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47-699: Hartbeespoort Dam (also known as Harties ) is an arch type dam situated in the North West Province of South Africa. It lies in a valley to the south of the Magaliesberg mountain range and north of the Witwatersberg mountain range, about 35 kilometres north west of Johannesburg and 20 kilometres west of Pretoria . The name of the dam means "dam at the gorge of the hartebeest " (a species of antelope ) in Afrikaans . This "poort" in

94-439: A thermocline a majority of the year. The distinct separation of these layers of the water column are collectively referred to as the thermal and density strata. Thermal and density stratification is a critical factor influencing the composition of the water column. Composition often refers to the presence of or lack of nutrients and organisms. In both cold and warm monomictic lakes, the epilimnion and hypolimnion are separated for

141-433: A 56.6 m long tunnel and also crosses the dam wall. Hartbeespoort Dam supplies irrigation water through a 544 kilometres (338 mi) long network of canals to 159.76 square kilometres (61.68 sq mi) of farmland on which tobacco, wheat, lucerne , fruit and flowers are produced. Deteriorating water quality, most notably Microcystin toxin. Hartbeespoort has become a very popular holiday and weekend resort for

188-718: A constituent college of the University of South Africa in 1921 and an independent university in 1951). These two universities have now merged and the new institution is called North-West University. As part of the Department of Education's proposed plans for higher education, the existing four higher learning institutions will be merged to form two. During 2003, as part of the Year of Further Education and Training project, three mega institutions, Taletso, ORBIT and Vuselela, were established to provide technical and vocational training to

235-618: A given lake is air temperature. Current changes and trends in global temperatures year round are a formidable threat to aquatic ecosystems. Current studies support that the combination of increased air temperatures and reduced precipitation impact shallow, monomictic lakes. In particular, their mixing may increase; this mixing lends to increased nutrient dispersal, anoxic conditions, and algal blooms . Southern regions may also see increases in salinity. Warm monomictic lakes that have experienced historically warm winters demonstrate greater thermal stability. This stability reduces mixing interactions and

282-541: A lake, river or seafront. Hartbeespoort Dam has become a robust example of the unintended consequence when an aquatic ecosystem flips from a stable but desirable state, into a stable but undesirable state, defying the best scientific interventions for decades. This is driven to a certain extent by the decline of data capture and processing systems that underpin water resource management in South Africa. The South African Department of Water Affairs and Forestry launched

329-482: A lake. Hypolimnetic withdrawal involves the withdrawal of water from a eutrophic lake at the hypolimnion at peaks of seasonal stratification. This water is removed to indirectly remove phosphorus. Upon addition of this water back into the hypolimnion, cyanobacteria growth is limited. This addition to the hypolimnion also reduces mixing of the water column and dispersal of nutrients to feed epilimnion algae. The physical removal of water can be either passive or active and

376-408: A legislature. The provincial assembly and premier are elected for five-year terms, or until the next national election. Political parties are awarded assembly seats based on the percentage of votes each party receives in the province during the national elections. The assembly elects a premier, who then appoints the members of the executive council. The premier of North West Province as of 14 June 2024

423-450: A majority of the year. In warm monomictic lakes, the water is in a uniform, liquid form; in cold monomictic lakes, the body contains a layer of ice and is cooler in temperature. Concerns and solutions pertaining to both warm and cold monomictic lakes are explored below. As warm monomictic lakes are entirely liquid, warmer in temperature, and highly productive, summer stratification commonly leads to eutrophication . This summer stratification

470-399: A mean depth of 9.6 metres (31 ft) and maximum depth of 45.1 metres (148 ft). It has a surface area of 20 square kilometres (7.7 sq mi), and its normal range of annual water level fluctuation is 0.8 metres (2.6 ft). The mixing type of the reservoir is monomictic . A single-laned, tarmac road skirts the water's edge on the north side; along its route it passes through

517-553: A number of issues surrounding the construction of the dam. Mother Nature caused further delays due to flooding. In 1914 and again in 1918, huge amounts of construction wood washed down the river and were never recovered. During 1915, the wall of the Geldenhuysdam further up the river broke and the flooding of the site also caused a delay. The disruption caused by the First World War, and the complications brought on by

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564-454: A population of just over 3 million. The province's white population is very unevenly distributed. In the southern and eastern municipalities, the white percentage in double figures such as the Tlokwe and Matlosana where the white percentages were 27% and 12% respectively. The province has the lowest number of people aged 35 years and older (5.9%) who have received higher education. Since 1994

