Water quality of the Modder River
Loading...
Date
1998-11
Authors
Koning, Nadene
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
English: The Modder River is a relatively small river which drains an area of 7 960 km² , in the central region of the Free State Province, South Africa and has a mean annual runoff of 184 x 10⁶ m³ . Botshabelo is a city which was developed in the catchment area of the river and its sewage outflows are discharged into the Klein Modder River, a tributary of the Modder River. This study was conducted in order to determine seasonal and spatial patterns in the system, the influence of Botshabelo's sewage outflow on the water quality of the river, as well as the presence of any toxic compounds. It was determined that the Modder and Klein Modder Rivers do not follow distinctive seasonal patterns in terms of chemical parameters, however, N0₃-N and P0₄-P concentrations usually increased with increasing flow in the river. Physical parameters such as turbidity, flow and temperaturefollowed distinctive seasonal patterns. Turbidity and flow was high during the rainy season and temperature followed the air temperature. The Modder River is a very turbid system, influenced by physical (flow, turbidity and temperature) as well as chemical factors (high nutrient availability). The Modder River showed similarities with other South African rivers, such as the Vaal and Orange Rivers, in terms of turbidity/conductivity relationships and the range of physical and chemical parameters. Phytoplankton growth also showed distinctive seasonal patterns, with low chlorophylla concentrations in the winter and higher chlorophyll-a concentrations when temperatures became more favourable. Diatoms (especially Cyclotella sp., Stephanodiscus sp. and Nitzchia sp.) dominated the algal community in both the Klein Modder and Modder Rivers for most of the time, with the euglenophyte, Trachelomonas dominating occasionally. In the Klein Modder River, algal blooms occurred more frequently, as well as with higher concentrations than in the Modder River. This could be ascribed to the higher nutrient concentrations in the Klein Modder River, which, together with low flow conditions, provide favourable conditions for algal growth. There were periods when the nutrient concentrations in the waters of the Modder and Klein Modder Rivers were low, however, Botshabelo has an enrichment effect on the water quality, in terms of the nutrient concentrations. The inflow of the Klein Modder River into the Modder River caused on average, a 112 % increase in P0₄-P₃, a 171 % increase in N0-N nitrates and a 50 % increase in chlorophyll-a concentration. However,the Modder River showed a self-purification capacity and nutrient concentrations decreased significantly downstream to Mazelspoort, restoring the water to almost the quality of the "unpolluted" reference point. Based on toxicity tests performed with Selenasfrum capricornufum and Daphnia pulex, no high concentrations of potentially toxic compounds were found in either the Klein Modder or Modder River. However, the occasional presence of heavy metals can not be excluded. Bacteria concentrations were high in both rivers and may pose a threat to human and animal health. The use of a water quality model (PC-QUASAR) on the Modder River system, showed no results to predict the conditions in the rivers and for planning and management purposes, since the model could not be calibrated with the available data. The parameters of the model also showed great insensitivities regarding manipulation of important parameters. Because the Modder River is a very turbid system, it is also important that light availability be taken into account in any forecasting procedures m³ . Botshabelo is a city which was developed in the catchment area of the river and its sewage outflows are discharged into the Klein Modder River, a tributary of the Modder River. This study was conducted in order to determine seasonal and spatial patterns in the system, the influence of Botshabelo's sewage outflow on the water quality of the river, as well as the presence of any toxic compounds. It was determined that the Madder and Klein Modder Rivers do not follow distinctive seasonal patterns in terms of chemical parameters, however, N0₃-N and P0₄ -P concentrations usually increased with increasing flow in the river. Physical parameters such as turbidity, flow and temperaturefollowed distinctive seasonal patterns. Turbidity and flow was high during the rainy season and temperature followed the air temperature. The Modder River is a very turbid system, influenced by physical (flow, turbidity and temperature) as well as chemical factors (high nutrient availability). The Modder River showed similarities with other South African rivers, such as the Vaal and Orange Rivers, in terms of turbidity/conductivity relationships and the range of physical and chemical parameters. Phytoplankton growth also showed distinctive seasonal patterns, with low chlorophylla concentrations in the winter and higher chlorophyll-a concentrations when temperatures became more favourable. Diatoms (especially Cyclotella sp., Stephanodiscus sp. and Nitzchia sp.) dominated the algal community in both the Klein Modder and Modder Rivers for most of the time, with the euglenophyte, Trachelomonas dominating occasionally. In the Klein