|
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 |