An assessment of the ecological impacts of anthropogenic activities on Palala River, Limpopo, South Africa

The Palala River, situated in South Africa’s Limpopo Province, flows through a diverse catchment encompassing the Lapalala Wilderness Reserve, agricultural lands, and rural settlements before discharging into the Limpopo River. Despite the ecological significance of this system, comprehensive assessments of land use impacts on water quality and aquatic biota remain scarce. This study provides the first integrated evaluation of physicochemical parameters and macroinvertebrate community structure in the Palala River in relation to surrounding land use practices. Water quality and macroinvertebrate data were collected seasonally over a 12 month period across multiple sites representing a gradient from conservation to human-impacted areas. Multivariate ordination and multimetric approaches, including the South African Scoring System (SASS5) and Average Score Per Taxon (ASPT), were employed to assess ecological condition. The study showed no water quality concerns within the Lapalala Wilderness Reserve, while downstream sections, particularly near rural settlements, exhibited elevated levels of chloride, electrical conductivity, and total dissolved solids. These stressors were significantly correlated with declines in macroinvertebrate abundance at site P5 (R ²  = 0,36, p = 0,02; R ²  = 0,35, p = 0,02; R ²  = 0,42, p = 0,03) respectively. Macroinvertebrate assemblages at impacted sites were dominated by pollution tolerant taxa (75%), 25% were intermediate with no sensitive taxa present. A clear pollution gradient was evident, with SASS5 scores declining from 151 at the upstream site (P1) to 91 at the downstream site (P6), and ASPT values dropping from 7.4 to 3.8, indicating severe ecological impairment. The findings underscore the detrimental influence of anthropogenic activities, particularly domestic wastewater inputs, on river health. This baseline assessment highlights the urgent need for community-based water management strategies and regulatory interventions to mitigate further degradation of this ecologically important river system.