Modder River, algal blooms occurred more frequently, as well as with higher concentrations than in the Modder River. This could be ascribed to the higher nutrient concentrations in the Klein Modder River, which, together with low flow conditions, provide favourable conditions for algal growth. There were periods when the nutrient concentrations in the waters of the Madder and Klein Modder Rivers were low, however, Botshabelo has an enrichment effect on the water quality, in terms of the nutrient concentrations. The inflow of the Klein Modder River into the Modder River caused on average, a 112 % increase in P04-P, a 171 % increase in N0₃ -N nitrates and a 50 % increase in chlorophyll-a concentration. However,the Modder River showed a self-purification capacity and nutrient concentrations decreased significantly downstream to Mazelspoort, restoring the water to almost the quality of the "unpolluted" reference point. Based on toxicity tests performed with Selenasfrum capricornufum and Daphnia pulex, no high concentrations of potentially toxic compounds were found in either the Klein Madder or Modder River. However, the occasional presence of heavy metals can not be excluded. Bacteria concentrations were high in both rivers and may pose a threat to human and animal health. The use of a water quality model (PC-QUASAR) on the Modder River system, showed no results to predict the conditions in the rivers and for planning and management purposes, since the model could not be calibrated with the available data. The parameters of the model also showed great insensitivities regarding manipulation of important parameters. Because the Modder River is a very turbid system, it is also important that light availability be taken into account in any forecasting procedures
Afrikaans: Die Modderrivier (met 'n afvloei van 184 x 10⁶ m³ per jaar) is 'n redelike klein rivier wat 'n area van 7 960 km² in die sentrale deel van die Vrystaat, Suid-Afrika dreineer. Botshabelo is 'n stad wat ontwikkel is in die opvanggebied van die Modderrivier en die riooluitvloeisel van die stad vloei in die Klein Modderrivier ('n sytak van die Modderrivier) in. Hierdie studie is gedoen om die seisoenale en ruimtelike veranderinge in die sisteem te bepaal. Die invloed van Botshabelo op die rivierstelsel is ook ondersoek, sowel as die teenwoordigheid van moontlike toksiese stowwe wat in die water mag wees. Die resultate het getoon dat die Modder- en Klein Modderriviere geen seisoenale patrone volg in terme van chemiese parameters nie, alhoewel die N0₃-N and P0₄-P konsentrasies gewoonlik toegeneem het met hoër reënval en dus hoër vloei. Fisiese parameters soos troebelheid, vloei en temperatuur het duidelike seisoenale patrone gevolg. Die troebelheid en vloei was hoog gedurende die reënseisoen en die temperatuur het die wisselinge in lugtemperatuur gevolg. Die Modderrivier is 'n baie troebel stelsel, en word beïnvloed deur beide fisiese (soos vloei, troebelheid en temperatuur) en chemiese faktore (hoë voedingstofkonsentrasies). Die Modderrivier toon egter ooreenkomste met ander Suid-Afrikaanse rivierstelsels, soos die Vaal en Oranje, in terme van die troebelheid/geleiding verhouding asook die fisiese en chemiese parameters. Fitoplanktongroei het ook duidelike seisoenale patrone getoon, met lae chlorofil-a konsentrasies in die winter en hoër chlorofil-a konsentrasies in die somer, wanneer temperature meer gunstig geraak het. Diatome (veral Cyclotella sp., Stephanodiscus sp. en Nitzchia sp.) het die alggemeenskap in beide die Modder- en Klein Modderrivier gedomineer. Trache/omonas ('n euglenofiet) was somtyds dominant. Daar het meer algopbloeie voorgekom in die Klein Modderrivier as in die Modderrivier. Die konsentrasies van hierdie opbloeie was ook hoër. Dit kan moontlik toegeskryf word aan die hoë voedingstofkonsentrasies in die Klein Modderrivier, wat, saam met lae vloei, gunstige toestande skep vir alggroei. Daar is tye wanneer die voedingstofkonsentrasies in die· Modder- en Klein Modderrivier laag is, maar Botshabelo het 'n nadelige effek op die water van beide riviere, in terme van die voedingstofkonsentrasies. Die invloei van die Klein Modderrivier na die Modderrivier het gemiddeld die volgende verhogings in voedingstof- en chlorofilkonsentrasies in die Modderrivier tot gevolg gehad: In 112 % verhoging in P0₄-P₃ , In 171 % verhoging in N0₃--N en In 50 % verhoging in chlorofil-a. Die Modderrivier het egter In self-reinigingsvermoë en die voedingstofkonsentrasies het stroom-af verminder. Gebaseer op die resultate van die toksisiteitstoetse met Se/enastrum capricornutum en Daphnia pulex, was daar geen hoë konsentrasies van moontlik toksiese verbindings teenwoordig in' enige van die twee riviere nie. Swaar metale kan egter van tyd tot tyd voorkom. Die konsentrasie van bakterieë was hoog in beide riviere en kan gesondheidsgevare vir mense en diere inhou. Toets van In watergehalte model (PC-QUASAR) op die Modderrivier, het geen aanvaarbare resultate gelewer om die toestande in die rivier te voorspel en om bestuursbesluite te neem nie. Die model kon nie gekalibreer word met die beskikbare data nie en sommige belangrike parameters was heeltemalonsensitief vir manipulasie. Omdat die Modderrivier egter In baie troebel stelsel is, is dit belangrik om die beskikbaarheid van lig ook in ag te neem voor enige voorspellings gemaak word.
