Underground reservoirs Alluvial plains and plateaus, criss-crossed by rivers, are highly permeable due to the accumulation of gravel, and a great deal of water infiltrates down through the soil. Thus these areas generally have plentiful groundwater.
埋在地下的水庫一般來說，大河流經的沖積平原、台地，由於礫石堆積、透水性高，入滲土壤的水量大，通常是地下水豐沛的地區。