
m).
Average 1992-93 1998-992000-01 2003-04 2004-05
Phnom Penh
0
400
800
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1600
2000
2400
Jun Jul Aug Sep Oct Nov Dec. Jan Feb
Acc
um
ula
tive
Ra
infa
ll (m
m).
Average 1992-93 1998-992000-01 2003-04 2004-05
average
2004
average
2004
Chau Doc
0
400
800
1200
1600
2000
2400
Jun Jul Aug Sep Oct Nov Dec. Jan Feb
Acc
um
ula
tive
Ra
infa
ll (m
m).
Average 1992-93 1998-992000-01 2003-04 2004-05
average
2004
1818
0
200
400
600
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1000
1200
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1600
Jun Jul Aug Sep Oct Nov Dec Jan Feb
Acc
umul
ativ
e R
ainf
all (
mm
).
1992-93 1998-99 2000-01
2003-04 2004-05 Average
•Rainfall average from 16 sites across the lower Mekong Basin
Rainfall Conditions Rainfall Conditions (con’t)(con’t)
Over the Basin
• 2004-05 rainfall (averaged from 9 stations)
Average
2003
2004
Jun-Feb
RainfallGenerally lower than normal rainfall esp. during the end wet season 2003 and 2004 after September
1919
1
10
100
1000
2004
2004 2004
2004
average
JanuaryFebruary
March
AprilMayJune
JulyAugust
September
OctoberNovemberDecember
3 month rainfall total
(mm)
Khon Kaen
Regionally during 2004, Regionally during 2004, rainfall during the first rainfall during the first 9 months of the year 9 months of the year was generally above was generally above average average
However, during the 4However, during the 4thth quarter of the year there quarter of the year there was little or no rainfall, was little or no rainfall, indicating an indicating an uncharacteristically uncharacteristically early end to the 2004 wet early end to the 2004 wet season.season.
Taking the year as a Taking the year as a whole, however, total whole, however, total rainfall during 2004 was rainfall during 2004 was average.average.
Rainfall 1Rainfall 1stst quarter 2 quarter 2ndnd quarter 3 quarter 3rdrd quarter 4 quarter 4thth quarter Year quarter Year
(mm) Jan - Mar Apr – Jun Jul – Sep Oct – Dec(mm) Jan - Mar Apr – Jun Jul – Sep Oct – Dec
Average Average
1950 -2004 60 410 620 130 1220 mm1950 -2004 60 410 620 130 1220 mm
2004 80 520 625 2 1227 mm2004 80 520 625 2 1227 mm
% average 133% 127% 100% <2% 100 % % average 133% 127% 100% <2% 100 %
KHON KAEN : Historical context of rainfall in 2004KHON KAEN : Historical context of rainfall in 2004
Adamson/03/05
2020
Seasonal percentage of normal rainfall: Oct 2004-Mar 2005Seasonal percentage of normal rainfall: Oct 2004-Mar 2005
Adamson/03/05
Seasonal % of Seasonal % of normal rainfall normal rainfall
October 1October 1stst 2004 2004
toto
March 30March 30thth 2005 2005
Although the image Although the image indicates less than 50% indicates less than 50% of normal seasonal of normal seasonal rainfall…………….rainfall…………….
… …..over most of NE over most of NE Thailand and Central Thailand and Central Laos the proportion was Laos the proportion was in fact between 0% in fact between 0% and 10% of normaland 10% of normal
Source: USDA Website:www.fas.usda.govSource: USDA Website:www.fas.usda.gov
2121
SE ASIA : INDEX OF CROP SE ASIA : INDEX OF CROP STRESS ON MARCH 20STRESS ON MARCH 20THTH 2005 2005
The early end to the 2004 wet season caused The early end to the 2004 wet season caused extremely low levels of reservoir storage and extremely low levels of reservoir storage and river flows which reduced the irrigation river flows which reduced the irrigation water available and increased pumping costs water available and increased pumping costs from rivers.from rivers.
Crop stress, caused by a lack of water is Crop stress, caused by a lack of water is particularly evident in Bangladesh, Yunnan, particularly evident in Bangladesh, Yunnan, Burma, Laos, Thailand and the southern Burma, Laos, Thailand and the southern provinces of Vietnam provinces of Vietnam
Source: USDA Website:www.fas.usda.govSource: USDA Website:www.fas.usda.gov
Adamson/03/05
http://www.fas.usda.gov/pecad/highlights/2005/03/sedrought/seasiadrought.htm
SPOT-veg NDVI Departure from 4-yr Average (derived from satellite imagery) March 20, 2005
2222
4. Conclusion and 4. Conclusion and RecommendationsRecommendations
Flood peaks and flow volumes in 2003 and 2004 wet seasons are slightly below or comparable
with the average value.