Afrikaans: Die Modderrivier (met 'n afvloei van 184 x 10⁶ m³ per jaar) is 'n redelike klein rivier wat 'n area van 7 960 km² in die sentrale deel van die Vrystaat, Suid-Afrika dreineer. Botshabelo is 'n stad wat ontwikkel is in die opvanggebied van die Modderrivier en die riooluitvloeisel van die stad vloei in die Klein Modderrivier ('n sytak van die Modderrivier) in. Hierdie studie is gedoen om die seisoenale en ruimtelike veranderinge in die sisteem te bepaal. Die invloed van Botshabelo op die rivierstelsel is ook ondersoek, sowel as die teenwoordigheid van moontlike toksiese stowwe wat in die water mag wees. Die resultate het getoon dat die Modder- en Klein Modderriviere geen seisoenale patrone volg in terme van chemiese parameters nie, alhoewel die N0₃-N and P0₄-P konsentrasies gewoonlik toegeneem het met hoër reënval en dus hoër vloei. Fisiese parameters soos troebelheid, vloei en temperatuur het duidelike seisoenale patrone gevolg. Die troebelheid en vloei was hoog gedurende die reënseisoen en die temperatuur het die wisselinge in lugtemperatuur gevolg. Die Modderrivier is 'n baie troebel stelsel, en word beïnvloed deur beide fisiese (soos vloei, troebelheid en temperatuur) en chemiese faktore (hoë voedingstofkonsentrasies). Die Modderrivier toon egter ooreenkomste met ander Suid-Afrikaanse rivierstelsels, soos die Vaal en Oranje, in terme van die troebelheid/geleiding verhouding asook die fisiese en chemiese parameters. Fitoplanktongroei het ook duidelike seisoenale patrone getoon, met lae chlorofil-a konsentrasies in die winter en hoër chlorofil-a konsentrasies in die somer, wanneer temperature meer gunstig geraak het. Diatome (veral Cyclotella sp., Stephanodiscus sp. en Nitzchia sp.) het die alggemeenskap in beide die Modder- en Klein Modderrivier gedomineer. Trache/omonas ('n euglenofiet) was somtyds dominant. Daar het meer algopbloeie voorgekom in die Klein Modderrivier as in die Modderrivier. Die konsentrasies van hierdie opbloeie was ook hoër. Dit kan moontlik toegeskryf word aan die hoë voedingstofkonsentrasies in die Klein Modderrivier, wat, saam met lae vloei, gunstige toestande skep vir alggroei. Daar is tye wanneer die voedingstofkonsentrasies in die· Modder- en Klein Modderrivier laag is, maar Botshabelo het 'n nadelige effek op die water van beide riviere, in terme van die voedingstofkonsentrasies. Die invloei van die Klein Modderrivier na die Modderrivier het gemiddeld die volgende verhogings in voedingstof- en chlorofilkonsentrasies in die Modderrivier tot gevolg gehad: In 112 % verhoging in P0₄-P₃ , In 171 % verhoging in N0₃--N en In 50 % verhoging in chlorofil-a. Die Modderrivier het egter In self-reinigingsvermoë en die voedingstofkonsentrasies het stroom-af verminder. Gebaseer op die resultate van die toksisiteitstoetse met Se/enastrum capricornutum en Daphnia pulex, was daar geen hoë konsentrasies van moontlik toksiese verbindings teenwoordig in' enige van die twee riviere nie. Swaar metale kan egter van tyd tot tyd voorkom. Die konsentrasie van bakterieë was hoog in beide riviere en kan gesondheidsgevare vir mense en diere inhou. Toets van In watergehalte model (PC-QUASAR) op die Modderrivier, het geen aanvaarbare resultate gelewer om die toestande in die rivier te voorspel en om bestuursbesluite te neem nie. Die model kon nie gekalibreer word met die beskikbare data nie en sommige belangrike parameters was heeltemalonsensitief vir manipulasie. Omdat die Modderrivier egter In baie troebel stelsel is, is dit belangrik om die beskikbaarheid van lig ook in ag te neem voor enige voorspellings gemaak word.
Description
Keywords
Water quality management -- South Africa -- Modder River, Freshwater ecology -- South Africa -- Modder River, Dissertation (M.Sc. (Botany and Genetics))--University of the Free State, 1998