Most creeks shown in blue on Sierra maps (e.g., Tom HarrisonMaps.com) will have water in them all year, when not frozen.
Rock Creek, if you are coming down from Army Pass, is a burbling and fast running spill of water...especially early season.
From about Guitar Lake up from the western side of Whitney, you should plan to carry all the water you will need until you get to just above Trail Camp later in the day.
The nice thing about the Sierra is that there is plenty of water all summer long, so you only have to carry as much water as you will need between stream crossings.
If the place you plan on spending the night doesn't have water, walk another mile or so until one does.
However, if above 11,000 feet or so, most bets are off and you have to plan what your water needs will be.
