Exploring Persistence in Stream Flow Forecasting

Abstract

In this study, the authors explore three persistence approaches in streamflow forecasting motivated by the need for forecasting model skill evaluation. The authors use stream flow observations with 15 minutes resolution from the year 2008 to 2017 at 140 U.S. Geological Survey (USGS) streamflow gauges monitoring the streams and rivers over the State of Iowa. The spatial scale of the basins ranges from about 7 km2 to 37,000 km2. The study explores three approaches: simple persistence, gradient persistence and anomaly persistence. The study shows that persistence forecasts skill has strong dependence on basin scales and weaker but non-negligible dependence on geometric properties of the river network for a given basin. Among the three approaches explored, anomaly persistence shows highest skill especially for small basins, under about 500 km2. The anomaly persistence can serve as a benchmark for model evaluations considering the effect of basin scales and geometric properties of river network of the basin. This study further reiterates that persistence forecasts are hard-to-beat methods for larger basin scales at short to medium forecast range.