© Copyright 2017 Hartbeespoort Dam Rehabilitation Steering Committee

History

Historical Context of Hartbeespoort Dam

The vision of Genl. Hendrik Schoeman to build an irrigation dam in the Crocodile River on his farm was realized when the Hartbeespoort Dam was constructed and commissioned in 1925. The project was based on The Water and Conservation Act, Act 8 of 1912 and approved in 1916. The 500 km downstream irrigation canals were added to source water to the newly established Brits community where 13000 ha of high agricultural potential was wetted seasonally to provide fresh vegetables and fruit to the thriving Johannesburg and Pretoria communities. The catchment of the dam is between Kempton Park in the east and Krugersdorp in the west, covering a 4112km² area. The growing demand in the downstream area including Thabazimbi and the Waterberg area for socio- economic development necessitated that the dam wall should be raised by 2.44 metres in 1971. to increase the capacity to 195 million m³ at full supply level. The impoundment has a surface area of approximately 20 km2 or about 2000 hectares. Water from the Hartbeespoort Dam is used mainly for irrigation (82%) and domestic consumption (about 12%) in growing urban settlements with 6% being released for ecological reserve along river flow. Outflow from the dam is through the two canals as well as 10 sluice gates that can be opened to control the level in case of flooding. The 1MW hydroelectric generator set is not in operation anymore. Over the more than 90 years since it was commissioned, the dam attracted city dwellers to the area due to the combination of a large water body within an idyllic mountainous setting. It became increasingly important as a regional recreational and tourist centre. Activities and facilities such as fishing, boating, water-skiing, holiday resorts, weekend cottages, conference venues, golf courses, etc., have all developed significantly over the last fifty years. Land-use upstream of the HBPD is primarily rural agricultural, although the origin of the main river flowing to the dam, namely the Jukskei River and Hennops River is highly urbanized north of the city of Johannesburg. Extensive urban development is present along the shorelands of the basin. Water resource is one which is heavily used and the overall condition of that water resource is significantly altered from its pre-development condition. For many years, the Crocodile River has been pouring an increasing load of phosphorus as phosphates into the HBPD. Phosphorous and nitrates are directly linked to the personal effluent of each user when flushing his toilet plus detergents used for personal hygiene. Industry also made a considerable contribution to pollution load. With growing population due to urbanisation together with changing focus in agricultural practices to produce food in chicken batteries, feedlots and piggeries the runoff of stormwater from rural areas also contributed significantly to nutrient flow in rivers. The concentration of nutrients in rivers and the dam causes eutrophication or over-enrichment of water bodies. This results in rapid growth of aqueous plants such as algae and various alien vegetation such as water hyacinth. The hyacinth can rapidly reach to nuisance levels of more than 30% of the surface of the dam. Under hot summer conditions, hyacinth cover can easily cover 60% and more of the surface of the dam. Such a situation occurred in 1977 and was brought under control by spraying herbicide. After the 300000-ton hyacinth stock sank to the bottom during the 1977 eradication, rotting plant material cause further problems due to bacteriological growth. The nutrients added to the sediment became the source of feedstock for cyanobacteria to bloom to thrive on the surface in summer conditions and for Barbell and Karp to feast on the sediment, thereby putting additional nutrients into circulation. The economic significance of the dam is also enabled by the ecosystem services provided by Hartbeespoort Dam, include provisioning (water availability for abstraction), regulatory (waste assimilation), and supporting services (residential, holiday and commercial). The economy with some 5,268 households generating (in 2010 values)  a local Gross Domestic Product (GDP) of approximately R1.3 billion per year according to the estimate in the 2010 draft edition of the Resource Management Plan. Of these households, 3,386 households (almost two- thirds) are low-income households.

Current situation and where we will be heading in future.

