But unfortunately rain doesn't fall in torrents straight into reservoirs--the higher reservoirs are built, the smaller their water catchment areas become, and the less water they are able to trap. Treating reservoirs as the only option also leads to them being used inefficiently.
問題是雨水又不是只對著水庫傾盆而下，水庫地點越蓋越高，集水區也越來越小，越攔不到水。