Parts of the 274 districts across 16 states have shown more than 20 cm annual decline in the groundwater levels, severely affecting of the availability of water for various purposes.Minister of Water Resources Jai Prakash Naraynan Yadav said in the Rajya Sabha a long term analysis of ground water levels by the central ground water board during the last two decades showed significant decline in ground water levels in Andhra Pradesh, Bihar etc.