Environmental Impacts Of Water Resource Projects and Transpiration – Introduction
76%of total water is used by agriculture, 6.2% by power generation, 5.7% by the industries.
Impacts of W.R.P. on the environment are quite diverse.
The diversity may be due to varieties of resources and associated transformation of these resources.
These impacts may be political, social, economical and environmental.
Impacts caused by dams and reservoirs.
Down stream effects caused by alternation in hydraulic regime. Regional effects in terms of overall aspects including resources use and socio-economic impacts. Impacts by the dams Effects on Floating debris, fish, boats
· Effects on Sediment load
· Effects on Sedimentation
· Effects on Nutrient transport
· Effects on Retention of water from small and moderate floods
· Effects on Tidal barriers and barrages
· Effects on sea
Effects on sediment load
A dam can completely blocks the passage of the sediments conveyed by river.
Blocked bed load may disturb the balance of delta areas.
Effects on sedimentation
The settled sediments reduce the storage capacity of the reservoir.
When desedimented water released from reservoir into river then it tends to reacquire its sediment load and erodes the bank of the canal.
This erosion reduces the stability of the canal
Effects on nutrient transport
Decomposition of suspended nutrients in reservoir may have consequence for aquatic biota downstream.
It also responsible for smaller sardine catches in delta
Action on retention of water from small and moderate floods
Small floods provides ready access to spawning and renew the water in them.
They prevent the river banks becoming overgrown with trees.
They brings nutrients into lake and ponds.
Effects on tidal barriers and barrages
These barriers and barrages are effected of preventing some upstream tidal flow.
Coastal protection works need to be raised against this effect.
Effects on sea
Large number of dams affect the food web structure of sea.
Bio-geo-chemical cycling of materials of coastal seas are also affected.
Effect of flooding on fauna
Many animals die due to new reservoir.
Some animals migrate to new areas.
A few animals accommodate to the new environment.
Birds such as water-fowl and waders move into new water habitat.
Effect on climate
Change in temperature
Formation of fog
Formation of a new microclimate
Change in rainfall pattern
Effects on reservoir water
Action on water other than in the reservoir
Drying up of water
Change in water table
Transpiration is the loss of water from a plant by evaporation
Water can only evaporate from the plant if the water potential is lower in the air surrounding the plant
Most transpiration occurs via the leaves
Most of this transpiration is via the stomata.
Environmental Factors Affecting Transpiration
Relative humidity:- air inside leaf is saturated (RH=100%). The lower the relative humidity outside the leaf the faster the rate of transpiration as the Y gradient is steeper
Air Movement:- increase air movement increases the rate of transpiration as it moves the saturated air from around the leaf so the Y gradient is steeper.
Temperature:- increase in temperature increases the rate of transpiration as higher temperature
Provides the latent heat of vaporisation
Increases the kinetic energy so faster diffusion
Warms the air so lowers the Y of the air, so Y gradient is steeper
Atmospheric pressure:- decrease in atmospheric pressure increases the rate of transpiration.
Water supply:- transpiration rate is lower if there is little water available as transpiration depends on the mesophyll cell walls being wet (dry cell walls have a lower Y). When cells are flaccid the stomata close.
Light intensity :- greater light intensity increases the rate of transpiration because it causes the stomata to open, so increasing evaporation through the stomata.
The Effect of Wind Speed on the Rate of Transpiration