Aspects of the phosphorus cycle in Hartbeespoort Dam (South Africa) Phosphorus loading and seasonal distribution of phosphorus in the reservoir

Abstract

Hartbeespoort Dam, a hypertrophic, warm monomictic impoundment in South Africa, receives extremely high phosphorus loads (14.6-25.9 g rnh2 a-') that are dominated by point source discharges from municipal wastewater treatment works. The reduced state of the phosphorus discharged from the works has led to the dominance of the dissolved phosphorus pool by low molecular weight orthophosphates which are analytically detectable as soluble reactive phosphorus (SRP; 60% of total phosphorus pool). Seasonality in the in-lake total phosphorus pool is regulated by a combination of abiotic and hydrological processes; biotic processes appear to play a minor role. Mass balance calculations indicate that between 62 and 77% of the annual total phosphorus inflow load is retained within the impoundment each year.

Multivariate Analysis of the Dynamics in Water Quality and Trophic Status of the Crocodile River and Hartbeespoort Dam

“…The high concentration of nutrients in the dam may also be a result of external loading through surface runoff as well as other sources/tributaries of the dam [8][9][10][11][12][13][14][15][16][17][18][19]35,36]. Similarly, elevated phosphate concentrations at the downstream site can be attributable to increased external phosphate loading resulting from domestic and industrial activities within the catchment [18,19,75,76,80], as well as internal recycling and regeneration through fish excretion and sediment resuspension [41,81,82].…”

“…Although several studies were undertaken to study the water quality, health, and integrity of the Crocodile River (including the Hartbeespoort Dam), as well as its biodiversity and ecosystem services [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], little is known on the impact of the bioremediation project which aimed at improving the overall water quality of the dam [33,34]. Moreover, majority of the studies in the catchment focus on the assessment of physico-chemical parameters as well as biomonitoring of the dam [9,[35][36][37][38][39][40][41], whereas the impact of rainfall on the variability of water quality parameters is rarely studied.…”

Relationship between water flow volume and in‐lake total phosphorus concentrations via dissolved oxygen concentrations and temperature in a warm temperate reservoir: Implications by path analysis

“…Focusing on deep lakes, the dammed ones (reservoirs) require even further attention in evaluating the effects of internal loading because of the erratic and highly seasonal nature of both hydrological inflows and nutrient inputs (Thornton & Ashton 1989; Thornton et al . 1990; Straskraba 1996).…”