The Second Draining of Castle Semple Loch

When wealthy sugar planter William McDowall purchase Castle Semple Estate in the 1720s, the drainage of Castle Semple Loch became his main pastime. He employed experts to assist in his plans and also to lay out his estate, water features and fish ponds. Improver William Boucher came from Edinburgh and land surveyor John Watt mapped the loch and took levels along its centre and down the Black Cart.

In May 1727, McDowall opened the sluice of the Semple’s old dam just at the mouth of the loch. His men began digging out the Semple’s central drain, which he called the ‘boat canal’. McDowall ordered the building of a small shallow-draught boat ‘light and neatly contrived, to hold about six people, to go either with oars or sails’, to impress his visitors. He dug a branch canal from the main drainage canal up to the wall of the old Castle of Semple, which fronted the loch. The bed of the Black Cart was blasted and dug out as far down as Thirdpart Hall. During the drainage works, several dug-out canoes were unearthed from the loch bed, dating from the prehistoric period.

Overall, the drainage works had limited effect. Maps and estate plans over the years provide a snapshot of the varying water level. Although the loch was dry in summer, the inflow, especially from the Calder Water at Lochwinnoch after heavy rain, could flood the loch and destroy the crops before they could be harvested. The outlet at the Black Cart end was simply too flat to drain the water away fast enough.

The falling water level in Castle Semple loch caused various difficulties for the local folk. McDowall also ‘threw down’ the bridges spanning the loch narrows at either end. The loch was now too shallow to cross by boat. It was also too muddy to wade across easily, and the central canal was a deeper hazard. The locals now faced with a long walk round via Elliston Bridge. Rather than face a detour around the loch, some locals were brave enough to risk wading across the loch and canal, especially near the mouth of the Calder Water at Lochwinnoch.

©2015, Stuart Nisbet, Renfrewshire Local History Forum