Comparisons of measured stream flow with drainage and runoff simulated by a soil-vegetation-atmosphere transport model parameterized with GLOBE student data

Predicting runoff and drainage from landscapes and correlating these with stream flow can be a powerful watershed management tool. We examined the feasibility of using runoff and drainage output of a simple soil-vegetation-atmosphere (SVAT) model as a predictor of monthly and daily changes in measured stream flow. Six watersheds in the eastern US were analyzed, located from approximately 35°N to 43°N. They ranged in area from 23 to 2463 km2 and were 35-65% forested. The SVAT model was parameterized with weather, soils and phenological data largely obtained from a secondary school in each watershed that is participating in the Global Learning and Observations to Benefit the Environment (GLOBE) program. This program is a United States government science education effort promoting scientific inquiry in grades K-12 by providing protocols for collecting environmental data. Monthly measured stream flow and simulated runoff + drainage over a one year period were normalized to the largest value in that period and were compared using linear regression. Simulated monthly runoff + drainage explained between 37% and 76% of the variability in monthly stream flow. Changes in daily simulated runoff + drainage and measured stream flow depended on the simulated volumetric soil water content (θv). At low θv, large precipitation events (>20 mm) did not result in increased daily simulated runoff + drainage or measured stream flow. At high or saturating θv, large precipitation events resulted in increased daily simulated runoff + drainage followed by increased measured stream flow within two days.