This has prevented Gulf sturgeon and other migratory species from accessing upstream areas.

Flooding is also a regular problem, caused by heavy rainfall in upstream areas of the Tana River.

Because the river's watershed is entirely within the Ventana Wilderness, the upstream area is in pristine condition.

The data showed that significantly higher level of water table was maintained in the catchment area (upstream area) compared to down stream area.

The natural drainage in the upstream areas, other than the main river channels, is everywhere impeded by extensive embankments and polders.

Communal spawning occurs in the spring and early summer in upstream areas with moderate to fast current and over fine gravel or small rocks.

Intensified agriculture allowed for population increase, but also led to deforestation in upstream areas with resultant flooding and over-irrigation, which raised soil salinity.

In many upstream areas cut off from the ocean by dams, sturgeon simply live upstream of the dam.

The dam's current problem is the annual loss of reservoir capacity due to the erosion of soil in upstream areas.

Under the past regulation, building factories was banned within a certain distance from the upstream areas of water source.