Basic Information | International Commission on Irrigation & Drainage (ICID)

Environmental Impact Assessment

Many institutions require an environmental impact assessment (EIA) prior to construction activities associated with new projects or the rehabilitation of existing projects. The objectives are to identify potential adverse environmental effects, the magnitude of these effects, and to develop mitigative measures. Positive benefits are also identified. In cases where the adverse impacts far outweigh the expected benefits, the project may be completely redesigned or suspended. This is also the case where mitigative measures would be either too costly or technically not feasible. The EIA should be conducted in the earliest stages of decision making, when crucial decisions are still being deliberated.

Environmental effects can be classified as:

Direct and indirect,or first order and higher order. These are chain effects which are felt throughout, and possibly downstream of a catchment.
Secondary.The primary activity of a drainage project may be extended to include secondary activities.
Synergistic.These effects include an increased threat to the survival of certain species of wildlife that are under pressure in several ways as a result of the same project.

Following is the ICID checklist of possible environmental impacts of irrigation, drainage and flood control projects.

ICID Checklist
Hydrology	1-1 Low flow regime
	1-2 Flood regime
	1-3 Operation of dams
	1-4 Fall of water table
	1-5 Rise of water table
Pollution	2-1 Solute dispersion
	2-2 Toxic substances
	2-3 Organic pollution
	2-4 Anaerobic effects
	2-5 Gas emissions
Soils	3-1 Soil salinity
	3-2 Soil properties
	3-3 Saline groundwater
	3-4 Saline drainage
	3-5 Saline intrusion
Sediments	4-1 Local erosion
	4-2 Hinterland effect
	4-3 River morphology
	4-4 Channel structures
	4-5 Sedimentation
	4-6 Estuary erosion
Ecology	5-1 Project lands
	5-2 Water bodies
	5-3 Surrounding area
	5-4 Valleys and shores
	5-5 Wetlands and plains
	5-6 Rare species
	5-7 Animal migration
	5-8 Natural industry
Socio-economic	6-1 Population change
	6-2 Income and amenity
	6-3 Human migration
	6-4 Resettlement
	6-5 Women's role
	6-6 Minority groups
	6-7 Sites of value
	6-8 Regional effects
	6-9 User involvement
	6-10 Recreation
Health	7-1 Water and sanitation
	7-2 Habitation
	7-3 Health services
	7-4 Nutrition
	7-5 Relocation effect
	7-6 Disease ecology
	7-7 Disease hosts
	7-8 Disease control
	7-9 Other hazards
Imbalances	8-1 Pests and weeds
	8-2 Animal diseases
	8-3 Aquatic weeds
	8-4 Structural damage
	8-5 Animal imbalances