Lake powell, formed by glen canyon dam, is not a lake. it is a reservoir, with a constantly fluctuating water level — more like a bathtub that is never drained than a true lake. as at hoover (or boulder) dam, the sole practical function of this impounded water is to drive the turbines that generate electricity in the powerhouse in the base of the dam. recreational benefits were of secondary importance in the minds of those who conceived and built this dam. as a result the volume of water in the reservoir is continually being increased or decreased according to the requirements of the basin states compact and the power-grid system of which glen canyon dam is a component.
the rising and falling water level entails various consequences. one of the most obvious, well known to all who have seen lake mead, is the "bathtub ring" left on the canyon walls after each drawdown of water, or what rangers at glen canyon call the bathtub formation. this phenomenon is perhaps of no more than aesthetic importance; yet it is sufficient to dispel any illusion one might have, in contemplating the scene, that you are looking upon a natural lake.
of much more significance is the fact that plant life, because of the unstable water line, cannot establish itself on the shores of the reservoir. when the water is low, plant life dies of thirst; when high, it is drowned. much of the shoreline of the reservoir consists of near-perpendicular sandstone bluffs, where very little flora ever did or ever could subsist, but the remainder includes bays, coves, sloping hills and the many side canyons, where the original plant life has been drowned and new plant life cannot get a foothold. and of course where there is little or no plant life there is little or no animal life.
the utter barrenness of the reservoir shoreline recalls by contrast the aspect of things before the dam, when glen canyon formed the course of the untamed colorado. then we had a wild and flowing river lined by boulder-strewn shores, sandy beaches, thickets of tamarisk and willow, and glades of cottonwoods.

based on this passage, the author most likely will argue that:

a. more dams should be built across the united states.
b. more people should visit recreational facilities such as glen canyon.
c. dams are beneficial to the environment.
d. glen canyon would have been better off without the dam.