5. The 2008 flood season
5.3 Temporal aspects of the 2008 Mekong flood season
Defining as usual, the onset of the flood season as the first sustained 'up-crossing' of the mean annual discharge and its end as the last 'down-crossing' the figures in Table 5.2 indicate that in the middle reaches, at Vientiane and Pakse the 2008 seasonal onset was two to three weeks early. Elsewhere, the timing of the start was 'normal' while throughout the Basin the season ended just two weeks later than average.
| Site | Onset of flood season | End of flood season | ||||
| Historical average | Standard Deviation | 2008 | Historical average | Standard Deviation | 2008 | |
| Chiang Saen | 28th June | 13 days | 27th June | 14th Nov | 14 days | 22nd Nov |
| Vientiane |
3rd May |
14 days |
15th June |
11th Nov |
15 days |
21st Nov |
| Pakse |
29th June |
16 days |
9th June |
5th Nov |
11 days | 20th Nov |
| Kratie |
1st June |
16 days |
5th July |
7th Nov |
12 days |
20th Nov |
The importance of employing a meaningful definition of the onset and end dates of the flood season was amply demonstrated in 2007. Then the onset of flood season conditions in the latter part of July and the first week of August was the latest observed in the last 80 to 90 years. As a consequence the low water levels observed during most of July were unprecedented and had negative impacts upon the environment, fisheries, agriculture and navigation.
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