Of course the dam will still be there, but the water levels may fall below the critical elevation of 1,050 necessary to make generation of power viable. I did a quick projection analysis based upon historicals and discovered that the water will fall to critically low levels by Dec. 2015:
I had the ability to visit the dam recently. Needless to say, I'm amazed by what my grandparent's generation was able to build for us as a part of their legacy. Equally amazing is how quickly we have managed to squander this precious set of resources. In disgust I decided to look at historic water levels by month for the last 80 years. I plotted this data in blue on the chart above. I also plotted the maximum water level that the dam can maintain, 1,241 ft., in a grey dashed line. I did the same for the minimum level at which it can generate power, 1,050 ft. Finally in red I projected the remaining months' of 2015 based upon this historic cyclical patterns present within the last two decades or so. (To see this, you can zoom in the chart using the widgets in the bottom left). Given that the average rate level is 1,058 ft. it follows that there will certainly be days in December where the level will fall either below or very close to the minimum level necessary for the dam to function. Here is a close up:
I suspected it could be based upon the population increase in the dessert. But, to my utter amazement, I discovered that the increase in population levels in Las Vegas and other dessert cities is not the sole contributing factor to the decline to in water levels. Instead, it's clear that we had plenty of water amidst periods of recent history where human consumption had been similar. This is quite clear since the water levels were at an all time high as recently as 2000. Most of these cities had nearly as many inhabitants then as they do no. So, instead, the decline probably has more to do with the critical droughts that seem to be increasing in frequency compared to what we had seen historically. Still, it's hard to imagine that the dam builders would have thought that giant cities in the dessert could have been the resultant consequence of the use of this technology. What's worse is that once the dam ceases operations the plan is for Vegas to receive the remaining water via an underwater aqueduct. Like a blood sucking mosquito, Las Vegas is ready to suck the reservoir dry leaving nothing for the rest of the South West.