b MULTIPLE PURPOSE RIVER DEVELOPMENT 



inhabited by several millipn people. It is an elongated basin bor- 

 dered on all sides by mountainous terrain, rising to elevations of 

 several thousand feet. Rainfall and melting snow in the many 

 mountain coves and valleys provide the runoff which becomes 

 small brooks initially; these join to form creeks, and finally become 

 tributary streams of the two main stems of rivers rising at each 

 end of the valley. The rivers meander from each end of the valley 

 floor toward a low area in the middle where they join, forming 

 a substantial alluvial delta. Eventually, they escape to the sea 

 through a gap in the coastal range. Precipitation on the outer side 

 of the coastal ranges collects into substantial streams draining the 

 watershed outside the rim of Grand Basin, but these, moving 

 directly toward the sea, are beyond the immediate reach of the 

 residents of the valley. 



Precipitation on the valley floor at one end of the basin is 

 moderate, increasing to very heavy in the mountains. At the other 

 end of the basin, average precipitation shades off to very little on 

 the valley floor, but increases to moderate in the mountains. This 

 geographic distribution is especially ungenerous from the stand- 

 point of valley residents, as the humid area having most of the 

 water has but a small fraction of the arable land, whereas the 

 arid section — where nearly all agricultural production requires 

 irrigation — contains the preponderant share of the arable land and 

 the majority of the population. 



Moreover, the seasonal distribution of precipitation does not 

 coincide with seasonal requirements. While little precipitation 

 occurs in the summer months when crops are growing, heavy 

 runoff from mountain areas during the winter and early spring 

 often produces disastrous floods. Irregularity in the precipitation 

 on the basin's watersheds is not only seasonal, but also cyclical. 

 Average runoff during years of abnormally high precipitation is 

 more than double that during dry phases. Thus the inhabitants 

 of Grand Basin, with a regular need for water from year to year 

 and seasonal peak requirements, are plagued by maldistribution of 

 water resources — seasonally, annually, and geographically. 



Given natural conditions of this kind, the original settlers of 

 Grand Basin attempted to adapt the undeveloped water resources 

 to their particular needs. As settlement progressed, successive 

 generations relied on the conservational and developmental tech- 

 niques appropriate to the time. In the early period of settlement. 



