South Africa will experience water rationing if consumers do not heed calls to cut consumption to avoid a collapse of the water system as dam levels fall after a drought, an official in the water department said on Thursday. Concerns over water supply in Africa's most industrialised country have risen after an El Nino weather pattern brought drought conditions to much of southern Africa, hurting agriculture output.The department of water in August asked municipalities to cut water supply by 15 percent to preserve dam levels, but said the response had been poor. Water and Sanitation Minister Nomvula Mokonyane said last week failure to cut water use would "trigger the next level of interventions" to avoid the collapse of the water system.Asked what the next level would be, the minister's spokesman Mlimandlela Ndamase said:"The next level will be rationing, which in turn has consequence referred to as shedding...The urgency of saving 15 percent cannot be over emphasized. It is critical."The water supply disruptions would be akin to power cuts - known locally as load shedding - such as those imposed by power utility Eskom after it faced supply problems.SHEDDING AND THROTTLINGDam levels nationally were at 51 percent as of Sept. 26, compared with 70 percent the same time last year, the water department said.The Vaal Dam, which supplies water to economic hub Johannesburg and the capital Pretoria among other areas, was at 30 percent capacity last week and the department expects capacity to fall to 25 percent by mid-November if there is no reduction in water consumption.Johannesburg Water, a water provider for the city, said on its twitter page on Thursday it was "moving closer to water shedding and residents will suffer if they continue ignoring water restrictions." The City of Johannesburg has already implemented 'water throttling', which is the reduction of water inflow into an area and different from 'shedding', which is when the supply is completely cut off for certain periods."Most areas will notice a drop in pressure. We already have a number of complaints from consumers about that, but we want to use that to get people to comply," Johannesburg councillor Anthony Still told Talk Radio 702.Severe drought conditions are still afflicting most of South Africa and temperatures are expected to remain above normal until December, the national weather service said...