Waterlogging and salinization
- On irrigated land salinization is the major cause of land being lost to production and is one of the most prolific adverse environmental impacts associated with irrigation
- Waterlogging and salinization of soils are common problems associated with surface irrigation. Waterlogging results primarily from inadequate drainage and over-irrigation and, to a lesser extent, from seepage from canals and ditches. Waterlogging concentrates salts, drawn up from lower in the soil profile, in the plants’ rooting zone.
- Alkalization, the build-up of sodium in soils, is a particularly detrimental form of salinization which is difficult to rectify.
Water-borne and water-related diseases
- Water-borne or water-related diseases are commonly associated with the introduction of irrigation.
- The diseases most directly linked with irrigation like malaria whose vectors proliferate in the irrigation waters. Other irrigation-related health risks include those associated with increased use of agrochemicals, deterioration of water quality, and increased population pressure in the area.
Potential environmental impacts of dams and reservoirs
- Damming the river and creating a lake-like environment profoundly changes the hydrology and limnology of the river system.
- Dramatic changes occur in the timing of flow, quality, quantity and use of water, aquatic biota, and sedimentation in the river basin.
- The area of influence of a dam project extends from the upper limits of the catchment of the reservoir to as far downstream as the estuary, coast and offshore zone.
- While there are direct environmental impacts associated with the construction of the dam (for example dust, erosion, borrow and disposal problems), the greatest impacts result from the impoundment of water, flooding of land to form the reservoir and alteration of water flow downstream.
Socio-economic impacts irrigation schemes
- The most significant issue arising from large dam construction is resettlement of people displaced by the flooding of land and homes.
- This can be particularly disruptive to communities and insensitive project development would cause unnecessary problems by lack of inadequate compensation of the affected population.
- Human migration and displacement are commensurate with a breakdown in community infrastructure which results in a degree of social unrest and may contribute to malnutrition.