938 



THE IRRIGATION AGE. 



be small, so that there seems to be a genuine need for such 

 plants, particularly in the northern portion of the valley and 

 wherever else the supply of ditch water is short and the 

 underflow sufficient. 



Where the underflow may not be adequate with a simple 

 well, a subterranean gallery will be found more efficacious. 

 The accompanying plan (fig. 2) of the city pumping plant 

 of Castle Rock, Colo., may be advantageously copied in de- 

 signing outfits of this sort. 



Canvas flumes. Along the west slope of the Sangre de 

 Cristo Range many streams afford water that is sufficient to 

 irrigate small tracts but in the irrigation season is entirely 

 lost in passing over the alluvial slope at the foot of the range. 

 A plan adopted by the placer miners of Alaska, and used in 

 irrigation in California, .might possibly be worked here to 

 advantage. At some places in Alaska water is carried on the 

 surface of the ground for miles in a flume made by sewing 

 together the two sides of a strip of cotton duck canvas, 

 making a long canvas pipe. Or the bottom of a ditch may be 

 lined with such canvas. The cloth will be less subject to 

 damage by cattle and rodents, however, when sewed up in 

 the form of a hollow cylinder and filled with water. Such 

 a flume might conceivably last for several irrigation seasons 

 of a couple of months each. A subsurface dam across the 

 canyon near its discharge upon the alluvial slope would help 

 by bringing all the underflow of the stream to the surface at 

 the intake of the flume. 



AGRICULTURE. 



The first population of the San Luis Valley was Mexican, 

 and the little Mexican "plazas" are scattered along both sides 

 of the valley but are more numerous in its southern part. 

 The Mexican constructed no large irrigation ditches, and their 

 settlements were perforce limited to the mountain valleys, to 

 the border of the San Luis Valley, and to the immediate 

 banks of the perennial streams in the valley. 



Following the advent of Americans came colonization 

 schemes and the construction of large canals, permitting the 

 central part of the valley to be settled. North of the Rio 

 Grande the country adjacent to the railway, irrigated by 

 the Farmers' Union, Prairie Ditch, and San Luis canals, 

 were first settled in preference to the more gravelly soil to 

 the west. Gradually, however, the gravelly land was found 

 to be fertile and suited to cultivation as well as the other, 

 and the cultivated territory spread farther westward. Then, 

 from a combination of causes, the land that lay to the east 

 along the railway and was the first to be cultivated was 

 practically abandoned. These causes were (1) exhaustion 

 of the soil by continuous cropping without rotation ; (2) ex- 

 haustion of the water in the canals by farms nearer the 

 heads of the canals; (3) failure of the canals in years of 

 drouth through lateness of their priorities; (4) injurious 

 accumulation of alkali in the soil. This accumulation of 

 alkali is due to the prevailing practice of subirrigation. The 

 alkali is largely of local origin, a result of the concentra- 

 tion at the surface of the salts in the soil of the affected 

 region itself, but is also partly derived from the soil of 

 the contiguous and higher regions to the west and carried 

 by seepage water to the lower land, there coming to the 

 surface and being precipitated. 



Remnants of the population brought in by colonization 

 schemes exist in different parts of the valley, as, for instance, 

 settlements of French Canadians about Carnero, of Scan- 

 dinavians at Swede Corners south of Saguache and in the 

 neighborhood of Swede Schoolhouse southwest of Alamosa, 

 and of Mormons at Manassa, Sanford, Richfield, Freedom, 

 and, until recently, at Zapato. 



The native vegetation of the valley varies with the 

 region and the ecologic conditions. On the high mountain 

 sides pine, aspen, and spruce, lower down pinon and cedar, 

 and in the valleys and along streams cottonwood and willow 

 constitute the forest growth. The valley bottom away 

 from streams is covered with a growth of "chico" and 

 "greasewood," the former predominating in adobe soils and 

 both growing in the loams. Sagebrush does not grow in 

 the valley bottom but is found in the foothills in places. 

 Wild currants and raspberries thrive abundantly, growing 

 well up the mountain slopes. Of the currants three varieties 

 are found, black, red and yellow. 



Much native hay is grown along the bottoms of the 

 streams that come down into the valley from either side. 

 These vegas, or native meadows, were among the first tracts 



taken up as homesteads, and on account of their value and 

 the ease of cropping are not plowed up to be planted in 

 other crops unless they run out. The market for hay is 

 largely local, yet some is shipped. 



The principal crops are wheat, oats, wild hay, alfalfa, 

 potatoes, peas and barley. Wheat was the first crop and 

 is the most important crop today. Very little trouble was 

 taken in planting wheat by the early settlers. The brush 

 was uprooted by dragging a heavy railroad rail across the 

 land, raked up into windrows and burned, and the wheat 

 drilled in directly without plowing. Such methods sufficed 

 to get large yields and led to the planting of large acreage 

 and the building of mills and elevators at Del Norte, Monte 

 Vista, Hooper, Mosca, Alamosa, La Jara and Conejos. In 

 time the heavy wheat returns failed and crops were rotated, 

 or the fields were planted in alternate years, lying fallow 

 in the intervals. 



In the last few years, however, a new industry has 

 sprung up, which yields good returns and which, in the 

 long run, will be more valuable, in that it will restore the 

 land to its pristine fertility. This is the business of fatten- 

 ing young lambs for the spring markets. Quarter sections 

 are grown with peas, or a mixture of peas and oats, and the 

 lambs are pastured on these, thus at one stroke doing 

 away with the need of harvesting the crop and hauling it 

 to market, besides resting the land by raising a leguminaceous 

 crop and returning nearly all the mineral plant food to 

 the soil. The practice promises to spread rapidly and will 

 unquestionably make for the good of the valley. The meat 

 of lambs fed on peas is said to be much improved in 

 flavor and at all times commands the best prices. 



The late and short growing season in the valley of ne- 

 cessity cuts out some fruits and crops. Early corn will in 

 a favorable year make small roasting ears. Apples and pears 

 have grown in protected places, but these are unimportant and 

 fruit is mostly imported from the outside. 



Methods of Irrigation. 



In the San Luis valley the method of irrigation prac- 

 ticed almost universally is a modification of subsurface 

 irrigation, locally known as "subirrigation." In subsurface 

 irrigation the water is carried in underground tile or per- 

 forated pipe directly beneath the roots of the plant to 

 be irrigated, as, for instance, beneath a row of fruit trees. 

 In subirrigation, as practiced in the valley, the water is 

 conducted onto the field in trenches at such distances apart 

 as experience and the character of the soil shall determine. 

 These trenches are closed at the lower ends and water is 

 supplied to them only so fast as it is taken up by the 

 sides and bottom of the trenches, care being taken to pre- 

 vent overflowing. The loamy character of the soil allows 

 it to absorb the water rapidly, while the level character of 

 the surface permits the raising of the level of ground 

 water to a height within reach of the rootlets of the grow- 

 ing crops. The object in view is to keep the level of the 

 underground water at this height. If the spring rains have 

 not left the water level near the surface, it may be brought 

 so by a preliminary flooding. 



Fig. 2. Plan of Pumping Plant Showing Subterranean Gallery. 



This method requires much less care and trouble than 

 the method of flooding or surface irrigation, and is as 

 efficacious as that method, though it requires much more 

 water. Its long-continued practice, however, brings a result 

 that is detrimental; that is to say, it renders the soil alka- 

 line. In countries of greater rainfall, where irrigation is 

 not needed, the constant flooding of the soil since its forma- 

 tion as a result of heavy rains and the consequent run-off 



