Diagnostic tools to differentiate soil moisture dynamics under contrasting land-uses

Recently, hydrologic signatures have been proposed as tools to diagnose hydrologic models. Hydrologic signatures are indices that quantify the target hydrologic processes, and model structures and parameters can be evaluated based on whether the models can reproduce the hydrologic signatures. Although soil moisture is a critical control of hydrologic models, there are few previous studies on hydrologic signatures for soil moisture (called soil moisture signatures), and those studies are limited in terms of land-uses. This study extracted nine soil moisture signatures from six observatories data worldwide to investigate the applicability of signatures in capturing soil moisture processes under contrasting land-uses. Each observatory has two land-use types within the watershed, allowing for a comparison of twelve land-use types. We first used multivariate analysis to test whether the signature values are different under contrasting land-uses. Second, we derived process implications from the signature differences based on literature review. We summarized our results at three levels of time scales (per storm event, season, and a complete timeseries). The signatures extracted per storm event were significantly different under most land-uses, and the differences were related to flow pathways. The signatures extracted per season showed significant differences under some land-uses (forested vs. deforested, greenspace vs. housing, and deep vs. shallow groundwater area), but it was difficult to derive an implication due to lack of previous studies. For the signatures extracted per a complete timeseries, visual differences were found under some land-uses (forested vs. deforested, deep vs. shallow groundwater, non-wetland vs. wetland, and ungrazed vs. grazed area), and the differences were related to soil wetness. Therefore, these signatures can be used as a performance measure to evaluate whether models correctly reproduce differences in flow paths and soil conditions between contrasting land uses.