During 2003 wet season, Mekong water levels are lower than the average while fluctuate
around the normal during the wet season in 2004.
Rainfall in basin was found to be lower than the normal esp. during the end of wet season after
September in 2003 and 2004, possibly resulting the lower than normal flows in the consequent
dry seasons.
Timely data and information sharing among the countries in the region is indispensable for
further detailed studies of flood occurrence and their impacts.
2323
4. Conclusion and 4. Conclusion and RecommendationsRecommendations
For a better understanding in the flood occurrences and their impacts, more
comprehensive studies should be carried out on:o Bivariate distribution of annual flood peak and volume
o Spatial rainfall distribution o Flood duration map, flood depth map, salinity intrusion map
and etc.oStatus of reservoir lake as compared to average, maximum
and minimum levelo etc…
Time series analytical tool in DSF is useful to analyse flood characteristic.
Mekong at Vientiane: Bivariate distribution of annual flood peak and volume. Note the 1966 event compared to the 1: 100 year bivariate relationship between peak & volume
1:100 year envelope
Adamson/03/05
2424
THANK YOU
THANK YOU
2525
4.Dry Season and Low flow 4.Dry Season and Low flow analysisanalysis
o Hydrographso Low flow frequency analysis
2626
Water level of Mekong at Chiang Saen
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
01-N
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2003-04 Minimum Water Level 2001-02 1992-93Average1980-03 2004-05
Water level of Mekong at Nong Khai
0.00
1.002.00
3.004.00
5.00
6.007.00
8.009.00
10.00
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2003-04 Minimum Water Level2001-02 1992-93Average1980-03 2004-05
Water level of Mekong at Pakse
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
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2003-04 Minimum Water Level2001-02 1992-93Average1980-03 2004-05
Water level of Mekong at Mukdahan
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
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2003-04 2004-05 Average1980-031992-93 2001-02 Minimum WL
Chiang Saen-PakseChiang Saen Nongkhai
Mukdahan
November-May
Pakse
2003-20042003-2004
average
2003-20042003-2004
average
2003-20042003-2004
average
2003-20042003-2004
average
2004-2005 2004-2005
2004-2005 2004-2005
Upper PartMekong water levels fluctuate around the normal level, slightly higher than previous year dry season (2003/04) at present
HydrographHydrograph
2727
Water level of Mekong at Tan Chau
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
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2003-04 Minimum Water Level 2001-02
1992-93 Average1980-03 2004-05
Water level of Mekong at Kratie
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
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2003-04 Minimum Water Level2001-02 1992-93Average1989-03 2004-05
Water level of Mekong at Kompong Cham
0.00
2.00
4.00
6.00
8.00
10.00
12.00
01-N
ov
01-D
ec
31-D
ec
30-J
an
29-F
eb
30-M
ar
29-A
pr
29-M
ay
Time in days
Gauge h
eig
ht in
metr
es
2003-04 Minimum Water Level2001-02 1992-93Average1980-03 2004-05
Water level of Bassac at Phnom Penh
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
01-N
ov
01-D
ec
31-D
ec
30-J
an
29-F
eb
30-M
ar
29-A
pr
29-M
ay
Time in days
Gauge h
eig
ht in
metr
es
2003-04 2001-021992-93 Average1980-032004-05 Minimum Water Level
Kg. Cham
Tan Chau
November-MayKratie-Tan ChauKratie
Phnom Penh
2003-20042003-2004average2003-20042003-2004
average
2003-20042003-2004
average
2003-20042003-2004
average
2004-20052004-2005
2004-20052004-2005
Lower Part (Kg.Cham downward)
Mekong water levels are very low compared with normal level, comparable or slightly worse than previous year dry season (2003/04)
HydrographHydrograph
2828
Return periods for low water levels in February 2005
Frequency AnalysisFrequency Analysis
Station DataWater Level in February
Min Mean
Chiang Saen 1961-2004 < 2 < 2Nongkhai 1960-2004 9 3Mukdahan 1960-2004 4 3Pakse 1960-2004 2 < 2Kratie 1980-2004 < 2 < 2Kg.Cham 1960-2004 8 7Phnom Penh 1960-2004 23 29Tan Chau 1980-2004 49 16
Unit: Year
Water Level
2929
ConclusionConclusion
Comparing with previous year, water level at present is slightly higher in the upper part (Chiang Saen to Kratie) but comparable or
slightly worse in the lower part (from Kompong Cham downward).
Water levels in upper part (from Chiang Saen to Kratie) fluctuate around the normal level while
very low compared with the normal level in lower part (from Kompong Cham downward)
More intensive rainfall data are indispensable for detailed analysis. Low flows are possibly a
result of low rainfall especially during the end of 2004 wet season
3030
Vegetative Index (Vins)-Vegetative Index (Vins)-NDVINDVI