Western Oregon Streamflow Permanence

Project Description

Streamflow fluctuates over time depending on snowmelt, precipitation, watershed characteristics and other factors. Understanding flow permanence in headwater streams, and where streams maintain surface flow even in the driest times of year, is important to forest management. It is also critical information when planning and managing water resources as the climate changes.

The variability of surface streamflow over space and time complicates decisionmaking for resource managers who implement these policies and practices. The challenge is often exacerbated by scarce data for streamflow conditions, particularly in the headwaters of stream networks.

A centralized database, where field observations across ownerships can be archived and are easily accessed by multiple parties, improves the current understanding of water availability. It also serves as a source of information for evaluating changes in surface flow over time into the future.

Figure 1: Example map of flow status predictions for an Oregon subwatershed using the Western Oregon WeT DRy (WOWTDR) model: orange = stream reaches with no surface flow in late summer; blue = reaches with year-round surface flow; yellow = reaches with uncertain surface flow (predictions were outside the 95% confidence interval); black = larger streams not modeled and expected to have year-round flow, or channels in very small watersheds not captured in training data.

The Western Oregon Streamflow Permanence Project is improving understanding of streamflow permanence in forested headwater streams by providing a framework for simple, standardized data collection of observations of surface water presence and a system for easy archiving in a centralized database. We are also using the latest digital mapping and modeling technologies to provide predictions on the presence of late summer surface flow of headwater streams in western Oregon (fig. 1). This project is helping to reduce the cost of pre-project planning and monitoring associated with forest management activities. The results of this project will also feed into efforts to update the National Hydrography Dataset and streamflow classifications.

Figure 1: Example map of flow status predictions for an Oregon subwatershed using the Western Oregon WeT DRy (WOWTDR) model: orange = stream reaches with no surface flow in late summer; blue = reaches with year-round surface flow; yellow = reaches with uncertain surface flow (predictions were outside the 95% confidence interval); black = larger streams not modeled and expected to have year-round flow, or channels in very small watersheds not captured in training data.

Project Deliverables

We have developed two key products:

(1) The FLOw PERmanence (FLOwPER) mobile application, which enables users to quickly and consistently collect field data for surface water (or its absence) and archive these data in a publicly accessible database. The FLOwPER field app is being used by natural resource managers and researchers on private, state, tribal and federal lands to collect, store and upload observations of surface water presence/absence and additional visual characteristics of the observation location.

(2) The Western Oregon WeT DRy (WOWTDR) model, which predicts the probability of presence of surface flow in late summer. The model uses FLOwPER data and multiple climatic and environmental parameters to accurately characterizes stream reaches as either wet or dry in late summer—thus identifying streams with year-round surface flow (perennial) and those that are not perennial.