Gamtoos Irrigation Board continues effective water management despite restrictions
Running a water management system, as the Gamtoos Irrigation Board does, requires ongoing maintenance, especially when the ‘stop-start’ approach to water delivery means only three days of water a week.
According to CEO Rienette Colesky, the Kouga Dam was at only 4.21% capacity on 1 July 2021 (the start of the 2021/2022 water year).
“Using this ‘on-off’ approach ensured there was some water delivery, but it resulted in a sharp increase of breaks in the pipes owing to the air that is trapped within them”.
Vigilance is essential, and so the GIB “also monitored, recorded and reported on water usage twice a month, as opposed to the usual monthly reportage”.
Colesky said a number of projects were carried out to curtail water losses and to ensure that the distribution system was maintained in a good functional order.
Some of the projects included:
- Servicing of the mechanical works of the Kouga Dam emergency sluice gate;
- Replacement of 280m of old concrete pipeline with new PVC pipes;
- Installation of numerous air valves on the pipelines to prevent leaks;
- Weed control at the edges of the canals;
- Treatment of 900m of the K branch canal; 85m of the B canal and 480m of the main canal with a rubber product for the sealing of cracks. Also, painting of the canal lining with a sealant to prevent seepage or losses from the canal;
- Repair of almost 15.5km of open canal with a flexible putty product (9.5km of the main canal; 4km of the B branch canal and 2km of the G branch canal);
- Installation of two additional rock traps in the main canal upstream from two siphons to prevent rock and rubble from washing into the siphons;
- Installation of mechanical seals in three siphons to prevent leakages;
- Sealing of a construction joint at the outlet chamber of the Muller balancing dam; and
- Replacement of the valves at one of the automatic sluice gates with stainless steel components.
An enormous amount of work was done, Colesky said.
Given that the drought and water restrictions had an impact on the lives of all in the community, these projects provided some much-needed relief in the form of work opportunities.
“We made use of local contractors and the previous staff complement to clean the canals and to seal them with the rubber product.
“A total of 14 contractors were used from the Thornhill, Loerie, Hankey and Patensie districts, with each contractor employing a team of 10 people. We also made use of local professionals to install the mechanical seals.”
Colesky said ongoing maintenance would help to reduce water loss and wastage. “Our system is more than 50 years old. It goes without saying that a system this old requires special attention when it comes to maintenance and planning for special repair projects.
“If proper planning is not done, or if ongoing maintenance is neglected, the system will reach a point where control is lost over reducing and fixing the breaks and leaks.
“We fixed 260 pipe breaks in 2021. Fixing those breaks saved valuable water from being lost.”
“Continuous observation of the scheme and identifying potentially problematic areas is crucial to curbing water losses. As it allows us to maintain vulnerable areas before they break down.
“The canals in the Gamtoos valley are subjected to the movement of the adjacent clayish or dispersive soils.
“For this reason, it is important to use a product that is flexible, and can accommodate movement when repairs are done.
“Maintenance of the entire scheme can be a daunting task, but proper maintenance and risk planning cannot be over-emphasised,” Colesky said.
Gamtoos-besproeiingsraad sit effektiewe waterbestuur voort ondanks beperkings
Om ’n waterbestuurstelsel te bedryf, soos die Gamtoos-besproeiingsraad doen, verg deurlopende instandhouding, veral wanneer die ‘stop-en-begin-weer’-benadering tot waterlewering slegs drie dae se water per week beteken.
Volgens die Raad se uitvoerende hoof, Rienette Colesky, was die Kougadam op 1 Julie 2021 (die begin van die 2021/2022-waterjaar) op slegs 4.21% kapasiteit.
“Deur hierdie ‘aan-af’-benadering te gebruik kon ons verseker dat daar ‘n mate van waterlewering was, maar dit het gelei tot ‘n skerp toename in breuke in die pype as gevolg van lug wat daarin vasgevang is.”
