For this Act, "surface water" means—
(a) water on or flowing over land (including in a waterway) after having—
(i) fallen as rain or hail or precipitated in any other way; or
(ii) risen to the surface naturally from underground; or
(iii) been returned to the environment following treatment or use; and
(b) water mentioned in paragraph (a) that has been collected in a dam, reservoir or rainwater tank.