611-529: Is Lazzy Mokgosi of the African National Congress . Much of the province consists of flat areas of scattered trees and grassland. The Magaliesberg mountain range in the northeast extends about 130 km (about 80 miles) from Pretoria to Rustenburg . The Vaal River flows along the southern border of the province. Temperatures range from 17 to 31 °C (63 to 88 °F) in the summer and from 3 to 21 °C (37 to 70 °F) in

658-581: Is South Australia's Blue Lake , where the change in circulation is signaled by a striking change in colour. A further, unusual, example is Deep Lake, in the Vestfold Hills , Antarctica . The surface of this hypersaline lake does not freeze in winter due to the depression of the freezing point by the high salt content. The identification and categorization of monomictic lakes relies on the formation of both an epilimnion (warmer, less dense water) and hypolimnion (cooler, more dense water) separated by

705-624: Is a province of South Africa . Its capital is Mahikeng . The province is located to the west of the major population centre and province of Gauteng and south of Botswana . North West was incorporated after the end of apartheid in 1994, and includes parts of the former Transvaal Province and Cape Province , as well as most of the former bantustan of Bophuthatswana . It was the scene of political violence in Khutsong , Merafong City Local Municipality in 2006 and 2007, after cross-province municipalities were abolished and Merafong Municipality

752-423: Is especially long in warm monomictic lakes. During eutrophication, excess nutrients are produced and depleted in a lake at opposite, vertical ends of the water column. This in turn dictates the growth and maturation of populations of organisms which tend to influence water oxygen and nutrient levels. In warm monomictic lakes, thermal stratification lends to oxygen depletion in the hypolimnion; a lack of mixing prevents

799-412: Is largely to blame, having distorted the food web with over 280 tons of phosphate and nitrate deposits. The town of Hartbeespoort is situated close to the dam wall and the villages of Kosmos , Melodie, Ifafi, Meerhof and The Coves, Pecanwood, Westlake and several other estates can be found alongside its shores. The town of Schoemansville was named after General Hendrik Schoeman, owner of the land during

846-486: Is required to sustain plant growth; an overabundance of ammonium is linked to poor plant growth and productivity. In a lake, the overabundance of ammonium also indicates anaerobic and acidic conditions. This lack of oxygen modifies a lake’s oxidation-reduction potential (ORP). The higher a lake’s ORP, the higher the levels of oxygen present in the water. Ideal ranges are between 300 and 500 millivolts. Ideally, higher levels of oxygen aid resident bacteria and microorganisms in

893-461: Is spoken primarily as a second language. Most of the population belong to Christian denominations. (Figures according to Census 2001 released in July 2003). According to the 2007 community survey 90.8% of the province's population was Black (mostly Tswana -speaking), 7.2% as White (mostly Afrikaans speaking), 1.6% as Coloured and 0.4% as Asian . The 2007 community survey showed the province had

940-521: Is typically limited to minimize quality impacts on the water level. This water can also be discharged downstream and can have unintended effects. The low quality water rich in toxins and nutrients removed from the hypolimnion when transferred to other lakes can destabilize their water columns. In some cases, lakes treated via hypolimnetic withdrawal may also experience undesirable water-level reductions and overall increases in average water temperature followed by mixing. Lastly, sediment dredging pertains to

987-620: The Harties metsi a me ( Harties, My Water ) programme to find solutions to the water quality problems. Budgeted government expenditure from 2004 to 2015 for the clean-up and rehabilitation of the dam and its catchment, and for related community projects, amounted to R900 million. Some biomanipulation methods applied to dams such as Hartbeespoort have come under scientific scrutiny. In 2020, the Rhodes University Centre for Biological Control reared Megamelus scutellaris and

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1034-472: The Hennops River . The extreme level of eutrophication is evident in excessive growth of microscopic algae and cyanobacteria , and macrophytes such as water hyacinth ( Eichhornia crassipes ). This is caused by the growing level of dysfunction in the many sewage works that drain the city of Johannesburg, which, unusually for a large city, straddles a continental watershed instead of being located on

1081-602: The 19th century. In 1906, the government ordered a public inquiry into the feasibility of building an irrigation dam in the Hartbeespoort of the Magaliesberg. The engineer of the Department of Irrigation that led the inquiry, submitted a favorable report to the government and the Hartebeestpoort Act. 32 of 1914 was accepted by Parliament. As early as 1909 there were test holes drilled at the bottom of

1128-470: The Magaliesberg was a popular spot for hunters, where they cornered and shot the hartebeest. The dam was originally designed for irrigation , which is currently its primary use, as well as for domestic and industrial use. The dam is considered to be in a hypereutrophic state since the early 1970s. Mismanagement of waste water treatment from urban zones within the Hartbeespoort Dam catchment area

