the three northern islands (Nanumanga, Niutao and Nanumea), Nanumanga suffered the most damage, with from 60 to 100 houses flooded, with the waves also causing damage to the health facility. Vasafua islet, part of the Funafuti Conservation Area, was severely damaged by Cyclone Pam. The coconut palms were washed away, leaving the islet as a sand bar. The Tuvalu Government carried out assessments of the damage caused by Cyclone Pam to the islands and has provided medical aid, food as well as assistance for the cleaning-up of storm debris. Government and Non-Government Organisations provided assistance technical, funding and material support to Tuvalu to assist with recovery, including WHO, UNICEF EAPRO, UNDP Asia-Pacific Development Information Programme, OCHA, World Bank, DFAT, New Zealand Red Cross & IFRC, Fiji National University and governments of New Zealand, Netherlands, UAE, Taiwan and the United States. King tides Tuvalu is also affected by perigean spring tide events which raise the sea level higher than a normal high tide. The highest peak tide recorded by the Tuvalu Meteorological Service is , on 24 February 2006 and again on 19 February 2015. As a result of the historical sea level rise, the king tide events lead to flooding of low-lying areas, which is compounded when sea levels are further raised by La Niña effects or local storms and waves. Water and sanitation Rainwater harvesting is the principal source of fresh water in Tuvalu. Nukufetau, Vaitupu and Nanumea are the only islands with sustainable groundwater supplies. The effectiveness of rainwater harvesting is diminished because of poor maintenance of roofs, gutters and pipes. Aid programmes of Australia and the European Union have been directed to improving the storage capacity on Funafuti and in the outer islands. Reverse osmosis (R/O) desalination units supplement rainwater harvesting on Funafuti. The 65 m3 desalination plant operates at a real production level of around 40 m3 per day. R/O water is only intended to be produced when storage falls below 30%, however demand to replenish household storage supplies with tanker-delivered water means that the R/O desalination units are continually operating. Water is delivered at a cost of A$3.50 per m3. Cost of production and delivery has been estimated at A$6 per m3, with the difference subsidised by the government. In July 2012, a United Nations Special Rapporteur called on the Tuvalu Government to develop a national water strategy to improve access to safe drinking water