LAND DRAINAGE - 1922 - CONTENTS - - PART I. - FIELD DRAINAGE CHAPTER I DEVELOPMENT, IMPORTANCE AND -E OF DRAINAGE PAGE Drainage in Europe. Notable European project. Drainage in the United States. Extent and importance of drainage. Ad- vantages of drainage reclamation. Federal and State aid. Drainage organizations and institutions. Questions. Refer- ences .................................................... l CHAPTER I1 Removes excess water. Increases the capillary supply of moisture. Improves the soil-structure. Increases the roobpasturage. Affords better air circulation. Makes soil warmer. Lengthens the growing season and firms the soil. Assists decay and nitrification. Prevents erosion. Diminishes the effect of drought. Prevents heaving and freezing out. Prevents the rise of, alkali. Successful drabage practise. Profits of farm drainage. Questions. References .............................. 9 CHAPTER I11 Surface geology and drainage conditions. EXfect of soil-texture on drainage. Heavy clay. Organic soils. Effect of soil-struc- ture on drainage. Importance of subsoil examination in drain- age. Effects of hard-pan upon drainage. Lands needing drainage. Preliminary studies. Questions. References.. ..... 16 CHAPTER IV Foaars OF SOIL-WATER Table I - te of flow of seepage-water as affected by soil-texture. Toleration of water by root crops. Water-table observation wells. Fluctuations in water-table. Supply of soil-water iii CONTENTS PAGE Effect of drainage on usable water capacity. Disposal of surplus water. Runoff. Percolation. Table I1 - Rainfall, . - percolation and evaporation at Rothamsted, England. Table I11 - Water applied and percolated from lysimeters, Umatilla, Oregon. Evaporation.Transpiration. Artificial control of soil-water. Table IV - Water cost of dry matter, different crops and climates, evapo-transpiration ratio. Movement of water into drains. uestions. References.. ................ 23 CHAPTER V Kinds of draidage. Open or surface drains. Disadvantages. Covered underdrains. Relation of surface-runs to tile systems. The parts of a drain system. The outlet. The head. A string of tile. A cutoff or intercepting drain. A main or conducting drain. Double mains. Sub-main. Lateral or collecting drains. Lateral systems. The grouping system. The Herring-bone system. The Gridiron system. A parallel system. Vertical drainage, the location of drains. Principles to be followed in locating drains. How to determine where drainage is needed. Location of drains with auger and level. Questions. References. ....................................... 35 CHAPTER V1 MATERIALS FOR COVERED DRAINS Box-drains. Cement tile. Effect of alkali on cement tile. Failures and requirements. Clay tiles. Vitrified tiles. Standards and tests. Inspection of clay tiles. Other simple tests for clay tiles. Table V- Physical-test requirements for different classes of drain-tile. Absorption test. Durability of tile. Questions. References.. .................................. 44 CHAPTER V11 Depth for drains. The soil. Frequency of Rains. The rainfall. Experiments relating to depth for drains. Results of experi- ments relat, ing to depth. A new experimental drainage system Experiments on heavy soil. Experiments relating to distance between drains...