HYDRAULIC ENGINEERING, that branch of civil engineering which deals with the application to the use and convenience of man of the natural laws governing water and other liquids. In practice it is closely connected with and utilizes the details of other branches, such as mechanical, electrical, mining and the almost infinite subdivisions of engineering. During recent years the range of uses of water has rapidly expanded and the hydraulic engi neer is being called upon to solve more and more intricate problems growing out of the in creasing density of population and multiplica tion of industries. In the practice of his pro fession, especially in relation to the larger problems, he must have available the results of meteorological observations,— of the occur rence of water in the form of rain or snow,— and obtain data as to variations in precipitation which takes place from day to day and from year to year and of the resulting stream flow. He must consider the topography of the coun try and the possibility of building storage reser voirs to conserve the supply; he must be pre pared to discuss the questions of river control, of erosion and sedimentation; and of the use of water in domestic and municipal supplies, also in the production of power in manufactur ing and for other purposes created by the ever growing needs of a civilized community. In earlier years when the sparse population was occupied mainly in agricultural pursuits and the industries were few, there was usually enough water and to spare, especially in the humid areas of Europe and America. No great difficulty was found in procuring ample drinking water and there was little interference of one community with another through pollu tion by discharging sewage or manufacturing wastes into the streams. With the rapid change from a rural to an urban population and with the growth of manufacturing centres, the question of obtaining adequate supplies has become more pressing; joined with this have been conflicts between the diverse interests of manufacturing, power production and naviga tion.
The operations of hydraulic engineering may be classified according to the uses to which the water is put. First is that for drinking, for domestic and municipal supply. Mankind under ordinary conditions can exist only a few days without water and to retain good health the water must be of a high degree of purity. It is obvious therefore that the procuring of water for immediate con sumption, for cooking and related purposes, must take precedence. Second in importance is the use of water in the production of food, in cluding in this the watering of live stock and the artificial application of water to agricultural soils or irrigation in arid or drought-stricken regions. Correlated with irrigation is drainage
or the removing of an excess of water from farm lands. The third class of uses of water is that of disposing of the sewage or the waste from cetres of population and manufacturing establishments. Wherever adequate supplies of water have been provided for municipal pur poses there arises at once the need of dispos ing of an equal quantity of sewage or industrial effluents. The importance of this has not always been recognized and the public health has been needlessly sacrificed because of neglect of this important detail of hydraulic engineer ing. A fourth use and one in which the hydraulic engineer has made the most rapid progress during the past quarter of a century has been in connection with water-power de velopment and employment of water in manu facturing, including the production of steam. For years following the development' of the steam engine the water powers of the country gradually fell into disuse; but with the im provement of methods of generating and trans mitting electricity the hydraulic engineer is called upon to co-operate with the electrician in developing hydro-electric power, often at remote points. At the same time the necessity of procuring an ample supply of pure water for certain manufacturing purposes as well as for the steam engine has become more pressing and requires that the hydraulic engineer co operate with the chemist in obtaining the de sired quality as well as quantity. In• the fifth group of uses are the details of transportation by water or navigation. The rapid development of the steam locomotive put out of use the canal boat and caused the abandonment of in land waterways in very much the same way as the stationary steam engine overshadowed the water powers. Similarly there is now a re vival of interest in navigation of inland waters. The hydraulic engineer is again called upon to take up questions of improvement of rivers, particularly of the deepening and maintenance j of channels. Closely joined with these are the problems of flood protection or prevention. i With the increase of industries upon the flood plains of the rivers, the annual losses have been becoming greater and greater and reach into millions or tens of millions of dollars. For in stance in the State of Kansas the flood losses for a little over a decade have been estimated at over $50,000,000 and at Pittsburgh, Pa., for 10 years they have amounted to over $12,000, 000.