The district is composed of all the territory in the watershed of the Cypress River and its tributaries in Harrison and Marion Counties as shown by the state contour maps on file in the office of the Texas Commission on Environmental Quality, unless the district's territory is modified under:
(1) Section 3 or 3a, Chapter 103, Acts of the 41st Legislature, 1st Called Session, 1929 (Article 8263a, Vernon's Texas Civil Statutes), after August 30, 1965, and before August 30, 1971;
(2) Subchapter H, Chapter 62, Water Code; or
(3) other law.