How can using a dam as a source of freshwater also harm agricultural resources?

The dam acts as a barrier between upstream and downstream.  Dams are also built for irrigation, but it is also deliberately destroyed in favor of irrigated farming. Though it provides freshwater, and makes people be protected by droughts, but it can also damage the agricultural resources by limiting the water in some areas. 

Dams can collect topsoil during floods.

an organism's phenotype is the  form of a trait  that it  displays. for  flowercolor, a pea  plant  can  display  a phenotype of purple or white flowers. an organism's  genotype  is the alleles of a gene it contains. based on his data, mendel concluded that a phenotype can be  determined  by more than one  genotype.

idk what the options are but

these is a strong electrostatic attraction between the ions hence a lot of energy is needed to overcome this attraction

this is why the boiling points are so high