On October 30, 1969, the governments Alberta, Saskatchewan, Manitoba, and Canada entered into the Master Agreement On Apportionment, which provided a formula for the sharing of the waters of eastward flowing interprovincial streams. The agreement also recognizes the problem of water quality and groundwater matters, and reconstituted the Prairie Provinces Water Board with its role being modified to administer the agreement and provide a forum to resolve and report on interprovincial water issues.

The Master Agreement on Apportionment has fives schedules which form part of the agreement. These are:

Schedule A

The Apportionment Agreement between Alberta and Saskatchewan.

Schedule B

The Apportionment Agreement between Saskatchewan and Manitoba.

Schedule C

The Prairie Provinces Water Board Agreement describing the composition, functions and duties of the Board.

Schedule D

A listing of Orders-in-Council for allocations of interprovincial waters made before 1969.

Schedule E

A Water Quality Agreement. This Schedule became part of the Master Agreement in 1992.

The sharing of waters of eastward flowing streams (including Cold River, Beaver River, North Saskatchewan River, Battle River, Eyehill Creek, South Saskatchewan River, Boxelder Creek, Battle Creek, Middle Creek and Lodge Creek,) between Alberta and Saskatchewan is governed Schedule A of the Master Agreement On Apportionment. The general principle of the agreement is outlined in Paragraph 3, Schedule A, which states:

"Alberta shall permit a quantity of water equal to one-half the natural flow of each watercourse to flow into the Province of Saskatchewan, and the actual flow into the Province of Saskatchewan shall be adjusted from time to time on an equitable basis during each calendar year, but this shall not restrict or prohibit Alberta from diverting or consuming any quantity of water from any watercourse provided that Alberta diverts water to which it is entitled of comparable quality from other streams or rivers into such watercourse to meet its commitments to Saskatchewan with respect to each watercourse."

"For the purpose of this agreement, the said natural flow shall be determined at a point as near as reasonably may be to the said common boundary."

While the above noted principle applies to streams flowing eastward from Alberta to Saskatchewan, several special provisions have been included in the agreement with respect to the sharing of the waters of the South Saskatchewan River and of Battle, Middle and Lodge Creek.

Currently, apportionment monitoring is carried out for the South Saskatchewan River, Battle Creek, Middle Creek and Lodge Creek and Cold River. It is not carried out for the Beaver River, North Saskatchewan River, Battle River, Boxelder Creek and Eyehill Creek as Alberta's consumptive water use in these streams is not a significant proportion of the natural flow.