The WRB Plan Trend 2050 future represents a straight-line projection of recent trends in mainstream zoning and land use to the year 2050. To the extent that long range plans indicate an intention of development and management trends, they are incorporated into the plan trend future. Forestry (Northwest Forest Plan) and urban land uses (Metro 2040) provide examples of management and future growth plans which are incorporated into this scenario.

In the Plan Trend scenario, forestry and agriculture land uses cover the largest area in the WRB. Urban land uses have grown in areal extent relative to 1990 conditions with population growth accommodated by density increases in the Portland metropolitan area and the other large cities, including Eugene/ Springfield, Salem/Keizer, and Albany/Corvallis. Residential densities also increase in the smaller cities and increase slightly in rural residential areas. Although by 2050 the population has doubled relative to 1990, the areas within urban growth boundaries have grown by approximately 50,000 acres (78 sq mi,) from approximately 6 % of the WRB area to 6.8%.

URBAN AND RURAL RESIDENTIAL POPULATION

The Plan Trend 2050 scenario population is based on the Oregon Dept. of Administrative Services Office of Economic Analysis population projection which forecasts an approximate doubling of the population of the WRB in the next 50 years. DAS projects the total population to increase from 1,972,207 in 1990 to 3,659,246 in 2040. Extending this projection to 2050 results in a total of approximately 3.9 million in 2050, a total increase of approximately 2 million people in the basin from 1990 to 2050.

To accommodate a doubling of the 1990 population, 2050 Plan Trend urban densities increase significantly relative to 1990 conditions. There is also expansion of urban areas from approximately 444,000 acres in 1990 to approximately 494,000 acres in 2050, with the comparative distribution of urban population and area in 2050 (north, mid, and south valley) consistent with the 1990 distribution.

AGRICULTURE

Agricultural land use remains similar to 1990 conditions with increases in the nursery sector and in hybrid poplar which appears more frequently in suitable former pasture lands at low elevations. Grass seed remains a major crop, with orchards, berries, and Christmas trees in stable production. Riparian buffers increase along currently regulated (Oregon Senate Bill 1010 and Clean Water Act section 303d) water-quality limited streams. Under Plan Trend assumptions, 2050 riparian buffers increase approximately 10% over 1990 conditions, and consist of woody vegetation in Christmas trees, vineyards/caneberries and pasturelands, with grass filter-strips forming riparian buffers in irrigated fields and row crop agricultural lands. The total area of land in agricultural production remains at approximately 20% of the basin area in 2050, with approximately 20,000 1990 agricultural acres being converted to 2050 urban land uses in areas adjacent to 1990 urban growth boundaries.

FORESTRY

Federally-managed public forest lands in this possible future follow the Northwest Forest Plan and their management prescriptions, including 300 ft. riparian buffers. Late Successional Reserves defined by the Northwest Forest Plan as areas of old growth forest are aged by 60 years. No change is expected in the management of the National Wildlife refuges. State and private forest lands in this scenario follow the 1995 Oregon Forest Practices Act where average 70 ft stream buffers exist and rotation schedules are based on average annual cutting rates from 1973 - 1995 published in the May 1997 "Timber Harvesting Practices on Private Forest Land in Western Oregon," which equates to 60 years for private industrial and 128 years for non-industrial. State harvest schedule is based on 100 yr. rotation, or 50% harvest probability.

Modeled harvest units are 5.6 acres in size for private non-industrial lands. Willamette National Forest and Mt. Hood NF clear-cutting based on the decadal harvest rates specified their respective management plans using 30 acre clearcut patches. State and private industrial harvest units are 30 acres. The total area of 2050 land in forest remains at approximately 67 % of the basin area, similar to the 1990 percentage.

WATER AVAILABILITY

The Plan Trend 2050 Scenario evaluates the economic pressure on water resources by assessing the supply of and demand for water in 178 "Water Availability Basins" (WABs), an administrative/hydrological unit defined by the Oregon Water Resources Department (OWRD).

The supply of surface water is represented in three sub-scenarios: a "normal" year, and a "dry" year, and a "wet" year. The supply is assumed to be insensitive to changes in the landscape, so the three sub-scenarios of supply are the same across time, and across the alternative futures.

The demand for surface water is represented by existing surface water rights and permits. Demand for surface water is summarized in six categories:

1. Municipal

2. Self-supplied industrial

3. In-stream

4. Agriculture

5. Self-supplied rural

6. Other non-consumptive uses

Increases in the demand for surface water through 2050 reflect population and economic growth and anticipated changes in agricultural cropping patterns. Most increases in demand occur within the constraints of existing rights and permits, with new permits available only for small self-supplied rural users and along the mainstems of the lower McKenzie and Willamette Rivers.

"Under all three sub-scenarios, mean annual flows remain unchanged in 140 WABs and decline in about 36 WABs: up to 3 percent under the "dry" sub-scenario and up to 1 percent under the "normal" sub-scenario, relative to 2000."