for the first time in 75 years the california department of water resources has found no snow during its survey of the sierra nevada in early april .
nasa images showing the snowpack across the tuolumne river basin show a marked decrease since last april .
california depends on the snow to melt into rivers and replenish reservoirs .
gov. brown ordered sweeping , unprecedented measures to save water in the state on wednesday .
cemeteries , golf courses and business headquarters must significantly cut back on watering the large landscapes .
the governor 's order contains no water reduction target for farmers .
initiatives are part of the goal to reduce water use by 25 percent compared to levels in 2013 .