Waaksaamheid is noodsaaklik, en daarom het die GIB “ook waterverbruik twee keer per maand gemonitor, aangeteken en gerapporteer, in teenstelling met die gewone maandelikse beriggewing”.
Colesky het gesê ‘n aantal projekte is uitgevoer om waterverliese te beperk en om te verseker dat die verspreidingstelsel in ‘n goeie funksionele orde in stand gehou kon word.
Van die projekte het ingesluit:
- Diens van die meganiese werke van die Kougadam-noodsluishek;
- Vervanging van 280m se ou betonpypleiding met nuwe PVC-pype;
- Installering van verskeie lugkleppe op die pypleidings om lekkasies te voorkom;
- Onkruidbeheer aan die rande van die kanale;
- Behandeling van 900m van die K-takkanaal; 85m van die B-kanaal en 480m van die hoofkanaal met ‘n rubberproduk om krake te verseël. Ook: Verf van die kanaalvoering met ‘n seëlmiddel om deursypeling of verliese uit die kanaal te voorkom;
- Herstel van byna 15,5km se oop kanaal met ‘n buigsame stopverfproduk (9,5km van die hoofkanaal; 4km van die B-takkanaal en 2km van die G-takkanaal);
- Installering van twee bykomende “rock traps” in die hoofkanaal stroomop van twee sifone om te verhoed dat rots en rommel by die sifone inspoel;
- Installasie van meganiese seëls in drie sifone om lekkasies te voorkom;
- Seël van ‘n konstruksielas by die sluiskamer van die Muller-balanseringsdam; en
- Vervanging van die kleppe by een van die outomatiese sluishekke met vlekvrye staal komponente.
‘n Enorme hoeveelheid werk is aangepak, het Colesky gesê.
Aangesien die droogte en waterbeperkings ‘n impak op die lewens van almal in die gemeenskap gehad het, het hierdie projekte broodnodige verligting in die vorm van werksgeleenthede gebied.
“Ons het van plaaslike kontrakteurs en die vorige personeelkomplement gebruik gemaak om die kanale skoon te maak en met die rubberproduk te seël.
“Daar is van altesaam 14 kontrakteurs vanuit die Thornhill-, Loerie-, Hankey- en Patensie-distrikte gebruik gemaak, en elke kontrakteur het ‘n span van 10 mense in diens gehad. Ons het ook van plaaslike professionele persone gebruik gemaak om die meganiese seëls te installeer.”
Colesky het gesê dat deurlopende instandhouding sou help om waterverliese en vermorsing te verminder. “Ons stelsel is meer as 50 jaar oud. Dit spreek vanself dat ‘n stelsel so oud spesiale aandag verg wanneer dit kom by instandhouding en die beplanning van spesiale herstelprojekte.
“Indien behoorlike beplanning nie gedoen word nie, of as deurlopende instandhouding afgeskeep word, sal die stelsel ‘n punt bereik waar beheer verloor word oor die vermindering en regstelling van die breuke en lekkasies.
“Ons het 260 pypbreuke in 2021 herstel. Deur hierdie breuke aan te spreek, het waardevolle water nie verlore geraak nie.”
“Deurlopende waarneming van die skema en die identifisering van potensiële probleemareas is van kardinale belang om waterverliese te beperk, aangesien dit ons in staat stel om kwesbare gebiede in stand te hou voordat hulle afbreek.
“Die kanale in die Gamtoosvallei word aan die beweging van die aangrensende kleiagtige of verspreidende grond onderwerp.
“Om hierdie rede is dit belangrik om ‘n produk te gebruik wat buigsaam is, en beweging kan akkommodeer wanneer herstelwerk gedoen word.
“Die instandhouding van die hele skema kan ‘n uitdagende taak wees, maar behoorlike instandhouding en risikobeplanning kan nie oorbeklemtoon word nie,” het Colesky gesê.