Présentations Colloques

Flash Poster
2.02
Session 2.02: Groundwater for sustainable water supplies in developing countries
Viossanges (orateur)
Hydrogeological assessment in upper Vientiane Plain, Lao PDR- implications for sustainable groundwater development in data-scarce regions
The abundance of surface water resources in Lao PDR has historically led to limited interest in groundwater, except for rural water supplies. However there is a recent interest in developing groundwater supplies for irrigation and increasing food production. A critical lack of knowledge on the resource availability and extent hinders effective development and management. A case study in the 600 kmC alluvial aquifer of the upper Vientiane Plain provides a first step towards addressing this issue. **Being almost the first study of this kind in Lao PDR, data availability was a major constraint. Simple methods have been used to characterize aquifer properties, flow systems and recharge rates. Water levels were monitored in more than 50 wells over 2 years to determine regional flow and seasonal changes. Permeability was estimated using pumping and slug tests at 12 locations. Water balance and water table fluctuation (WTF) methods allowed calculating specific yield and recharge rates. For comparative purposes recharge was also calculated using Chloride Mass Balance (CMB) method. **The aquifer permeability averaged 1.6*10-5 m.s-1 for alluvium and 8.5*10-6 m.s-1 for deeper sandstone. Specific yield was estimated at 0.14. Recharge values from both methods are in the order of 400 mm.yr (17% of rainfall). Water level observations also show a probable influence from flow variations of the hydropower-controlled Nam Ngum River.**With average groundwater use of only 24 mm.yr-1 equivalent to 6 % of annual recharge, there is potential scope for further groundwater irrigation development. If managed sustainably, it could support enhancing food production and improve livelihoods. Finally, these results are being used by local authorities to build a model and management plan for sustainable development of the Vientiane Plain.**
Lao People 's Democratic Republic