Some of the effects of the dam on the water cycle in that region are as follows-
1) The river water carries various type of nutrients which are blocked at the reservoir. as a result of which the number of algae increases that are toxic in nature. This degrades the quality of the water and makes it unfit for drinking.
2) The rate of evaporation is very high when the water is trapped in the dams providing a huge surface area. As a result of which most of the water gets evaporated and is stored in the atmosphere.
3) The deepening of the river bed also occurs, which extends for a long distance below the reservoir dam. This causes the groundwater level to drop down and affects the flood plain areas and the vegetation-covered regions.
Explanation: When a dam is built to create a reservoir, some impacts on water cycle would be like:-Rate of vaporization will increase in the local area.Speed of flow of water slows down, so percolation of water in the soil will increase. Water storage in the reservoir will improve agriculture in the local area.Vegetation at the construction site will affect in negative way.