ISLAMABAD (Commodity Online): Pakistan's wheat production is expected to decline sharply by 1.5 million tons to 22.5 million tons in 2010-11 due to lower availability of irrigation water and dip in rainfall.

Pakistan - one of the world's biggest wheat producer - is being undermined by the silting of its national irrigation network, which has cut water availability to a fraction of historic levels.

While demand for water has risen by more than 50% since the irrigation system was built in the 1970s, the network's capacity has shrunk by about a third thanks to silt deposits, the US Department of Agriculture's Islamabad office said.

This has left per capita water availability at a fraction of its earlier levels, a report from the bureau said. As a result, chronic shortfalls in water available for irrigation are expected to impose an increasingly larger constraint on Pakistan's agricultural prospects.

Much of Pakistan's irrigation water, based around two large reservoirs, comes from snow and glacier melts, sources noted for bringing down rock particles.