All sources of water can be broadly classified under the following two categories: Surface water, and Ground water.
The surface water can further be sub divided into the following categories: Streams, Lakes, Ponds, Rivers, and Impounded Reservoir.
The surface water sources are discussed with reference to the following impurities: Colour, Odour, Taste, Physical, Chemical, Bacterial.
(i) Streams. The impurities in the stream water are on account of clay, sand, colloidal and minerals by and large the water is colourless, odourless and tasteless.
Depending upon the strata through which water passes, it is likely to have mineral impurities, which may or may not be harmful. Water from streams and springs is the best source of supply.
(ii) Lakes. Lakes are formed in impervious bed. Since the water is not as free flowing as in the case of stream and springs, it is likely to be affected by bacterial impurities.
Lake water forms a good source of water supply, particularly if the lake is located at high altitude.
(iii) River. Because of the flowing nature of the water and continuous exposure to heat and light, it has self purification property. It is the major source of water supply for most of the water works.
The water carries sand，silt and clay with it. The intake point should be a good distance up-stream from the point at which sewage is discharged into the river.
(iv) Ponds Comparatively small quantities of water may be collected from ponds, which are formed by depression in the plain, Because of the stagnant nature of water it contains physical, chemical and bacterial impurities. It is invariably contaminated and unstable for water supply purposes.
(v) Impounded Reservoir. In most of the rivers there is considerable variation in the discharge between rainy season and dry season. Whereas water during the rains goes waste and occasionally cause flooding there may be water scarcity or water famine during he summer months.
The difficulty has been partly overcome by storing water by constructing bund, weir or dam across the river.
The various sources of ground water are: Spring, Infiltration ,Galleries,Porous, Pipe Galleries, Wells.
The ground water is obtained by means wells and tube wells. Wells may be classified into the following three categories :
(i)Open well or Dug well. These are normally 3 to5 metres deep and are a normal source of supply for the villages.
(ii)Lined well. The wells are lined with bricks stone or concrete These wells are 10to20 metres deep.
(iii)Deep wells and Tube wells. These are the normal source of water supply in cities. They are used either alone or to augment the supply from rivers. In remote areas where irrigation facilities are not available, tube wells form the only source of irrigation wells.
一切水源可概略分为以下两类: 地表水和地下水。
地表水可进一步细分为以下几种:溪流、湖泊、池塘、河流、蓄水库。
本文将按照下列所含杂质的情况:讨论地表水源:色度、气味、口感、物理杂质、化学杂质、细菌。
(1)溪流。溪流中的杂质主要是黏土、砂、胶体和矿物质。一般而言， 溪水无色、无臭、无味。根据水流通过的岩层不同，水中很可能含有矿物杂质。这些杂质可能无害，也可能有害。溪水和泉水是优良的供水水源。
(2)湖泊。湖泊形成于不透水的基层之上。由于湖水不能像溪流和泉水那样通畅地流动，因而很可能被含有细菌的杂质污染。
湖水是良好的供水水源，特别是位于海拔较高的湖泊。
(3)河流。由于河水的流动性以及不断暴露于热和阳光中，河流具有自净作用。河流是绝大多数给水工程的主要供水水源。
河水带有砂砾，淤泥和黏土。河水取水点应位于污水排放口上游足够远的地方。
(4)池塘。池塘由平坦地区的凹地形成，从池塘中可汇聚的水量相对而言较少。因为水流停滞不畅，使其中含有物理的、化学的和细菌类的杂质。这种水总受到污染，因而不适于作为供水水源。
(5)蓄水库。大多数河流在雨季和旱季的水量变化相当大。降雨时期，水量过剩，有时还造成洪水泛滥:而在夏季，水量缺少，供不应求。
横跨河流修建堤、堰、坝以蓄水，已使上述困难得到了一定程度的解决。
各地下水源有泉、渗渠、多孔管渗渠和井。
地下水可通过井和管井取得，井可分为以下三种:
(1)敞口井或开挖井。一般深3~5m,是乡村主要的供水水源。
(2)衬砌井。井内壁有砖、石或混凝土的衬砌。这种井深度为10~ 20m。
(3)深水井和管道井。这是城市给水工程通常的水源。它们可以作为单独的供水水源，也可作为河流供水水源的补充水源。在没有灌溉设施的偏远地区，管井就成为唯一的灌溉水源了。
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