1175-486: The Rebellion of a group of Afrikaners, brought further delays to the building. Then the first company was liquidated due to financial losses resulting from the floods and delays. In 1921 a second company took on the project and appointed an engineer, F. W. Scott, who tackled the project with renewed energy. In April 1923, after all the setbacks and political upheaval, the project was completed. In September of that same year

1222-555: The agricultural land north of the Magaliesberg much more valuable, especially land close to canals and the Crocodile River. The dam wall is 149.5 metres (163.5 yd) long and 59.4 metres (195 ft) high, built across a gorge cutting through the Magaliesberg. The reservoir is fed by the waters of the Crocodile River and Magalies River and covers approximately 18.83 square kilometres (7.27 sq mi), with

1269-532: The dam officially started in August 1916. Initially, work was delayed pending a court judgment with General Hendrik Schoeman and a certain Mr. Marshevin about the expropriation of their properties. The dispute was later resolved but discontent remained after a hastily passed law to facilitate the expropriation. In his book "Agter die Magalies", Bertus de Beer argues that the government acted in a heavy-handed manner to resolve

1316-485: The dam. Hartbeespoort Dam has been renowned for its poor water quality since the mid twentieth century. The Dam suffers severe eutrophication , in 2003 resulting from high phosphate and nitrate concentrations in the Crocodile River, the major inflow. The primary pollution sources are industrial and domestic effluent from Gauteng. The catchment area includes Bruma lake in the Jukskei River and Centurion lake in

1363-459: The decomposition of organic matter and dispersal of necessary nutrients into the water column. Conversely, a low ORP and low oxygen drives the release of sediment phosphorus via diffusion along concentration gradients through a process known as internal loading. Together, the increases in phosphorus, ammonium, and nitrate can drive the production of toxic algal blooms. Such blooms create a positive feedback loop of depleting nutrients and oxygen, and

1410-459: The direct collection and removal of sediment at the bottom of the lake. Removal of the top layer of the sediment aims to remove organic matter containing undesired nutrients. This method has measurable impacts on benthic organisms . It can take up to three years to restore the benthic organisms removed by dredging. Such organisms are essential to nutrient cycling in lakes and aquatic environments. The largest factor that controls water temperature in

1457-489: The economy of North West Province is mining, which generates more than half of the province's gross domestic product and provides jobs for a quarter of its workforce. The chief minerals are gold, mined at Orkney and Klerksdorp ; uranium, mined at Klerksdorp; platinum , mined at Rustenburg and Brits ; and diamonds, mined at Lichtenburg , Christiana , and Bloemhof . About 85% of all money-making activities take place between Klerksdorp and Potchefstroom. The economic heart of

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1504-400: The epilimnion. Some propose the development of interventions personalized to lakes to reduce these conditions. Such personalization refers to the manipulation of a lake’s residence time to combat internal loading and eutrophication by reducing the length of a stratification time period. Current models utilize the redirection of water flow into and out of monomictic lakes to assist in overturn and

1551-779: The hypolimnion, one aims to increase the ORP and reduce the rate and incidence of internal loading. Aerators are utilized to introduce oxygen, pure or atmospheric, directly into the water column. This is an especially expensive intervention given the electrical demands required to power such equipment. These costs make these aerators rather unsustainable as they are economically costly, and production of electricity can have environmental implications. Ecological threats have also been demonstrated. Use of aerators correlates to increased prevalence of gas bubble disease amongst fish. Yet, other organisms, such as zooplankton and fish, benefit from this process as increased aerobic conditions expand their territory in

1598-402: The inhabitants of Johannesburg and Pretoria ; it is the principal water recreation area of northern Gauteng and many types of water sports are enjoyed on the dam. The TYC Yacht Club has been operating at the dam since its construction in 1923. NSRI Station 25, located at the dam, is one of only three National Sea Rescue Institute inland stations and provides a water rescue service at

1645-463: The introduction of oxygen from the atmosphere into the water. This measure is known as dissolved oxygen (DO). When DO is lowered in the hypolimnion, nutrients like ammonium, nitrate, and phosphates tend to dominate. When oxygen levels are extremely low, the water is considered hypoxic and cannot support many forms of life. A lack of oxygen also limits natural chemical processes like the conversion of ammonium to nitrate. A mixture of ammonium and nitrates

