NO SUBSTITUTE: Updated studies suggest that overall national water demand will increase to almost 19km3 per year by 2035, whereas reliable supplies will only amount to 17.8km3. Picture: Paballo Thekiso

Tony Carnie

DURBAN: South Africa will be short of reliable water supplies every year for the next 20 years – even if the country manages to build all newly planned dams on time and also curb water demand in several cities.

This is the disturbing conclusion of a comprehensive study which revises nationwide water supply calculations made in a similar study two years ago.

Part of a joint project involving the Institute for Security Studies, the Water Research Commission and the University of Denver, the study suggests that even if the second phase of the Lesotho Highlands water project and other new dams are commissioned on schedule, there will still not be reliable water supply to meet growing demand as more people move from rural areas into cities.

Titled Parched Prospects II, the study finds that South Africa appears to be overexploiting available water resources and there will continue to be a gap between water demand and reliable supply from now to the end of the modelling period in 2035.

“Overexploitation occurs when more water is withdrawn from a water source than is sustainable… If a river has a yield of 1km3/year at a 98 percent assurance of supply this means that one cubic kilometre can be extracted from this river for 98 out of 100 years.

“If there is above average rainfall in a given year, more than 1km3 of water may be extracted without immediate consequence. But when withdrawals exceed reliable supply, the system is being overexploited and becomes more vulnerable – this is especially a problem when there is below average rainfall.”

The study notes that as of 2012, South Africa had enjoyed 16 consecutive years of above average rainfall, but this was unlikely to continue – as shown by the current critical drought.

It finds that, in a country ranked as the 30th driest in the world, water use is still considerably above the world average.

Water use in the Vaal River system was calculated at about 330 litres per person per day, well above the international average of 173 litres per person per day.

The study recognises that per capita water use statistics can be misleading, given that most water in South Africa is used for irrigating cash crops and food crops, and that several water-intensive industries receive water from the municipal supply system.

At a national level, 2 percent of total water supplies were used to cool coal-fired power plants.

“Although this figure may not seem like much at the national level, power-generation water requirements often occur in catchment areas that are moderately or severely constrained,” said main report author Steve Hedden, a researcher at the Centre for International Futures in Denver, Colorado.

Hedden said the latest study revised forecasts made in 2014 and now included a detailed analysis of more recent government-commissioned water reconciliation studies for Johannesburg/Pretoria, Durban, Richards Bay, Cape Town and other large urban areas.

The study suggests that agriculture remains the largest water user (about 57 percent), followed by municipalities (36 percent) and industries (about 7 percent).

By 2035, municipal water use was expected to increase by almost 8 percent of current total use as more people moved from rural to urban areas.

Updated studies suggested that overall national water demand would increase to almost 19km3 per year by 2035, whereas reliable supplies would only amount to 17.8km3.

Even with construction of new dams and extra water conservation measures, there would still be a gap between demand and reliable supply every year until 2035. While costly new infrastructure projects were often necessary “there are additional ways to reconcile supply and demand”.

As a result, the authors recommend that more attention is focused on heavier exploitation of groundwater, recycling industrial and municipal waste water and reducing leaks. Currently only 54 percent of municipal waste water is treated and nearly 25 percent of waste-water treatment works are in a “critical state”.

At a national level, 36.8 percent of municipal water was not paid for, with an estimated 25 percent loss from leaking municipal pipes infrastructure.