15.3 RIVER NAVIGATION & ENGINEERING
Navigation of the Mekong River is restricted by numerous natural obstructions.
These include complete barriers to vessel movement such as Khone Falls
in Lao PDR. In other areas, rapids, shoals and sharp bends may block all
traffic or limit passage to smaller vessels important locations
include lengths of the Mekong River in Yunnan (Lancang River) and extending
southward along the Myanmar-Lao PDR border and into northern Thailand,
and along the southern portion of Lao PDR.
River navigation is also constrained by low discharge in the dry season
and in some areas, riverbank erosion and channel sedimentation. In many
areas, safe navigation suffers from a lack of recent hydrographic data
and navigation aids in combination with aging vessels involved in transport
on the river, weak navigation skills and limited port facilities and operation.
Improvements are planned for navigation along the Mekong River and major
tributaries. Important improvements to navigation that are being considered
include large-scale removal of obstructions on the Lancang-Mekong River
from Yunnan to northern Thailand, dredging of the Great Lake junction
with Tonle Sap, and dredging and other navigation improvements in the
delta. Collectively, activities may include blasting of rocks and rapids,
channel dredging to increase water depth, construction of locks and construction
of upstream reservoirs for dry season water release.
Situated at the 'crossroads' between the Upper and Lower Mekong, and the
Bassac and Tonle Sap Rivers, Chaktomuk junction in Phnom Penh is the key
to flow distribution between the four river branches, and to their morphological
and hydrological development. Changes in river flow have led to increased
siltation at Chaktomuk junction over the years. There are concerns that
this will result in potential blocking of the navigation channel to the
port of Phnom Penh, so stabilization plans are under way to ensure that
this essential shipping channel remains open.
Improvement of port facilities is also planned, through construction of
new ports or upgrading existing ones. Port improvements may include shoreline
development, measures that will increase vessel traffic, dredging and
disposal of channel material.
Hydrologic regimes are subject to direct and indirect changes as a result
of navigation improvements, dredging and other development activities
in the basin. Undesirable results of changes to the hydrological regime
include impairment of quality and quantity of the water supply, and ecological
effects such as degradation of critical fish habitat.