The falling Rupee indicates the scarcity of the US $, which means that while the outflow continues, the inflow is missing. The so called Foreign Exchange reserves appear to have already [mis]used for political purposes, such as donation to farmers, mutual funds, etc etc
Such and similar conditions do not seem to be present in China. The politicians there do not need to adapt cheap tactics to secure their vote banks. And therefore, may be [repeat, may be] their Foreign Exchange reserves are high, so that they can now consider loaning some to US to pull US out of economic crises.