The first steps taken to develop the Sundays River were made by James Somers Kirkwood who established the Sundays River Land and Irrigation Company in 1883.
He dreamed of having a continuous water supply for the valley, but, unfortunately his dreams were to early for his time, as at that stage ostrich farming was at a high and the returns on investments were guaranteed and thus a better investment in Oudshoorn, instead of the valley.
James Kirkwood's dream went sour on him and his company was declared insolvent in 1887 and his assets were taken over by the Guardian Assurance and Trust Company. In 1903 these assets passed to the Strathsomers Estate Co, who started selling lands in the upper valley and commenced with the planning of the diversion weir out of the river and a canal system.
The construction of the diversion weir, Korhaans Weir commenced during 1911 and was completed in 1913.
In 1906 the Addo Land and Irrigation Co. came into being and was responsible for development in the Selbourne area and in 1912 the Cleveland Estate was established which was responsible for the construction of the Cleveland Diversion Weir with it's associated works.
At this point in time the situation was that three separate Diversion weirs existed on the Sundays River controlled by their respective owners and irrigation was based on the natural flow in the river when it occurred.
As the origins of the Sundays River is in the Karroo, which is a dry region and prone to thunderstorms, the applied irrigation in the valley was erratic and was subject to either drought or flood and therefore the need arose to establish a dam to conserve the floodwater so that a more consistent flow for irrigation to the valley farmers could be provided.
For this purpose an Act of Parliament established the Sundays River Irrigation Board in 1917 with the sole purpose of constructing Darlington Dam (Lake Mentz).
A loan was provided by the State to construct Darlington Dam (Lake Mentz) and the repayment of the loan was the responsibility of the Irrigators by the imposition of a canal levy by the Irrigation Board.
Because of this and that many farmers were experiencing financial difficulties as well as some of the Irrigation Companies, the State stepped in and decreased the area by approximately 9 000 morgen and took over the assets and liabilities of the private companies and vested them in an enlarged Irrigation Board in 1934, which took complete control of the three-diversion weir's as well as their separate canal systems.
Due to the deterioration of the quality of the water as it progressed down the river it was decided to link the canal systems and to only use Korhaans weir and exclude the other two diversion weirs.
During the construction period (1985 – 1991) it was attempted to bring Cleveland Weir into operation (1988), but this exercise highlighted the problems that were encountered during the 30's of the deterioration of the quality of the water due to return flows from applied irrigation adjacent to the river.
After the second raising of Darlington Dam the Board embarked on what was termed as the Betterment Program, which entailed the concrete lining of some 70 kms of main canal and some 155 kms of subsidiary distribution canals, and was completed by 1962.
The main purpose of the Betterment Program was to improve the practical distribution of water in the valley and to limit transit losses to a minimum, as well as decrease the cost of maintenance of the old earth canals.