Drainage Principles and Applications III. [antikvár]

¦ "v.- . i. PREFACE (to VolumeTllK>.,.''- The International Institute for Land Reclamation and Improvement has been organizing the International Course on Land Drainage in Wageningen, The Netherlands, each year since 1962. In 1969 the Board of the course decided to have the entire lecture notes re-edited and issued by the Institute in a simple four-volume publication. Readers interested in the reasons for this decision are referred to the Preface and Introduction of Volume I, which was issued in 1972, followed by Volume II in 1973. These two volumes deal with introductory subjects and the theories of field drainage and watershed runoff. This book is the third volume in the series and describes the various surveys and investigations required before an artificial field drainage system can be planned and designed. After an introductory chapter on surveys and their sequence (Chapter 17) currently applied methods for the analysis of rainfall data are treated in Chapter 18 and the methods for determining évapotranspiration in Chapter 19. In general, common soil surveys do not provide an adequate factual basis for drainage designs. An additional or special survey is usually necessary to determine such hydro-logical soil properties as infiltration and percolation rates, the storage of water in the soil, and the movement of the groundwater through the soil layers. These aspects are presented in Chapter 20. Chapter 21 describes the basic elements of a groundwater survey for drainage purposes. The assessment of a groundwater balance, presented in Chapter 22, can be regarded as a means of determining the actual cause of the drainage problem. Determining the physical and hydrological properties of a soil (soil moisture tension, soil moisture content, hydraulic conductivity, transmissivity of aquifers, hydraulic resistance of confining layers, and effective porosity) are important subjects in nearly