The main problems experienced in Hartbeespoort Dam are the direct or indirect result of eutrophication. These includes (a) algal (cyanobacterial) blooms, (b) proliferation of nuisance aquatic vegetation such as Eichhornia crassipes (water hyacinth), (c) problems with water purification (odours, micro-toxins, water clarity, etc.) and limitations to irrigation use downstream (water quality unsuitable for producing tobacco and vegetables that are consumed raw, etc.). The recreational user is also affected with unsightly green water due to cyanobacterial blooms, micro-toxins that causes dermatitis, foul smells, the physical impact of water hyacinth on boating, skiing, sailing, etc. In the short to medium term a serious problem has developed after previous programmes such as Metsi-a-me was discontinued due to financial difficulties in the DWS to uphold and further implement the plans previously approved and trusted to Rand Water as the implementing agent. Alien plants cannot “cause eutrophication”.  The overabundance of alien vegetation is a symptom or the result of eutrophication. Water hyacinth is recognised as a problem that should be addressed in a holistic “Integrated Aquatic Vegetation Management Plan” (IAVMP) that should be designed and implemented for the control of hyacinth on Hartbeespoort Dam as well as in the river systems. There are four main methods for vegetation control, i.e. physical control, chemical control, biological control and mechanical control. WH removal was a well managed process to remove alien vegetation as implemented. From History of Metsi-a-me Biomass and debris removal and how it was achieved so successfully it can be concluded that the involvement of “Work for water” (WFW) played pivotal role and could again be deployed as soon as possible to support a new strategy for control of alien vegetation. Demarcation noodles (floating chain barriers) assisted to create supporting infrastructure restricting the mobility of macrophytes to areas where mechanical removal was economical and safe. Mechanical removal in collaboration with estates and shore line owners was a win-win situation as long as WFW co-operated. WFW was instrumental in managing the required permits to handle the illegal alien vegetation. Biological control and chemical control with herbicides are not recommended, due to cost considerations but more importantly due to the poor results of the previous (1977) chemical spraying of WH with herbicides and the creation of rotting organic waste in the areas covering the sediment layer in the dam. Due to the current situation where Water Hyacinth (WH) proliferation is estimated to grow exponentially (multiplication due to vegetative birth within 2 weeks), alternative innovative control mechanisms must be considered to enhance the mechanical /manual harvesting of WH. The technical subcommittee of the HBPD rehabilitation committee considered the knowledge, experience and feasibility of options to make an immediate impact on the crisis situation and opted to go for the mechanical harvesting option. A management plan has been developed and will be applied by water managers within the expectations of stakeholders. Mainly to harvest hyacinth to be used a valuable component om agriculture. Biological control is a viable longer term programme using insects, other invertebrates and pathogens (fungi and bacteria) to control aquatic weed proliferation. Also Sterile Grass Carp can be used. Water hyacinth is an erect, free-floating, stoloniferous (a long stem or shoot that arises from the central rosette of a plant), perennial (recurring) herb. The mature WH consist of thick roots, long stem, leaves, flowering part and fruit clusters (Figure 1). Possible uses of WH as dictated by local socio-economic conditions, regulations and entrepreneurial initiatives.
© Copyright 2017 Hartbeespoort Dam Rehabilitation Steering Committee  

History

Historical Context of Hartbeespoort

Dam

The vision of Genl. Hendrik Schoeman to build an irrigation dam in the Crocodile River on his farm was realized when the Hartbeespoort Dam was constructed and commissioned in 1925. The project was based on The Water and Conservation Act, Act 8 of 1912 and approved in 1916. The 500 km downstream irrigation canals were added to source water to the newly established Brits community where 13000 ha of high agricultural potential was wetted seasonally to provide fresh vegetables and fruit to the thriving Johannesburg and Pretoria communities. The catchment of the dam is between Kempton Park in the east and Krugersdorp in the west, covering a 4112km² area. The growing demand in the downstream area including Thabazimbi and the Waterberg area for socio-economic development necessitated that the dam wall should be raised by 2.44 metres in 1971. to increase the capacity to 195 million m³ at full supply level. The impoundment has a surface area of approximately 20 km2 or about 2000 hectares. Water from the Hartbeespoort Dam is used mainly for irrigation (82%) and domestic consumption (about 12%) in growing urban settlements with 6% being released for ecological reserve along river flow. Outflow from the dam is through the two canals as well as 10 sluice gates that can be opened to control the level in case of flooding. The 1MW hydroelectric generator set is not in operation anymore. Over the more than 90 years since it was commissioned, the dam attracted city dwellers to the area due to the combination of a large water body within an idyllic mountainous setting. It became increasingly important as a regional recreational and tourist centre. Activities and facilities such as fishing, boating, water-skiing, holiday resorts, weekend cottages, conference venues, golf courses, etc., have all developed significantly over the last fifty years. Land-use upstream of the HBPD is primarily rural agricultural, although the origin of the main river flowing to the dam, namely the Jukskei River and Hennops River is highly urbanized north of the city of Johannesburg. Extensive urban development is present along the shorelands of the basin. Water resource is one which is heavily used and the overall condition of that water resource is significantly altered from its pre-development condition. For many years, the Crocodile River has been pouring an increasing load of phosphorus as phosphates into the HBPD. Phosphorous and nitrates are directly linked to the personal effluent of each user when flushing his toilet plus detergents used for personal hygiene. Industry also made a considerable contribution to pollution load. With growing population due to urbanisation together with changing focus in agricultural practices to produce food in chicken batteries, feedlots and piggeries the runoff of stormwater from rural areas also contributed significantly to nutrient flow in rivers. The concentration of nutrients in rivers and the dam causes eutrophication or over-enrichment of water bodies. This results in rapid growth of aqueous plants such as algae and various alien vegetation such as water hyacinth. The hyacinth can rapidly reach to nuisance levels of more than 30% of the surface of the dam. Under hot summer conditions, hyacinth cover can easily cover 60% and more of the surface of the dam. Such a situation occurred in 1977 and was brought under control by spraying herbicide. After the 300000-ton hyacinth stock sank to the bottom during the 1977 eradication, rotting plant material cause further problems due to bacteriological growth. The nutrients added to the sediment became the source of feedstock for cyanobacteria to bloom to thrive on the surface in summer conditions and for Barbell and Karp to feast on the sediment, thereby putting additional nutrients into circulation. The economic significance of the dam is also enabled by the ecosystem services provided by Hartbeespoort Dam, include provisioning (water availability for abstraction), regulatory (waste assimilation), and supporting services (residential, holiday and commercial). The economy with some 5,268 households generating (in 2010 values)  a local Gross Domestic Product (GDP) of approximately R1.3 billion per year according to the estimate in the 2010 draft edition of the Resource Management Plan. Of these households, 3,386 households (almost two-thirds) are low-income households.

