In the Upper Colorado River Basin, irrigated agriculture is associated
with increasing stream salinity. In areas targeted for control of sal
inity transport to streams, as much as 90% of stream salinity has been
estimated to originate from ground water flowing through salt-bearing
stratum. Primary salt sources are the marine shales and the shale res
iduum that underlie the soils throughout much of the basin. Shallow su
bsurface flow systems, created by seepage from canals and deep percola
tion of irrigation water, are believed to be the primary agents leachi
ng the salts from underlying shale deposits and carrying them to strea
ms. This study attempts to determine the relative importance of advect
ive, dispersive, and diffusive salt transport processes from the alluv
ium covered, shale hillslopes of the region. The results of various ir
rigation management schemes for appraising the possibility of controll
ing salt loading to streams are presented.