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calitzdorp dam

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Calitzdorp dam was built as an agricultural irrigation dam on the Nel’s river on the outskirts of town. Its construction made history as the first mass concrete dam wall for irrigation purposes in the country. The dam supplies water for both agriculture and the town’s domestic use.

2017 has been one of the driest years in a long time and the dam level had dropped to a very low level. On 14 and 15 November, gentle soaking rains fell in the district, and water flowed into the dam for a short spell. However, the drought has persisted and the dam level has continued to drop.
Dam level square3


Current water level

 

January 2018 photo: Yvonne Bayly

January 2018
photo: Yvonne Bayly

Calitzdorp dam
Calitzdorp dam August 2015

 

Being a semi-arid area, prone to bouts of severe drought, water has always been of great concern for the Calitzdorp fruit producers.  Right from the earliest days of farming in the area, fruit of exceptional quality has been produced.

Calitzdorp’s main irrigation river is the Nel’s river – known previously and shown on old maps as the Kango river – whose catchment area is in the Swartberg mountains.

The river flows from Groenfontein valley and on through the town.

reflections at wall + wmDSCF1797

By the 1890s farming activities were increasing and water was becoming more thinly distributed. A group of far sighted farmers investigated the possibility of building a dam on the river 5 kilometers north of Calitzdorp to secure the water supply for their farms for the future. In 1893 planning for the dam began, although irrigation from the Nel’s river had already been practiced for some one hundred years.

The farmers founded the Water Board with Mr B L Saayman as their first Chairman.

Two dams planned

A little known fact is that when the Irrigation scheme was first planned, provision was made for two dams, one below the other on the Nel’s river.  This is shown on the historic map of the scheme housed in the University of Cape Town’s Special Collections map archives, in the Report of the Chief Inspector of Public Works for the year 1895 – see below.  How useful this additional dam would have been with the extreme drought experienced today (2017-2018)

UCT Special Collections map detail of 2 dams 1895

UCT Special Collections map detail of 2 dams 1895

 

UCT Special Collections-Map of Calitzdorp Irrigation Scheme 1895

UCT Special Collections-Map of Calitzdorp Irrigation Scheme 1895

Progress was halted by the South African war of 1899-1902 and the acute depression that followed.

Calizdorp dam – construction begins

In 1913 work started on Dam number 2. The designs had been drawn up by the Union Irrigation Department and would make history as the first mass concrete dam wall for irrigation purposes in the country. Dam number 1 was never built.

wall undr construction image006The Resident Engineer was Mr R J Garratt, his assistants Messrs P A Taylor and L Levinkind, student engineers seconded to the project to gain experience.

  • The dam wall contained about 110,000 tons of concrete,
  • 700 feet (213.36m) in length at the coping,
  • 100 feet (30.48m)  in height from the original river bed level to the top
  • 112 feet (34.14m) in height from the lowest foundation level to the top.
  • 74 feet (22.5m) Maximum thickness at the bottom
  • 8 feet (2.44m).top thickness
  • The capacity of the dam when full would be 205 million cubic feet (5 804 954 cubic meters) with the spillway capable of discharging 11,900 cusecs.

Routine construction difficulties occurred – amongst other things for example – the works being held up by erratic, infrequent cement deliveries. and work hours having to be altered due to periods of extreme summer heat when all workers remained under shelter for the three hottest hours of the day. There were few accidents.

nels river dam - during buildingMajor plant included a cable way of 1,100 feet (335 meter) span, capable of delivering 3 tons of material, stone or concrete, to any part of the works every six minutes; a stone crushing and concrete mixing unit capable of turning out a cubic yard (.765 cubic meters) of concrete every six minutes – and all driven by one 36 BHP suction gas engine; two subsidiary portable concrete mixing plants, and an extra stone crusher, hand cranes, light rail track, cocopans and trollies, wagons, Scotch carts, mules and donkeys and water supply plant. The concrete was mixed all through in the ratio of 6 crushed stone to 2.5 parts sand to 1 part cement.  It was placed, tamped and spaded against timber shuttering and worked out at 36/- per cubic yard inclusive.

All carting of cement and stores from Oudtshoorn, 40 miles distant (64.37 kilometers), was done by contract.

dam catchment map

Dam catchment map

The cement cost 8/- per 188 lb bag delivered. Sand was carted 5 miles (8 kilometers) both in the Board’s own wagons using donkeys and mules in the transport, as well as by many small contractors.

The canal system consisted of one canal cut in rock on the left bank for nearly two miles (3.21 kilometers)  below the dam and designed to carry 21 cusecs. At the end of this section the canal bifurcated, the left bank continuation of 13 miles (20.92 kilometers) taking 12 cusecs and the right bank canal continuation of 9 miles (14.5 kilometers) taking 8 cusecs.

Construction of both canals included 3 road crossings by deep cut pipes, 12 pipe kloof crossings, 7 siphons and flood escapes.

 

It was also during 1917/18 that the great Spanish  ‘flu epidemic struck, and it is believed – but not verified – that during the last stages of the dam’s construction, there were workers on the site who fell to this deadly disease. It is said that they were treated in a hastily erected field hospital on the koppie above the field of white quartz pebbles near the dam wall.

Mr Garrett, site engineer and staff, sit eoffice 1917

Mr Garrett, Chief ngineer and staff, site office 1917

Fearing the spread of the disease, those who died were buried right there. If true, this historical episode seems to be completely forgotten and the graves – thought to be under that white quatz field,  are no longer visible.  It has been believed for centuries that white quartz promotes healing and repels illness. What better substance to cover graves of those who died from such a dangerous disease and to act as a sterilizer of sorts!  If true, it would be nice to mark this cemetery as a place of remembrance.

 

The dam overflowed for the first time on 19 March 1922.

Dam safety legislation was implemented in South Africa in 1987. Under the National Water Act 36 of 1998, compulsory evaluations of DWA (Department of Water Affairs) dams were done. It was found that Calitzdorp dam did not meet with the requirements in that the concrete structure’s drainage system was not functional and the capacity of the spillway was insufficient.  Remedial action was undertaken in the early 1990’s improving spillway capacity and the internal drainage system to decrease the influence of uplift.

Site office August 2015

Site office August 2015 

 

The dam was completed in 1918 and remains Calitzdorp’s main water supply. The inclusive cost of the concrete work was thirty-six shillings per cubic yard and the all inclusive, total cost of the dam was £168,053.18.07.

 

Construction on the Kammanassie dam near Oudtshoorn started shortly after completion of the Nel’s river dam. Mindful of expenses and difficulty in obtaining necessary equipment from Europe or America, the Kamanassie irrigation board purchased second hand equipment from the Calitzdorp Water Board. These included the reliable, hard working three-ton capacity, 335 m-span cableway together with the 36 HP suction gas engine, a few small crushers and other odd plant.

 

Site office interior August 2015

Site office interior showing construction,  August 2015

Dam wall 2