BHUBANESWAR: With drinking water supply in rural areas emerging as one of the major challenges, the State Government has decided to cover at least 35 percent rural population under the safe and sustainable piped water scheme (PWS). Official sources maintained that sustainability and water quality have emerged as two problems in rural water supply sector. The ground water estimate made in 1994 identified 43 blocks as hydrologically critical and estimation of 1999 shows two blocks, Bhograi and Baliapal, in Balasore district over-exploited with limited scope for further extraction.