Edinburgh Water Company and its successors have provided a public water supply and latterly sewerage and sewage treatment services to the Scottish capital of Edinburgh since 1819. The original company was established to supply drinking water and did so until 1870, when it was taken over by a public water trust, with representatives from Edinburgh, Leith and Portobello. The company built an associated railway, the Talla Railway and a rural manor house, with an associated station Victoria Lodge railway station. The trust was taken over by Edinburgh Corporation and in 1975, responsibility passed to the Lothian Regional Council, as did the duty to provide sewerage and sewage treatment services. Both services were moved out of local authority control, and taken over by the East of Scotland Water Authority in 1996. The three Scottish regional water authorities were merged to form Scottish Water in 2002.

During the time of the Edinburgh Water Company and the Edinburgh Water Trust, major projects were carried out to construct reservoirs, some for the impounding of water supplies, and others to provide compensation water, to ensure that rivers could still provide water power to mills, when some of their sources had been tapped to supply Edinburgh. James Jardine was the company's first engineer, and was succeeded by James Leslie, who became part of J & A Leslie and Reid, when he entered into partnership with his son Alexander Leslie and son-in-law Robert Reid in the early 1870s. The last major project of this early period was Talla Reservoir, completed in 1905, but there were further civil engineering projects in the 1960s and 1980s. Alexander Leslie compiled a dosier of photographs, showing the construction of some of the later Victorian reservoirs, which has recently been rediscovered in the archives of Edinburgh Library.

With the population growing rapidly, a major project to divert sewage away from the Water of Leith, the main river through the city, took place in 1864, probably with Napier Bell as the engineer. A new sewer intercepted the existing sewers and drains, and carried the raw sewage to the sea. Edinburgh did not have a sewage treatment works until 1978, when construction of Seafield Treatment Works on reclaimed land near Leith Docks was completed. It now produces 2.3 MW of electric power, generated from the gas which is a product of the sludge digesters which treat the effluent, and it is expected to become self-sufficient for power in the near future.

History The City of Edinburgh had a number of wells, from which water could be obtained, and Nor Loch also acted as a source for water. Water was first brought in from outside the city in 1676, when a lead pipe was installed from springs at Comiston, now a suburb to the south of the city. As more water was required, additional springs in Comiston were tapped, and the pipe was progressively replaced by a lead pipe between 1704 and 1720. Iron pipework replaced the lead in 1820. The network was extended in 1760, when wooden pipes were laid into the city from springs near Swanston, a little further to the south, but now also a suburb. iron pipes replaced the wooden pipes around 1790, but there was then a lull in development due to the Napoleonic Wars. The piped water reached a fairly limited number of dwellings, and many people had to buy water from water porters, called 'caddies' locally, who were registered by the magistrates, and sold water for one penny for a barrel containing .

There was general disquiet that the supply of water was "extremely deficient both in quantity and quality," and the editor of the Edinburgh Review, Francis Jeffrey, convened a public meeting, at which a committee was formed to take the matter forwards. The committee included two prominent authors, Henry Mackenzie and Henry Cockburn. The Edinburgh Water Company was formed, and obtained an act of Parliament, the (59 Geo. 3. c. cxvi) in July 1819. This authorised several schemes, including obtaining water from the Crawley springs, some to the south of Edinburgh in the Pentland Hills, an idea that had first been suggested by Thomas Telford in 1811. They could also take water from the Glencorse Burn, and in order to maintain supplies to mill owners on the River Esk, the Glencorse Reservoir was to be built, as a source of compensation water.

James Jardine was appointed as the company's first engineer, who had been involved in the construction of the Union Canal, and who had also been the first person to work out the mean level of the sea. He was responsible for the pipeline from Crawley springs, which was long, as it followed the contours, and acted as resident engineer for the Glencorse dam, with Telford acting as the chief designer. The water pipeline, which varied in diameter from , was completed in August 1823, and delivered per day to the city. The Glencorse dam, which impounded of water, was one of the tallest earth dams at the time it was built, with the crest around above ground level. The total cost of these projects was around £145,000, and they received high praise from The Scotsman newspaper. Jardine had originally calculated water levels and potential yields from the springs in the Pentland Hills in 1810, while working for Telford.

The new scheme worked well until 1842, when there was a severe drought, resulting in many of the smaller streams and brooks drying up completely. Less than of rain fell between April and October, and the Glencorse Reservoir emptied. Millers on the River Esk demanded that water from the Crawley springs should be diverted into the Glencorse Burn, and this was only avoided by paying them an indemnity of between £4,000 and £5,000. The company rushed through the (6 & 7 Vict. c. lxxxix) to allow them to abstract water from streams at Listonshiels, Bavelaw and Black Springs, all of which are on the north side of the Pentland Hills. Two more reservoirs were required to provide compensation water, at Threipmuir and Harlaw, and despite difficulties in buying the required land, Jardine pressed on with the project. However, he retired in 1846 before either reservoir had been finished, having reached the age of 70, and it was James Leslie who took over and saw them completed.

