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dc.contributor.advisorVermeulen, P. D.
dc.contributor.authorVerwey, Philippus Marthinus Jacobus
dc.date.accessioned2017-11-10T08:30:04Z
dc.date.available2017-11-10T08:30:04Z
dc.date.issued2009
dc.identifier.urihttp://hdl.handle.net/11660/7470
dc.description.abstractEnglish: Vaalharts Irrigation Scheme is not only the largest in the country it is known as "The Food Basket". In 1875, Mr Ford, a Government Surveyor got the idea that the Vaalharts area has irrigation scheme possibilities due to the topography of the area. The proposal was approved by government in 1833. Planning, soil tests and more surveys to investigate the possibility were done. A weir was constructed, in the Vaal River, 8.5 km upstream from Warrenton, to deviate water to the Jan Kempdorp/ Hartswater area. In 1938 the first farmers received plots. Today there are almost 1200 plots vary in size from 25 - 75 ha it cover a total area of 35 302 ha. At the start of the irrigation project the water table was 24 mbgl by 1971 it has risen to 1.5 mbgl and waterlogging was experienced. Streutker studied what the cause of the watertabie rising were. The feeder canals were ground canals and it leached to the water table causing the rise, the canals were lined. The water table remained high, in 1976 Gombar & Erasmus investigated the possibility to drain the area with boreholes. It was a solution but to expensive, The water in the Spitskop dam in the Harts River, were all the drain water flow to do not show parallel deterioration and accumulation of salt as the groundwater in the irrigated areas. A research done by Haroldt & Bailey investigated where does the salts and water go. Findings was that there are a "salt sink" present, mainly due to a perched water table and if at some stage the sink will be exhausted it would have severe effects. A 2004 research was done to find the "salt sink". Boreholes were drilled to study the groundwater characteristics, piezometers were installed, to check the possibility of two aquifers. The study concluded that water levels do not differ more than centimetres in the deep and shallow water systems. Water quality as profiled in piezometers indicated no major stratification of groundwater. The deep lying aquifer does not perform separately, thus no "salt sink". This study was done to conclude what is the effect of the irrigation on the groundwater and the following was done: • Planning and Installation of piezometer network • EC profiling of the piezometers • Monitor groundwater levels and EC's • Determine Hydraulic Conductivity • Sample collection and chemical analyses • Monitor flow of drains in the K block • Develop groundwater level contour maps • Develop and run a model to estimate drainage needs • Calculate salt and water balance A Piezometer network consisting of 246 piezometers were installed between Taung in the North and Jan Kempdorp in the south, 208 were surveyed for XYZ coordinates and used for monitoring. The water levels and EC values were measured four times over a period of a year to cover all seasons. The average water level was 1.63 mbgl and the EC average were 191.5 mS/m. Twenty five piezometer sites were selected to cover as much of the soil types present as possible, to determine the hydraulic conductivity. It was between 0.002 and 5.2 m/d. A map was generated to visualize it, and the values were used in the modeling of the drain zones. Water and salt Balance: The leaching requirement to ensure sustainable farming is 611.5 mm/a. According to the water balance it is 562 mm/a. Incoming salts through irrigation water = 4.65 tlha/a. The TDS determined in 1976 averaged 1005 mg/I, in 2004 it was 1350 mg/I, an average increase of 13 mg/I/a. During the research period it were 1476 mg/I, an increase of 96 mg/I in 5 years an average increase of 19.25 mg/I/a. Irrigation salt not drained = 0.8 t/ha/a Upgrading of all infra structure is essential. Internal subsurface drainage should be cleaned and replaced and the spacing should be decreased to drain the area more effective. Effective drainage would minimize the salt loss prevent a salt build up and have a positive influence on farming and crop quality in the area. The drained water can be reticulated to a transpiration pond to recover the salt thus preventing it from influencing nature and activities downstream.en_ZA
