### Estimates of ground-water recharge, base flow, and stream reach gains and losses in the Willamette River basin, Oregon

By: Karl K. LeeJohn C. Risley**

                            https://doi.org/10.3133/wri014215

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#### Abstract

First posted March 19, 2002

**For additional information, contact:**
Director, Oregon Water Science CenterU.S. Geological Survey2130 SW 5th AvenuePortland, Oregon 97201http://or.water.usgs.gov

Precipitation-runoff models, base-flow-separation techniques, and stream gain-loss measurements were used to study recharge and ground-water surface-water interaction as part of a study of the ground-water resources of the Willamette River Basin. The study was a cooperative effort between the U.S. Geological Survey and the State of Oregon Water Resources Department. Precipitation-runoff models were used to estimate the water budget of 216 subbasins in the Willamette River Basin. The models were also used to compute long-term average recharge and base flow. Recharge and base-flow estimates will be used as input to a regional ground-water flow model, within the same study. Recharge and base-flow estimates were made using daily streamflow records. Recharge estimates were made at 16 streamflow-gaging-station locations and were compared to recharge estimates from the precipitation-runoff models. Base-flow separation methods were used to identify the base-flow component of streamflow at 52 currently operated and discontinued streamflow-gaging-station locations. Stream gain-loss measurements were made on the Middle Fork Willamette, Willamette, South Yamhill, Pudding, and South Santiam Rivers, and were used to identify and quantify gaining and losing stream reaches both spatially and temporally. These measurements provide further understanding of ground-water/surface-water interactions.

#### Suggested Citation

Lee, K.K., and Risley, J.C., 2002, Estimates of ground-water recharge, base flow, and stream reach gains andlosses in the Willamette River Basin, Oregon: U.S. Geological Survey Water-Resources InvestigationsReport 01–4215, 52 p.

#### Table of Contents

- Abstract
- Introduction
- Methods
- Results
- Summary and Conclusions
- Selected References
- Appendixes

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