In general, the water quality of rivers within the country and the Mekong is considered to be good, based on international standards. The level of oxygen is high and the nutrient concentration is low. Sediment is the primary pollutant source affecting rivers. Sedimentation loads in tributaries vary considerably, from 41 to 345 tonnes/km2 per year. Tributaries and river reaches with high sedimentation are the Banghiang, Done, Ou, and the upper and lower stretches of the Mekong.
With the pressure of rapid demographic growth, socio-economic development and urbanization, however, the water quality is increasingly exposed to deterioration. Currently there are some problems related to waste and polluted water in major urban areas from varied community use (residential density, hotels, hospitals and entertainment centres). In addition there is water pollution from agricultural and industrial sectors, including mineral exploitation. This is not yet a major problem, but it could become one (WEPA, 2010).
A study on wastewater management and building in Vientiane (2004) reported that, with a rapidly growing population in the urban area of Vientiane Capital City, sewerage is becoming a serious problem because of the lack of a sufficient drainage system and lack of sewerage systems, while on-site sewerage disposal or septic tanks are often poorly designed. Further contributing to the problem in urban area is stagnant untreated wastewater from households and some small industries with open road-side drains, flowing directly into marsh or natural channels. This mixing of sewerage in the storm drainage system will continue to have a detrimental impact on public health (WEPA, 2010).