Midmar Dam clean-up: baseline for monitoring of litter input into water reservoirs

A working group clears the stream entering the bay. Each item was recorded. At 100% capacity the water is over the edge of the bank. A group of three clears the extensive mudflats which develop as drawdown proceeds. A green flush has developed, which attracts zebra and antelope.

By Prof. Tim O’Connor, Observation Science Specialist, SAEON

Urban dwellers in our country are accustomed to switching on a tap at home and drinking the water that pours forth without hesitation.

Water quality has, up until recently, been an expectation rather than a privilege. In a drought-prone country it was always of greater concern whether the dams would be full. If so, it was believed that engineers could sort out the quality.

Impacts on our freshwater resource

Threats to water quality continue to escalate throughout the country. Industrial spills, agricultural runoff containing fertilisers, pesticides and herbicides, road run-off containing heavy metals and petroleum products, and leakage from sewage plants are a few of the ever-escalating impacts on our freshwater resource. Engineers would no longer object to a helping hand.

It has been argued that a society can be measured by the manner and success with which it manages its waste. Maybe this is a hyperbole, but it raises the question of the amount of waste entering our freshwater systems. Litter may seem innocuous compared with some of the impacts listed above, but if our society cannot control something as simple as litter, then what hope might it hold for some of the more serious impacts.

How much litter and of what nature might be entering important water reservoirs? In KwaZulu-Natal, the Umngeni River is, without debate, the single most important river providing fresh water to more than 4 million people in the Ethekwini metro and uMsundusi municipality. Midmar Dam is one of four regulating the release of this water. It seemed an ideal candidate for examining this issue.

Over the past eight years I have conducted a weekly census of waterfowl and other aquatic birds in ‘Thurlow Bay’ at Midmar (Figure 1). The river feeding this bay runs past the edge of the Mpophomeni township a couple of kilometres upstream. It is a safe assumption that almost all litter within this bay has arrived via this one stream, or has been left by people using the shoreline for recreation.

My impression was that the amount of litter entering the bay had increased over time. If the bay was cleaned when the water was at its lowest then any litter accumulating thereafter would have entered during a period of known duration. All that was required was a bit of willing humanpower, and some organisation.

Exposed mudflats now relatively clear of litter. A portion of the Mpophomeni township, the source of most of the litter, is visible in the background.

Through the relentless effort of Monique Nunes, a DST/NRF intern with SAEON’s Grassland, Forest and Wetland Node, 15 members of the Mpophomeni Environmental Club, under the guidance of Louine Boothway of the Wildlife and Environment Society of South Africa (WESSA), assembled at Thurlow Bay on a bleak Saturday morning in August 2014. Howling winds and cold temperatures did not deter this group of young learners from amassing over 174 kg of waste (64 kg plastic, 50 kg glass, 6 kg cans, 54 kg other) from a designated strip of the shore within a couple of hours.

The team from the Mpophomeni Environmental Club atop a portion of the spoils of their endeavour.

Nature of waste

The composition of the collected waste was perhaps not too surprising (Figure 2). Plastic items predominated in the collection. The nature of the plastic items was varied, although cooldrink bottles and bucket-like containers were the most common. Soft plastic such as supermarket bags were not uncommon, as were bottles (mainly beer) and cans. Nappies were conspicuous and are of obvious concern to human and animal health.

Figure 1. The shoreline of ‘Thurlow Bay’ at Midmar Dam in the KwaZulu-Natal midlands is marked in red. This was the focus of the clean-up.

A bit of detective-like deduction led to the conclusion that almost all the items had originated from household discard. The collapse of waste removal within Mpophomeni township was an obvious contributing factor. Allegation that many disposed of household waste by throwing it into the stormwater drain system is consistent with what we observed.

Plastic is not benign for human (or other animal) health when it breaks down. In addition, many of the containers were for detergents or similar harmful products. It can easily be argued that the amounts are too small to be of any consequence for a large water body like Midmar, but a zero-tolerance approach is an alternative arguable aim.

Many feel overwhelmed by ever-increasing environmental problems - a few simple solutions would be welcome. Is it really that difficult to keep a water body like Midmar relatively free of litter? A municipality meeting its obligations of waste removal would be a useful start.

Figure 2. Composition of the litter (percent by number) collected at Thurlow Bay, Midmar Dam. Key to litter types: 1, plastic bottles; 2, other hard plastic; 3, soft plastic; 4, plastic tubs (e.g., margarine); 5, glass bottles; 6, cans; 7, other; 8, nappies; 9, polystyrene; 10, foil-lined packets (e.g., for chips).

Recycling of waste

Plastic, glass and cans have emerged as the bread and butter of an emerging industry based on recycling. The challenge is to lock in the Mpophomeni community to a far greater extent than occurs at the current time. A recycling depot already operates - people need to be made aware of the economic opportunity.

As for future monitoring, this event demonstrated yet again what can be achieved through citizen participation. It may be simple science, but it goes to the heart of our own well-being. Congratulations to a young group concerned about the state of their own environment.