It depends on what you mean by "a lot of water". For good tree health and the development of a good crop of fruit, established trees need 1 inch of water every 7-10 days. And that can come from rainfall or irrigation. Newly plant stock will require more.

WA state is the largest commercial producer of apples in the country and the vast majority of orchards are located in the rather arid eastern half of the state that receives only 7-9 inches of rainfall a year and almost none of that in the summer months of high fruit production. Irrigation is an absolute requirement!!

Thanks!