Dam Liners in the Eastern Cape

Rainfall differs widely across the province. The coastal strip in the west receives rain throughout the year, the east and north-east are mainly summer-rainfall, and the Karoo interior is semi-arid with low, erratic totals. The north-eastern highlands get cold winters with frost and snow, while coastal areas stay mild. Hot berg winds can raise evaporation sharply over a few days. The province has also lived through severe multi-year droughts in recent years, which drained supply dams and left many farms dependent on boreholes — a reminder that stored water has to last well beyond an average season.

Much of the interior lies on Karoo shales, mudstones and sandstones, cut by dolerite dykes and sills. Shales weather into fissured, flaky material that lets water escape along bedding planes, and dolerite leaves hard, sharp stone near the surface. River valleys such as the Sundays, Gamtoos and Fish have deeper alluvial soils, some of them saline, while coastal areas include sandy soils that drain quickly. Sites with broken rock need a smooth, compacted subgrade and often a geotextile underlay before lining, and fissured shale basins benefit especially from a continuous liner. On many Karoo farms, older dams were scooped out of shale decades ago and have leaked to some degree ever since.

Citrus in the Sundays River and Gamtoos valleys runs on drip and micro-irrigation, with farms drawing water from canal schemes into on-farm balancing dams. The Fish River valley around Cradock relies on water transferred from the Orange River for lucerne, maize and vegetables. Coastal dairy farms irrigate pastures under pivots, and the Gamtoos area also grows vegetables. Because canal water is allocated and scheduled, a balancing dam must hold what it receives until the orchard or pasture needs it; seepage directly reduces what reaches the crop, which matters most during water restrictions. Karoo farms away from the rivers depend instead on boreholes and windmills filling reservoirs for stock.

Citrus, dairy, wool and mohair, beef cattle, chicory, pineapples and game ranching are the main agricultural sectors. The Nelson Mandela Bay and Buffalo City areas are home to vehicle manufacturing and other industry, where stormwater and process water are managed on site. Game reserves and hunting farms need dependable water for wildlife through dry periods, and lodges keep reserves for guests and fire-fighting. Mining is limited compared with the northern provinces, but quarries and construction sites still store water for dust suppression and wash-down. Timber growers in the north-east keep water for nurseries and fire protection, and mixed farms in the former Transkei rely on dams and reservoirs to carry livestock through the dry winter months.

Common needs are balancing dams for citrus and pasture irrigation, stock-water dams and reservoirs on Karoo farms, drinking water for game reserves, and dairy effluent containment. HDPE suits larger earth dams, with thickness chosen per site; PVC can suit smaller ponds and reservoirs; bitumen torch-on can refurbish older cement dams and round reservoirs; and corrugated steel tanks suit homesteads and stock posts. Damtech quotes and installs across South Africa, including the Eastern Cape, and recommends a system after reviewing dimensions, photos and water use. Costs depend on dam size, material and site work — our dam lining cost guide sets out the main factors.