dc.description.abstractAfrikaans: Vaalharts Besproeiingskema is nie net die grootste in die land nie dit staan bekend as die "kosmandjie". In 1875, het Mnr Ford, 'n opmeter wat vir die staat gewerk het met die idée gekom dat die Vaalharts Area die ideale topografie het vir 'n beproeiingskema. Die voorstel is deur die regering goedgekeur in 1933. Beplanning, grondondersoeke en verdere opmetings is gedoen. 'n Uitkeer stuwal is in die Vaalrivier 8.5 km stroom op van Warrenton gebou om die kanaal, na die Jan Kempdorp/ Hartswater area, te voed. In 1938 het die eerste boere hoewes ontvang. Vandag is daar ongeveer 1200 hoewes wat wissel tussen 25 - 75 ha wat 'n totale area van 35 302 ha beslaan. Met die aanvang van die besproeiingskema was die watertafel 24 meter onder grondvlak (mbgl) teen 1971 het dit gestyg tot 1.5 mmbgl, versuipte areas was sigbaar. Streutker het die oorsaak ondersoek, op daardie stadium was alle voederkanale, grondkanale dit het water deurgelaat na die groundwater en die kanale is toe belyn. Die watertafel het egter steeds hoog gebly. In 1976 het Gombar & Erasmus die moontlikheid om die area met 'n netwerk van boorgate te dreineer ondersoek. Dit het moontlik geblyk maar ongelukkig onuitvoerbaar duur. Die skema water dreineer na die Harts Rivier waarin die Spitskop Dam stroomaf is. Die kwaliteit van die water en die soutinhoud verswak nie eweredig met die van die groundwater in die skema nie. 'n Volgende ondersoek is deur Harold & Bailey gedoen in 1996 om te bepaal waar gaan die sout dan heen. Die bevinding was dat daar 'n "perched" watertafel en soutkom is. Dit vergroot die probleem, die gevolge van 'n versadige kom kan rampspoedig wees. In 2004 is 'n ondersoek geloods om te bepaal of die bewerings van Harold en Bailey waar is. Boorgate is geboor om die grondwater eiensakppe te ondersoek, piesometers is instaleer om die bestaan van twee akwifere te ondersoek. Watertafels van die vlak en diep water sisteme verskil egter net centimetres, en geen stratifikasie bestaan nie, dus geen soutkom nie. Hierdie studie is gedoen om te bepaal wat die effek van die besproeiing op die grondwater in die area is. Die volgende is gedoen: • Beplanning en Installering van 'n network piesometers • EC profiele van die piesometers • Monitering van grondwatervlakke en elektriese geleiding (EC) • Bepaling van die hidroliese geleiding • Chemiese ontleding van die grondwater • Monitering en meting van dreinering in Blok K • Ontwikkeling van grondwater kontoerkaarte • Ontwikkel en modellering van dreinering • Berekening van die sout en water balans Om die doelwitte te bereik was 'n piesometer netwerk van 246 piesometers installeer, tussen Taung in die noorde en Jan Kempdorp in die suide. Die x : y: z koördinate van 208 piesometers is bepaal en die is gebruik vir die monitering. Watervlakke en EC's is vir 'n periode van een jaar gemeet om al die seisoene te dek. Die gemiddelde watervlak was 1.63 mbgl en die gemiddelde EC 191.5 mS/m. Vir die bepaling van K waardes is 25 piesometers gebruik vir toetse met die doelom soveel moontlik verskillende grondtipes te dek. Die waardes het gewissel tussen 0.002 and 5.2 mld. Die waardes is gebruik in die opstel van 'n model en die bepaling van die soutbalans. Water en Soutbalans: Die dreinerings behoefte vir volhoubare landbou is 611.5 mm/j en volgens die waterbalans 562 mm/j 'n ooreenkoms van 91%. Inkomende sout as gevolg van besproeiing = 4.65 tlha/j. Die TOS bereken in 1976, 1005 mg/l, in 2004, 1350 mg/l, 'n gemiddelde styging van 13mg/l/j. TOS gedurende die navorsing, 1476 mg/l, 'n toename van 96mg/l in 5 jaar, of gemiddeld 19.25 mg/l/j. Beproeiingsoute nie gedreineer = 0.8 tlha/j Opgradering van infrastruktuur is belangrik. Die interne ondergrondse dreinering benodig 'n skoonmaak en selfs vervanging, spasiëring moet verminder word om effektiwiteit te verhoog. Effektiewe dreinering sal die afvoer van besproeiingswater verhoog, meer soute sal die area in die bogrond verlaat. Die water kan herlei word in verdampingspanne om die sout te herwin sodoende nie 'n nadelige uitwerking op die natuur en aktiwiteite stroom af te hê nie. Dit sal lei to verbeterde landbou toestande hoër opbrengste van beter kwaliteit.af
dc.description.sponsorshipWater Research Commissionen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectIrrigation -- Environmental aspects -- South Africaen_ZA
dc.subjectGroundwater -- Quality -- South Africaen_ZA
dc.subjectDissertation (M.Sc. (Hydrogeology))--University of the Free State, 2009en_ZA
dc.titleThe influence of the irrigation on groundwater at the Vaalharts Irrigation Schemeen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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