Silicon Valley venture capitalists raise more money, give less away

The Alphabet Inc. campus, also known as Googleplex, is shown in this aerial photo in Mountain View, California, United States on April 6, 2016.

Venture capitalists are raising money at the fastest rate in a decade, raking in about $13 billion in the first quarter of 2016.

But much of that cash won't flow into new startups anytime soon. Rather, venture firms are bracing for a downturn and boosting reserves to keep companies they have already backed from going bust, said venture capitalists and limited partners.