A diurnal· .study of bio1~gical, chemical, and physical parameters was made on the middle course of the Tualatin , River, which drains a 1840 km 2 (711 mi 2 ) basin adjacent to metropolitan Po~t1and, Or~gon. This portion. of the river lies a1o~g land in transition of use from rural agriculture to h~ghly urbanized development.There is no nutrient loading of the river from farming practices because there was no return of water from summer, sprinkler irrigation of commercial crops. However, irrigation significantly reduces the volume of water in the river in the summers.Effluents from sewage treatment plants flowing into the tributaries that drain the highly urbanized eastern areas of the river basin are the main cause of degraded water quality and algal biomass in the lower reaches of the river. TheTualatin River above the mouth of Rock Creek is relatively unpolluted, but downstream from Rock Creek the river is highly eutrophic and during the periods of low flow 'in the summer serves as a sewage oxidation channel. In this s~ne.portion of the river there is also evidence that nitrification occurs.'Winter floods leach ni t:r.'at.e.-.ni trogen from the basin, but in the summer the possibility exists. that nitrate-nitrogen may be a 1imiti~g nutrient for a~gal productivity in the river above Hillsboro. A diurnal study was especially valuable from April to September, inclusive, when insolation and temperatures favored biol~gical activities such as photosynthesis and decomposition. From November to January little diurnal change in the water quality was found.Farming had its. greatest impact in the quantity of water and municipalities had a more serious impact on the water quality in the middle course of the Tualatin River.Even with the reduced flow from agricultural irrigation~ the river can maintain relatively good water quality, except when effluents from sewage plants caused highly eutrophic conditions. ACKNOWLEDGMENTS
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.