Current situation and where we will be heading in

future.

The main problems experienced in Hartbeespoort Dam are the direct or indirect result of eutrophication. These includes (a) algal (cyanobacterial) blooms, (b) proliferation of nuisance aquatic vegetation such as Eichhornia crassipes (water hyacinth), (c) problems with water purification (odours, micro-toxins, water clarity, etc.) and limitations to irrigation use downstream (water quality unsuitable for producing tobacco and vegetables that are consumed raw, etc.). The recreational user is also affected with unsightly green water due to cyanobacterial blooms, micro-toxins that causes dermatitis, foul smells, the physical impact of water hyacinth on boating, skiing, sailing, etc. In the short to medium term a serious problem has developed after previous programmes such as Metsi-a-me was discontinued due to financial difficulties in the DWS to uphold and further implement the plans previously approved and trusted to Rand Water as the implementing agent. Alien plants cannot “cause eutrophication”.  The overabundance of alien vegetation is a symptom or the result of eutrophication. Water hyacinth is recognised as a problem that should be addressed in a holistic “Integrated Aquatic Vegetation Management Plan” (IAVMP) that should be designed and implemented for the control of hyacinth on Hartbeespoort Dam as well as in the river systems. There are four main methods for vegetation control, i.e. physical control, chemical control, biological control and mechanical control. WH removal was a well managed process to remove alien vegetation as implemented. From History of Metsi-a-me Biomass and debris removal and how it was achieved so successfully it can be concluded that the involvement of “Work for water” (WFW) played pivotal role and could again be deployed as soon as possible to support a new strategy for control of alien vegetation. Demarcation noodles (floating chain barriers) assisted to create supporting infrastructure restricting the mobility of macrophytes to areas where mechanical removal was economical and safe. Mechanical removal in collaboration with estates and shore line owners was a win-win situation as long as WFW co-operated. WFW was instrumental in managing the required permits to handle the illegal alien vegetation. Biological control and chemical control with herbicides are not recommended, due to cost considerations but more importantly due to the poor results of the previous (1977) chemical spraying of WH with herbicides and the creation of rotting organic waste in the areas covering the sediment layer in the dam. Due to the current situation where Water Hyacinth (WH) proliferation is estimated to grow exponentially (multiplication due to vegetative birth within 2 weeks), alternative innovative control mechanisms must be considered to enhance the mechanical /manual harvesting of WH. The technical subcommittee of the HBPD rehabilitation committee considered the knowledge, experience and feasibility of options to make an immediate impact on the crisis situation and opted to go for the mechanical harvesting option. A management plan has been developed and will be applied by water managers within the expectations of stakeholders. Mainly to harvest hyacinth to be used a valuable component om agriculture. Biological control is a viable longer term programme using insects, other invertebrates and pathogens (fungi and bacteria) to control aquatic weed proliferation. Also Sterile Grass Carp can be used. Water hyacinth is an erect, free-floating, stoloniferous (a long stem or shoot that arises from the central rosette of a plant), perennial (recurring) herb. The mature WH consist of thick roots, long stem, leaves, flowering part and fruit clusters (Figure 1). Possible uses of WH as dictated by local socio-economic conditions, regulations and entrepreneurial initiatives.