Creation of the reservoir was first discussed in 1892. A council sub-committee discussed the Largo water supply on 22 August that year, where a "plan for a supply of water from Gilston Burn was submitted" (as reported in the Courier). This scheme was deemed more worthy of further exploration than the costly laying and maintenance of pipes to connect Largo to the Leven supply (which extended only to Lundin Mill at that time).
By January 1893 the Gilston Burn scheme had been costed and tenders had been drawn up for the work. In 1905 enlargement of Largo Reservoir was discussed and eventually carried out by removing a large part of the north embankment, thus increasing capacity by around a third.
"The water supply in Largo Reservoir is so far down that, in order to conserve it, it has to be cut off each night. Further restrictions are expected every day. There is barely eight days full store on hand, the feeders being long since dry. An extension scheme was proposed in March, but owing to the cost it was turned down."
By 1935, the supply problems has not improved and on 29 August the Courier ran a story under the headline "Largo Water Development". Fife County Water Authority called upon Leven to help augment the water supply with water from Leven Reservoir. The neighbouring town responded immediately to the request by joining up the Largo and Leven pipe systems at a point in Lundin Links. The story went on...
"For some time the matter of additional supplies for Largo has caused concern, and during last year a bore was put down in the region of Largo Law, at a spot selected by a well-known English water diviner. Results from the bore were disappointing and only two courses were left to the authorities - either they had to enlarge the present storage at Largo, which owing to the configuration of the land would prove costly, or seek help from neighbouring authorities."
Although under normal circumstances the Largo Reservoir should have had ample supply a prolonged dry spell combined with a high influx of summer visitors had necessitated the call for aid. It was thought at the time that this link up may be the first step in a larger scheme to pool supplies across Fife. Over time, small local water supply networks increasingly did join up and these days all of Fife's water supply comes from Glen Devon, near Auchterarder, Perthshire.