Environmental Impacts Impacts from Irrigation Management: External Impacts: • Reduction in biodiversity and/or abundance of terrestrial and aquatic flora and fauna• Reduction of downstream flows affecting floodplain and watershed hydrology, ecology and landuse, riverine and estuarine fisheries and users of water (including navigation) • Reduction in river's pollution assimilation capabilities for domestic and industrial wastes through reduced base flow • Deterioration of water quality below an irrigation project through agrochemical inputs, harming aquatic species and inducing aquatic weed growth that clogs drainage channels and downstream watercourses • Contamination of local groundwater with nitrates and pesticide residues Environmental Impacts Significance of Impacts: The significance of certain environmental impacts can be assessed by contrasting the predicted magnitude of impact (eg. location, volume, concentration) with the relevant environmental quality standards. Impact significance should also be assessed by taking due account of the environmental priorities and preferences held by society but for which there are no quantifiable objectives. Particular attention needs to be focused on the environmental preferences and concerns of those likely to be directly affected by the project. See Significance of Impacts section of AGRICULTURE Sector Checks Additional information pertaining directly to irrigation projects and programmes is given below. Environmental lmpactsj Significance of Impacts: Environmental Priorities and Preferences: Unregulated environmental issues that need to be evaluated to determine whether project benefits die likely to outweigh adverse effects • Biodiversity, tropical forest, and arid and semi-arid environments • A community's immediate environment, revered areas or sites, flora and fauna of cultural (sometimes medicinal) value, and the visual landscape Health and welfare of local people (eg risk of disease from waterlogged fields and distance of fields from human settlements) • demands over water supplies, ullers) Environmental Impacts Significance of Impacts: The significance of certain environmental impacts can be assessed by contrasting the predicted magnitude of impact (eg. location, volume, concentration) with the relevant environmental quality standards. Impact significance should also be assessed by taking due account of the environmental priorities and preferences held by society but for which there are no quantifiable objectives. Particular attention needs to be focused on the environmental preferences and concerns of those likely to be directly affected by the project. See Significance of Impacts section of AGRICULTURE Sector Checks Additional information pertaining directly to irrigation projects and programmes is given below. OK, Mitigation Measures • In order to protect the environment from the adverse effects of irrigation programmes and projects there are a number of mitigation and management options that can be implemented. Some key options are given below. • These may be undertaken individually or combined into an action plan. • To achieve the best results, mitigation options should be de mined through the close participation of those for whom is intended and those others likely to be adversely Environmental Impacts Significance of Impacts: Environmental Priorities and Preferences: To evaluate the significance of their thi, ,tsses,or (.-in use tuals the following : • Government policy • Regional and international agreements between governments and official organisations • Policies of international and national NGOs • Representations at public enquiries • For information on valued ecological areas, habitats and species and international agreements on the environmental protection of biodiversity, tropical forest and arid and semi-arid areas set AGRICULTURE Sector Checklist.
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