1692-553: The number of people receiving higher education has increased. After the disbanding of the bantustans , many people migrated to the economic centres of Cape Town and Gauteng . The province had two universities: the North-West University , which was formerly called the University of Bophuthatswana (founded in 1979), in Mmabatho ; and Potchefstroom University for Christian Higher Education (founded in 1869; became

1739-451: The physical “flushing” of phytoplankton and excess nutrients. Such methods have shown to reduce residence time and stratification by days. While these time frames are limited in scope, they show potential to be lengthened for greater results in future studies and various lake models. Hypolimnetic aeration and oxygenation aims to directly address lowered DO levels in a given lake which leads to eutrophication. By increasing oxygen levels in

1786-561: The province is Klerksdorp. The northern and western parts of the province have many sheep farms and cattle and game ranches. The eastern and southern parts are crop-growing regions that produce maize (corn), sunflowers, tobacco, cotton, and citrus fruits. The entertainment and casino complex at Sun City and Lost City also contributes to the provincial economy. The majority of the province's residents are Tswana people who speak Tswana , as in neighbouring Botswana . Smaller groups include Afrikaans , Sotho , and Xhosa speaking people. English

1833-442: The river to determine whether the rock formation was suitable for building such a huge dam. The size of the catchment area was calculated, the water flow was measured and estimates made of the potentially irrigable land. Downstream claims to the existing water stream were established. The topography of the riverbank and rock formations were examined to evaluate the viability of the port for the construction project. The construction of

1880-639: The road over the wall of the Dam and through the tunnel was opened to traffic. The dam first overflowed in March 1925. The dam was built on the farm Hartebeestpoort, once owned by the Boer General Hendrik Schoeman (1840–1901). The farm and adjacent land were acquired by the State, mainly through the facilitation of his son, Johan Schoeman (1887–1967), around 1912. The completion of the dam made

1927-521: The subsequent release of nutrients needed to support their continued growth. Eutrophication can be both a natural and an anthropologic process; anthropogenic inputs are typically through sewage and waste water, or agricultural soil erosion and run-off. A rather new hypothesis is a link between residence time of water and seasonal stratification in monomictic lakes leading to eutrophication. Increased residence time leads to longer periods of stratification, reduced water mixing, and increased eutrophication in

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1974-411: The water hyacinth weevils Neochetina eichhorniae and N. bruchi en masse for biological control of the water hyacinth at dams in South Africa, including the Hartbeespoort Dam. [REDACTED] Media related to Hartbeespoort Dam at Wikimedia Commons North West (South African province) North West ( Tswana : Bokone Bophirima ; Afrikaans : Noord-Wes [ˈnuərt.vɛs] )

2021-648: The winter. Annual rainfall totals about 360 mm (about 14 in), with almost all of it falling during the summer months, between October and April. North West borders the following districts of Botswana : Domestically, it borders the following provinces: North West Province is traversed by the northwesterly line of equal latitude and longitude. The North West Province is divided into four district municipalities . The district municipalities are in turn divided into 18 local municipalities : Population 200,000+ Population 50,000+ Population 25,000+ Population 10,000+ Population < 10,000 The mainstay of

2068-607: The year. During their brief "summer", the surface waters remain at or below 4 °C. The ice prevents these lakes from mixing in winter. During summer, these lakes lack significant thermal stratification , and they mix thoroughly from top to bottom. These lakes are typical of cold-climate regions (e.g. much of the Arctic). An example of a cold monomictic lake is Great Bear Lake in Canada . Warm monomictic lakes are lakes that never freeze, and are thermally stratified throughout much of

2115-456: The year. The density difference between the warm surface waters (the epilimnion ) and the colder bottom waters (the hypolimnion ) prevents these lakes from mixing in summer. During winter, the surface waters cool to a temperature equal to the bottom waters. Lacking significant thermal stratification, these lakes mix thoroughly each winter from top to bottom. These lakes are widely distributed from temperate to tropical climatic regions. One example

2162-401: The youth. These institutions have been incorporated into many of the former education and technical colleges and manpower centres. Monomictic Monomictic lakes are holomictic lakes that mix from top to bottom during one mixing period each year. Monomictic lakes may be subdivided into cold and warm types. Cold monomictic lakes are lakes that are covered by ice throughout much of

2209-427: Was transferred entirely to North West. Merafong has since been transferred to Gauteng province in 2009. This province is the birthplace of prominent political figures: Lucas Mangope , Moses Kotane , Ahmed Kathrada , Abram Onkgopotse Tiro , Ruth Mompati , J. B. Marks , Aziz Pahad , and Essop Pahad , among others. The Provincial Government consists of a premier , an executive council of ten ministers, and

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