reference number. For F-notes, M-notes and X-notes, the number also appears in bold superscript at the relevant location in the text. All annotations contain links to the affecting legislation. " watercourse " includes all rivers, streams, ditches, drains, cuts, culverts, dykes, sluices, sewers, and passages through which water flows except mains and other pipes which belong to the water authority or are used by a water authority or any other person for the purposes only of providing a supply of water to any premises. (2) In this Part of this Act --  (a) any reference to the waters of any loch or pond or of any river or watercourse includes a reference to the bottom, channel or bed of any loch, pond, river or, as the case may be, watercourse which is for the time being dry; and (b) any reference to water contained in underground strata is a reference to water so contained otherwise than in a sewer, pipe, reservoir, tank or other underground works constructed in any such strata. (3) For the purposes of the definition of " trade effluent " in subsection (1) above any premises (whether on land or not) wholly or mainly used (whether for profit or not) for agricultural purposes or for the purposes of fish farming or for scientific research or experiment shall be deemed to be (and in the case of fish farms, always to have been) premises used for carrying on a trade. shall be treated as having given the authority's