PROBLEMS FROM LAND OCCUPANCY 193 



for the landowners or their neighbors. But taking an opti- 

 mistic long view, they all show that it is possible to manipulate 

 ground-water levels and make considerable changes in the 

 quantity of water stored underground by nature. 



RISING WATER TABLE IN IRRIGATED AREAS 



The use of surface water for irrigation has almost every- 

 where been accompanied by a rising of the water table due to 

 downward percolation from the irrigated areas. Under natural 

 conditions, ground water is at shallow depth in the low central 

 portions of most western valleys and near the channels of 

 through-flowing streams. In valleys where there is irrigation 

 by surface water, the water table has risen under many of 

 these lowlands because of lateral movement from higher ir- 

 rigated lands. In the mountain valleys of Montana (see page 

 86) and several other states, thousands of acres of bottom land 

 have been abandoned because of waterlogging, and the water- 

 logging still continues because of irrigation of lands at higher 

 elevation. In Utah, where irrigation has been practiced for 

 more than a century, many areas once irrigated have been 

 abandoned because of high water table and increasing salinity 

 of the soil due to evapotranspiration; most of the abandoned 

 farms are in the lower parts of the intermontane valleys. The 

 use of the Snake River for irrigation in southern Idaho has 

 in some places increased ground-water storage and raised the 

 water table until lands have become water looked; in other 

 places it resulted in marked increase in discharge from springs 

 (see page 89). 



The effects of percolation from irrigation have been bene- 

 ficial in many areas. In several valleys in Utah, irrigated lands 

 are so high on the alluvial fans of the tributary streams that 

 water has percolated into the recharge areas of artesian reser- 

 voirs, thus benefiting the users of ground water in those val- 

 leys. And just above the waterlogged areas in many Western 

 valleys, the water table is at optimum depth for farming with- 

 out application of water to the surface, for the crops depend 

 upon "subirrigation." 



