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Date Permissions Signed


Date of Award

Fall 1988

Document Type

Masters Thesis

Degree Name

Master of Science (MS)



First Advisor

Kelsey, H. M.

Second Advisor

Burmester, Russell F.

Third Advisor

Brugman, Melinda M.


The Fishtrap Creek basin is located in northwest Washington State and south central British Columbia. Land use in the basin is predominantly agricultural. Moderate urbanization in the past thirty-five years has increased impervious surface area in the basin from 1.8 to 8.0 percent. Monthly water balances were derived in order to quantify the effect of changing land use on the discharge of Fishtrap Creek. Stream discharges calculated from these water balances, constructed for 1952 through 1953 and 1987 through 1988, compare well with measured monthly and annual stream discharges. The favorable comparison indicates that the water- balance variables are in general reliable. However, in months following long periods of dry weather, calculated discharge was much higher than measured discharge. The discrepancy is probably because the standard water balance method does not account for water stored in the vadose zone below the rooting depth of the vegetation or the time lag required for the water to infiltrate through this zone and into the groundwater reservoir. To interpret the results of changing land use on the discharge of Fishtrap Creek, a hypothetical water balance was calculated incorporating the climatic data for 1952 through 1953 and the land use as of 1988. In effect, climate was held constant while land use changed with time. The hypothetical water balance predicted that, as a result of changing land use, a 7.8 percent increase in annual stream discharge would have occurred if the 1952 through 1953 climate had occurred again in 1987 through 1988. Of this 7.8 percent increase, 2.7 percent is due to increased overland flow and 5.1 percent to increased groundwater discharge. The predictions based on the hypothetical water balance are supported by comparison of actual storm events. For comparable storms, stream discharge was higher in the 1987 - 1988 period than in 1952 - 1953.




Fishtrap Creek basin, Urbanization, Water balances



Western Washington University

OCLC Number


Subject – LCSH

Water balance (Hydrology)--Fishtrap Creek Watershed (B.C. and Wash.); Land use--Fishtrap Creek Watershed (B.C. and Wash.); Water resources development--Fishtrap Creek Watershed (B.C. and Wash.)

Geographic Coverage

Fishtrap Creek Watershed (B.C. and Wash.)




masters theses




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