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As the river level drops below a dam, there may not be enough water to sustain communities or irrigate fields downstream. Farmers may need to use more fertilizer on their crops because there are fewer spring floods to renew topsoil. If the river does not carry enough sediment to replenish islands and beaches, they begin to erode away. How might plant and animal life change downstream of a new dam? Would there be much seasonal difference in the river’s depth? ©1997 National Geographic Society. All rights reserved. |
