Find a patch of Melilotus (Yellow sweet clover = Melilotus officinalis), it grows along wild along ditches and irrigated fields in Nevada. Get your bees on that - for August flow. Melilotus is likely your best immediate target for August Desert honey. White sweet clover (Melilotus albus) can also be found, but the wild patches are typically yellow http://en.wikipedia.org/wiki/Melilotus_officinalis
Your bees are starving out. Unless you are certain you will have a fall flow, you need to take action now to bring them to health for the Nevada winter. I would find some ditch or streamcourse with Melilotus and Rabbit Brush ready to bloom nearby. Up near the hills, there will be some "Eriogonum nudum" - a wild buckwheat, though the flowering of the buckwheats were very poor this year. Rabbit Brush honey is not great for humans-- distinctly rubbery in taste, but great to carry your bees through winter. Melilotus honey is top-notch, clear, light and fragrant.
Cucurbits produces some pollen, but virtually no usable nectar. Veg gardens in the desert west will not
support a hive. Most garden plants have had nectar bred out of them-- as it is a metabolic drag on the plant to produce human food. Most Cucurbits (squash, pumpkin) are new world plants and are not coevolved to support honey bee polination. (Cukes are from Nepal, and may have a different make-up). Yup, they like Oregano, but how much oregano would you need to support a hive....
Rabbit brush ( Chrysothamnus and Ericameria) will come on soon, and bees will work that with relish. Look for a stand of fireweed (Epilobium angustifolium), Fireweed is a prolific nectar source in mid summer along streams and ditches. Chicory (Cichorium intybus) -- like a blue dandelion, or Stephanomeria , ( a pink dandelion aka poverty weed) in an abandoned horse pastures, will sustain a hive in the high desert in summer. Find an alfalfa farmer who is letting the last cutting go to seed. Alfalfa will fatten bees, if the cutting is delayed until the flowers set. Farmers want bees to set the alfalfa to reseed the pasture-- they have bee boards for solitary leaf cutter bees, but honeybees can work the crop.
(I'm in Carson Valley for the next 3 weeks).