Action |
Water-related consequences |
Negative impacts |
|
Urbanization: water supply from the upstream part of the basin or
from the groundwater system |
Increase in impervious areas Increase in peak discharge and surface
runoff Point and diffuse source pollution Decrease in groundwater
recharge
|
Higher flood risk Possible water quality problems downstream |
Intensification of agriculture: high amounts of fertilizers,
pesticides, and herbicides in use; irrigation; high livestock densities
|
Higher runoff in the nongrowing season Lower runoff in the growing
season |
Associated diffuse source pollution Eutrophication of waterbodies
Salinization |
Extensification of agriculture: use of more land for agricultural
production, ploughing of extensive areas, irrigation
|
Higher runoff |
Diffuse source pollution |
Forestation |
Increase in water storage Enhanced evaporative losses Reduced runoff Reduced
total annual streamflow
|
Depend on local conditions |
Dam construction: reservoirs and impoundments for flow
regulation to meet human requirements, water supply, hydropower production,
flood control, and navigation
|
Changes in downstream flow Streamflow regulation, i.e., storing water when
abundant and releasing when scarce Flood control |
Barrier to movement of fish and to transport of sediment Change in water
regime downstream with possible consequences for water quality |
Channelization by straightening, shortening, and converting natural
channels to concrete ones |
Reduction in the times to peak Faster conveyance |
Direct impacts: increased flow velocities, enhanced stream power, and
higher risk of floods Indirect impacts: reduced water storage in
watersheds, reduced self-purification capacity of rivers, elimination of
wetlands
|
Irrigation |
Persistent water loss through deep percolation, causing local groundwater table to rise Entrance of natural salts into soil horizon close to the surface by capillary rise Irrigation with salt water Salt washes off the land during stormflow or enters river with baseflow
|
Soil and river salinization resulting from irrigation |
Excessive water withdrawals from groundwater |
Lower groundwater table |
More dry conditions during the vegetation period |