Water filters and filtration systems firm Amiad has warned that first half revenues and profits are likely to miss forecasts as it struggles to negotiate the economic downturn.The company, which first flagged difficulties at its 2009 results in April, said its irrigation business and industrial projects in the US had been hardest hit.Revenue for the first six months of 2010 is now thought to be about $37m, including $6m from the Arkal acquisition, little changed from a year ago.But the group expects trading in the second half will improve and that Arkal will provide a further boost to the full-year numbers.Panmure Gordon thinks the core Amiad business is likely to deliver $1m in net profit for the period to 30 June, down from $3.5m in 2009. "With a higher presence of irrigation in the mix and with some pricing pressure the gross margin has fallen to 42% from a long term range of 45-48%," says the broker, which has placed its estimates and target price under review ahead of a meeting with the company.Interim results are scheduled for early September.