英语翻译
1.Floods disrupt normal drainage system in cities and typically overwhelm sewer systems.Thus,raw or partially raw sewage spills are common in flooded area.Additionally,（if the flood is severe enough）,destruction of building（ that can contain a large array of toxic materials） can cause the release of these materials into the local environment,which leads to severe environment pollution.
2.The zone of saturation is the area of soil and rock （whose pore spaces are completely filled with water）,and which is entirely devoid of soil air.This zone is technically termed ground water （even though the term broadly includes water in the zone of aeration）.
3.Drip irrigation,（also known as trickle irrigation）,functions as its name suggests.Water is delivered at or near the root zone of plants,drop by drop.This method can be the most water-efficient method of irrigation,if managed properly,（since evaporation and runoff are minimized）.In modern agriculture,drip irrigation is often combined with plastic mulch,further reducing evaporation,and is also the means of delivery of fertilizer.The process is known as fertigation.
4.Reservoir,（designed for one purpose,incidentally serving other purposes）,shall not be called a multipurpose reservoir,（but will be called so,only if designed to serve those purposes also in addition to its main purpose）.
5.The most important of forces on dams are （gravity,hydrostatic pressure,uplift,ice pressure,and earthquake forces）.These forces are transmitted to the foundation and abutments of the dam,which react against the dam （with an equal and opposite force）,the foundation reaction.