Question

why are the dams considered to be a good source of conserving and managing water resources

Answer 1

because they mainly help in preserving water during flood and during rain, it stops outflow, hence it is Good source

Answer 2

As you get your salary and keep it in your bank and use it as per your requirements,Likewise Dams basically store rainwater and the water is used for irrigation,hydroelectric power generation,drinking water etc. as and when required.If you use it for irrigation, groundwater table improves in addition to irrigation benefits..In case of Hydro electricity.the river in the down stream of power plants becomes perennial due to release of water.If the dam is for sole purpose of domestic water supply,then this will improve quality of life due to better hygiene.