KEPORT OF THE SECEETAEY. 227 



Tracts of the fertile wet prairie lands of the Louisiana gulf coast 

 are being surrounded by embankments and drained by means of 

 pumps. This development will ultimately iuA^olve problems equal 

 to those of reclaiming the lowlands in England and Holland. 



Communities embracing large overflowed areas in the Missouri and 

 Mississippi Valleys are organizing and constructing drainage im- 

 provements. The levees along the lower Mississippi River have in 

 some measure complicated the drainage problems there, as they make 

 it necessary to divert waters from their natural channels and dis- 

 charge them at considerable distances farther down the valley. No 

 little judgment is required to devise drainage systems that will be 

 economical and efficient, at the same time subdividing the natural 

 drainage units into such parts that the necessary cooperation of the 

 landowners can be secured to complete the work of reclamation. 



SEEPAGE AND ALKALI. 



The injury to irrigated lands from seepage and alkali has un- 

 doubtedly been hastened in many instances by the unnecessarily 

 lavish use of water, but except where soil conditions are unusual, the 

 same effects, in a modified degree, will follow sooner or later even 

 with the greatest economy of irrigation. Not all the water applied 

 can be retained in the root zone of the plants ; the balance percolates 

 downward until checked by some impervious stratum, accumulating 

 until the plane of saturation is raised sufficiently to render the 

 ground surface swampy in the lower places. 



Injurious salts in solution may be carried to the surface by capil- 

 larity, and there deposited as the water is evaporated, even when the 

 ground is not saturated to the surface. The investigations have de- 

 termined that while methods of drainage used in the humid sections 

 are often valueless in the irrigation region, seeped lands can be re- 

 claimed by drains properly designed and installed. The drains are 

 usually laid at considerable depth to intercept the underflow from 

 higher lands. Relief wells may be below the drains to offer the water 

 an easy passage upward from a loose underlying stratum, rather 

 than above the drain to admit surface water. Each irrigated tract 

 requires a study of subsurface soil and water conditions, such as is 

 not considered in drainage east of the one-hundredth meridian. 



COLLECTION OF TECHNICAL DATA. 



The collection of technical data is an important part of the drain- 

 age investigations. This includes determining the quantity of water to 

 be removed and how it is affected by rainfall, topography, soil, vege- 

 tation, and size of watershed area ; the capacity of drainage channels 

 under various conditions of smoothness and of uniformity of cross 

 section; the special requirements for draining muck and peat soils; 



