Precision of Headwater Stream Permanence Estimates from a Monthly Water Balance Model in the Pacific Northwest, USA

Stream permanence classifications (i.e., perennial, intermittent, ephemeral) are a primary consideration to determine stream regulatory status in the United States (U.S.) and an important indicator of environmental conditions biodiversity. However, at present, no models or products adequately describe surface water presence for determinations. We modified Thornthwaite monthly balance model (MWBM) with flow threshold parameter estimate evaluated model’s accuracy precision more than 1.3 million headwater reaches U.S. Pacific Northwest (PNW). were assigned one eight calibration groups by unsupervised classification based on sensitivity MWBM parameters. Suitable sets identified comparing modeled estimates observations (SWPO). Parameter accuracies > 65% considered suitable. The estimated high 40% reaches, poor 20% suitable reaches. Results highlight need increased SWPO collection improve assessment models. Additionally, implementation indicates potential process-based predict future development.