James Leslie Leslie had previously worked with Jardine on a report about a water supply scheme for Dundee, for which an act of Parliament, the Dundee Water Act 1837 (7 Will. 4 & 1 Vict. c cxxvi), was obtained, but no work was undertaken at the time. Construction of the dam for the Threipmuir Reservoir may have been completed before Jardine retired, but the Harlaw dam was definitely Leslie's work. The main outlet for the reservoir was through a cast iron pipe sitting on the foundations for the dam. A masonry tower was built at the inner end of the pipeline, near the upstream toe of the dam, and a rod passing up the tower enabled the sluice to be controlled. To enable the outlet valve to be inspected or maintained, a sluice made of oak could be lowered in guides, cutting off the incoming water and allowing the pipeline to drain. A second similar structure allowed water to be taken from about above the bottom of the reservoir. When the dam was nearly completed, there was evidence of slippage on the upstream face, which displaced the tower slightly. Leslie put this down to the dam being built too quickly, with insufficient attention being paid to consolidating the hard boulder clay from which much of the dam was constructed, and all his subsequent dams were constructed in layers less than thick, to mitigate such problems. Despite the movement of the tower, no remedial work was undertaken, and it has remained standing ever since. Leslie completed the work specified by the Edinburgh Water Company Act 1843 in 1848.

Before the two reservoirs had been completed, Leslie could see that they would still not be sufficient to provide the water that Edinburgh needed, and so the company applied for the (10 & 11 Vict. c. ccii). This made provision for the construction of three more reservoirs, at Clubbiedean, Torduff and Bonaly on the northern parts of the Pentland Hills, while on the southern side of the hills they could raise the dam at Glencorse Reservoir, to increase the amount of water impounded, and build a reservoir at Loganlea, above that at Glencorse. The three northern reservoirs were designed to store up spring water, so that supplies to the city of Edinburgh could be maintained even if there were future droughts. The Loganlea Reservoir and the improvements to Glencorse were to ensure that the statutory compensation water could always be supplied for the mills on the River Esk, while allowing the water company to always keep the pipeline from Crawley Springs full. The 1847 act was innovative, in that it contained a clause requiring the company to provide a constant water supply to homes, a concept that had been championed by the sanitary reformer Edwin Chadwick.

Two other engineers, James Rendel and Nathaniel Beardmore worked on the proposals, and the setting out of the works once the act was obtained, but it was Leslie who supervised the construction. The northern reservoirs were constructed with earth dams, with a 3-to-1 slope on the upstream side of the central clay puddle wall, and a 2.5 to 1 slope on the downstream side. The outlet arrangements for Torduff and Loganlea were similar to those at Harlaw, with two outlets, although the bottom outlets fed into tunnels cut through solid rock, but at Clubbiedean, the outlet was a single cast iron pipe buried beneath the dam. Leslie's regime of compacting thin layers worked well, and it was not until the 1970s that some remedial work was required at Clubbiedean to grout the embankment and foundations, as the underlying limestone had gradually dissolved, creating some leakage through the dam. Remedial work was also required at Torduff after some leakage was discovered in the 1980s.

The volume of water needed to supply the residents of Edinburgh continued to increase, and so the (19 & 20 Vict. c. xci) was obtained, allowing the company to take water from the Colzium springs. To maintain flows in the Water of Leith, a compensation reservoir was required at Harperrig. Leslie refined his designs for the outlets of the reservoir, with both the upper and lower outlets feeding into a culvert which ran beneath the bottom of the dam, and had been used to channel the river while the dam was being constructed. This project was completed in 1859, but was still not sufficient, so the (26 & 27 Vict. c. clxxxvii) was obtained to enable exploitation of the Crosswood springs, with a compensation reservoir at Crosswood to feed the Crosswood Burn. The dam that Leslie designed was similar to that at Harperrig, and the work was completed in 1868. Leslie had improved his designs in other respects, and after the catastrophic failure of the Bilberry Dam in 1852, had insisted that dams should be built up in layers not more than thick, to ensure adequate consolidation. He also specified that where excavated material was used to build the dams, clay and earth should be used against the central puddle wall, particularly on the upstream side, and that stones, gravel and sandy material should only be used for the slopes, and restricted to the downstream side if possible. These latter requirements were probably influenced by the findings of the inquest into the Bilberry disaster, but Leslie's insights meant that the Harperrig and Crosswood dams were among the best-designed earth dams at the time of their construction. Although less details are available, Leslie was also responsible for construction of water mains and treatment works.

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